Effects of Acid Deposition on Poultice-Induced Automotive Corrosion

12 Effects of Acid Deposition on Poultice-Induced Automotive Corrosion 1

R. C. Turcotte, T. C. Comeau , and Robert Baboian

Downloaded by UNIV OF MASSACHUSETTS AMHERST on May 18, 2018 | https://pubs.acs.org Publication Date: September 25, 1986 | doi: 10.1021/bk-1986-0318.ch012

Texas Instruments Incorporated, 34 Forest Street, Attleboro, M A 02703

The chemistry of wet poultice deposits (road dirt and debris) on automobiles is affected by factors such as road salts and the composition of wet and dry deposition. The rate of metallic corrosion where poultice deposits accummulate on automobiles is highly dependent on this chemistry. The composition of aggressive species in poultice deposits was determined by sampling in Montreal, Detroit, Boston, and Dallas. A correlation between the corrosivity and the poultice chemistry was made by mounting corrosion test coupons on vehicles in each city and by simulating poultice effects in the laboratory. Results show that corrosion damage increases in a complex manner in areas of heavy road salt use and acid deposition. F a c t o r s a f f e c t i n g t h e c o r r o s i o n o f auto-body s t e e l and t r i m a r e i n two major c a t a g o r i e s , d e s i g n a n d e n v i r o n m e n t a l . Design f a c t o r s i n c l u d e the choice o f material o f construction, galvanic coupling o f d i s s i m i l a r m e t a l s , t h e c r e a t i o n o f l i p s o r c u p s t h a t may h o l d a g g r e s s i v e environments and o t h e r entrapment a r e a s . Environmental f a c t o r s i n c l u d e a l l the v a r i o u s c h e m i c a l s p e c i e s t o which t h e a u t o m o b i l e i s s u b j e c t e d ; major c o n t r i b u t o r s i n c l u d e r o a d s a l t s such as sodium c h l o r i d e and c a l c i u m c h l o r i d e , s e a s a l t a e r o s o l s , a n d p r e c i p i t a t i o n , e s p e c i a l l y i f i t has been a c i d i f i e d . Figure 1, which g r a p h i c a l l y d e p i c t s t h e a u t o m o t i v e c o r r o s i o n m i l e s t o n e s t h a t h a v e a c c o m p a n i e d r o a d s a l t u s a g e i n t h e U n i t e d S t a t e s ( 1 - 2 ) , and F i g u r e 2 , which superimposes automobile c o r r o s i o n r a t e s a n d average r a i n pH i n t h e U n i t e d S t a t e s (JO, s u p p o r t t h e s e c l a i m s . P o u l t i c e d e p o s i t s a r e a c c u m u l a t i o n s o f road d i r t , v e g e t a t i o n , t a r , a n d o t h e r d e b r i s which c o l l e c t s i n c r e v i c e s around t r i m m a t e r i a l s , i n w h e e l w e l l s , a n d i n o t h e r e n t r a p m e n t a r e a s (3,). S i n c e t h e b a s i c design i n those l o c a t i o n s allows p o u l t i c e d e p o s i t s t o become wetted w i t h o u t b e i n g washed away, p o u l t i c e s r e m a i n f o r a c o n s i d e r a b l e p e r i o d o f t i m e and can cause s e v e r e c o r r o s i o n l e a d i n g 'Current address: University of Rhode Island, Kingston, RI 02881 0097-6156/ 86/ 0318-0200$06.00/ 0 © 1986 American Chemical Society

Baboian; Materials Degradation Caused by Acid Rain ACS Symposium Series; American Chemical Society: Washington, DC, 1986.


12. TURCOTTE ET AL.

0· 1945

Effects of Acid Deposition

1

1

I

1950

1955

1960

on Automotive

I

1965 YEAR

Corrosion

201

I

I

I

I

1970

1975

1980

1985

F i g u r e 1. Automobile c o r r o s i o n m i l e s t o n e s a s a f u n c t i o n o f road s a l t usage.

Acid Rain —

pH

5.0 6.0 5.0 4.7 4.3

•

Severe

Hfljj

Moderate

HI

Mild

•

Negligible

F i g u r e 2. Geographic c o r r o s i o n i n the United

distribution States.

o f a c i d r a i n and a u t o m o b i l e


202

M A T E R I A L S D E G R A D A T I O N C A U S E D BY A C I D R A I N

even to p e r f o r a t i o n ( 4 ^ . T h i s paper examines the c h e m i s t r y o f a g g r e s s i v e s p e c i e s i n p o u l t i c e samples from Boston, D a l l a s , D e t r o i t , and M o n t r e a l . A c o r r e l a t i o n b e t w e e n c o r r o s i v i t y and p o u l t i c e chemistry i s presented.


Theory When o r g a n i c f u e l s a r e burned, carbon d i o x i d e and water vapor a r e r e l e a s e d a l o n g w i t h v a r i o u s amounts o f s u l f u r d i o x i d e and n i t r o g e n o x i d e s . The s u l f u r and n i t r o g e n o x i d e s i n the atmosphere a r e then f u r t h e r o x i d i z e d w i t h the a s s i s t a n c e of u l t r a v i o l e t solar r a d i a t i o n ; when t h e s e g a s e s a r e s c r u b b e d f r o m t h e a i r by p r e c i p i t a t i o n , a d i l u t e s o l u t i o n o f s u l f u r i c a c i d and n i t r i c a c i d forms. C a r b o n d i o x i d e i t s e l f hydro l y ζ es to c a r b o n i c a c i d and i s i m p o r t a n t i n the marine carbonate b u f f e r s y s t e m ; h o w e v e r , i t i s a weak o r g a n i c a c i d and a t m o s p h e r i c c o n c e n t r a t i o n s t y p i c a l l y lower the pH o f d i s t i l l e d water o n l y t o about 5.7 ( 5 - 6 ) . M e t a l o x i d e s a r e t y p i c a l l y more s o l u b l e i n a c i d i c m e d i a . Hence, low pH s o l u t i o n s s h o u l d a d v e r s e l y a f f e c t t h e f o r m a t i o n o f p r o t e c t i v e f i l m s on m e t a l s u r f a c e s . C h l o r i d e s , on t h e o t h e r h a n d , are known t o induce c o r r o s i o n through a c a t a l y t i c mechanism. C h l o r i d e i o n s a r e s m a l l and m o b i l e and t h e r e f o r e a f f e c t the p r o t e c t i v e f i l m s on m e t a l s c a u s i n g l o c a l breakdown and p i t t i n g . Once p i t t i n g has i n i t i a t e d , m i g r a t i o n o f c h l o r i d e i o n i n t o t h e p i t c a u s e s a l o w e r i n g o f pH w i t h i n t h e r e s t r i c t i o n by t h e f o r m a t i o n o f HC1 h y d r o l y s i s p r o d u c t s . This o c c u r s i n b o t h p i t s and c r e v i c e s and i s shown i n F i g u r e 3 ( 7 ) . A d d i t i o n a l l y , calcium c h l o r i d e i s deliquescent, absorbing m o i s t u r e f r o m t h e a i r a n d m a i n t a i n i n g a wet s u r f a c e a b o v e a c r i t i c a l humidity. I t i s known t h a t c a l c i u m c h l o r i d e i s h i g h l y c o r r o s i v e t o a u t o m o b i l e s , a t l e a s t p a r t l y because o f t h i s d e l i q u e s c e n c e (8). The mechanism o f p o u l t i c e c o r r o s i o n i s shown d i a g r a m a t i c a l l y i n F i g u r e 4. C o r r o s i o n i n i t i a l l y o c c u r s u n i f o r m l y o v e r the whole m e t a l s u r f a c e . However, as t h e p r o c e s s c o n t i n u e s , t h e o x y g e n r e d u c t i o n c a t h o d i c r e a c t i o n may become r e s t r i c t e d t o a band near the s u r f a c e where oxygen i s r e a d i l y a v a i l a b l e . C o r r o s i o n o f m e t a l t h e n t a k e s p l a c e p r e f e r e n t i a l l y s l i g h t l y below the band. The pH r i s e s i n t h e c a t h o d i c r e a c t i o n area due t o an i n c r e a s e i n h y d r o x y l i o n c o n c e n t r a t i o n w h i l e the a n o d i c a r e a decreases i n pH due t o t h e h y d r o l y s i s of metal c h l o r i d e r e a c t i o n products. Wet

P o u l t i c e Chemistry

F i g u r e 2 shows t h a t the n o r t h e a s t e r n U n i t e d S t a t e s s u f f e r s e s p e c i a l l y severe automotive c o r r o s i o n . Annual automobile c o r r o s i o n s u r v e y s c o n d u c t e d by T e x a s I n s t r u m e n t s I n c . have i n d i c a t e d t h a t M o n t r e a l , Canada i s a l s o h i g h l y c o r r o s i v e . T h e r e f o r e B o s t o n , D e t r o i t , and M o n t r e a l were chosen as i d e a l s a m p l i n g s i t e s t h a t s h o u l d have the g r e a t e s t a m o u n t s o f c o r r o s i v e s p e c i e s ; f o r c o m p a r i s o n , D a l l a s , Texas was chosen as t y p i c a l o f what s h o u l d be a mildly corrosive area. R e p r e s e n t a t i v e samples (100 grams) o f p o u l t i c e s were c o l l e c t e d from c a r s i n each c i t y ( M o n t r e a l 31, D e t r o i t 24, Boston 15, D a l l a s 4 ) . S o l u b l e s p e c i e s were t h e n e x t r a c t e d i n t o d i s t i l l e d water by means o f a b a l l m i l l , which r a n 8 hours on and 16 h o u r s o f f f o r 3



TURCOTTE

ETAL.

Effects of Acid Deposition on Automotive Corrosion 203

F i g u r e 3·

Initial

A u t o c a t a l y t i c p i t t i n g mechanism.

Advanced

F i g u r e 4. Mechanism o f p o u l t i c e c o r r o s i o n o f a u t o s t e e l i n i t i a l and advanced s t a g e s .


showing

204

M A T E R I A L S D E G R A D A T I O N C A U S E D BY A C I D RAIN

days; t h e s o l u t i o n was t h e n f i l t e r e d (0.45 jum) b e f o r e a n a l y s i s (9). Q u a l i t a t i v e a n a l y s e s were done u s i n g D C - P l a s m a emission s p e c t r o s c o p y and a s e r i e s o f a n i o n i c s p e c i f i c methods. The p r i m a r y c h e m i c a l c o n s t i t u e n t s were t h e n q u a n t i t a t i v e l y d e t e r m i n e d by methods l i s t e d i n T a b l e I ( 9 - 1 0 ) . EPA water q u a l i t y s t a n d a r d s were used as a check on the methods used.


Table I .

Methods o f A n a l y s i s

Species

Technique Employed

CATIONS

Na+ Ca2+ K+ Mg2+

ATOMIC ABSORPTION SPECTROSCOPY OR ATOMIC EMISSION SPECTROSCOPY

ClANIONS

NOo-

ION SELECTIVE ELECTRODE ION SELECTIVE ELECTRODE UV-VISIBLE SPECTROSCOPY UV-VISIBLE SPECTROSCOPY TITRIMETRY TITRIMETRY

S0]J2P0 34

HCOo-

C0 23

F i g u r e 5 c o m p a r e s t h e i o n s t h a t might be a t t r i b u t e d t o road s a l t use and a c i d i c d e p o s i t i o n i n t h e n o r t h e r n c i t i e s . T h e s e i n c l u d e s o d i u m , c a l c i u m , c h l o r i d e , and s u l f a t e ; they were major constituents. W h i l e t h e n o r t h e r n c i t i e s have e x p e c t e d l y h i g h l e v e l s o f these i o n i c s p e c i e s , t h e l e v e l s i n D a l l a s were unexpected. F u r t h e r o b s e r v a t i o n p o i n t e d o u t i m p o r t a n t d i f f e r e n c e s i n t h e c h e m i s t r y o f t h e environments as d e s c r i b e d below. Comparisons o f t h e p e r t i n e n t i o n i c s p e c i e s i n t h e p o u l t i c e s a r e shown i n F i g u r e 6. I n B o s t o n , D e t r o i t , and M o n t r e a l , t h e r e i s an a p p r o x i m a t e b a l a n c e b e t w e e n e q u i v a l e n t s o f c h l o r i d e s a n d s u l f a t e s v e r s u s e q u i v a l e n t s o f c a l c i u m and sodium; i n D a l l a s , t h e r e i s an o v e r a b u n d a n c e o f c a t i o n s , i n d i c a t i n g t h a t u n i d e n t i f i e d anionic species e x i s t . The p o u l t i c e s f r o m d i f f e r e n t c i t i e s a l s o h a v e v a r y i n g c h a r a c t e r i s t i c soluble species. Montreal p o u l t i c e s a r e t y p i c a l l y v e r y h i g h i n s u l f a t e and c a l c i u m i o n s w i t h s i g n i f i c a n t l e v e l s o f c h l o r i d e and sodium. D e t r o i t p o u l t i c e s a r e h i g h e s t i n c h l o r i d e and c a l c i u m i o n s w i t h s i g n i f i c a n t l e v e l s o f s u l f a t e and sodium i o n s . Boston, while possessing l e s s o f these s o l u b l e s p e c i e s , c o n t a i n s m a i n l y s u l f a t e and c a l c i u m i o n s w i t h a f a i r p r o p o r t i o n o f c h l o r i d e and s o d i u m i o n s . D a l l a s has high c a t i o n l e v e l s , e s p e c i a l l y c a l c i u m , b u t c h l o r i d e and s u l f a t e l e v e l s were s i m i l a r t o those o f Boston.


12. TURCOTTE ET AL. Effects of Acid Deposition on Automotive Corrosion

205

3.5 3H

^

i

S

2A 2

-


g

< °-

Na+

•

Ca 2

0

ci-

^

1

DC (Ο a

•

+

NOS

ES S04-2

15-1

Β

HC03-

1

0.5

BOSTON

MONTREAL

F i g u r e 5. C o n c e n t r a t i o n poultices.

o f road

DETROIT s a l t and

DALLAS

acid deposition ions i n

BOSTON

DALLAS S04 (10.1%) 2

cr (2.4%)

DETROIT

MONTREAL N a (10.5%) +

N a (2.4%) +

CI" (1.2%)

Figure 6.

Proportions

o f p o u l t i c e i o n s on an e q u i v a l e n t b a s i s .



206


Automotive Corrosion In the winter of 1984-1985, test samples on Plexiglass plates were exposed i n each of the test c i t i e s . These included samples of bare weighed auto-body s t e e l , weighed g a l v a n i z e d s t e e l , and painted auto-body steel with s t a i n l e s s s t e e l t r i m . Where p a i n t e d panels were i n v o l v e d , cut edges were coated; i n the s t a i n l e s s s t e e l trimmed panels, the ends o f the s t a i n l e s s s t e e l b o l t s used f o r e l e c t r i c a l continuity were coated as w e l l . Nylon bolts were used to a t t a c h the other test specimens to the Plexiglass plate which was mounted on the front bumper of an automobile. Bare s t e e l from a l l s i t e s except Dallas generally had the same v i s u a l appearance, with F i g u r e 7 being t y p i c a l . Dallas steel p l a t e s showed very l i t t l e r u s t i n g . Upon r e t r i e v a l a l l the s t e e l plates were cleaned using Clarke's solution (ASTM G1) to determine the weight loss. The calculated mils per year penetration rates are l i s t e d i n Table I I . The c i t i e s may be l i s t e d i n decreasing order of aggressiveness as: Montreal >

Boston > Detroit

»

Dallas

with differences i n aggressiveness being s l i g h t i n the Northeast i n this test.

Table I I .

City

Boston

Dallas

Detroit

Montreal

Atmospheric Corrosion Rates of Bare Automotive Steel Plates During the Winter of * 84 - •85

Corrosion Rate (ropy) 1.83 2.24 2.68 0.0491 0.114 0.143 0.148 1.41 1.75 2.19 1.99 2.28 2.29 3.64

Average Corrosion Rate (mpy)

2.25

0.114

1.78

2.55


12.

Effects of Acid Deposition on Automotive Corrosion 207

TURCOTTE ET AL.

G a l v a n i z e d s t e e l p l a t e s showed some v i s u a l d i f f e r e n c e s between c i t i e s , as seen i n F i g u r e 8. Some d i f f e r e n c e s w e r e a l s o o b s e r v e d w i t h i n t h e same c i t y ( e . g . F i g u r e 9 ) . These p l a t e s were c l e a n e d u s i n g an ammonia wash f o l l o w e d by a chromic a c i d and s i l v e r n i t r a t e d i p (ASTM G 1 ) . M i l s p e r y e a r p e n e t r a t i o n r a t e s a r e shown i n T a b l e III. Decreasing c o r r o s i v i t y f o l l o w s the order: Montreal

>

Boston > D e t r o i t

>

Dallas


G a l v a n i z i n g n o t o n l y p r o t e c t s t h e s t e e l , b u t a c t u a l l y c o r r o d e s more slowly.

Table I I I .

Atmospheric C o r r o s i o n Rates o f G a l v a n i z i n g on Automotive S t e e l D u r i n g t h e W i n t e r o f '84 - '85

City

Boston

Dallas

Detroit

Montreal

C o r r o s i o n Rate (mpy)

Average C o r r o s i o n (mpy)

0.0590 0.0932 0.193 0.0152 0.0185 0.0202 0.0319 0.0364 0.0560 0.0626 0.198 0.238 0.284 0.319

Rate

0.115

0.0214

0.0517

0.260

Galvanic couples o f s t a i n l e s s s t e e l t r i m with painted auto-body s t e e l p r o d u c e d v e r y d r a m a t i c d i f f e r e n c e s i n c o s m e t i c c o r r o s i o n b e t w e e n c i t i e s , a s s e e n i n F i g u r e 10. N u m e r i c a l c o r r o s i o n r a t i n g s a r e l i s t e d i n Table IV. The d e c r e a s i n g o r d e r o f aggressiveness i s : Montreal >

Detroit

> Boston > D a l l a s

I n a d d i t i o n , r u s t i n g o f t h e s t a i n l e s s s t e e l t r i m m a t e r i a l was observed i n t h e n o r t h e r n c i t i e s , e s p e c i a l l y i n M o n t r e a l . To r e p r o d u c e p o u l t i c e c o r r o s i o n i n t h e l a b , s a m p l e s w e r e immersed i n washed sand s a t u r a t e d w i t h a s o l u t i o n o f i n t e r e s t , a s d e s c r i b e d p r e v i o u s l y (8). When bare s t e e l s a m p l e s w e r e t e s t e d i n


208



Figure one

7.

Typical

season

Figure

8.

plates,

Visual

one season

Detroit,

9.

auto-body

steel

comparison

auto-body

steel

of t y p i c a l galvanized

exposure.

10.

Examples steel

Visual

galvanic

Boston,

of bare

following

i n Detroit.

Right

to l e f t :

steel

Boston,

auto-body

Dallas,

Montreal.

Figure

Figure

appearance

exposure

Dallas,

of the range

following

comparison

exposure

of stainless

c o u p l e s , one season Detroit,

of appearance

one season

f o r galvanized i n Detroit.

steel/painted

exposure.

Right

to

auto-body left:

Montreal.


12.

T U R C O T T E ET AL.

Table IV.

Effects of Acid Deposition

on Automotive

Corrosion

209

R a t i n g o f SS T r i m / P a i n t e d Auto Body S t e e l Galvanic Corrosion

Average C o r r o s i o n Severity Rating

Corrosion Severity Rating

City

1.9


Boston

2.1

2.1 2.3 1.1 1.4 1.4 1.9

Dallas

1.4

Detroit

2.2 3.3 3.6

3.0

Montreal

3.6 4.1 4.1

3.9

Note:

I n c r e a s i n g c o r r o s i o n i s 0 t o 5 w i t h 5 the most

severe.

a c i d r a i n ( d i s t i l l e d w a t e r a d j u s t e d t o pH 4 w i t h a 3:7 n i t r i c a c i d / s u l f u r i c a c i d m i x t u r e ) and 1? c a l c i u m c h l o r i d e , t h e d a t a i n Table V r e s u l t e d . T h a t l e v e l o f c a l c i u m c h l o r i d e i s more a g g r e s s i v e than a c i d r a i n ; however, i f t h e two a r e combined, t h e r e i s i n i t i a l l y a s y n e r g i s t i c e f f e c t that greatly increases corrosion. W i t h repeated w e t t i n g and d r y i n g , t h e s y n e r g i s t i c e f f e c t i s l o s t . The r e a s o n f o r t h i s phenomenon i s t h a t a l t e r n a t e w e t t i n g and d r y i n g of p o u l t i c e s can a f f e c t s o l u t i o n chemistry.

T a b l e V.

C o r r o s i o n Data f o r Auto-Body S t e e l i n P o u l t i c e Test

Acid

Avg. P e n e t r a t i o n 2 weeks; no d r y i n g (mpy)

Avg. P e n e t r a t i o n 12 weeks; d r y i n g and w e t t i n g (mpy)

Rain

1.3

19.3

CaCl

2

A c i d R a i n and CaClp

12.5

26.3

87.4

82.8



210

A s o l u t i o n o f s u l f u r i c and n i t r i c a c i d s , w i t h and without c a l c i u m c h l o r i d e a d d i t i o n , was s u b j e c t e d t o c y c l i c d r y i n g . A f t e r t h r e e w e t / d r y c y c l e s , t h e pH o f b o t h h a d r i s e n , w i t h t h e CaCl2 s o l u t i o n r i s i n g more. A n a l y s i s o f t h e o r i g i n a l a n d o f t h e c y c l e d s o l u t i o n s i s shown i n T a b l e V I . Note t h a t t h e n i t r i c a c i d e v a p o r a t e d away and t h a t c h l o r i d e was d e p l e t e d t o v e r y l o w v a l u e s . T h i s i s due t o e v a p o r a t i o n and t h e r e a c t i o n : CaCl

2

+ H2SO4

CaSOiii +

2HC1 +


i n w h i c h HC1 i s d r i v e n o f f upon d r y i n g .

Table VI.

E f f e c t o f Repeated W e t t i n g and D r y i n g on A c i d Rain Chemistry

S0 -2 (mg/1) 4

Sample

PH

H S0i| HNO3 CaCl

NO3(mg/1)

+2 (mg/1)

C a

ci(mg/l)

2

0.96

590

291

350

940

3 wet-dry cycles

1.57

350

6.8

390

w o u l d e x p e c t B o s t o n t o be t h e l e a s t a g g r e s s i v e o f t h e t h r e e n o r t h e r n c i t i e s . The f a c t t h a t i t i s more a g g e s s i v e than D e t r o i t i n two o f t h e f i e l d t e s t s may i n d i c a t e t h e i n f l u e n c e o f increased a c i d d e p o s i t i o n a c t i v i t y i n the Boston a r e a . In D a l l a s , CaCl2 i s used f o r dust c o n t r o l p u r p o s e s . The a b s o l u t e l e v e l s o f c h l o r i d e and s u l f a t e s a r e s i m i l a r t o t h o s e found i n B o s t o n . However, e n v i r o n m e n t a l f a c t o r s such as p r e c i p i t a t i o n and h u m i d i t y a r e d i f f e r e n t and t h e r e f o r e D a l l a s i s l e s s a g g r e s s i v e . I n a d d i t i o n , D a l l a s a n a l y s e s do n o t a p p e a r t o a c c o u n t f o r a l l i o n i c species. R e g a r d l e s s o f t h e environment, t e s t s i n d i c a t e t h a t a u t o m o b i l e m a n u f a c t u r e r s can s i g n i f i c a n t l y reduce c o r r o s i o n i n a c i d d e p o s t i o n a r e a s by u s i n g g a l v a n i z e d s t e e l . Even i n t h e v e r y s e v e r e M o n t r e a l environment, the c o r r o s i o n o f g a l v a n i z i n g i s r o u g h l y an o r d e r o f m a g n i t u d e l e s s than t h a t o f b a r e s t e e l . C o r r o s i o n performance can a l s o be improved by c a r e f u l c o n s i d e r a t i o n o f g a l v a n i c e f f e c t s i n the t r i m a r e a s .


o

n

e

Summary and C o n c l u s i o n s R e p r e s e n t a t i v e a u t o m o b i l e p o u l t i c e s a m p l e s from B o s t o n , D a l l a s , D e t r o i t , and M o n t r e a l show a common c h e m i s t r y i n t h e n o r t h e r n s t a t e s i n v o l v i n g r o a d s a l t s and a c i d d e p o s i t i o n . There were a l s o s i g n i f i c a n t amounts o f c h l o r i d e f r o m d u s t c o n t r o l o p e r a t i o n s i n D a l l a s . However, t h e d i f f e r e n t s i t e s v a r i e d i n t h e l e v e l s o f i o n i c s p e c i e s and a l s o i n t h e i r p r o p o r t i o n s . As i n p a s t s u r v e y s , f i e l d t e s t s d u r i n g t h e w i n t e r o f 8 4 - 8 5 showed t h a t a r e a s o f h i g h road s a l t use and s e r i o u s a c i d d e p o s i t i o n are v e r y c o r r o s i v e . T o t a l t i m e o f wetness i s a l s o i m p o r t a n t . T h i s r e s e a r c h i n d i c a t e s a d e c r e a s i n g o r d e r o f a g g r e s s i v e n e s s on b a r e o r g a l v a n i z e d s t e e l t o be: f

Montreal

>

Boston

>

Detroit >

f

Dallas

Simple l a b o r a t o r y t e s t s may not be adequate t o reproduce f i e l d r e s u l t s . The r e a s o n f o r t h i s was demonstrated i n t h e l a b w i t h an a r t i f i c i a l solution containing road s a l t and a c i d rain c o n s t i t u e n t s . A l l o w i n g such a s o l u t i o n t o e v a p o r a t e d r i v e s o f f t h e v o l a t i l e n i t r i c a c i d component and h y d r o c h l o r i c a c i d f o r m e d when c a l c i u m s u l f a t e p r e c i p i t a t e s . Hence t h e h i s t o r y o f a p o u l t i c e i s important i n determining the a g g r e s s i v e n e s s o f a p a r t i c u l a r environment.


212

MATERIALS DEGRADATION CAUSED BY ACID RAIN


Literature Cited 1. Baboian, R. "Automotive Corrosion by Deicing Salts"; National Association of Corrosion Engineers: 1981. 2. Baboian, R. "Causes and Effects of Corrosion Relating to Exterior Trim on Automobiles;" (831835) in Proceedings of the 2nd Automotive Corrosion Prevention Conference; Society of Automotive Engineers, Inc.: Dec. 1983. 3. Rowe, L. C.; and Chance, R. L. "Fundamentals of Corrosion Testing"; in AUTOMOTIVE CORROSION BY DEICING SALTS; R. Baboian, Ed.; N.A.C.E.: 1981. 4. Baboian, R. "Chemistry of the Automotive Environment"; Society of Automotive Engineers; Reprint 780908: 1978. 5. Riley, J. P.; and Chester, R. "Introduction to Marine Chemistry"; Academic Press: N.Y., N.Y., 1971. 6. Pierce, W. C.; Haenisch, E. L.; Sawyer, D. T. "Quantitative Analysis"; 4th ed.; John Wiley & Sons Inc.: New York, N.Y., 1966. 7. Fontana, M.; Greene, N. D. "Corrosion Engineering"; McGraw -Hill Book Co., N.Y., 1967. 8. Baboian, R.; and Turcotte, R. C. "Development of Poultice Corrosion Tests for Automobiles"; National Assoc. of Corrosion Eng.: Paper Number 383, presented at N.A.C.E. Corrosion/85, March, 1985. 9. "Soil Survey: Laboratory Methods and Procedures for Collecting Soil Samples"; Soil Conservation Service, U.S. Dept. of Agriculture. 10. Franson, Μ. A. H., Managing ed. "Standard Methods for the Analyses of Water and Wastewater"; 15th edition; American Pub. Health Assoc.: 1981. RECEIVED January 2, 1986


Effects of Acid Deposition on Poultice-Induced Automotive Corrosion

Recommend Documents