Use of Surface Analytical Techniques to Examine Metal Corrosion

11

Downloaded by CALIFORNIA INST OF TECHNOLOGY on December 5, 2017 | http://pubs.acs.org Publication Date: September 22, 1982 | doi: 10.1021/bk-1982-0199.ch011

Use of Surface Analytical Techniques to Examine Metal Corrosion Problems D. R. BAER and M. T. THOMAS Pacific Northwest Laboratory, Richland, WA 99352 The applications of several surface analytical techniques to the solution of corrosion problems are reviewed in this paper. The use of surface techni ques in corrosion work is increasing both because the methods are more widely available than previously and because the techniques themselves are being refined. However, the application of these methods to particu lar corrosion problems is not always straightforward and care must be taken to match the use of any method to the specific problem. Some general guidelines concerning the applicability of surface tools are discussed before several examples of their applica tion are given. Techniques discussed include: X-ray photoelectron spectroscopy (XPS), Auger electron spectroscopy (AES), Rutherford backscattering (RBS) and nuclear reaction spectroscopy. Corrosion affects our lives in many different ways and has been termed the "silent scourge" and a "cancer of materials" (1). Although these terms may seem overly dramatic, a 1976 study found that metallic corrosion cost the United States $70 b i l l i o n a year or roughly 4.2% of the gross national product (2). If corrosion of paints, plastics, wood, glasses and other materials were i n cluded, the cost would be over $1 trillion a year (3). Either amount is considerably larger than the $45 b i l l i o n expense for importing foreign crude o i l in 1977. Corrosion is simply the destruction or deterioration of a ma terial because of a chemical reaction with its environment (4). Types of corrosion range from rust on an automobile to intergranular cracking of a pipe in a gas well. In addition to its economic impact, corrosion affects our health and safety, the development of new technology, the existence of ancient works of art and even, through material availability, national security (2).

0097-6156/82/0199-0251$08.75/0 © 1982 American Chemical Society

Casper and Powell; Industrial Applications of Surface Analysis ACS Symposium Series; American Chemical Society: Washington, DC, 1982.

SURFACE

252

ANALYSIS


The enormous e c o n o m i c and o t h e r c o s t s o f c o r r o s i o n h a v e m o t i v a t e d c o n s i d e r a b l e r e s e a r c h t o w a r d m i n i m i z i n g c o r r o s i o n and u n d e r standing i t s causes. D u r i n g the past f i v e years^ a n a l y t i c a l t o o l s s e n s i t i v e t o t h e s u r f a c e ( o r t h e o u t e r 10 t o 500A o f a m a t e r i a l ) have been i n c r e a s i n g l y a p p l i e d to the s t u d y o f c o r r o s i o n . This paper o u t l i n e s g e n e r a l c r i t e r i a to h e l p determine the u s e f u l n e s s of s u r f a c e t e c h n i q u e s f o r the study o f s p e c i f i c c o r r o s i o n problems and g i v e s s e v e r a l e x a m p l e s s h o w i n g how t h e t e c h n i q u e s h a v e b e e n applied. TYPES OF CORROSION

AND THEIR RELATIONSHIP

TO SURFACE AND INTERFACE

ANALYSES C o r r o s i o n n e c e s s a r i l y involves a r e a c t i o n of a m a t e r i a l with i t s environment at a s o l i d - g a s , s o l i d - l i q u i d or s o l i d - s o l i d i n t e r face. One m i g h t t h i n k , t h e r e f o r e , t h a t c o r r o s i o n s c i e n t i s t s w o u l d b e among t h e most e n t h u s i a s t i c u s e r s o f s u r f a c e a n a l y t i c a l t e c h n i q u e s , w h i c h by t h e i r n a t u r e examine s u c h i n t e r f a c e s (_5). Howe v e r , as M c l n t y r e (_5) n o t e s a b o u t X P S , " t h e i m p a c t on c o r r o s i o n s c i e n c e has b e e n r a t h e r m o d e s t , " and a c c o r d i n g t o an e d i t o r i a l i n C o r r o s i o n ( 6 ) , any s i g n i f i c a n c e o f s u r f a c e s c i e n c e i n s o l v i n g c o r r o s i o n p r o b l e m s i s n o t o b v i o u s t o many c o r r o s i o n p r o f e s s i o n a l s and plant operators. Recent advances i n s u r f a c e s c i e n c e techniques h a v e i n c r e a s e d t h e u s e f u l n e s s o f t h e s e methods i n a p p l i e d a r e a s s u c h as c o r r o s i o n . To u n d e r s t a n d t h e c u r r e n t r o l e o f s u r f a c e a n a l y s i s i n c o r r o s i o n r e s e a r c h and p r o b l e m s o l v i n g , i t i s n e c e s s a r y t o know a b o u t t h e many forms o f c o r r o s i o n and t h e a d v a n t a g e s and l i m i t a t i o n s o f s u r f a c e t e c h n i q u e s i n e a c h a r e a . Types

of

Corrosion

T h e r e a r e many t y p e s o f c o r r o s i o n , as w o u l d be e x p e c t e d f r o m its general d e f i n i t i o n . I t has b e e n t r a d i t i o n a l (4) t o d i v i d e t h e s t u d y o f c o r r o s i o n i n t o two a r e a s : t h e s t u d y o f low t e m p e r a t u r e c o r r o s i o n b y aqueous o r o t h e r s o l u t i o n s , c o n t r o l l e d b y e l e c t r o c h e m i c a l p r o c e s s e s ( w e t ) ; and t h e s t u d y o f g a s e o u s c o r r o s i o n a t h i g h t e m p e r a t u r e s , c o n t r o l l e d b y t h e r m o d y n a m i c s and d i f f u s i o n p r o cesses ( d r y ) . In a d d i t i o n t o t h e o b v i o u s d i f f e r e n c e s , t h e two a r e a s h a v e many phenomena i n common. N e a r l y a l l m e t a l s a r e t h e r m o d y n a m i c a l l y u n s t a b l e i n most e n v i r o n m e n t s and t h e r e s u l t o f t h i s i n s t a b i l i t y i s c o r r o s i o n , s u c h as o x i d a t i o n o r some o t h e r r e a c t i o n w i t h t h e e n v i r o n m e n t . In b o t h "wet" and " d r y " c o r r o s i o n t h r e e g e n e r a l phenomena o c c u r . First, m a t e r i a l from the metal can d i s s o l v e i n the e n v i r o n m e n t . This t a k e s forms s u c h as e v a p o r a t i o n and v o l a t i l e compound f o r m a t i o n a t h i g h t e m p e r a t u r e s and m a t e r i a l d i s s o l u t i o n i n aqueous solutions. M a t e r i a l l o s s b y s u c h p r o c e s s e s may weaken a s t r u c t u r e o r c a u s e l o s s of a p r o t e c t i v e l a y e r . S e c o n d , a r e a c t i o n l a y e r may f o r m on the s u r f a c e of the m e t a l . F r e q u e n t l y , t h e s e l a y e r s reduce the r a t e o f a r e a c t i o n and t h u s p r o t e c t t h e m a t e r i a l ( p a s s i v a t e a



11.

BAER AND THOMAS

Metal Corrosion Problems

253

metal). However, not a l l f i l m s are p r o t e c t i v e and i n some c o r r o s i o n environments normally p r o t e c t i v e f i l m s are themselves attacked. The c o n d i t i o n s f o r which passive p r o t e c t i v e f i l m s are formed and attacked are subjects of a c t i v e i n v e s t i g a t i o n i n c o r r o s i o n research. Several common types of c o r r o s i o n i n v o l v e the a t t a c k of these p r o t e c t i v e f i l m s and replacement by f a s t e r growing non-protective l a y e r s . This a t t a c k may be uniform (general c o r r o s i o n ) , l o c a l i z e d at d i s c r e t e p o i n t s ( p i t t i n g ) o r induced by s t r e s s ( s t r e s s c o r r o s i o n ) . T h i r d , m a t e r i a l from the environment may be incorporated i n t o the metal. Oxides may p r e c i p i t a t e w i t h i n the metal or hydrogen may be adsorbed and i n e i t h e r case the m a t e r i a l can be e m b r i t t l e d and unable t o withstand design loads. Hydrogen-induced embrittlement occurs i n both aqueous and gaseous environments. The nature of c o r r o s i o n depends c r i t i c a l l y on both the e n v i ronment and the m a t e r i a l . Often c o r r o s i o n i s l o c a l i z e d i n part i c u l a r areas because of n o n - u n i f o r m i t i e s i n the m a t e r i a l (near welds or corners) o r n o n - u n i f o r m i t i e s i n the environment such as s h i e l d e d areas near gaskets ( c r e v i c e c o r r o s i o n ) . I t i s important t o r e a l i z e that c o r r o s i o n rates may be cont r o l l e d by any of s e v e r a l thermodynamic o r k i n e t i c p r o p e r t i e s of the alloy-scale-environment system and not j u s t by surface o r i n t e r f a c e r e a c t i o n s . The three stages of high temperature o x i d a t i o n of a metal, shown s c h e m a t i c a l l y i n F i g . 1, serve as an example (7). The f i r s t or t r a n s i e n t stage includes i n i t i a l gas a d s o r p t i o n , two-dimensional oxide n u c l e a t i o n , i n i t i a l t h r e e dimensional oxide formation and f i n a l l y , formation of the dominant oxide that w i l l c o n t r o l the o x i d a t i o n r a t e i n Stage I I . Various p o r t i o n s o f Stage I have been widely studied using s u r face a n a l y t i c a l techniques, but i t s d u r a t i o n can be very short and i t i s u s u a l l y assumed (not always c o r r e c t l y ) that Stage I has l i t t l e impact on u l t i m a t e c o r r o s i o n p r o p e r t i e s of the m a t e r i a l . In the second or steady-state stage of o x i d a t i o n , s c a l e growth i s o f t e n determined by d i f f u s i o n parameters and thermodynamics of the oxide-metal system. This stage has been widely studied by standard c o r r o s i o n methods and has been modeled by many o x i d a t i o n t h e o r i e s . The f i n a l stage involves oxide s c a l e f a i l u r e and often the onset of damaging c o r r o s i o n . Stage I I I i s f r e q u e n t l y induced by accumulated s t r e s s at the oxide metal i n t e r f a c e o r by weakening of the i n t e r f a c e due t o a compositional change. Although surface and i n t e r f a c e r e a c t i o n s play a major r o l e i n Stage I , any of s e v e r a l processes may be the slowest o r r a t e cont r o l l i n g step i n Stages I I o r I I I . Surface and i n t e r f a c e methods may not be very h e l p f u l when surface and i n t e r f a c e r e a c t i o n s are not c o n t r o l l i n g the c o r r o s i o n r a t e . R e l a t i o n s h i p t o Surface A n a l y s i s Techniques Although some stages of c o r r o s i o n are not c o n t r o l l e d by the r a t e of surface o r i n t e r f a c e r e a c t i o n s , surface r e a c t i o n s must



254

S U R F A C E ANALYSIS

TIME Figure 1. Scheme of three stages of high temperature gaseous oxidation (7). Key: I, transient; II, steady state; and III, breakaway.



11.

BAER AND THOMAS


255

occur i n c o r r o s i o n and surface a n a l y t i c a l methods are the p r i n c i p a l t o o l s that e x i s t to study these processes. The wide range of surface a n a l y t i c a l techniques provide chemical and composit i o n a l i n f o r m a t i o n at surfaces and i n t e r f a c e s that i s not u s u a l l y a v a i l a b l e to other methods. These techniques are c o n t i n u a l l y be ing developed and a p p l i e d i n s o p h i s t i c a t e d ways to c o r r o s i o n work. I t i s impossible, t h e r e f o r e , to provide more than a general overview i n t h i s review. The s p e c i f i c natures of surface techniques and, i n some cases, t h e i r a p p l i c a t i o n s to c o r r o s i o n have been d i s c u s s e d by a number of authors. General use of surface t o o l s i n Corrosion has been discussed by Larson ( 8 ) , J o s h i (9, 10) and i n the PHI I n t e r face Volume 3 #2 (1980). There has been c o n s i d e r a b l e a p p l i c a t i o n of s u r f a c e methods to e l e c t r o c h e m i c a l c o r r o s i o n (11-15) i n c l u d i n g use of various types of vacuum compatible c o r r o s i o n c e l l s (16, 17). C a s t l e (l^L, JJO and Mclntyre (5) have shown how X-ray photoelectron spectroscopy (XPS or ESCA) can be a p p l i e d to c o r r o s i o n problems and uses of Auger e l e c t r o n spectroscopy (AES) i n c o r r o s i o n have been given by Clough (18, 19) and Thomas et a l (^0). P o s s i b l e uses of i o n beams i n c o r r o s i o n s t u d i e s were presented by Dearnaley (21). Raman spectroscopy (22, 23) and e l l i p s o m e t r y (19) are not d i s c u s s e d i n d e t a i l i n t h i s paper, but they o f f e r the advantage of allowing i n s i t u measurements i n a wide v a r i e t y of c o r r o s i v e environments. A s e r i e s of c r i t e r i a that should be met before XPS can be f u l l y a p p l i e d to c o r r o s i o n s t u d i e s of t h i n f i l m s has been establ i s h e d by C a s t l e (11, 12). These c r i t e r i a , when g e n e r a l i z e d to other s u r f a c e science techniques, suggest four general areas or concerns (Table I) that should be addressed before a surface technique (or i n f a c t any experimental technique) i s a p p l i e d to a c o r r o s i o n problem. Although these concerns or questions seem very elementary, the s p e c i f i c problem and s o l u t i o n s they imply may be very d i f f i c u l t to s o r t out. In f a c t , i n some cases, answers can not be obtained without t e s t i n g or t r y i n g the method i n s i m i l a r or known c o n d i t i o n s . Technique S e l e c t i o n . The design of an experiment i s d i c t a t e d by the nature of the a n a l y t i c a l techniques a v a i l a b l e . The "alphabet soup" of surface methods provide many a l t e r n a t i v e s to the researcher, but they a l s o add confusion because few workers have a complete array of methods at t h e i r l a b o r a t o r y nor do they have a working knowledge of the many p o s s i b l e techniques. Comparison c h a r t s , such as Table I I ( a l s o see r e f . 25) can help i n s e l e c t i o n of appropriate techniques, but operator experience, equipment s t y l e and a c c e s s o r i e s , and a v a i l a b i l i t y a l l make important d i f ferences. Frequently i t i s u s e f u l to apply two or more complimentary methods to s o l v e a problem. The d i f f e r e n t types of data can be used to confirm or r u l e out any p a r t i c u l a r model or theory.



3.

acquired?

analyzed?

r e q u i r e d d a t a be

Can t h e d a t a be u s e f u l l y

Are t h e r e p o t e n t i a l p r o b l e m s i n the use o f t h e s e l e c t e d t e c h n i q u e s ?

appropriate?

General Questions

Is t h e t e c h n i q u e

Can t h e

I

Is t h e r e a s u f f i c i e n t d a t a base f o r the t e c h n i q u e t o a p p l y t o my n e e d s o r must i t b e g e n e r a t e d ? Can I a n a l y z e t h e d a t a t o p u l l o u t t h e i n f o r m a t i o n I need? Can s u r f a c e compounds be d i f f e r e n t i a t e d from a l l o y c o m p o n e n t s ? Can a t o m i c c o m p o s i t i o n be o b t a i n e d from t h e d a t a ? Can d i f f e r e n t s t r u c t u r e s ( i s l a n d o r l a y e r ) be d i s t i n g u i s h e d from the data? Does d a t a r e l a t e t o c o r r o s i o n p r o c e s s o f i n t e r e s t ?

Can t h e d e s i r e d a r e a s o f i n t e r e s t ( a p p r o p r i a t e i n t e r f a c e o r c o r r o s i o n a r e a ) be i d e n t i f i e d f o r a n a l y s i s ? Is data a c q u i s i t i o n f a s t enough t o g e n e r a t e d e s i r e d d a t a i n r e a s o n a b l e time f o r a l l o w a b l e cost? Can c o n t a m i n a t i o n mask t h e d e sired signals? Is the a p p r o p r i a t e type o f d a t a b e i n g taken?

Do t h e e x p e r i m e n t a l r e q u i r e m e n t s o f t h e t e c h n i q u e and t h e a p p r o p r i a t e c o r r o s i o n c o n d i t i o n s combine t o g i v e i n f o r m a t i o n t h a t i s n o t a l t e r e d b y s a m p l e h a n d l i n g o r t h e measurement process i t s e l f ? I s t h e s a m p l e s t a b l e u n d e r vacuum? Is the c h e m i s t r y o r s u r f a c e c o m p o s i t i o n a l t e r e d by e l e c t r o n , i o n o r X - r a y beam e x c i t a t i o n ? Does t h e c o r r o s i o n l a y e r change upon c o o l i n g o r r e m o v a l from s o l u t i o n ?

What i s t h e b e s t t e c h n i q u e f o r t h i s p r o b l e m ? Can s e v e r a l t e c h n i q u e s c o m b i n e t o p r o v i d e a more d e f i n i t i v e a n s w e r ? What t e c h n i q u e s a r e r e a d i l y a v a i l a b l e ? W i l l I be a b l e t o compare my d a t a t o o t h e r t y p e s o f m e a s u r e m e n t s ?

S p e c i f i c Examples

QUESTIONS TO ASK WHEN APPLYING A SURFACE TECHNIQUE TO A CORROSION PROBLEM

Table


Casper and Powell; Industrial Applications of Surface Analysis ACS Symposium Series; American Chemical Society: Washington, DC, 1982. Scattered light Polarization s t a t e of polarized light

H D He 0.2-2MeV

Monochromatic light Monochromatic polarized light

L i g h t element, isotope a n a l y s i s

Compound i d e n t i f i t i o n on s u r f a c e s

Thickness, d e n s i t y , defect s t r u c t u r e , i n t e r f a c e width

Nuclear Reaction Spectroscopy

RAMAN S c a t t e r i n g

Ellipsometry

analysis,

+

He

+

+

3

+

2meV

Reaction products

Backscattered ion

-4

page.

F r a c t i o n of monolayer

Needs ~1 monol a y e r o r more

1-10

1

10" -10-

lCT^-lO"

10"3

4

Sensitivity 10-3

C o n t i n u e d on n e x t

RAMAN a c t i v e molecules

Selected elements isotopes

He-U

H-U

ions

Secondary

Elemental profiling

+

Rutherford Backs c a t t e r i n g Spectroscopy

+

Ar Ar +0 0.5-10keV

+

Surface composition, isotope i d e n t i f i c a tion

Secondary Ion Mass Spectrometry

Li-U

Li-U

Elements Detected

Photo and other electrons

X-rays

Surface composition, bonding and chemical information

X-ray Photoelectron Spectroscopy

Electrons l-2200eV

Electrons 1-lOkeV

C o r r o s i o n Use

Atomic composition, elemental mapping

Technique

Analyzed Particle

TECHNIQUES

Auger E l e c t r o n Spectroscopy

Probing P a r t i c l e and Energy

CHARACTERISTICS OF SOME SURFACE

Table I I


3

ι

1'

g,

I

Η

§

• w >


-5-20A

-5-20A

5A

~10,000A

-ΙΟ,ΟΟΟΑ

X-ray Photoelectron Spec t roscopy

Secondary Ion Mass Spectrometry

Rutherford Backscattering Spec troscopy

Nuclear Reaction Spectroscopy -mm

-mm

3mm-lum

30um-500A

/ s i s Volume Width

Auger E l e c t r o n Spec t roscopy

Technique

Vacuum compat i b l e





Sample Res t r i c r i o n s

Fast, isotope s e l e c t i o n , can detect H, D, T.

Fas t-quant i t a t i v e . Non-des t ruct ive depth p r o f i l i n g .

High s e n s i t i v i t y . Hydrogen d e t e c t i o n .

Minimum surface damage. Chemical information. Spe c i f i c elemental idenfication. Semi quantitative.

S p e c i f i c element ident i f icat ion. High s e n s i t i v i t y to low Ζ m a t e r i a l . Fast-easy. Semi quantitative. Good spatial resolution.

Advan tages

Table II (contd)

Limited elements detec t a b l e .

Low s e n s i t i v i t y low Z. Needs accelerators.

to

D i f f i c u l t to quantify. Wide v a r i a t i o n i n sen sitivity.

Poor l a t e r a l r e s o l u t i o n , slow p r o f i l i n g

Needs standards to quantify, p o s s i b l e beam damage to su rf aces.

Concerns


29

29

28

27

26

Handbook or General Reference

C/3

*!

>

>

> Ο M

τι

οο


Light pene trable layers

-Ι,ΟΟΟΑ

down to lum

A n a l y s i s Volume Depth Width

Reflecting surface

None

Sample Restrictions

Can be done i n s i t u in aqueous or gaseous e n v i r o n ments .

Can be done i n s i t u at temperature in complex gaseous or l i q u i d environments.

Advantages

Table II (contd)

No elemental i d e n t i f i c a t i o n , need model to understand.

Need comparative standards f o r compound r e c o g n i t i o n , d i f f i c u l t to see t h i n l a y e r s , l i m i t e d data base.

Concerns


24

22 23

Handbook or General Reference

SURFACE ANALYSIS

260 Many c o m p l e x

problems u s i n g

nated

among s e v e r a l

effort

knowing

as

much a b o u t

the

two

o r more methods

researchers

require a coordi-

with everyone

p r o b l e m and e x i s t i n g

involved

results

as


possible. P o t e n t i a l Problems. M o s t , but not a l l , o f the s u r f a c e s e n s i t i v e t e c h n i q u e s r e q u i r e measurements t o be made i n a v a c u u m , f r e q u e n t l y n e a r room t e m p e r a t u r e . Because these c o n d i t i o n s are u s u a l l y d i f f e r e n t from the c o r r o s i o n c o n d i t i o n s , the p o s s i b i l i t y t h a t t h e d e s i r e d i n f o r m a t i o n w i l l be l o s t i n t h e t r a n s f e r f r o m t h e c o r r o s i o n chamber t o s u r f a c e a n a l y s i s chamber i s a m a j o r c o n c e r n . T h e r e i s a l s o a p o s s i b l i t y t h a t t h e measurement i t s e l f w i l l a l t e r the c o m p o s i t i o n o r c h e m i s t r y of i n t e r e s t . Various aspects of t h o s e p r o b l e m s may a p p l y t o any method f o r w h i c h a n a l y s i s o c c u r s under c o n d i t i o n s d i f f e r e n t from t h o s e i n w h i c h the sample i s g e n e r a t e d , b u t t h e y a r e o f p a r t i c u l a r c o n c e r n f o r s u r f a c e methods t h a t examine t h e v e r y o u t e r l a y e r s o f t h e m a t e r i a l . E a c h o f t h e p r o b l e m s m e n t i o n e d o c c u r on some s p e c i m e n s , b u t many e x a m p l e s e x i s t where u s e f u l i n f o r m a t i o n was n o t o b s c u r e d b y d e h y d r a t i o n i n t h e v a c u u m , beam damage, o r o x i d a t i o n d u r i n g h a n d ling. F o r e x a m p l e , XPS m e a s u r e m e n t s b y C a s t l e (II), Asami et a l ( ^ 0 ) , B a e r and Thomas (_31), and o t h e r s c o n t a i n r e s u l t s t h a t w o u l d not have been p o s s i b l e i f the vacuum, sample t r a n s f e r o r X - r a y beam were a l t e r i n g t h e m e a s u r e m e n t s . I n some s i t u a t i o n s , special s a m p l e h a n d l i n g and modes o f d a t a a c q u i s i t i o n a r e n e c e s s a r y to o b t a i n r e l i a b l e r e s u l t s ( 1 4 , . 3 1 ) · Most e x p e r i m e n t s s h o u l d i n c l u d e some method t o c h e c k f o r s p e c i m e n damage d u r i n g h a n d l i n g and d a t a a c q u i s i t i o n . Data A c q u i s i t i o n . F r e q u e n t l y , d a t a a n a l y s i s t a k e s as much o r more t i m e t h a n d a t a a c q u i s i t i o n , and a p p r o p r i a t e a n a l y s i s c a n be done o n l y i f a d e q u a t e d a t a were t a k e n i n i t i a l l y . Because c h o o s i n g an a p p r o p r i a t e s u r f a c e t e c h n i q u e d o e s n o t a d e q u a t e l y d e f i n e what i s t o be d o n e , c o n s i d e r a b l e t h o u g h t n e e d s t o go t o w a r d s d e t e r m i n i n g t h e t y p e s o f d a t a t o be t a k e n and i n t o p o s s i b l e c o n t r o l samples o r o t h e r checks to i n s u r e t h a t the d a t a a r e meaningful. The n u l l o r n o n - i n f o r m a t i v e r e s u l t i s a p a r t i c u l a r p r o b l e m i n s u r f a c e a n a l y s i s b e c a u s e i t c a n o c c u r f o r many r e a s o n s . For e x a m p l e , i f a c o n t a m i n a n t , s u c h as C I , i s s u s p e c t e d o f c a u s i n g a c o r r o s i o n p r o b l e m and i t i s s e a r c h e d f o r and n o t f o u n d , t h e r e are several p o s s i b l e reasons. I t may n o t be t h e p r o b l e m and t h u s s h o u l d n o t be f o u n d . However, t h e r e a r e s e v e r a l o t h e r l e s s d e s i r able p o s s i b i l i t i e s i n c l u d i n g : i t was washed o f f as t h e s a m p l e s were b e i n g p r e p a r e d ; i t c a u s e d t h e c o r r o s i o n , b u t i s n o t p r e s e n t i n the c o r r o s i o n l a y e r b e i n g examined ( t h e sample i s b e i n g e x a m i n e d i n wrong c o n d i t i o n ) ; i t i s p r e s e n t a t c o n c e n t r a t i o n s b e l o w t h e s e n s i t i v i t y l e v e l o f t h e t e c h n i q u e ; i t i s removed by t h e a n a l y s i s c o n d i t i o n s (probe e f f e c t ) ; i t i s at a l o c a t i o n o t h e r than t h a t b e i n g e x a m i n e d ( i n a d i f f e r e n t a r e a o f t h e sample o r a t an


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i n t e r f a c e not being measured). Because there are many p o s s i b l e reasons f o r a n u l l measurement, i t i s o f t e n important t o have various types of c o n t r o l samples i n "known" c o n d i t i o n s . Data A n a l y s i s . Data a n a l y s i s i s , of course, d i r e c t l y r e l a t e d to data a c q u i s i t i o n . However, not a l l good data i s o r can be completely analyzed. F o r example, Mclntyre (_5) has observed that "a broad base i n chemical s h i f t data has been slow i n d e v e l oping" f o r XPS data. U n t i l such a data base e x i s t e d , i t was d i f f i c u l t f o r both expert and non-expert to i n t e r p r e t s p e c t r a from c o r r o s i o n products, p a r t i c u l a r l y on complex a l l o y s . The Handbook of X-Ray Photoelectron Spectroscopy (27) and c o l l e c t i o n s o f Auger parameter data (_32) are examples of data compilations very u s e f u l to a researcher t r y i n g to i n t e r p r e t measurements of c o r r o s i o n products. Refinements i n the use of any techniques o f t e n involve advances i n the method of data a n a l y s i s . One of the major concerns i n using XPS, f o r example, i s a l a c k of l a t e r a l s p a t i a l r e s o l u t i o n . However, work by C a s t l e ( J ^ , _12) shows how t h i s weakness i s turned into an advantage. Often f i l m s formed i n aqueous s o l u t i o n are l e s s than 50 A t h i c k and d i s t i n c t photopeaks from both the base m a t e r i a l and the o x i d i z e d f i l m can be simultaneously measured. F o r uniform f i l m s , the oxide-to-metal peak r a t i o s w i l l depend upon the e l e c t r o n escape depth and thus the i n c i d e n t photon energy. By determining the change i n the peak r a t i o f o r d i f f e r e n t photon energies, the f i l m thickness can be determined. I f the peak r a t i o does not change with photon energy, the presence of an i s l a n d - l i k e surface phase i s i n d i cated (j^2). Thus XPS can determine the general s t r u c t u r e o f a t h i n l a y e r i n s p i t e of very l i m i t e d s p a t i a l r e s o l u t i o n . It is i n t e r e s t i n g to note that the presence of the i s l a n d - l i k e d i s t r i b u t i o n could be detected by XPS even i f i t were of too small a s c a l e to be r e s o l v e d with a high s p a t i a l r e s o l u t i o n (, 36)· Specific objectives of these experiments w e r e t o d e t e r m i n e f r a c t u r e p r o p e r t i e s o f t h e m a t e r i a l s as a f u n c t i o n of b o t h g r a i n boundary c h e m i s t r y and h y d r o g e n p o t e n t i a l . C o n s i d e r a t i o n of Surface Tool Concerns. D i r e c t measurements of g r a i n boundary chemistry u s u a l l y require a n a l y s i s of fracture surfaces. A E S was s e l e c t e d f o r u s e i n d e t e r m i n a t i o n o f g r a i n b o u n d a r y c o m p o s i t i o n b e c a u s e the s i z e o f the e l e c t r o n beam a l l o w s m e a s u r e m e n t s o n i n d i v i d u a l g r a i n s a n d t h e SEM i m a g e a l l o w s n o n i n t e r g r a n u l a r f r a c t u r e areas o f the sample to be e x c l u d e d from analysis. Some w o r k e r s h a v e p r e f e r r e d a n a l y s i s o v e r l a r g e a r e a s i n o r d e r t o o b t a i n and " a v e r a g e " g r a i n b o u n d a r y c o m p o s i t i o n . I n d i v i d u a l g r a i n a n a l y s i s allows the d i s t r i b u t i o n of i m p u r i t i e s to d i f f e r e n t b o u n d a r i e s to be measured. A numerical average of g r a i n b o u n d a r y c o m p o s i t i o n was u s e d i n t h i s s t u d y , a l t h o u g h M c M a h o n (3^) a n d c o - w o r k e r s n o w u s e a " p r o b a b l e M a x i m u m G r a i n Boundary C o n c e n t r a t i o n " . I d e n t i f i c a t i o n of i m p u r i t i e s at g r a i n boundaries i s the most s t r a i g h t f o r w a r d u s e s o f A E S . However, a n a l y s i s t u r e d s u r f a c e s does have t h r e e p o t e n t i a l p r o b l e m a r e a s .

one o f of fracFirst, it



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i s not always p o s s i b l e to obtain an i n t e r g r a n u l a r f r a c t u r e , p a r t i c u l a r l y with a standard low-temperature impact-fracture device. M a t e r i a l s such as n i c k e l must be charged with hydrogen to f a c i l i - ? tate the f r a c t u r e and t h i s treatment i s not always s u c c e s s f u l . Second, there i s a p o s s i b l i t y that impact or other f r a c t u r e methods may s e l e c t i v e l y open c e r t a i n g r a i n boundaries and give r e s u l t s that are not r e p r e s e n t a t i v e o f true average g r a i n boundary composition. T h i r d , absolute measurements of g r a i n boundary coverages r e q u i r e c a r e f u l c a l i b r a t i o n s f o r the m a t e r i a l systems of i n t e r e s t . C a l c u l a t i o n s using s e n s i t i v i t y f a c t o r s and e l e c t r o n escape depths provide u s e f u l estimates of coverages, but c a l i b r a t i o n s should be made when absolute coverages are important (^7, 38). Experimental. Iron and n i c k e l a l l o y s were produced from vacuum melted and zone r e f i n e d m a t e r i a l s . Specimens of approp r i a t e shapes and s i z e s were machined from the m a t e r i a l and heat treated i n d i f f e r e n t ways to s e t g r a i n s i z e and t o induce d i f ferent l e v e l s of g r a i n boundary segregation. One s e t of specimens was designed f o r Auger a n a l y s i s of impact f r a c t u r e surfaces using P h y s i c a l E l e c t r o n i c s 545 and 590 scanning Auger microprobe (SAM) systems. A second s e t of samples was designed t o f i t a s t r a i n i n g e l e c t r o d e apparatus where t e n s i l e p r o p e r t i e s of the materials were measured as a f u n c t i o n of cathodic hydrogen p o t e n t i a l . AES measurements on a f r a c t u r e surface were taken to represent the g r a i n boundary composition of s t r a i n i n g e l e c t r o d e samples that had undergone i d e n t i c a l heat treatments. A f t e r AES impact f r a c t u r e and s t r a i n i n g e l e c t r o d e f r a c t u r e , surfaces were examined with a conventional scanning e l e c t r o n microscope. Results. AES a n a l y s i s of impact f r a c t u r e surfaces on n i c k e l showed considerable spread i n s u l f u r composition at g r a i n boundar i e s as shown i n F i g . 2. The composition v a r i e d from approximately 0.04 to 0.20 monolayers on the sample heated to 1100°C f o r one hour and 0.15 t o 0.25 monolayers on a sample that had received a d d i t i o n a l heating at 600°C f o r 240 hours. The a d d i t i o n a l heat treatment s h i f t e d the average g r a i n boundary composition by n e a r l y 0.1 monolayer of coverage. A d i r e c t r e l a t i o n s h i p between s u l f u r content at g r a i n bound a r i e s and f r a c t u r e mode i n hydrogen was found f o r both i r o n and n i c k e l . The f r a c t u r e mode as a f u n c t i o n of g r a i n boundary s u l f u r i n n i c k e l i s shown at three d i f f e r e n t hydrogen p o t e n t i a l s (39) i n F i g . 3. At a given hydrogen p o t e n t i a l , the mode changes from duct i l e t o i n t e r g r a n u l a r as the s u l f u r concentration changes. For a p a r t i c u l a r g r a i n boundary composition, the f r a c t u r e mode can change as the p o t e n t i a l i s changed. I f the c r i t i c a l concentration of s u l f u r i s defined as that causing 50% i n t e r g r a n u l a r f r a c t u r e , i t i s observed that t h i s c r i t i c a l concentration decreases as the amount of hydrogen i n the m a t e r i a l (increased negative p o t e n t i a l ) increases. I t has a l s o been p o s s i b l e t o compare e f f e c t s of v a r i ous segregated elements f o r e m b r i t t l i n g both i r o n and n i c k e l (40).



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< -

1000

Composition Downloaded by CALIFORNIA INST OF TECHNOLOGY on December 5, 2017 | http://pubs.acs.org Publication Date: September 22, 1982 | doi: 10.1021/bk-1982-0199.ch011

A f t e r surfac treatment mV (SCE)

A f t e r mechanical polishing (800 mesh) mV (SCE)

A d a p t e d from R e f . 4 3 .

80

J

I

I

I

I

I

SPUTTERING DEPTH (a.u.) Figure 9. Chromium depth profile in Fel3Cr after normal (a) and controlled or modified annealing (b). (Reproduced, with permission, from Ref. 43. Copyright 1980, Elsevier Sequoia.)



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10

20

30

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60

70

80

S P U T T E R I N G T I M E (min)

Cr ( - 3 5 % )

15%)

0

10

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30

40

50

60

70

80

S P U T T E R I N G T I M E (min) SPUTTER RATE 200 A/min 3

Figure 10. Sputter depth profile of oxide formed at 10 Pa oxygen pressures (top) as formed (bottom) after additional oxidation in air. Key to top plot: , Fe (v-77%); , Ο (~64%); — · —, Cr (as indicated); · · ·, Ni (~7%); and 0(LT 1%). Key to bottom plot: , Fe (~78%); ,Ο (~65%); — · —, Cr (as indicated); · · -, Ni (~7%); and Ο (LT 1%). (Reproduced, with permis sion, from Ref. 45. Copyright 1981, North-Holland Publishing Co.)



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BAER AND THOMAS

Metal Corrosion

Problems

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The bellow-form s p r i n g female pins were f a b r i c a t e d p r i m a r i l y from a beryllium-copper a l l o y , but r e l y on t h i n f i l m coatings f o r c o r r o s i o n r e s i s t a n c e . The p i n was coated with a 15 ym l a y e r of s i l v e r and then -0.8 ym of gold. A t a r n i s h l a y e r formed on the gold when s i l v e r s u l f i d e formed at defects i n the gold f i l m and migrated across the gold s u r f a c e . This t a r n i s h , plus accumulated organic m a t e r i a l from sources such as g a l l e y greases, caused the e l e c t r i c a l problems. Although r e p l a c i n g the contacts with s i l v e r - f r e e connectors was the long-range s o l u t i o n i n submarines and i n a l l other c i r c u i t board a p p l i c a t i o n s , some short-term p r e v e n t a t i v e measures were d e s i r a b l e i n the e f f o r t to avoid expensive r e t r o f i t s . A modified chromate c o a t i n g process was found to extend u s e f u l l i f e of the connectors. Because the nature of the chromate f i l m growth i s influenced by the e l e c t r o c h e m i c a l behavior of the contacts and imp u r i t i e s , the exact nature of the f i l m s formed on r e a l and model contacts was examined as w e l l as e f f e c t s of i m p u r i t i e s . The s p e c i f i c goals of the experiment were to c h a r a c t e r i z e the passive f i l m and determine i f i t was p r i m a r i l y p r o t e c t i v e with chromium i n the +3 s t a t e or i f some chromium was i n the +6 s t a t e i n d i c a t i n g the p o s s i b i l i t y of a s e l f - h e a l i n g f i l m . The e f f e c t s of various i m p u r i t i e s on chromate f i l m growth were a l s o examined. C o n s i d e r a t i o n of Surface A n a l y s i s Concerns. The researchers i n t h i s study used a wide range of s u r f a c e and other t o o l s , taking appropriate advantage of the strengths of the various methods. Previous work had shown that AES and XPS could be used to study chromate f i l m s without unreasonable problems and provided a b a s i s f o r the current study. XPS was used to o b t a i n s p e c i f i c chemical information while AES was used whenever s p a t i a l r e s o l u t i o n and e l e c t r o n imaging were d e s i r e d . RBS and e l e c t r o n microprobe work was used to analyze composition s t r u c t u r e s of t h i c k e r l a y e r s . This study i s a good example of multitechnique use. Experimental. Much of the XPS and AES work was done on coupons made of a BeCu a l l o y which had been e l e c t r o p l a t e d with Ag or Au or both. The chromate f i l m s were grown i n a manner c o n s i s t e n t with s p e c i f i c a t i o n s f o r r e f u r b i s h i n g contacts on submarine navigat i o n a l computers. R e s u l t s . XPS s p e c t r a of the chromate f i l m s on the b i m e t a l l i c s t r i p s , on pure s i l v e r and on pure gold showed no i n d i c a t i o n of a C r 6 s t a t e ( F i g . 11) suggesting that flaws i n the chromate f i l m would not heal and t h e r e f o r e would be s u s c e p t i b l e to c o r r o s i v e attack. This non-healing aspect of the chromate f i l m s on the Ag/Au contacts d i f f e r s from the e f f e c t of chromate f i l m s on A l (51) and was confirmed i n f i e l d s t u d i e s . Therefore, the chromate f i l m s formed on the Au/Ag/Be-Cu contact are p r o t e c t i v e , but w i l l not heal over scrapes and other damage caused by usage. +



278

SURFACE ANALYSIS

F i e l d a p p l i c a t i o n s o f the c h r o m a t i n g p r o c e d u r e o c c a s i o n a l l y produced l a r g e d e p o s i t s of i n s u l a t i n g f i l m s . Although these films c o u l d b e c l e a n e d o f f by r e p e a t e d c l e a n i n g and d e t a r n i s h i n g s t e p s , s u c h d e p o s i t s were s u f f i c i e n t l y t r o u b l e s o m e t o w a r r a n t l e a r n i n g t h e c a u s e and t a k i n g s t e p s t o e l i m i n a t e t h e p r o b l e m . AES p r o f i l e s (Fig. 12) o f t h e d e p o s i t s showed them t o be low i n C r and h i g h i n Cu. E m p i r i c a l s t u d i e s showed t h a t t h e p r e s e n c e o f C u C l 2 w o u l d s t i m u l a t e excess f i l m growth i n the chromate p r o c e s s . The p r e s e n c e o f Cu i n t h e c o n t a c t s t h e m s e l v e s ( u n c o v e r e d a t t h e edge o f m a l e c o n n e c t o r s ) and t h e p r e s e n c e o f CI i n s a l t s i n t h e s u b m a r i n e atmosphere lead to f a v o r a b l e c o n d i t i o n s f o r the f o r m a t i o n of C u C l 2 and t h e r e f o r e , t h e f i l m g r o w t h p r o b l e m s . RBS and e l e c t r o n m i c r o p r o b e a n a l y s i s o f good c o n n e c t o r s and i n s u l a t i o n f i l m s s u g g e s t e d t h a t damage t o t h e g o l d f i l m was n o t t h e p r o b l e m . There was no e v i d e n c e o f Cu d i f f u s i o n i n p o r e s o r s c r a t c h e s i n t h e g o l d contact. Thus, the l i k e l y cause i s submarine atmospheric a t t a c k o f Cu e x p o s e d a t e d g e s o f contacts. T h i s s t u d y showed t h a t t h e c h r o m a t i n g p r o c e s s w o u l d n o t p r o v i d e l o n g - t e r m p r o t e c t i o n o f PCB c o n n e c t o r s i f u s e p r o d u c e d damage t o the f i l m and t h a t c a r e f u l c l e a n i n g was n e c e s s a r y i n o r d e r to a v o i d i n s u l a t i n g f i l m b u i l d u p d u r i n g the chromating process. CONCLUSIONS C o r r o s i o n p r o c e s s e s c a n b e v e r y c o m p l e x a n d , as t h e above e x a m p l e s show, s u r f a c e a n a l y t i c a l t e c h n i q u e s c a n o f t e n p r o v i d e unique i n f o r m a t i o n i m p o r t a n t f o r the u n d e r s t a n d i n g o f these p r o c e s s e s and t o t h e s o l u t i o n o f c o r r o s i o n p r o b l e m s . By t h e i r b a s i c n a t u r e , s u r f a c e s e n s i t i v e methods e x c e l a t e x a m i n i n g t h i n l a y e r s a t s u r f a c e s and i n t e r f a c e s t h a t a r e d i f f i c u l t t o d e t e c t and a n a l y z e b y o t h e r methods b u t w h i c h c a n h a v e a l a r g e i n f l u e n c e i n corrosion. The h i g h e r s p a t i a l r e s o l u t i o n s u r f a c e t e c h n i q u e s a r e p a r t i c u l a r l y u s e f u l f o r a n a l y s i s of s m a l l area c o r r o s i o n problems s u c h as p i t t i n g and c o r r o s i o n o f e l e c t r o n i c components and integrated c i r c u i t s . The use o f s u r f a c e t o o l s need n o t be l i m i t e d o n l y t o t h i n layers or small dimension c o r r o s i o n . C r e a t i v e a p p l i c a t i o n of s u r f a c e methods t o l a r g e r s c a l e c o r r o s i o n p r o d u c t s , more c h a r a c t e r i s t i c o f i n d u s t r i a l p r o b l e m s , has p r o v i d e d u s e f u l i n f o r m a t i o n not p r e v i o u s l y a v a i l a b l e . More s o p h i s t i c a t e d u s e s o f s u r f a c e methods t h a t a r e b e i n g d e v e l o p e d and t e s t e d c o n t i n u a l l y w i l l p r o v i d e e v e n more i n f o r m a t i o n f o r c o r r o s i o n r e s e a r c h . A l t h o u g h s u r f a c e t o o l s c a n p r o v i d e a l a r g e amount o f i m p o r tant d a t a , t h e i r a p p l i c a t i o n to c o r r o s i o n problems i s not always straightforward. C o n s i d e r a b l e c a r e must be t a k e n t o e n s u r e t h a t t h e i n f o r m a t i o n o b t a i n e d i s b o t h c o r r e c t and r e l a t e d t o t h e p r o b lem under i n v e s t i g a t i o n . B e c a u s e t h e methods a r e u s u a l l y a p p l i e d o u t s i d e of the c o r r o s i o n e n v i r o n m e n t , i t i s o f t e n n e c e s s a r y to


11.

BAER AND THOMAS

Metal

279

COYYOSWH PYoblems

Na Cr04 2


CHROMATED G O L D PLATE BULK G O L D

B U L K SILVER

590

580

570

P H O T O E L E C T R O N BINDING E N E R G Y (eV)

Figure 11.

Chromium 2p XPS peaks of Na CrO . 2

k

100

>

0

200

400

600

800

S P U T T E R ION D O S A G E ( /xA-min/cm ) 2

Figure 12. Auger sputter profile of insulatingfilmformed during chromating of male PCB connector. Key: - Δ - chromium; - A ~ copper; · · · · · · · , oxygen; and -Ο-, carbon. (Reproduced, with permission, from Ref. 50. Copyright 1980, North-Holland Publishing Co.)



280

SURFACE ANALYSIS

d e s i g n t e s t s t o d e t e r m i n e d a t a c o n s i s t e n c y and r e l e v a n c e . Analys i s b y more t h a n one s u r f a c e method c a n o f t e n c l a r i f y ambiguous results. The i n f o r m a t i o n o b t a i n e d u s i n g s u r f a c e t e c h n i q u e s c a n be r a t h e r d i f f e r e n t t h a n t h a t g a t h e r e d b y more t r a d i t i o n a l methods of c o r r o s i o n r e s e a r c h . The g r e a t e s t u n d e r s t a n d i n g o f c o r r o s i o n p r o c e s s e s i s l i k e l y to i n v o l v e a t h o r o u g h knowledge of b o t h t y p e s o f r e s u l t s and much i n f o r m a t i o n may be g a i n e d by t h e e f f o r t to r e l a t e the d i f f e r e n t types of measurements. As o b s e r v e d b y E g o n M a t i j e v i c ( 6 ) , "Only a c o l l a b o r a t i o n of workers i n d i f f e r e n t d i s c i p l i n e s , i n c l u d i n g c o l l o i d and s u r f a c e s c i e n c e , c a n b r i n g a b o u t a d v a n c e s i n e x p l o r i n g and c o m b a t i n g v a r i o u s c o r r o s i o n phenomena." ACKNOWLEDGMENTS The a u t h o r s w o u l d l i k e t o t h a n k S. M . Bruemmer, R. H . J o n e s , J . T . P r a t e r f o r c r i t i c a l r e a d i n g of the m a n u s c r i p t . T h i s work was s u p p o r t e d by t h e M a t e r i a l s S c i e n c e D i v i s i o n o f the O f f i c e of B a s i c E n e r g y S c i e n c e s , U . S . Department of E n e r g y under c o n t r a c t DE-AC06-76RLO-1830. and

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8. 9.

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11. 12.

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Kruger, J. "1980 Yearbook of Science and the Future;" Encyclopedia Britannica: 1980; pp. 134-145. Kruger, J. ASTM Standardization News May 1981, 9(5):21. "Costly Corrosion Not Licked--Yet," News a r t i c l e Department of Energy Insider, February 2, 1981. Fontana, M.G.; Greene, N.D. "Corrosion Engineering--2nd ed.," McGraw-Hill, New York, NY, 1978. McIntrye, N.S. The PHI Interface 1980, 3(2):3, Physical Electronics, Eden Prairie, MN. Matijevic, E. Corrosion 1979, 35:229. Whittel, D.P. "Proceedings of the International Conference on High Temperature Corrosion-San Diego;" NACE: Houston, March 1981. Larson, D.T. Corrosion Science 1979, 19, pp. 657-673. Joshi, A. "Fractography in Failure Analysis," ASTM STP645, ed. by B.M. Straus and W.H. Cullen, Jr. Am. Soc. Test Mat. 1978, pp. 275-293. Joshi, A. "Reviews on Coatings and Corrosion"; ed. J. Yahalom, Freund Publishing House, Tel-Aviv, Israel, 1979, pp. 51-77. Castle, J.E. Surface Science 1977, 68, pp. 583-602. Castle, J.E. "Applied Surface Analysis ASTM STP699"; ed. T.L. Barr and L.E. Davis, Am. Soc. Test. Mat. 1980, pp. 182-198. Sherwood, P.M.A. Surf. Sci. 1980, 101, pp. 619-623.



11.

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Problems

281

14. McIntyre, N.S.; Sunder, S.; Shoesmith, D.W.; Stanchell, F.W. J. Vac. S c i . Tech. 1981, 18, pp. 714-721. 15. Burstein, G.T. Corrosion 1981, 37, pp. 549-556. 16. O'Grady, W.E.; Yang, C.Y. J. Vac. S c i . Tech. 1982, 20. 17. Stout, D.A.; Gavelli, G.; Lumsden, J.B.; Staehle, R.W. "Applied Surface Analysis ASTM STP699"; ed. T.L. Barr and L.E. Davis, Am. Soc. Test Mat. 1980, pp. 42-53. 18. Clough, S.P. "The PHI Interface"; Physical Electronics, Eden Prairie, MN, 1980, 3(2):4. 19. Clough, S.P. "Modern Surface Analysis: Metallurgical Applications of AES and XPS"; Metallurgical Soc. of AIME, New York, NY, 1979. 20. Thomas, M.T.; Jones, R.H.; Baer, D.R.; Bruemmer, S.M. "The PHI Interface"; Physical Electronics, Eden Prairie, MN, 1980, 3(2):3. 21. Dearmaley, G. "Ion Irradiation for Materials Analysis"; ed. S.T. Picraux, Plenum Press, New York, NY, 1974. 22. Thibeau, R.H.; Brown, C.W.; Heidersbach, R.H. Applied Spec troscopy 1978, 32, pp. 532-535. 23. Farrow, R.L.; Mattern, P.L.; Nagelberg, A.S. Appl. Phys. Lett. 1980, 36, p. 212. 24. Aspnes, D.E. J. Vac. Sci. Tech. 1981, 18, pp. 289-295. 25. Evans, C.A. Jr. "ARPA/NBS Workshop IV, Surface Analysis for Silicon Devices"; National Bureau of Standards Special Publication 400-23, 1976. 26. Davis, L.E.; MacDonald, N.C.; Palmberg, P.W.; Riach, G.E.; Weber, R.E. "Handbook of Auger Electron Spectroscopy--2nd ed."; Physical Electronics, Eden Prairie, MN, 1976. 27. Wagner, C.D.; Riggs, W.M.; Davis, L.E.; Moulder, J.F.; Muilonberg, G.E. "Handbook of X-ray Photoelectron Spectroscopy"; Perkin-Elmer, Eden Prairie, MN, 1979. 28. Benninghoben, Α.; Evans, C.A. Jr.; Powell, R.A.; Shimizu, R.; Storms, H.A. "Secondary Ion Mass Spectrometry-SIMS II"; Springer-Verlag, New York, NY, 1979. 29. Mayer, J.W.; Rimini, E., Eds. "Ion Beam Handbook for Material Analysis"; Academic Press, New York, NY, 1977. 30. Asami, K.; Hashimoto, K.; Shimodaira, S. Corrosion Science 1978, 18, pp. 125-137. 31. Baer, D.R.; Thomas, M.T. J. Vac. Sci. Tech. 1981, 18, pp. 125-137. 32. Wagner, C.D.; Zatko, D.A.; Raymond, R.H. Anal. Chem. 1980, 52, pp. 1445-1451. 33. McMahon, C.J. J. Mat. Sci. Eng. 1980, 42, pp. 215-226. 34. Bruemmer, S.M.; Jones, R.H.; Thomas, M.T.; Baer, D.R. Scripta Metallurgica 1980, 14, pp. 1233-1237. 35. Bruemmer, S.M.; Jones, R.H.; Thomas, M.T.; Baer, D.R. Scripta Metallurgica 1980, 14, pp. 137-141. 36. Jones, R.H.; Bruemmer, S.M., Thomas, M.T.; Baer, D. R. Met. Trans. Aug. 1981, 12A. 37. Seah, M.P. J. Vac. S c i . Tech. 1980, 17, pp. 16-24.


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42.

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RECEIVED May 4,

1982


Use of Surface Analytical Techniques to Examine Metal Corrosion

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