Polymeric Materials for Corrosion Control: An Overview - ACS

1 Polymeric Materials for Corrosion Control: An Overview 1

Downloaded by MIDDLE TENNESSEE STATE UNIV on July 16, 2013 | http://pubs.acs.org Publication Date: October 14, 1986 | doi: 10.1021/bk-1986-0322.ch001

Ray A. Dickie and F. Louis Floyd 1

2

2

Ford Motor Company, Dearborn, MI 48121 Glidden Coatings and Resins Division, SCM Corporation, 16651 Sprague Road, Strongsville, OH 44136

Polymeric materials are widely used to control the corrosion of metals, both to maintain appearance and to prevent loss of structural integrity. In this chapter, the fundamentals of metallic corrosion are briefly reviewed. Methods of studying corrosion, and of evaluating the performance of polymeric materials used in corrosion protection, are outlined. Factors that influence the corrosion protective performance of polymeric materials are discussed, and some of the research needs and important unsolved problems are highlighted. The economic c o s t s and e n v i r o n m e n t a l impact o f m e t a l l i c c o r r o s i o n are w e l l known, and need not be d i s c u s s e d i n depth h e r e . I t has been e s t i m a t e d (1) t h a t the t o t a l c o s t o f c o r r o s i o n i n the U n i t e d S t a t e s may be as much as 4% o f the g r o s s n a t i o n a l p r o d u c t , and t h a t about 15% o f t h e t o t a l c o s t might be a v o i d a b l e t h r o u g h the economic use o f a v a i l a b l e technology. Most s t u d i e s o f c o r r o s i o n and i t s e f f e c t s understandably concentrate on the c o s m e t i c and s t r u c t u r a l e f f e c t s o f m e t a l l i c c o r r o s i o n ; most o f the papers i n the p r e s e n t volume f a l l i n t o t h i s category. I t s h o u l d be n o t e d , however, t h a t m e t a l l i c c o r r o s i o n and the p r o d u c t s o f m e t a l l i c c o r r o s i o n can d e l e t e r i o u s l y a f f e c t the p r o p e r t i e s o f n o n - m e t a l l i c m a t e r i a l s , p a r t i c u l a r l y a t j o i n t s between m e t a l s and non-metals. There a r e a l s o e n v i r o n m e n t a l d e g r a d a t i o n phenomena t h a t c a n a f f e c t n o n - m e t a l l i c m a t e r i a l s such as p l a s t i c s , c o m p o s i t e s and g l a s s d i r e c t l y ; some o f t h e s e phenomena resemble m e t a l l i c c o r r o s i o n p r o c e s s e s i n the e f f e c t s o b s e r v e d on appearance and structural integrity. S e v e r a l papers i n t h i s volume d e a l w i t h c o r r o s i o n e f f e c t s on a d h e s i v e j o i n t s and n o n - m e t a l l i c m a t e r i a l s . The present chapter begins w i t h a b r i e f overview o f m e t a l l i c c o r r o s i o n and mechanisms o f c o r r o s i o n c o n t r o l . Methods o f e v a l u a t i n g polymer performance and e l e c t r o c h e m i c a l c h a r a c t e r i z a t i o n t e c h n i q u e s are d i s c u s s e d . B a r r i e r and a d h e s i o n a s p e c t s o f c o r r o s i o n c o n t r o l are r e v i e w e d , and some c r i t i c a l i s s u e s n e e d i n g f u r t h e r s t u d y are o u t l i n e d . 0097-6156/ 86/ 0322-0001 $06.00/ 0 © 1986 American Chemical Society

In Polymeric Materials for Corrosion Control; Dickie, R., et al.; ACS Symposium Series; American Chemical Society: Washington, DC, 1986.

POLYMERIC MATERIALS FOR CORROSION C O N T R O L

2


Metallic

Corrosion

M e t a l l i c c o r r o s i o n has been t h e s u b j e c t o f many t e x t b o o k s and s c h o l a r l y compendia (e.g., 2-4), and a number o f i n t r o d u c t o r y t r e a t m e n t s d e a l i n g w i t h c o r r o s i o n and c o r r o s i o n p r o t e c t i o n a r e a l s o a v a i l a b l e (e.g., 5-7). I n t h i s c o n t e x t , t h e term " c o r r o s i o n " r e f e r s t o t h e c h e m i c a l d e g r a d a t i o n o f a m e t a l by i t s environment. The r e a c t i o n s a r e most o f t e n heterogeneous redox r e a c t i o n s and o c c u r a t t h e m e t a l - e n v i r onment i n t e r f a c e . The a n o d i c r e a c t i o n i s t y p i c a l l y t h e o x i d a t i o n o f the m e t a l ; t h e c a t h o d i c r e a c t i o n i s r e d u c t i o n o f a non-metal, t y p i c a l l y oxygen. I f t h e p r o d u c t o f t h e m e t a l o x i d a t i o n forms a t i g h t and adherent f i l m , t h e c o r r o s i o n p r o c e s s may be s e l f - l i m i t i n g . I f the products o f the c o r r o s i o n r e a c t i o n are s o l u b l e i n the c o r r o s i v e medium, o r a r e permeable t o i t , t h e n m e t a l l i c c o r r o s i o n c a n proceed. Corrosion i s often represented i n terms o f a s i m p l e e l e c t r o c h e m i c a l model. The a n o d i c and c a t h o d i c h a l f r e a c t i o n s o f t h e c o r r o s i o n c e l l may o c c u r a t a d j a c e n t o r w i d e l y s e p a r a t e d s i t e s on t h e m e t a l s u r f a c e ; the e l e c t r i c a l c i r c u i t i s completed by e l e c t r o n i c c o n d u c t i o n w i t h i n the c o r r o d i n g m e t a l and i o n i c c o n d u c t i o n w i t h i n t h e aqueous e l e c t r o lyte. I n n a t u r a l c o r r o s i o n , i t i s common f o r t h e s i t e s o f t h e a n o d i c and cathodic c o r r o s i o n r e a c t i o n s t o become more o r l e s s w i d e l y separated. I n such c a s e s , t h e a n o d i c s i t e s t e n d t o become a c i d i c and the c a t h o d i c s i t e s t e n d t o become b a s i c . These changes i n pH can be l a r g e , and c a n have s e r i o u s i m p l i c a t i o n s f o r t h e performance o f polymeric materials. The c o r r o s i o n o f i r o n i s one o f t h e most w i d e s p r e a d and technol o g i c a l l y i m p o r t a n t examples o f m e t a l l i c c o r r o s i o n . I n t h e presence o f w a t e r and oxygen, t h e c o r r o s i o n o f i r o n proceeds t o form a c o m p l i c a t e d m i x t u r e o f h y d r a t e d i r o n o x i d e s and r e l a t e d s p e c i e s ; a complete d e s c r i p t i o n i s beyond t h e scope o f t h e p r e s e n t d i s c u s s i o n , and the i n t e r e s t e d reader i s r e f e r r e d t o the p r e v i o u s l y c i t e d general r e f e r ences on c o r r o s i o n as w e l l as t o t h e w e l l known d e s c r i p t i o n s o f e l e c t r o c h e m i c a l e q u i l i b r i a i n aqueous s o l u t i o n g i v e n by P o u r b a i x ( 8 , 9). I r o n i s a base m e t a l , s u b j e c t t o c o r r o s i o n i n aqueous s o l u t i o n s . In the presence o f o x i d i z i n g s p e c i e s , i r o n surfaces c a n be p a s s i v a t e d by the formation o f an o x i d e l a y e r ; i f t h e o x i d e l a y e r formed i s i m p e r f e c t , r a p i d c o r r o s i o n may o c c u r . In simplest form, t h e r e a c t i o n o f i r o n t o form i r o n o x i d e c a n be w r i t t e n a s : 4 Fe + 2 H 0 +3 0 2

-> 2 F e 0 . H 0

2

2

3

2

The f i r s t step i n the c o r r o s i o n process i s the d i s s o l u t i o n o f i r o n to form f e r r o u s i o n : Fe

-> F e

+ +

+ 2 e"

I n g e n e r a l , t h e pH d e c r e a s e s a t h y d r o l y s i s r e a c t i o n s such a s : Fe

+ +

+ H 0 -> FeOH 2

+

+ H

sites of

anodic d i s s o l u t i o n

due t o

+

The c a t h o d i c r e a c t i o n s commonly o b s e r v e d a r e t h e e v o l u t i o n o f hydrogen and t h e r e d u c t i o n o f oxygen; hydrogen e v o l u t i o n i s k i n e t i c a l l y f a v o r e d under a c i d i c c o n d i t i o n s , w h i l e oxygen r e d u c t i o n i s k i n e t i c a l l y f a v o r e d under n e u t r a l and b a s i c c o n d i t i o n s .


1.

DICKIE A N D

H 0+ + e"

-> 1/2

H

2

+

H0

(acid

H0

+ e"

-> 1/2

H

2

+

OH"

(neutral/basic

1/2

0

2

+ H30

1/2

0

2

+ H0

3

2


3

Overview

FLOYD

2

+

+ 2 e" + 2 e"

2

solutions) solutions)

-> 3 H 0

(acid solutions)

-> 2 OH'

(neutral/basic

2

solutions)

The pH a t c a t h o d i c s i t e s tends to i n c r e a s e due t o the p r o d u c t i o n of h y d r o x i d e i o n and/or consumption o f hydrogen i o n . I t i s i n t e r e s t i n g t o c o n t r a s t the b e h a v i o r o f i r o n w i t h t h a t of aluminum. Aluminum i s a v e r y base m e t a l ; y e t aqueous s o l u t i o n s i n the n e u t r a l pH range t h a t are q u i t e a g g r e s s i v e toward i r o n o f t e n have l i t t l e e f f e c t on aluminum. I n the p r e s e n c e o f a c i d s o l u t i o n s , aluminum d i s s o l v e s w i t h the formation o f A l ^ i o n s , w h i l e under a l k a l i n e c o n d i t i o n s , i t d i s s o l v e s as a l u m i n a t e i o n s , A 1 0 " . Over the mid-range o f pH from about 4 t o 9, a p a s s i v a t i n g f i l m o f aluminum o x i d e tends t o form. The s t r u c t u r e and c o m p o s i t i o n o f the o x i d e depend on the c o n d i t i o n s under w h i c h i t i s formed, and the c o r r o s i o n performance o f aluminum tends t o be dominated by the performance o f the oxide l a y e r . C e r t a i n s o l u t i o n s p e c i e s , n o t a b l y c h l o r i d e , can d i s r u p t the o x i d e l a y e r and cause l o c a l i z e d p i t t i n g . C o n t r o l and m o d i f i c a t i o n o f the aluminum s u r f a c e o x i d e l a y e r has been e x t e n s i v e l y s t u d i e d , and i s o f p a r t i c u l a r importance i n the p r o t e c t i o n o f aluminum substrates. +

2

Mechanisms o f C o r r o s i o n

Control

Corrosion can be c o n t r o l l e d by i s o l a t i o n o f the m e t a l from the c o r r o s i v e environment; by s u p p r e s s i o n o f the anodic d i s s o l u t i o n of m e t a l ; and by s u p p r e s s i o n o f the c o r r e s p o n d i n g c a t h o d i c r e a c t i o n . I s o l a t i o n o f c o r r o s i o n prone m e t a l s from c o r r o s i v e environments i s p r o b a b l y the most g e n e r a l mechanism o f the corrosion protection a f f o r d e d by p a i n t f i l m s , s e a l e r s , and s i m i l a r polymer-based m a t e r i a l s . Effective i s o l a t i o n requires that polymeric materials have good b a r r i e r p r o p e r t i e s and remain adherent i n the p r e s e n c e o f w a t e r and the p r o d u c t s o f m e t a l l i c c o r r o s i o n . B a r r i e r p r o p e r t i e s and a d h e s i o n a s p e c t s o f c o r r o s i o n c o n t r o l are d i s c u s s e d in detail i n subsequent sections. The a n o d i c d i s s o l u t i o n o f m e t a l can be s u p p r e s s e d by l o w e r i n g the p o t e n t i a l so t h a t o x i d a t i o n o f the m e t a l i s t h e r m o d y n a m i c a l l y impossible; this i s the p r i n c i p l e o f c a t h o d i c p r o t e c t i o n of steel. C a t h o d i c p r o t e c t i o n r e l i e s on e i t h e r an e x t e r n a l s o u r c e o f e l e c t r i c c u r r e n t or c o u p l i n g o f the m e t a l t o be p r o t e c t e d w i t h a more a c t i v e m e t a l (e.g., s t e e l i s p r o t e c t e d by coupling to z i n c ) . W i t h the e x c e p t i o n o f some z i n c - c o n t a i n i n g organic coatings a p p l i e d to s t e e l , c a t h o d i c p r o t e c t i o n i s not a major mechanism o f p r o t e c t i o n by p o l y meric m a t e r i a l s . The mechanism o f a c t i o n o f z i n c c o n t a i n i n g c o a t i n g s has been the s u b j e c t o f some disagreement. P a r t o f the e f f e c t i v e n e s s o f z i n c pigmented c o a t i n g s may be due t o the f o r m a t i o n o f z i n c c o r r o s i o n p r o d u c t s a f t e r an i n i t i a l p e r i o d of true cathodic protection. The a c t i o n o f the z i n c compounds formed has been v a r i o u s l y a s c r i b e d to a b l o c k i n g o f the pores o f the f i l m and t o p a s s i v a t i o n of the s u r f a c e . The e v a l u a t i o n ( u s i n g impedance methods, see a l s o Ref.



4


10) and m o d i f i c a t i o n o f z i n c pigmented c o a t i n g s a r e d i s c u s s e d i n t h i s volume by Szauer and M i s z c z y k . The chemistry o f z i n c - r i c h and m o d i f i e d z i n c - r i c h c o a t i n g s were a l s o d i s c u s s e d by Fawcett i n the symposium on w h i c h t h i s book i s based. The paper was not made a v a i l a b l e f o r i n c l u s i o n i n t h i s volume, b u t the p r e p r i n t v e r s i o n i s a v a i l a b l e (11). S u p p r e s s i o n o f the a n o d i c r e a c t i o n can be a c h i e v e d by the use o f o x i d i z i n g i n h i b i t o r s ; e s s e n t i a l l y , the i n h i b i t o r i s c a l l e d upon t o form (and m a i n t a i n ) an i m p e r v i o u s and p a s s i v a t i n g o x i d e f i l m on the s u r f a c e o f the m e t a l . I f the o x i d e f i l m formed i s i m p e r f e c t , however, i t i s p o s s i b l e f o r r a p i d l o c a l i z e d c o r r o s i o n t o t a k e p l a c e . I n the case o f aluminum, i n h i b i t o r s can be used t o s t a b i l i z e the o x i d e f i l m a g a i n s t h y d r a t i o n , as d i s c u s s e d i n t h i s volume by M a t i e n z o e t a l . Organic coatings designed f o r c o r r o s i o n p r o t e c t i o n of f e r r o u s metals o f t e n i n c o r p o r a t e m e t a l chromâtes as o x i d i z i n g i n h i b i t o r s . The use o f i n h i b i t o r s i n c o a t i n g s , and the r e q u i r e m e n t s f o r an i d e a l i n h i b i t o r , have been d i s c u s s e d by L e i d h e i s e r ( 1 2 ) . As d i s c u s s e d by Funke b o t h i n t h i s volume and elsewhere (.13), the u s e f u l n e s s of a c t i v e c o r r o s i o n i n h i b i t i n g pigments i s open t o q u e s t i o n : the b i n d e r s used f o r p a i n t s c o n t a i n i n g c o r r o s i o n i n h i b i t i n g pigments must be somewhat w a t e r permeable f o r the pigments t o work, a t l e a s t p a r t i a l l y v i t i a t i n g the b a r r i e r e f f e c t o f the c o a t i n g . A d s o r p t i o n i n h i b i t o r s a c t by f o r m i n g a f i l m on the m e t a l s u r f a c e . The a c t i o n of t r a d i t i o n a l o i l - b a s e d red lead p a i n t formulations presumably i n v o l v e s the f o r m a t i o n o f soaps and the p r e c i p i t a t i o n o f complex f e r r i c s a l t s t h a t r e i n f o r c e the o x i d e f i l m . There has been s u b s t a n t i a l i n t e r e s t i n r e c e n t y e a r s i n development o f replacements f o r lead-based and chromate-based i n h i b i t o r systems. Adsorption i n h i b i t o r s based on polymers have been o f p a r t i c u l a r i n t e r e s t . In t h i s volume, Johnson e t a l . and Eng and I s h i d a d i s c u s s i n h i b i t o r s f o r copper; 2 - u n d e c y l i m i d a z o l e i s shown t o be e f f e c t i v e i n a c i d media, where i t s u p p r e s s e s the oxygen r e d u c t i o n r e a c t i o n a l m o s t c o m p l e t e l y . P o l y v i n y l i m i d a z o l e s are shown t o be e f f e c t i v e o x i d a t i o n i n h i b i t o r s f o r copper a t e l e v a t e d t e m p e r a t u r e s . A l s o i n t h i s volume, Chen d i s c u s s e s the use o f N - ( h y d r o x y a l k y l ) a c r y l a m i d e copolymers i n c o n j u n c t i o n w i t h phosphate-orthophosphate i n h i b i t o r systems f o r c o o l i n g systems. I n many i n d u s t r i a l c o a t i n g a p p l i c a t i o n s , i n o r g a n i c c o n v e r s i o n c o a t i n g s a r e used as s u r f a c e p r e t r e a t m e n t s f o r metals. Such t r e a t ments t y p i c a l l y r e s u l t i n the f o r m a t i o n o f an i n s o l u b l e m e t a l chromate or phosphate on the m e t a l s u r f a c e . The e f f e c t i v e n e s s o f z i n c phosphate c o n v e r s i o n c o a t i n g s has been r e l a t e d t o t h e i r r o l e i n supp r e s s i n g the c a t h o d i c r e d u c t i o n o f oxygen ( 1 4 ) . Bender e t a l . (15) have r e v i e w e d the l i t e r a t u r e e x t e n s i v e l y . The performance o f i n o r g a n i c c o n v e r s i o n c o a t i n g systems i s dependent on b a t h c o m p o s i t i o n and d e p o s i t i o n c o n d i t i o n s , on the i n i t i a l c o n d i t i o n o f the s u b s t r a t e , and on the f i n a l r i n s e o r p o s t - t r e a t m e n t used. I n t h i s volume, L i n d e r t and Maurer d i s c u s s a n o v e l f i l m - f o r m i n g o r g a n i c p o s t - t r e a t m e n t f o r i n o r g a n i c phosphate c o n v e r s i o n coatings. Agarwala discusses a m o d i f i e d chromate c o n v e r s i o n c o a t i n g f o r aluminum. Methods o f E v a l u a t i n g Polymer Performance Performance T e s t s . The underlying goal of c o r r o s i o n t e s t i n g i s g e n e r a l l y the p r e d i c t i o n o f s e r v i c e performance, whether d i r e c t l y f o r a d e v i c e o r system, o r i n d i r e c t l y i n the d e s i g n o r f o r m u l a t i o n o f a



1.

DICKIE A N D

FLOYD

Overview

5

new m a t e r i a l o r p r o c e s s . The u l t i m a t e t e s t i s performance i n the i n t e n d e d a p p l i c a t i o n ; a c l o s e second i s exposure o f t e s t p a n e l s t o the normal s e r v i c e environment. T e s t i n g based on n a t u r a l exposure i s , o f c o u r s e , time consuming, and a l a r g e number o f l a b o r a t o r y t e s t methods have been d e v e l o p e d t o a s s e s s a s p e c t s o f polymer p r o p e r t i e s and c o r r o s i o n p r o t e c t i o n system performance. Performance t e s t s g e n e r a l l y i n v o l v e exposure o f a system, component, o r t e s t p i e c e t o a s i m u l a t e d or a c c e l e r a t e d c o r r o s i o n environment; e v a l u a t i o n o f r e s u l t s i s t y p i c a l l y based on an assessment o f the type and e x t e n t of corrosion failure. Property t e s t s g e n e r a l l y i n v o l v e the measurement o f a s i n g l e , i s o l a b l e , material property, o r o f a change i n m a t e r i a l p r o p e r t y w i t h exposure t o an a g g r e s s i v e environment. E v a l u a t i o n o f r e s u l t s i s t y p i c a l l y i n terms o f a c o r r e l a t i o n w i t h performance t e s t s o r f i e l d performance d a t a . The fundamental problems o f a c c e l e r a t e d performance t e s t i n g are the s e l e c t i o n o f a p p r o p r i a t e t e s t c o n d i t i o n s , and the d e t e r m i n a t i o n and v a l i d a t i o n o f a c c e l e r a t i o n f a c t o r s . I d e a l l y test conditions s h o u l d be s e l e c t e d t o a c c e l e r a t e a l l the r e l e v a n t c h e m i c a l r e a c t i o n s and p h y s i c a l p r o c e s s e s e q u a l l y . The d e t e r m i n a t i o n o f a c c e l e r a t i o n f a c t o r s t y p i c a l l y r e q u i r e s , and hence poses the same problems a s , performance t e s t s under n a t u r a l exposure c o n d i t i o n s . Organic coatings a r e commonly e v a l u a t e d u s i n g s a l t w a t e r immers i o n , s a l t f o g o r s p r a y , m o d i f i e d s a l t exposure t e s t s ( e . g . , s a l t fog w i t h added SO2), and v a r i o u s c y c l i c exposure t e s t s . H u m i d i t y exposure and w a t e r immersion, and, f o r many a p p l i c a t i o n s , p h y s i c a l r e s i s t a n c e t e s t s (adhesion, impact r e s i s t a n c e , e t c . ) a r e w i d e l y u s e d p r e l i m i n a r y tests. S t a n d a r d methods f o r most o f t h e s e t e s t s a r e g i v e n i n c o m p i l a t i o n s of standard t e s t s such as the A n n u a l Book o f ASTM Standards ( 1 6 ) . T e s t methods have been e x t e n s i v e l y r e v i e w e d (e.g., 17-23). D e s p i t e t h e i r l o n g and common use, none o f the p o p u l a r l a b o r a t o r y c o r r o s i o n t e s t s are e n t i r e l y s a t i s f a c t o r y . The use o f s t a n d a r d l a b o r a t o r y t e s t s to e s t a b l i s h comparative rankings o f the c o r r o s i o n performance o f d i f f e r e n t m a t e r i a l s i s e s p e c i a l l y s u s c e p t i b l e t o e r r o r . I n one r e c e n t s t u d y , f o r example, the r e s u l t s o f e x t e r i o r exposure and s t a n d a r d l a b o r a t o r y t e s t s were used t o compare c o r r o s i o n i n h i b i t i v e p r i m e r s ( 2 4 ) ; i t was found t h a t s t a n d a r d s a l t f o g t e s t s showed s u b s t a n t i a l d i f f e r e n c e s i n p a i n t performance t h a t were n o t observed under f i e l d exposure c o n d i t i o n s . C y c l i c exposure t e s t s have been p r o p o s e d t h a t i n c o r p o r a t e p e r i o d s o f exposure t o h u m i d i t y , s a l t water immersion, temperature c y c l i n g , and d i r t (25, 2 6 ) ; such t e s t s a r e s u b s t a n t i a l l y more c o m p l i c a t e d t h a n c o n v e n t i o n a l l a b o r a t o r y t e s t s , b u t i n some c a s e s g i v e b e t t e r agreement w i t h c o r r o s i o n performance i n service. C y c l i c exposure t e s t s have a l s o been a p p l i e d t o p r e c o a t e d s t e e l s , b o t h w i t h and w i t h o u t p a i n t c o a t i n g s (27.). The mechanism o f failure i n c y c l i c exposure t e s t i n g has been the s u b j e c t o f some discussion. S t a n d i s h (2£) argues t h a t the c y c l i c t e s t allows corrosion products l i k e those o b s e r v e d i n s e r v i c e t o form under the c o a t i n g ; such c o r r o s i o n p r o d u c t s a r e t y p i c a l l y n o t o b s e r v e d i n s a l t spray. Jones (29) has a l s o d i s c u s s e d the f o r m a t i o n o f a b u l k y o x i d e l a y e r . Elsewhere i n t h i s volume, D i c k i e d i s c u s s e s surface a n a l y t i c a l r e s u l t s on the c y c l i c immersion f a i l u r e o f o r g a n i c c o a t i n g s on phosphated s t e e l s u b s t r a t e s ; d e l a m i n a t i o n o f the c o a t i n g i s found t o be a s s o c i a t e d w i t h d i s s o l u t i o n o f the c o n v e r s i o n c o a t i n g . T h i s r e s u l t i s c o n s i s t e n t w i t h o b s e r v a t i o n s o f v a n O o i j (30) on l o c u s and mechanism o f c o a t i n g d e l a m i n a t i o n on phosphated s t e e l .



6

POLYMERIC MATERIALS FOR

CORROSION C O N T R O L

Electrochemical C h a r a c t e r i z a t i o n Techniques. S i n c e c o r r o s i o n i s an e l e c t r o c h e m i c a l p r o c e s s , i t i s not s u r p r i s i n g that a considerable amount o f work has been r e p o r t e d o v e r the y e a r s on e l e c t r i c a l and e l e c t r o c h e m i c a l t e c h n i q u e s f o r the s t u d y o f the c o r r o s i o n p r o c e s s . L e i d h e i s e r (31) and Szauer (32, 33) have p r o v i d e d good r e v i e w s o f the p r i n c i p a l techniques. W a l t e r has r e c e n t l y p r o v i d e d a r e v i e w o f DC e l e c t r o c h e m i c a l t e s t s f o r p a i n t e d m e t a l s (34)· B o t h AC and DC methods have been employed t o s t u d y a v a r i e t y o f i s s u e s r e l a t e d t o c o r r o s i o n and corrosion protection. DC t e c h n i q u e s are e s p e c i a l l y u s e f u l f o r s t u d y i n g s u b s t r a t e p r o c e s s e s , w h i l e AC impedance t e c h n i q u e s are most u s e f u l f o r s t u d y i n g p r o c e s s e s r e l a t i n g t o c o a t e d s u b s t r a t e s and the performance o f c o a t i n g s . DC t e c h n i q u e s i n c l u d e measurement o f DC r e s i s t a n c e , d e t e r m i n a t i o n o f p o l a r i z a t i o n b e h a v i o r , and measurement o f p o l a r i z a t i o n r e s i s t a n c e . C o a t i n g r e s i s t a n c e has been c o r r e l a t e d w i t h c o r r o s i o n performance by a number o f w o r k e r s . As summarized by L e i d h e i s e r ( 3 1 ) , the r e s u l t s o f s e v e r a l independent i n v e s t i g a t i o n s suggest t h a t c o a t i n g r e s i s t a n c e below about 10^ ohm/cm^ i s a s s o c i a t e d w i t h the f o r m a t i o n o f v i s i b l e u n d e r - f i l m c o r r o s i o n . P a r a l l e l DC r e s i s t a n c e measurements on t h i n f i l m m e t a l s u b s t r a t e s have been u s e d t o s t u d y the d e t e r i o r a t i o n o f c o a t e d m e t a l s ; the technique s u c c e s s f u l l y detected the e f f e c t s o f w a t e r a f t e r m i g r a t i o n t o the c o a t i n g / m e t a l i n t e r f a c e (3j>) . P o l a r i z a t i o n methods i n v o l v e c h a n g i n g the p o t e n t i a l ( o r c u r r e n t ) o f a c o r r o d i n g system i n b o t h the a n o d i c and c a t h o d i c d i r e c t i o n s w h i l e monitoring current (or p o t e n t i a l ) . By m a n i p u l a t i n g the r e s u l t i n g i n f o r m a t i o n , an u n d e r s t a n d i n g o f the c o r r o s i o n p r o c e s s can be o b t a i n ed. For example, Beese (36) has used the l i n e a r p o l a r i z a t i o n t e c h n i q u e t o d e v e l o p i n f o r m a t i o n r e l a t e d t o c o r r o s i o n i n b e e r and beverage cans t h a t are c o a t e d w i t h an o r g a n i c enamel. Such i n f o r m a t i o n was u l t i m a t e l y employed t o develop improved c o a t i n g s f o r the c o n t a i n e r . G r o s e c l o s e e t a l . (37) employed an a n o d i c p o l a r i z a t i o n t e c h n i q u e t o q u a n t i f y the q u a l i t y and v a r i a b i l i t y o f b o t h c o l d r o l l e d and hot rolled steels. This i n f o r m a t i o n was used t o a c c u r a t e l y p r e d i c t the r e l a t i v e s a l t s p r a y performance o f the s u b s e q u e n t l y c o a t e d s t e e l s , and evaluate the e f f e c t o f a b r a s i v e p o l i s h i n g and s a n d b l a s t i n g o f the substrate. The p o l a r i z a t i o n r e s i s t a n c e method w i d e l y used f o r s t u d y i n g m e t a l c o r r o s i o n has a l s o been a p p l i e d t o p a i n t e d m e t a l s . In p r i n c i p l e , the p o l a r i z a t i o n r e s i s t a n c e i s i n v e r s e l y p r o p o r t i o n a l to the c o r r o s i o n r a t e o f the m e t a l . For c o a t e d m e t a l s , the method i s c o m p l i c a t e d by the c o r r e c t i o n f o r ohmic p o t e n t i a l drop, d i f f u s i o n l i m i t a t i o n s , and changes i n f i l m p r o p e r t i e s under the a p p l i e d potent i a l (32). AC t e c h n i q u e s are h i g h l y v a r i e d , b u t t e n d t o converge upon the use o f impedance s p e c t r o s c o p y . I n r e c e n t p u b l i c a t i o n s , Hubrecht e t a l . ( 3 8 ) , M a n s f i e l d and K e n d i g ( 3 9 ) , and K e n d i g e t a l . (40) have r e v i e w e d the a p p l i c a t i o n o f impedance s p e c t r o s c o p y t o c o a t i n g systems. By e x a m i n i n g the AC impedance o f the c o a t e d system as a f u n c t i o n o f f r e q u e n c y , u s e f u l i n f o r m a t i o n i s o b t a i n e d r e g a r d i n g b o t h the b a r r i e r p r o p e r t i e s o f the c o a t i n g and the c o r r o s i o n s u s c e p t i b i l i t y o f the substrate. Under p r o p e r c o n d i t i o n s , i n f o r m a t i o n can be e x t r a c t e d r e l a t i n g t o the i n t e r f a c i a l l a y e r as w e l l . I n f o r m a t i o n can a l s o be e x t r a c t e d r e l a t i v e t o the p r e s e n c e o f w a t e r and i o n s i n p a i n t f i l m s as shown by L i n d q v i s t ( 4 1 ) . A good example o f the l a t t e r has been g i v e n by Padget and M o r e l a n d ( 4 2 ) . I n most c a s e s , b a r r i e r p r o p e r t i e s o f c o a t i n g s are u l t i m a t e l y found t o be h i g h l y i m p o r t a n t t o the p r e v e n t i o n



1.

DICKIE A N D

FLOYD

Overview

1

o f c o r r o s i o n o f the s u b s t r a t e . I n t h i s p a r t i c u l a r c a s e , i t was a l s o shown t h a t the p r e s e n c e o f a b a r r i e r f i l m seems t o augment the f o r m a t i o n o f a s t r o n g l y p a s s i v e l a y e r a t the i n t e r f a c e between the c o a t i n g and the s u b s t r a t e . An i n t e r e s t i n g a p p l i c a t i o n o f e l e c t r o c h e m ical techniques i n v o l v e s the c h a r a c t e r i z a t i o n o f z i n c r i c h p a i n t s . F e r n a n d e z - P r i n i and K a p i s t a (43) and L i n d q v i s t e t a l . (44) d e s c r i b e b o t h DC and AC techniques f o r c h a r a c t e r i z i n g z i n c r i c h coatings i n such a way t h a t subsequent s a l t spray t e s t i n g i s r a t i o n a l i z e d . The p r e s e n t volume c o n t a i n s a number o f papers r e l a t i n g t o the i s s u e o f e l e c t r o c h e m i c a l t e s t i n g . M o r c i l l o e t a l . compare the r e s u l t s o f AC impedance measurements w i t h a c c e l e r a t e d and o u t d o o r exposure test results. V i j a y a n r e p o r t s the use o f AC impedance t e s t i n g to s t u d y the e f f e c t s o f v a r i o u s components o f the p h o s p h a t i n g p r e t r e a t ment p r o c e s s , p a i n t t h i c k n e s s , and t e s t v a r i a b l e s on subsequent s a l t s p r a y r e s u l t s . M o r e l a n d and Padget update t h e i r work on AC impedance as i t p e r t a i n s t o the study o f the p a s s i v e l a y e r w h i c h forms between a b a r r i e r c o a t i n g and a s t e e l s u b s t r a t e . B u t l e r and Bartoszek-Loza d e s c r i b e t h e i r use o f DC open c i r c u i t p o t e n t i a l s t o c o r r e l a t e w i t h s a l t s p r a y d a t a as a f u n c t i o n o f p o s t - b a k e temperature o f UV c u r e d coatings. Eden and co-workers d e s c r i b e their studies involving e l e c t r o c h e m i c a l n o i s e measurements t o s t u d y c o r r o s i o n as i t progresses. The a u t h o r s ' p o s i t i o n i s t h a t the c o a t i n g b r e a k d o w n / f a i l u r e on a s t e e l s u b s t r a t e i s accompanied by a change i n the e l e c t r o c h e m i c a l noise s i g n a l , w h i c h g i v e s a r a p i d i n d i c a t i o n o f the s t a t e o f the coating. Lomas e t a l . d e s c r i b e t h e i r n o v e l work w i t h harmonic a n a l y s i s , combined w i t h AC impedance t e s t i n g i n an attempt t o d e t e c t c o r r o s i o n of t h i c k l y coated substrates. B a r r i e r Aspects of Corrosion

Control

The r e l a t i v e importance o f the b a r r i e r f u n c t i o n o f o r g a n i c c o a t i n g s i n c o r r o s i o n p r o t e c t i o n has been debated f o r y e a r s . I t i s clear that, i f a m e t a l l i c s u b s t r a t e c o u l d be c o m p l e t e l y i s o l a t e d from i t s e n v i r o n ment, no c o r r o s i o n would o c c u r . The degree t o w h i c h a p r o t e c t i o n system b a r s oxygen, w a t e r , and i o n s from the s u b s t r a t e would seem l i k e l y t o be a measure o f the e f f e c t i v e n e s s o f the system i n p r e v e n t ing c o r r o s i o n . H i s t o r i c a l l y , a number o f d i f f e r e n t t h e o r i e s r e g a r d i n g the r o l e o f the b a r r i e r f u n c t i o n i n c o r r o s i o n p r o t e c t i o n have emerged. Studies by Mayne and h i s co-workers (45-49), Bacon e t a l . ( 5 0 ) , and Cherry (51) i n d i c a t e d t h a t n e i t h e r the p e r m e a b i l i t y o f w a t e r nor the permeab i l i t y o f oxygen c o u l d be the r a t e d e t e r m i n i n g factor i n corrosion c o n t r o l by organic c o a t i n g s , s i n c e n e i t h e r was s u f f i c i e n t l y low to p r o v i d e e f f e c t i v e i s o l a t i o n o f the m e t a l l i c s u b s t r a t e . P r o t e c t i o n was a t t r i b u t e d t o the h i g h e l e c t r i c a l r e s i s t a n c e and low i o n i c p e r m e a b i l i t y o f c o a t i n g s t h a t a f f o r d e d good p r o t e c t i o n . To v a r y i n g e x t e n t s , G u r u v i a h ( 5 2 ) , Bauman ( 5 3 ) , and K r e s s e (54) d i s a g r e e d w i t h the e a r l i e r w o r k e r s r e g a r d i n g the l i m i t s o f oxygen and w a t e r p e r m e a b i l i t y i n f i l m s . Haagen.and Funke (55, 56) agreed w i t h G u r u v i a h and Bauman t h a t oxygen p e r m e a b i l i t y was the c o n t r o l l i n g f a c t o r ; t h e y o b s e r v e d t h a t w a t e r p e r m e a b i l i t y was the d e t e r m i n i n g f a c t o r f o r the l o s s o f adhes i o n , but not f o r c o r r o s i o n . More r e c e n t l y , workers i n the f i e l d have r e c o g n i z e d the p r o b a b l e need f o r a m u l t i p l e parameter model t o u n d e r s t a n d the c o r r o s i o n p r o t e c t i o n process. Funke (57) p r o p o s e d a model b a s e d on water


8


p e r m e a b i l i t y , oxygen p e r m e a b i l i t y , and a d h e s i o n under h i g h h u m i d i t y c o n d i t i o n s . The model was used t o r a t i o n a l i z e the r a n k o r d e r o f s a l t spray r e s u l t s o f seven d i f f e r e n t e l e c t r o c o a t i n g systems. No mathemati c a l t r e a t m e n t o f the d a t a was offered. F l o y d e t a l . (58, 59) i n t r o d u c e d a m a t h e m a t i c a l a n a l y s i s o f a wide range o f p r o p e r t i e s i n c o m p a r i s o n w i t h s a l t s p r a y r e s u l t s . A b a r r i e r mechanism f o r c o r r o s i o n c o n t r o l was postulated. This technique was a l s o a p p l i e d t o F u n k e s e a r l i e r d a t a , w i t h a s i m i l a r r e s u l t . The model was f u r t h e r e l a b o r a t e d t o take i n t o account the e x i s t e n c e o f an e l e c t r o c h e m i c a l component i n the model as a back-up t o the p r i m a r y b a r r i e r component. F l o y d e t a l . f u r t h e r o b s e r v e d t h a t no adequate c h a r a c t e r i z a t i o n o f t h i s e l e c t r o c h e m i c a l i n t e r a c t i o n between p a i n t and s u b s t r a t e e x i s t e d . The p e r m e a b i l i t y o f polymer systems i s i n f l u e n c e d by the propert i e s o f the polymer, by the p r e s e n c e o f pigments o r f i l l e r s , and by the i n t e r a c t i o n between polymer and f i l l e r s . Hulden and Hansen (60) have r e c e n t l y r e v i e w e d w a t e r p e r m e a t i o n i n c o a t i n g s . R e g u l a r i t y o f s t r u c t u r e , c r y s t a l l i n i t y , and low segmental m o b i l i t y a r e s t a t e d t o g i v e low p e r m e a b i l i t y . C r o s s - l i n k d e n s i t y has a l s o been c i t e d as r e s u l t i n g i n reduced p e r m e a b i l i t y , b u t r e s u l t s presented i n this volume by M u i z e b e l t and H e u v e l s l a n d suggest t h a t c r o s s - l i n k d e n s i t y may be i r r e l e v a n t i n t h i s r e s p e c t . As Funke n o t e s e l s e w h e r e i n t h i s volume, some o f the f a c t o r s t h a t c o n t r i b u t e t o low p e r m e a b i l i t y may i n t e r f e r e w i t h a d h e s i o n ; i n p a r t i c u l a r , p o l a r f u n c t i o n a l groups appear t o be e s s e n t i a l t o a c h i e v i n g good a d h e s i o n , b u t are l i k e l y t o i n c r e a s e p e r m e a b i l i t y and c o n t r i b u t e t o w a t e r s e n s i t i v i t y . P i g m e n t a t i o n can have a p r o f o u n d e f f e c t on p e r m e a b i l i t y . The use o f b a r r i e r pigments has been s u g g e s t e d as an a l t e r n a t i v e t o the use o f a c t i v e i n h i b i t i v e pigments, many o f w h i c h are o b j e c t i o n a b l e on e n v i r o n m e n t a l grounds ( 1 3 ) . F l a k e shaped pigments a r e p a r t i c u l a r l y e f f e c t i v e , b u t pigment geometry i s not the o n l y i m p o r t a n t f a c t o r . If w a t e r can accumulate a t the p i g m e n t - b i n d e r i n t e r f a c e , as e v i d e n t l y happens i n the case o f m i c a , w a t e r a b s o r p t i o n tends t o i n c r e a s e w i t h pigment volume c o n c e n t r a t i o n and, although permeability i s s t i l l r e d u c e d by i n c o r p o r a t i o n o f the pigment, the e f f e c t i s much s m a l l e r t h a n w i t h , f o r example, comparable l o a d i n g s o f aluminum f l a k e ( 1 3 ) . The i n f l u e n c e o f i n e r t pigments on p e r m e a b i l i t y and corrosion protect i v e p r o p e r t i e s has been r e v i e w e d b r i e f l y by Hulden and Hansen ( 6 0 ) , and has been d i s c u s s e d i n a number o f papers by K r e s s e ( e . g . , 61, 62). The mechanism o f a c t i o n o f i n e r t b a r r i e r pigments i s commonly s t a t e d t o be t o i n c r e a s e the d i f f u s i o n pathway t o the s u b s t r a t e ; i t i s a l s o p o s s i b l e t h a t pigments may t e n d t o b l o c k o r p r e v e n t the f o r m a t i o n o f pathways f o r d i r e c t i o n i c c o n d u c t i o n t o the s u b s t r a t e .


1

I n t e r f a c i a l and A d h e s i o n A s p e c t s o f C o r r o s i o n

Control

B a s i c Mechanisms o f A d h e s i o n : A c i d - B a s e I n t e r a c t i o n s . The understandi n g o f polymer a d h e s i o n has been g r e a t l y advanced i n r e c e n t y e a r s by the r e c o g n i t i o n o f the c e n t r a l r o l e o f a c i d - b a s e i n t e r a c t i o n s . The c o n c e p t o f an a c i d was broadened by G. N. Lewis t o i n c l u d e those atoms, m o l e c u l e s , o r i o n s i n w h i c h a t l e a s t one atom has a v a c a n t o r b i t a l i n t o w h i c h a p a i r o f e l e c t r o n s can be a c c e p t e d . S i m i l a r l y , a base i s r e g a r d e d as an e n t i t y w h i c h p o s s e s s e s a p a i r o f e l e c t r o n s which are not already i n v o l v e d i n a c o v a l e n t bond. The p r o d u c t s o f acid-base i n t e r a c t i o n s have been c a l l e d c o o r d i n a t i o n compounds, adducts, acid-base complexes, and o t h e r such names. The concept t h a t



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a c i d s and bases v a r y i n t h e i r a b i l i t y t o i n t e r a c t w i t h one a n o t h e r was i n t r o d u c e d by P e a r s o n i n 1968 (63, 64). He i n t r o d u c e d the concept o f p o l a r i z a b i l i t y o f the a c i d o r base u n i t , d e s c r i b i n g i t on a h a r d - s o f t scale. Hard a c i d s a r e t h o s e o f h i g h e l e c t r o n e g a t i v i t y and low polarizability. S o f t a c i d s , i n c o n t r a s t , a r e l a r g e i n s i z e , have h i g h p o l a r i z a b i l i t y , and low e l e c t r o n e g a t i v i t y . For the purposes o f t h i s book, i t i s i m p o r t a n t t o remember t h a t h a r d a c i d s r e a c t most r e a d i l y and form the s t r o n g e s t complexes w i t h h a r d b a s e s , w h i l e s o f t a c i d s r e a c t most r e a d i l y and form the s t r o n g e s t complexes w i t h s o f t bases. Drago and co-workers i n t r o d u c e d an e m p i r i c a l c o r r e l a t i o n t o c a l c u l a t e the e n t h a l p y o f adduct f o r m a t i o n o f Lewis a c i d s and bases ( 6 5 ) . I n 1971, he and h i s co-workers expanded the concept t o a c o m p u t e r - f i t t e d s e t o f parameters t h a t a c c u r a t e l y c o r r e l a t e d over 200 e n t h a l p i e s o f adduct f o r m a t i o n ( 6 6 ) . These parameters were t h e n used t o p r e d i c t o v e r 1200 e n t h a l p i e s o f i n t e r a c t i o n . The parameters Ε and C a r e l o o s e l y i n t e r p r e t e d t o r e l a t e t o the degree o f e l e c t r o s t a t i c and c o v a l e n t n a t u r e o f the i n t e r a c t i o n between the a c i d s and bases. T h i s model was used t o g e n e r a l i z e the o b s e r v a t i o n s i n v o l v e d i n the Pearson h a r d - s o f t a c i d - b a s e model and r e n d e r i t more q u a n t i t a t i v e l y a c c u r a t e . I n 1975, Sorensen (67) used the a c i d - b a s e i n t e r a c t i o n concept t o r a t i o n a l i z e c o l o r s t r e n g t h , g l o s s , and f l o c c u l a t i o n p r o p e r t i e s o f c o a t i n g systems h a v i n g b i n d e r s o f d i f f e r i n g a c i d - b a s e c h a r a c t e r i s t i c s . Anomalies t h a t appear when u s i n g s o l u b i l i t y parameter c o n c e p t s were s u c c e s s f u l l y e x p l a i n e d by the a c i d - b a s e c o n c e p t . Drago e t a l . (68) were s t a r t i n g t o address the i s s u e o f c o r r e c t i o n s t o the s o l u b i l i t y parameter concept u s i n g t h i s t e c h n i q u e a t about the same t i m e . A good r e v i e w o f the s u b j e c t was w r i t t e n i n 1978 by J e n s e n (69). The a p p l i c a t i o n o f a c i d - b a s e i n t e r a c t i o n s t o the phenomenon o f a d h e s i o n was d i s c u s s e d by J e n s e n a t an ACS meeting i n 1981 (70). Fowkes and co-workers had a l r e a d y been d i s c u s s i n g the c o m p e t i t i v e a b s o r p t i o n o f polymers onto pigment s u r f a c e s i n the c o n t e x t o f a c i d - b a s e i n t e r a c t i o n s by t h i s time (e. g., 7 1 ) . Manson (72) expanded the concept t o the s o l i d s t a t e by o b s e r v i n g t h a t the s t r e n g t h o f composite m a t e r i a l s a l s o depended upon the a c i d - b a s e i n t e r a c t i o n between c o n t i n u o u s and d i s p e r s e d phases. More d i r e c t l y , Vanderhoff et a l . (73) a d d r e s s e d the i s s u e o f a d h e s i o n o f polymeric materials to corroded s t e e l . They s y n t h e s i z e d e i g h t c o r r o s i o n p r o d u c t s o f i r o n , and used the i n t e r a c t i o n scheme d e v e l o p e d by Fowkes and Manson f i r s t t o c h a r a c t e r i z e t h e i r o n c o r r o s i o n p r o d u c t s as Lewis a c i d s o r bases and t h e n t o s e l e c t polymer v e h i c l e s f o r p r a c t i c a l c o a t i n g systems. Such r e s u l t s were employed t o enhance the a d h e s i o n o f epoxy systems t o s u b s t r a t e s w h i c h were p r e d o m i n a n t l y i r o n oxide i n nature. A good o v e r v i e w o f t h e s e i s s u e s was p r e s e n t e d by Fowkes i n 1983 ( 7 4 ) . Fowkes and co-workers a l s o c l e a r l y demonstrated t h a t the p h y s i c a l i n t e r a c t i o n o f polymers w i t h n e i g h b o r i n g m o l e c u l e s was d e t e r m i n e d by o n l y two k i n d s o f i n t e r a c t i o n s : London d i s p e r s i o n f o r c e s and Lewis acid-base i n t e r a c t i o n s ( 7 5 ) . C a l c u l a t i o n s b a s e d on t h i s concept were shown t o c o r r e c t many o f the problems i n h e r e n t i n the s o l u b i l i t y approach. They were a l s o a b l e t o use the c o n c e p t t o s t u d y the d i s t r i b u t i o n o f molar h e a t s o f a b s o r p t i o n o f v a r i o u s polymers onto f e r r i c o x i d e s , and t h e r e b y more a c c u r a t e l y d e s c r i b e d the r e q u i r e m e n t s f o r adequate a d h e s i o n t o s t e e l s u b s t r a t e s (7j>) . I n the symposium on w h i c h t h i s book i s based, Fowkes summarized work showing t h a t the p o l a r i n t e r a c t i o n s between polymers and m e t a l s u r f a c e s t h a t are


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POLYMERIC MATERIALS FOR

CORROSION C O N T R O L


important t o a d h e s i o n are e n t i r e l y o f Lewis a c i d - b a s e c h a r a c t e r . C a l o r i m e t r i c and i n f r a - r e d s p e c t r o s c o p i c methods f o r d e t e r m i n i n g the Ε and C c o n s t a n t s f o r polymers and m e t a l o x i d e s were p r e s e n t e d . The f u l l m a n u s c r i p t was not made a v a i l a b l e f o r p u b l i c a t i o n i n t h i s volume, and the r e a d e r i s t h e r e f o r i n v i t e d t o c o n s u l t the p r e p r i n t m a n u s c r i p t (77). Role of Adhesion i n Corrosion P r o t e c t i o n . Many o f the t h e o r i e s r e g a r d i n g the mechanism o f c o r r o s i o n f a i l u r e suggest t h a t the l o s s o f a d h e s i o n p r e c e d e s the o n s e t o f c o r r o s i o n , and i s t h e r e f o r e o f c r i t i c a l importance i n u n d e r s t a n d i n g the p r o c e s s ; Parker and G e r h a r t (78) c o n s i d e r e d a d h e s i o n t o be c r u c i a l t o c o r r o s i o n performance. For o r g a n i c c o a t i n g s , the s t r e n g t h o f the a d h e s i v e bond between c o a t i n g and s u b s t r a t e does not appear t o be the c r i t i c a l i s s u e ; what does appear t o be i m p o r t a n t i s t h a t d u r i n g and a f t e r e n v i r o n m e n t a l exposure the c o a t i n g s h o u l d be a b l e t o w i t h s t a n d the forces a p p l i e d to i t i n i t s intended application. The a d h e s i o n o f v i r t u a l l y a l l c o a t i n g s i s a d v e r s e l y a f f e c t e d by exposure t o w a t e r o r humid e n v i r o n m e n t s . Walker (79) f o u n d t h a t the a d h e s i v e s t r e n g t h o f a wide v a r i e t y o f c o a t i n g s dropped from 20 t o 40 MPa t o 5 t o 15 MPa i n a d i r e c t p u l l - o f f t e s t a f t e r exposure t o humid environments. The i n i t i a l ( d r y ) bond s t r e n g t h was n o t a good p r e d i c t o r o f performance. Haagen and Funke (56) o b s e r v e d t h a t good p r o t e c t i o n was o b t a i n e d i f wet a d h e s i o n was good, even i f the p a i n t was h i g h l y w a t e r permeable. The importance o f a d h e s i o n t o c o r r o s i o n p r o t e c t i o n i s f u r t h e r d i s c u s s e d i n t h i s volume and elsewhere (80) by Funke. Mechanisms o f a d h e s i o n l o s s under v a r i o u s exposure c o n d i t i o n s have been e x t e n s i v e l y s t u d i e d . A survey i s given elsewhere i n t h i s volume by L e i d h e i s e r , and s p e c i f i c examples o f a d h e s i o n l o s s are d i s c u s s e d i n d e t a i l by T h o r n t o n e t a l . , Maeda e t a l . , and Troyk e t a l . , among o t h e r s . A c o u s t i c e m i s s i o n has been u s e d t o s t u d y c o a t i n g a d h e s i o n and the e f f e c t s o f w a t e r immersion on c o a t i n g s on w a t e r (see, - g-» 81-83)· I n t h i s volume, C a l l o w and S c a n t l e b u r y d i s c u s s the p o s s i b i l i t y of using acoustic emission as a m o n i t o r i n g t o o l to i n v e s t i g a t e c o r r o s i o n - i n d u c e d debonding. Modern s u r f a c e a n a l y t i c a l methods have l e d t o much more d e t a i l e d u n d e r s t a n d i n g o f the i n t e r f a c i a l c h e m i s t r y o f a d h e s i o n l o s s p r o c e s s e s . Surface a n a l y t i c a l studies of i n t e r f a c i a l chemistry are reviewed i n t h i s volume by D i c k i e ; i n t h i s paper, as i n a r e c e n t paper by C a s t l e and Watts ( 8 4 ) , i t i s c o n c l u d e d t h a t no s i n g l e c h e m i c a l mechanism a d e q u a t e l y a c c o u n t s f o r a l l o f the o b s e r v e d b e h a v i o r . I n the s i m p l e s t c a s e s , l o s s o f a d h e s i o n appears t o i n v o l v e d i s p l a c e m e n t by water. D i s p l a c e m e n t o f c o a t i n g s by c o r r o s i o n g e n e r a t e d h y d r o x i d e , chemical degradation o f the o r g a n i c c o a t i n g , and chemical a t t a c k on the underlying substrate surface or conversion c o a t i n g have a l s o been o b s e r v e d . F u r t h e r examples o f i n t e r f a c i a l s t u d i e s are g i v e n i n t h i s volume by Maeda e t a l . , and a d i s c u s s i o n o f the r e a c t i o n s i n conver s i o n c o a t i n g s d u r i n g c o r r o s i o n has been g i v e n by van O o i j ( 3 0 ) . A r e l a t e d but l i t t l e s t u d i e d a r e a o f a d h e s i o n and c o r r o s i o n p r o t e c t i o n i n v o l v e s the c h e m i c a l e f f e c t s o f m e t a l s u b s t r a t e s on c o a t i n g s and o t h e r p o l y m e r i c m a t e r i a l s and conversely of polymeric m a t e r i a l s on m e t a l s . I n the c u r i n g o f c e r t a i n a i r - o x i d i z i n g c o a t i n g s on s t e e l , f o r example, r e d u c t i o n o f f e r r i c t o f e r r o u s s p e c i e s i n the s u r f a c e m e t a l o x i d e , s u b s t a n t i a l t h i n n i n g o f the o x i d e , and o x i d a t i o n o f the c o a t i n g m a t e r i a l have been r e p o r t e d t o o c c u r i n the i n t e r f a c i a l e



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Overview

region. These phenomena have been s t u d i e d by i n f r a - r e d and X-ray photoelectron spectroscopic techniques, and are d i s c u s s e d i n t h i s volume by Nguyen and B y r d and by D i c k i e . The s t o r e d components used to make p o l y u r e t h a n e foams are s u b j e c t t o l o n g term c h e m i c a l degradat i o n ; the d e g r a d a t i o n p r o d u c t s have been a s s o c i a t e d w i t h the c o r r o s i o n o f s t o r a g e c o n t a i n e r s . Wischmann d i s c u s s e s the problem, and suggests f o r m u l a t i o n changes f o r improved performance. Adhesives and s e a l e r s can be an i m p o r t a n t part of a t o t a l c o r r o s i o n p r o t e c t i o n system. S t r u c t u r a l bonding procedures and adhesives f o r aluminum, polymer composites, and t i t a n i u m are w e l l e s t a b l i s h e d i n the aerospace i n d u s t r y . S t r u c t u r a l b o n d i n g o f s t e e l i s g a i n i n g i n c r e a s i n g prominence i n the a p p l i a n c e and a u t o m o t i v e i n d u s tries. The d u r a b i l i t y o f a d h e s i v e bonds has been d i s c u s s e d by a number o f a u t h o r s ( s e e , e.g., 85)· The e f f e c t s o f a g g r e s s i v e e n v i r o n ments on a d h e s i v e bonds are o f p a r t i c u l a r concern. Minford (86) has p r e s e n t e d a comparative e v a l u a t i o n o f aluminum j o i n t s i n s a l t water exposure; Smith (87) has d i s c u s s e d s t e e l - e p o x y bond endurance under h y d r o t h e r m a l s t r e s s ; D r a i n e t a l . (88) and Dodiuk e t a l . (89) have p r e s e n t e d r e s u l t s on the e f f e c t s o f w a t e r on performance o f v a r i o u s adhesive/substrate combinations. I n t h i s volume, the d u r a b i l i t y o f a d h e s i v e bonds i n the p r e s e n c e o f water and i n c o r r o s i v e environments i s d i s c u s s e d by Matienzo et a l . , G o s s e l i n , and Holubka e t a l . The e f f e c t s o f a g g r e s s i v e environments on a d h e s i v e l y bonded s t e e l s t r u c t u r e s have a number o f f e a t u r e s i n common w i t h t h e i r e f f e c t s on c o a t e d s t e e l , b u t the m e c h a n i c a l r e q u i r e m e n t s p l a c e d on a d h e s i v e bonds add an a d d i t i o n a l l e v e l of complication. E f f e c t s o f Polymer C o m p o s i t i o n

on C o r r o s i o n C o n t r o l

Polymer c o m p o s i t i o n poses not one b u t many c r i t i c a l i s s u e s f o r the development o f m a t e r i a l s f o r c o r r o s i o n c o n t r o l . As outlined in p r e v i o u s s e c t i o n s o f t h i s c h a p t e r , the elements o f m o l e c u l a r d e s i g n f o r good a d h e s i o n , good b a r r i e r p r o p e r t i e s , and e f f e c t i v e use o f pigments i n o r g a n i c c o a t i n g s are o f t e n i n c o n f l i c t . There does not appear t o be a u n i f y i n g t h e o r e t i c a l b a s i s on w h i c h these c o n f l i c t i n g f a c t o r s can be r e s o l v e d , and an e m p i r i c a l b a l a n c i n g o f p r o p e r t i e s remains an e s s e n t i a l p a r t o f new product development f o r c o r r o s i o n control. I t i s not s u r p r i s i n g t h a t the d e t a i l s o f c o m p o s i t i o n c r i t i c a l t o performance o f t e n remain p r o p r i e t a r y o r appear o n l y i n the patent l i t e r a t u r e . In a d d i t i o n t o the customary d e s i r e f o r improved m a t e r i a l p e r f o r m a n c e , the development o f new m a t e r i a l s has, i n r e c e n t y e a r s , been shaped by the demand f o r n o n - p o l l u t i n g o r e c o l o g i c a l l y n e u t r a l m a t e r i a l s . R e s t r i c t i o n s on s o l v e n t e m i s s i o n s from i n d u s t r i a l and maintenance p a i n t s , and l i m i t a t i o n s on l e a d - b a s e d and chromate c o r r o s i o n - i n h i b i t i v e pigments has had a major impact on c o r r o s i o n p r o t e c t i v e m a t e r i a l technology. I n the f i e l d o f o r g a n i c c o a t i n g s , t h e r e has been major emphasis on water-borne and s o - c a l l e d h i g h s o l i d s c o a t i n g s . H i l l and Wicks (90) have d i s c u s s e d d e s i g n c r i t e r i a f o r h i g h s o l i d s c o a t i n g s ; a r e c e n t book on r e a c t i v e o l i g o m e r s discusses a number o f polymer systems o f i n t e r e s t i n h i g h s o l i d s c o a t i n g s ( 9 1 ) . A v a r i e t y o f w a t e r - s o l u b l e and w a t e r - d i s p e r s i b l e r e s i n s have been d e s c r i b e d i n the l i t e r a t u r e ( e . g . , 90-96); the T e c h n i c a l Committee o f the New England S o c i e t y f o r C o a t i n g s Technology has p u b l i s h e d a s e r i e s o f a r t i c l e s on the d e s i g n o f waterborne c o a t i n g s f o r the c o r r o s i o n


POLYMERIC MATERIALS FOR CORROSION CONTROL


12

p r o t e c t i o n o f s t e e l (97-99). The development and commercial implem e n t a t i o n o f a n o d i c and, subsequently, of cathodic e l e c t r o d e p o s i t i o n coatings binders f o r e l e c t r o d e p o s i t i o n have made p o s s i b l e major improvements i n the c o r r o s i o n p r o t e c t i o n o f a p p l i a n c e s and motor v e h i c l e s . The c h e m i s t r y o f b i n d e r s f o r e l e c t r o d e p o s i t i o n has been r e v i e w e d by Schenk e t a l . (100) and by Kordomenos and Nordstrom (101): the c a t h o d i c e l e c t r o d e p o s i t i o n p r o c e s s has been d i s c u s s e d by Wismer e t a l . (102). I n the p r e s e n t volume, s e v e r a l papers d e a l w i t h unique m a t e r i a l s or a p p l i c a t i o n s : S c h r e i b e r d e s c r i b e s work on p l a s m a - d e p o s i t e d f i l m s from o r g a n o - s i l i c o n e and i n o r g a n i c (SiN) s t a r t i n g m a t e r i a l s . M o r e l a n d and Padget d i s c u s s studies of a c h l o r i n e - c o n t a i n i n g v i n y l a c r y l i c copolymer t h a t i s a p p l i e d as an a c i d i c aqueous f o r m u l a t i o n and t h a t promotes i n s i t u f o r m a t i o n o f a p r o t e c t i v e f i l m . White and L e i d h e i s e r d i s c u s s c o a t i n g r e s i n s f o r the p r o t e c t i o n o f s t e e l exposed t o s u l f u r i c a c i d ; Hojo e t a l . , the b e h a v i o r o f epoxy and polyester resins i n alkaline solution. D r e y f u s e t a l . p r e s e n t r e s u l t s on c o a t i n g s d e s i g n e d t o p r o t e c t g l a s s i n a l k a l i n e environments. Ibbitson et a l . discuss structure-property relationships i n tin-based a n t i - f o u l i n g paints. The p r o t e c t i o n o f m i c r o e l e c t r o n i c s from the e f f e c t s o f h u m i d i t y and c o r r o s i v e environments p r e s e n t s e s p e c i a l l y demanding r e q u i r e m e n t s on p r o t e c t i v e c o a t i n g s and e n c a p s u l a n t s . S i l i c o n e polymers, epoxies, and i m i d e r e s i n s are among the m a t e r i a l s t h a t have been used f o r the encapsulation of microelectronics. The p h y s i o l o g i c a l environment t o which implanted medical e l e c t r o n i c devices are exposed poses an e s p e c i a l l y c h a l l e n g i n g p r o t e c t i o n problem. I n t h i s volume, Troyk e t a l . o u t l i n e the demands p l a c e d on such systems i n m e d i c a l a p p l i c a t i o n s , and d i s c u s s the p r o p e r t i e s o f a v a r i e t y o f s i l i c o n e - b a s e d encapsulants. Critical

Issues

A t o p i c a l symposium p r o v i d e s a forum f o r the r e v i e w and u p d a t i n g o f work i n a g i v e n field, and provides an o p p o r t u n i t y to i d e n t i f y c r i t i c a l issues. The e d i t o r s o f t h i s volume w o u l d l i k e t o suggest t h a t the f o l l o w i n g i s s u e s are among those n e e d i n g a d d i t i o n a l s t u d y : Systems. C o r r o s i o n i s u s u a l l y s t u d i e d i n an i s o l a t e d f a s h i o n i n the l a b o r a t o r y , but i n p r a c t i c e i s c l e a r l y the r e s u l t o f i n t e r a c t i n g systems i n the environment. S t u d i e s need t o be c o n d u c t e d on the way i n w h i c h the component p a r t s o f c o r r o d i n g systems i n t e r a c t under a c t u a l e n v i r o n m e n t a l c o n d i t i o n s , and on the way i n w h i c h the compone n t s o f the environment i n t e r a c t w i t h the t o t a l c o r r o d i n g system. T h i s would suggest not o n l y d e s i g n work f o r c o r r o s i o n p r o t e c t i o n systems, b u t a l s o a d d i t i o n a l work on the s e n s i n g and m o n i t o r i n g o f c o r r o s i o n i n r e a l h o s t i l e environments. Methods. To observe t h a t c o r r o s i o n t e s t i n g i n the l a b o r a t o r y f r e q u e n t l y f a i l s t o p r e d i c t what happens i n r e a l - w o r l d environments i s to admit t h a t the mechanisms c o n t r o l l i n g c o r r o s i o n i n such environments are not u n d e r s t o o d , even a t t h i s l a t e date o f s t u d y . Mechanism-based t e s t methods f o r m o n i t o r i n g c o r r o s i o n are needed t h a t w i l l p r o v i d e r e l i a b l e and r a p i d p r e d i c t i o n of s e r v i c e l i f e f o r corrosion-suscept i b l e systems. I t i s e x p e c t e d t h a t s t a t i s t i c a l a n a l y s i s w i l l p l a y a


1.

DICKIE A N D

FLOYD

Overview

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l a r g e r o l e i n any such e f f o r t , s i n c e the f a i l u r e modes o b s e r v e d o f t e n vary widely w i t h i n a s t a t i s t i c a l d i s t r i b u t i o n . Such a r e c o g n i t i o n has l e d t o the development o f s t a t i s t i c a l methods f o r the d e s c r i p t i o n o f m e c h a n i c a l f a i l u r e o f m a t e r i a l s , and i t i s s u g g e s t e d t h a t a s i m i l a r e f f o r t would b e a r f r u i t i n the a n a l y s i s o f c o r r o s i o n phenomena. P a i n t s . E p o x i e s and c a t h o d i c e l e c t r o c o a t s r e p r e s e n t major advances i n the f i e l d o f c o r r o s i o n c o n t r o l by o r g a n i c c o a t i n g s . The performance of these coatings represents a p l a t e a u w h i c h has not been d e p a r t e d from i n over a decade. A g r e a t d e a l o f a t t e n t i o n has been devoted t o i n t e r f a c i a l p r o c e s s e s i n c o r r o s i o n over the l a s t several years, y e t c o n t r o l o f t h e s e p r o c e s s e s remains an e l u s i v e g o a l . I t i s c o n c e i v a b l e t h a t , i f means can be found t o c o n t r o l i n t e r f a c i a l f a i l u r e p r o c e s s e s , a new g e n e r a t i o n o f c o a t i n g s c a n be d e v e l o p e d t h a t w i l l establish a considerably higher p l a t e a u o f performance. C o n v e r s i o n c o a t i n g s and s u r f a c e t r e a t m e n t s may p l a y a v i t a l r o l e i n t h i s development. Plastics. Part o f the trend t o substitute p l a s t i c and composite substrates f o r m e t a l s c a n be a t t r i b u t e d t o a d e s i r e t o a v o i d the p r o c e s s o f m e t a l l i c c o r r o s i o n and subsequent f a i l u r e . Relatively little a t t e n t i o n has been c a l l e d t o the p o s s i b l e f a i l u r e modes o f p l a s t i c s under environments c o n s i d e r e d corrosive t o metals. More e x t e n s i v e work s h o u l d be conducted on the d u r a b i l i t y and l i f e expect a n c y o f p l a s t i c and composite m a t e r i a l s under end-use environments. A f u r t h e r c o n s i d e r a t i o n i s the p o t e n t i a l f o r polymer d e g r a d a t i o n by the products o f metal c o r r o s i o n i n h y b r i d s t r u c t u r e s comprising m e t a l and polymer components. Since i t i s expected that coatings w i l l continue t o be used t o p r o t e c t p l a s t i c and composite s u b s t r a t e s , a n c i l l a r y programs need t o be conducted on the mechanisms b y w h i c h c o a t i n g s c a n p r o t e c t such s u b s t r a t e s . A d h e s i v e s . I n many a p p l i c a t i o n s , t h e r e are s u b s t a n t i a l f u n c t i o n a l and economic r e a s o n s t o p r e f e r a d h e s i v e b o n d i n g o v e r m e c h a n i c a l f a s t e n i n g o f m e t a l s , o f p l a s t i c s , and o f m i x e d - s u b s t r a t e j o i n t s . The r o l e o f c o r r o s i o n i n the f a i l u r e o f a d h e s i v e bonds i s t h e r e f o r e becoming an i n c r e a s i n g l y c r u c i a l one. The performance demands p l a c e d on a d h e s i v e bonds b y the c o m b i n a t i o n o f m e c h a n i c a l l o a d i n g and a g g r e s s i v e e n v i r o n ments are p a r t i c u l a r l y s e v e r e , and i t i s c l e a r t h a t s t u d i e s i n v o l v i n g combined mode t e s t i n g need t o be g r e a t l y expanded. I t i s a n t i c i p a t e d t h a t i n f o r m a t i o n d e v e l o p e d i n the s t u d y o f a d h e s i v e s and the study o f coatings should inter-relate i n a s u f f i c i e n t l y strong fashion that b o t h f i e l d s w i l l b e n e f i t from such s t u d i e s .

Literature Cited 1. NBS Special Publication 511-1. Economic Effects of Metallic Corrosion in the United States. A Report to Congress by the National Bureau of Standards. SD Stock No. SN-003-01926-7, 1978; NBS Special Publication 511-2. Economic Effect of Metallic Corrosion in the United States. Appendix B. A report to NBS by Battelle Columbus Laboratories. SD Stock No. SN-00301927-5, 1978. 2. Evans, U. R. "The Corrosion and Oxidation of Metals", St. Martins Press: New York, 1960; ibid.. 1st Supplementary Volume,


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3. 4. 5. 6. Downloaded by MIDDLE TENNESSEE STATE UNIV on July 16, 2013 | http://pubs.acs.org Publication Date: October 14, 1986 | doi: 10.1021/bk-1986-0322.ch001

7. 8. 9. 10. 11. 12. 13. 14. 15. 16. 17. 18. 19. 20. 21. 22. 23. 24. 25. 26. 27. 28. 29. 30. 31. 32. 33. 34.

POLYMERIC MATERIALS FOR CORROSION CONTROL

St. Martins Press: New York, 1968; ibid., 2nd Supplementary Volume, Edward Arnold: London, 1976. Uhlig, H. H. "Corrosion and Corrosion Control", 2nd ed., Wiley: New York, 1971. Shreir, L. L. "Corrosion", 2nd ed., Newnes-Butterworths: London, 1976. Evans, U. R. "An Introduction to Metallic Corrosion", 2nd ed., Edward Arnold: London, 1972. Scully, J. C. "The Fundamentals of Corrosion", 2nd ed., Perg amon: Oxford, 1975. Van Delindes, L. S., Ed. "Corrosion Basics: An Introduction", National Association of Corrosion Engineers: Houston, 1984. Pourbaix, M. "Lectures on Electrochemical Corrosion", Plenum: New York, 1973. Pourbaix, M. "Atlas of Electrochemical Equilibria in Aqueous Solutions", 2nd English ed., National Association of Corrosion Engineers: Houston, 1974. Szauer, T.; Brandt, A. J. Oil Col. Chem. Assoc. 1984, 67, 13. Fawcett, N. C. Polym. Mat. Sci. Eng. 1985, 53, 855. Leidheiser, H., Jr. J. Coat. Technol. 1981, 53(678), 29. Funke, W. J. Coat. Technol. 1983, 55(705), 31. Zurilla, R. W.; Hospadaruk, V. Trans. SAE 1978, 87, 762. Bender, H. S.; Cheever, G. D; Wojtkowiak, J. J. Prog. Org. Coat. 1980, 8, 241. "Annual Book of ASTM Standards", Part 27, "Paint - Tests for Formulated Products and Applied Coatings", American Society for Testing and Materials: Philadelphia, issued annually. Von Fraunhofer, J. Α.; Boxall, J. "Protective Paint Coatings for Metals", Portcullis Press: Redhill, 1976. Funke, W. J. Oil Col. Chem. Assoc. 1979, 62, 63. Funke, W. Farbe Lack 1978, 84, 380. Funke, W.; Machunsky, E.; Handloser, G. Ibid., 1979, 84, 498. Funke, W.; Zatloukal, H. Ibid., 1979, 84, 584. Funke, W. in "Corrosion Control by Coatings", Leidheiser, Η., Jr., Ed.; Science Press: Princeton, 1979, p. 35. Rowe, L. C.; Chance, R. L. in "Automotive Corrosion by De-icing Salts", Baboian, R., Ed.; National Association of Corrosion Engineers: Houston, 1981, p. 133. Athey, R; Duncan, R.; Harmon, E.; Hartmann, M.; Iszak, D.; Nakabe, H.; Ochoa, J . ; Shaw, P.; Specht, T.; Tostenson, P.; Warness, R. J. Coat. Technol. 1985, 57(726), 71. Opinsky, A. J . ; Thompson, R. F.; Boegehold, A. L. ASTM Bull. 1953 (Jan), 47. Hospadaruk, V.; Huff, J . ; Zurilla, R. W.; Greenwood, H. T. Trans. SAE. 1978, 87, 755. Lambert, M. R.; Townsend, H. E.; Hart, R. G.; Frydrych, D. J. Ind. Eng. Chem. Prod. Res. Dev. 1985, 24, 378. Standish, J. V. Ind. Eng. Chem. Prod. Res. Dev. 1985, 24, 1985. Jones, D. A. Polym. Mat. Sci. Eng. 1985, 53, 470. van Ooij, W. Polym. Mat. Sci. Eng. 1985, 53, 698. Leidheiser, Η., Jr. Prog. Org. Coat. 1979, 7, 79. Szauer, T. Prog. Org. Coat. 1982, 10, 157. Szauer, T. Prog. Org. Coat. 1982, 10, 171. Walter, G. W. Corr. Sci. 1986, 26, 39.



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35. McIntyre, J. F.; Leidheiser, Η., Jr. Ind. Eng. Chem. Prod. Res. Dev. 1985, 24, 348. 36. Beese, R. E.; Allman, J. C. in "Modern Container Coatings", Strand, R. C., Ed.; ACS Symposium Series No. 78, American Chemical Society: Washington, DC, 1978. 37. Groseclose, R. G.; Frey, C. M; Floyd, F. L. J. Coatings Tech nol. 1984, 56(714), 31. 38. Hubrecht, J . ; Vereecken, J . ; Piens, M. J. Electrochem. Soc. 1984, 131, 2010; see also Piens, M.; Verbist, R.; Vereecken, J . ; in "Organic Coatings: Science and Technology"; Parfitt, G. D.; Patsis, Α. V., Eds.; Dekker: New York, 1984; Vol. 7, p. 249. 39. Mansfield, F.; Kendig, M. W. Werkst. Korros. 1985, 36, 473. 40. Kendig, M. W.; Allen, A. T.; Jeanjaquet, S. L.; Mansfield, F. NACE Paper No. 74, presented at National Association of Cor rosion Engineers National Meeting, Boston, 1985. 41. Lindqvist, S. A. Corrosion. 1985, 41(2), 69. 42. Padget, J. C.; Moreland, P. J. J. Coatings Technol. 1983, 55(698), 39. 43. Fernandez-Prini, R.; Kapista, S. J. Oil Col. Chem. Assoc. 1979, 62, 93. 44. Lindqvist, S. Α.; Meszaros, L.; Svenson, L. J. Oil Col. Chem. Assoc. 1985, 68, 10. 45. Mayne, J. E. O. J. Oil Col. Chem. Assoc. 1957, 40, 183. 46. Mayne, J. Ε. O.; Cherry, Β. W. Intern. Congr. Metallic Cor rosion. 1st. London. Engl., Butterworths: London, 1961. p. 539. 47. Mayne, J. E. O.; Maitland, C. C. Off. Dig.. Fed. Socs. Paint Technol. 1962, 34, 972. 48. Mayne, J. E. O. Trans Inst. Metal Finishing 1964, 41(4), 121. 49. Mayne, J. E. O.; Cherry, B. W. Off. Dig. Fed. Soc. Paint Technol. 1965, 37, 13. 50. Bacon, R. C.; Smith, J. J . ; Rugg, F. M. Ind. Eng. Chem. 1948, 40, 161. 51. Cherry, B. W. Australas. Corr. Eng. 1974, 18(10), 23. 52. Guruviah, S. J. Oil Col. Chem. Assoc. 1970, 53, 660. 53. Bauman, K. Plast. Kautsch., 1972, 19, 455. 54. Kresse, P. Pigm. Resin Technol. 1973, 2(11), 21. 55. Haagen, H.; Funke, W. J. Oil Col. Chem. Assoc. 1975, 58, 359. 56. Funke, W.; Haagen, H. Ind. Eng. Chem. Prod. Res. Dev. 1978, 17, 50. 57. Funke, W. J. Oil Col. Chem. Assoc. 1979, 62, 63. 58. Floyd, F. L.; Frey, C. M. Org. Coatings Plastics Chem. 1980, 43, 580. 59. Floyd, F. L.; Groseclose, R. G.; Frey, C. M. J. Oil Col. Chem. Assoc. 1983, 66, 329. 60. Hulden, M.; Hansen, C. M. Prog. Org. Coat. 1985, 13, 171. 61. Kresse, P. Farbe Lack 1974, 80, 817. 62. Kresse, P. Ibid. 1977, 83, 85. 63. Pearson, R. G. J. Chem. Ed. 1968, 45, 581. 64. Pearson, R. G. Ibid. 1969, 45, 643. 65. Drago, R. S.; Wayland, Β. B. J. Am. Chem. Soc. 1965, 87, 3571. 66. Drago, R. S.; Vogel, G. C.; Needham, T. E. J. Am. Chem. Soc. 1971, 93, 6014. 67. Sorensen, P. J. Coat. Technol. 1975, 47(602), 31. 68. Drago, R. S.; Parr, L. B.; Chamberlain, C. S. J. Am. Chem. Soc. 1977, 99, 3203.




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69. Jensen, W. B. Chem. Rev. 1978, 78, 1. 70. Jensen, W. B. Rubber Chem. Technol. 1981, 55, 881. 71. Fowkes, F. M.; Mostafa, M. A. Ind. Eng. Chem. Prod. Res. Dev. 1978, 17, 3. 72. Manson, J. Α.; Lin, J. S.; Tibureio, A. Org. Coat. Appl. Polym. Sci. Proc. 1982, 46, 121. 73. Vanderhoff, J. W.; Bennetch, L. M.; Cantow, M. J.; Earhart, K. Α.; El-Aasser, M. S.; Huang, T. C.; Kang, M. H.; Micale, F. J.; Shaffer, O. L.; Timmons, D. W. Org. Coat. Appl. Polym. Sci. Proc. 1982, 46, 12. 74. Fowkes, F. M. in "Physicochemical Aspects of Polymer Surfaces", Mittal, K. L., Ed.; Plenum: New York, 1983. p. 583. 75. Fowkes, F. M. J. Polym. Sci. Polym. Chem. Ed. 1984, 22, 547. 76. Joslin, S. T.; Fowkes, F. M. Ind. Eng. Chem. Prod. Res. Dev. 1985, 24, 369. 77. Fowkes, F. M. Polym. Mat. Sci. Eng. 1986, 53, 560. 78. Parker, E.; Gerhart, H. Ind. Eng. Chem. 1967, 59(8), 53. 79. Walker, P. Off. Dig. Fed. Soc. Paint Technol. 1965, 37, 1561. 80. Funke, W. J. Oil Col. Chem. Assoc. 1985, 68, 229. 81. Rawlings, R. D.; Strivens, T. A. J. Oil Col. Chem. Assoc. 1980, 63, 412. 82. Rooum, J. Α.; Rawlings, R. D. J. Mater. Sci. 1982, 17, 1745. 83. Rooum, J. Α.; Rawlings, R. D. J. Coat. Technol. 1982, 54(695), 43. 84. Castle, J. E.; Watts, J. F. Ind. Eng. Chem. Prod. Res. Dev. 1985, 24, 361. 85. Kinloch, A. J., Ed. "Durability of Adhesive Bonds", Applied Science Publishers: London, 1983. 86. Minford, J. D. J. Adhesion 1985, 18, 19. 87. Smith, T. J. Adhesion 1984, 17, 1. 88. Drain, K. F.; Guthrie, J.; Leung, C. L.; Martin, F. R.; Otterbrun, M. S. J. Adhesion 1984, 17, 71. 89. Dodiuk, H; Drori, L.; Miller, J. J. Adhesion 1985, 18, 1. 90. Hill, L. W.; Wicks, Z. W. Prog. Org. Coat. 1982, 10, 55. 91. Harris, F. W.; Spinelli, H. J., Eds. "Reactive Oligomers", American Chemical Society: Washington, 1985. 92. Krishnamurti, K. Prog. Org. Coat. 1983, 11, 167. 93. Hopwood, J.J. J. Oil Col. Chem. Assoc. 1965, 48, 157. 94. Lerman, M. A. J. Coat. Technol. 1976, 48(623), 35. 95. Qaderi, S. Β. Α.; Bauer, D. R.; Holubka, J. W.; Dickie, R. A. J. Coat. Technol. 1984, 56(719), 71. 96. Woo, J. T. K.; Ting, V.; Evans, J.; Marcinko, R.; Carlson, G.; Ortiz, C. J. Coat. Technol. 1982, 54(689), 41. 97. New England Society for Coatings Technology Technical Committee J. Coat. Technol. 1981, 53(683), 27. 98. Ibid. 1982, 54(684), 63. 99. Lein, M. M.; Brakke, B.; Keltz, G.; Kiezulas, M. P.; Leavy, C. M.; Marderosian, R.; Withington, D. Ibid. 1983, 55(703), 81. 100. Schenk, H. U; Spoor, H.; Marx, M. Prog. Org. Coat. 1979, 7, 1. 101. Kordomenos, P. I.; Nordstrom, J. D. J. Coat. Technol. 1982, 54(686), 33. 102. Wismer, M.; Pierce, P. C.; Bosso, J. F.; Christenson, R. M.; Jerabek, R. D.; Zwack, R. R. J. Coat. Technol. 1982, 54(688), 35. RECEIVED

June 16, 1986


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