The atmospheric corrosion behaviour of three structural steels in eight Canadian atmospheres: summary of ten years' results

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The atmospheric corrosion behaviour of three structural steels in eight

Canadian atmospheres: summary of ten years' results

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NATIONAL RESEARCH COUNCIL O F CANADA DIVISION O F BUILDING RESEAR CH

THE ATMOSPHERIC CORROSION BEHAVIOWK O F T H R E E STRUCTURAL S T E E L S IN EIGHT CANADIAN ATMOSPHERES-

-

SUMMARY O F T E N YEARS' RESULTS

D.

B.

Clay and J. M. Tudhope, T h e S t e e l Company of Canada, L i m i t e d ,

Hamilton, O n t a r i o

and

_ANALYZED

v E. V. Gibbons,

Division of Building R e s e a r c h ,

National R e s e a r c h Council of Canada, Ottawa, Canada

A joint r e p o r t of t h e S t e e l Company of Canada, L i m i t e d and t h e Division of Building R e s e a r c h , National R e s e a r c h

Council of C a n a d a I n t e r n a l R e p o r t No. 3 5 7 of the Division of Building R e s e a r c h OTTAWA M a r c h 1968

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P R E F A C E

T o fulfil t h e need f o r m o r e published i n f o r m a t i o n on the c o r r o s i o n b e h a v i o u r of d i f f e r e n t a r c h i t e c t u r e m e t a l s a t v a r i o u s l o c a t i o n s a c r o s s Canada, a n outdoor m e t a l s e x p o s u r e p r o g r a m w a s u n d e r t a k e n by t h e f o r m e r A s s o c i a t e C o m m i t t e e on C o r r o s i o n R e s e a r c h and P r e v e n t i o n . T h i s i n f o r m a t i o n i s f r e q u e n t l y r e q u e s t e d by t h o s e r e s p o n s i b l e f o r t h e d e s i g n and m a i n t e n a n c e of buildings. It w a s a c o -ope r a t i v e u n d e r t a k i n g involving C a n a d i a n m e t a l s u p p l i e r s , u s e r s and r e s e a r c h o r g a n i z a t i o n s . The f i r s t m e t a l s w e r e s e l e c t e d in 1953 f o r e x p o s u r e a t eight outdoor s i t e s a c r o s s Canada.

The i n i t i a l g r o u p of m e t a l s e x p o s e d included t h r e e t y p e s of s t e e l , t h r e e s t a i n l e s s s t e e l s , two m a g n e s i u m a l l o y s , a r o l l e d zinc, t h r e e

a l u m i n u m a l l o y s and r i v e t t e d galvanic c o u p l e s of a l u m i n u m 35 a l l o y coupled t o zinc, c o p p e r and m i l d s t e e l . In s u b s e q u e n t y e a r s s p e c i m e n s of l e a d a l l o y s , m o n e l , c o p p e r , m u n t z m e t a l and a n u m b e r of d i f f e r e n t m e t a l and o r g a n i c c o a t i n g s applied t o s t e e l s u b s t r a t e s w e r e s e t out a t t h e d i f f e r e n t s i t e s . T h i s r e p o r t d e s c r i b e s t h e 1 0 - y e a r p e r f o r m a n c e of t h e s t e e l s of t h r e e c o m p o s i t i o n s . R e p o r t s c o v e r i n g t h o s e m e t a l s t h a t h a v e c o m p l e t e d t h e i r 10 y e a r s of e x p o s u r e have been i s s u e d . T h e s p e c i m e n s of s t e e l w e r e f u r n i s h e d by t h e S t e e l Company of C a n a d a L i m i t e d , Hamilton, who w e r e a l s o r e s p o n s i b l e f o r a s s e s s i n g t h e i r p e r f o r m a n c e and i n compiling t h i s r e p o r t . T h i s p a r t of t h e s t u d y w a s u n d e r t h e d i r e c t i o n of M r .

D. B .

C l a y , with t h e a s s i s t a n c e of M r .

J . M. Tudhope, The a r r a n g e m e n t s f o r e x p o s u r e and e x a m i n a t i o n of s p e c i m e n s , and s o m e o v e r - a l l c o - o r d i n a t i o n of t h e p r o g r a m w e r e c a r r i e d out u n d e r t h e d i r e c t i o n of M r . E. V. Gibbons of t h e Division of Building R e s e a r c h .

T h e D i v i s i o n i s i n d e b t e d , not only t o t h o s e c o m p a n i e s who c o - o p e r a t e d i n making t h i s study p o s s i b l e , but a l s o t o t h o s e who have c o n t r i b u t e d i n t h e p r o v i s i o n and s e r v i c i n g of c e r t a i n of t h e e x p o s u r e s i t e s . Ottawa M a r c h

1968

N.

B . Hutcheon A s s i s t a n t D i r e c t o r

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THE ATMOSPHERIC CORROSION BEHAVIOUR O F T H R E E STRUCTURAL S T E E L S IN EIGHT CANADIAN ATMOSPHERES-

-

SUMMARY O F T E N YEARS1 RESULTS

D. B. Clay a n d J. M. Tudhope, The S t e e l Company of Canada, L i m i t e d ,

H a m i l t o n , O n t a r i o

and

E. V. Gibbons,

Division of Building R e s e a r c h ,

N a t i o n a l R e s e a r c h Council of Canada, Ottawa, C a n a d a

Outdoor e x p o s u r e of v a r i o u s a r c h i t e c t u r a l m e t a l s a t C a n a d i a n s i t e s w a s u n d e r t a k e n by t h e A s s o c i a t e Comlzlittee on C o r - r o s i o n R e s e a r c h a n d P r e v e n t i o n of t h e N a t i o n a l R e s e a r c h C o u n c i l of Canada. T h e p u r p o s e w a s t o p r o v i d e a b e t t e r u n d e r s t a n d i n g of t h e b e h a v i o u r of m e t a l s and m e t a l c o a t i n g s e x p o s e d f o r long d u r a t i o n s in v a r i o u s a r e a s of Canada. T h e e x p o s u r e s i t e s u s e d w e r e s e t up a n d

o p e r a t e d by t h e Division of Building R e s e a r c h of t h e Council. T h e f i r s t g r o u p of m e t a l s e x p o s e d , in a d d i t i o n t o t h e t h r e e s t r u c t u r a l s t e e l s b e i n g r e p o r t e d on a t t h i s t i m e , included s p e c i n l e n s oi a l u i n i n u m , and

r i v e t t e d g a l v a n i c c o u p l e s of 3 s a l u m i n u m a l l o y t o c o p p e r , zinc a n d s t e e l , t h r c e s t a i n l e s s s tee1 a l l o y s , two magnesiurm al.1 oys, r o l i e d zinc, two l e a d a l l o y s , m o n e l c o p p e r and m u n t z m e t a l . T h e s t e e l s p e c i n l e n s w e r e i u r n i s h e d by t h e S t e e l C o m p a n y of C a n a d a L i m i t e d anci w e r e s e t out f o r e x p o s u r e in 1953. T h i s r e p o r t d e s c r i b e s t h e 1 0 - y e a r p c r f o r - m a n c e of t h e s e m a t e r i a l s and g i v e s a b r i e f d e s c r i p t i o n of the t e s t i n g p r o c e d u r e a n d t e s t i n g s i t e s . A m o r e d e t a i l e d d e s c r i p t i o n of t e s t i n g p r o c e d u r e a n d c o r r o s i o n s i t e s w a s p u b l i s h e d e a r l i e r (1, 2 , 3, 4 ) . TESTING P R O C E D U R E FOR S T E E L M A T E R I A L S T h e s t e e l m a t e r i a l s , f r o m n o r m a l p r o d u c ion, had b e e n h o t r o l l e d and pickled. The pickling o p e r a t i o n w a s p e r l o r n l e c i on a con- t i n u o u s s u l p h u r i c a c i d p i c k l i n g line. Then 4-in. by

6-32,

s a m p l e s w e r e s h e a r e d off, identified by d r i l l i n g 1 / 8 in. h o l e s t h r o u g h t h e s a m p l e s , a n d

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weighed on an a n a l y t i c a l b a l a n c e p r i o r to s h i p m e n t to t h e i r a p p r o - p r i a t e e x p o s u r e site.

E a c h m a t e r i a l was exposed in t r i p l i c a t e f o r p e r i o d s of one, two, f i v e and ten y e a r s a t each c o r r o s i o n s i t e on s p e c i a l l y con-

s t r u c t e d f r a m e s which held the s a m p l e s in p l a c e with p o r c e l a i n i n s u l a t o r s a t 30" to the h o r i z o n t a l and facing due south.

After completing the p r e s c r i b e d e x p o s u r e p e r i o d the s a m p l e s w e r e photographed, d e s c a l e d and reweighed. S e s c a l i n g was a c c o m p l i s h e d in a molten c a u s t i c bath containing 1 t o 2 p e r c e n t s o d i u m hydride. One t e n - y e a r s a m p l e of e a c h s t e e l composition was withheld f o r m i c r o s c o p i c examination.

TEST SITES

Seven t e s t s i t e s of the National R e s e a r c h Council and

one s i t e of Consolidated Mining and Smelting Company of Canada, Limited, n e a r T r a i l w e r e u s e d f o r t h e s e e x p o s u r e s . A b r i e f d e s c r i p t i o n of the location and c l a s s i f i c a t i o n of e a c h s i t e follows.

S i t e No. 1, Ottawa

-

T h i s s i t e i s l o c a t e d on the e a s t e r l y c i t y l i m i t s and c a n be c l a s s i f i e d a s s e m i - r u r a l .

S i t e No. 2, Saskatoon

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T h i s i s a r u r a l s i t e located on the c a m p u s of t h e Univ.ersity of Saskatchewan on t h e o u t s k i r t s of Saskatoon.

S i t e No. 3, M o n t r e a l

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T h i s is a n i n d u s t r i a l s i t e located on t h e roof of a CNR S t o r e s building in the P o i n t St. C h a r l e s d i s t r i c t .

S i t e No. 4, Halifax

-

This i s a m a r i n e - i n d u s t r i a l s i t e l o c a t e d on the roof of a F e d e r a l Public building in t h e downtown a r e a , two c i t y b l o c k s f r o m the h a r b o u r .

S i t e No. 5, York Redoubt

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This i s a r u r a l - m a r i n e site, located a p p r o x - i m a t e l y 7 m i l e s f r o m Halifax. I t i s a t an elevation of about 100 f t and 300 f t f r o m t h e ocean.

S i t e No.

6,

N o r m a n Wells

-

This i s a f a r n o r t h e r n s i t e located in t h e M a c k e n z i e R i v e r Valley a p p r o x i m a t e l y 9 0 m i l e s south of t h e A r c t i c C i r c l e .

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S i t e No. 7, E s q u i m a l t , B, C.

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T h i s i s a r u r a l - m a r i n e s i t e l o c a t e d a t t h e s o u t h e a s t e x t r e m i t y of Vancouver Island, 15 m i l e s f r o m t h e c i t y of V i c t o r i a . I t is a t a n e l e v a t i o n of 50 f t a n d a p p r o x i m a t e l y 1500 f t f r o m t h e ocean. S i t e No. 8, T r a i l , B. C.

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T h i s i s a s e m i - r u r a l s i t e l o c a t e d a t B i r c h b a n k i n t h e C o l u m b i a R i v e r Valley

6

m i l e s n o r t h of t h e c i t y of T r a i l , I n a d d i t l o n t o m e t e o r o l o g i c a l d a t a a v a i l a b l e f r o m D e p a r t m e n t of T r a n s p o r t w e a t h e r s t a t i o n s n e a r t h e s i t e s , t h e s u l p h u r d i o x i d e (SO ) c o n t e n t of t h e a t m o s p h e r e w a s d e t e r m i n e d , u s i n g t h e l e a d 2 p e r o x i d e m e t h o d . T h i s m e t h o d d o e s n o t m e a s u r e t h e v o i u m e t r l c c o n - c e n t r a t i o n of SO2 i n t h e a t m o s p h e r e d i r e c t l y , b u t p r e s e n t s an i n t e g r a t e d m e a s u r e of t h e SO ' ' a c t i v i t y " d u r i n g a p e r i o d o l e x p o s u r e . I t was found 2 t h a t t h i s i n s t r u m e n t w a s well s u i t e d to m e a s u r e t h e r e l a t l v e l e v e l s of SO2 a t t h e e x p o s u r e s i t e s when m e t a l s a r e u n d e r t e s t . T h e m e a s u r e - m e n t s w e r e m a d e on a m o n t h l y b a s i s a t e a c h s i t e . T h e r e s u l t s h a v e b e e n c o n d e n s e d a n d t h e a v e r a g c l e v e l s d u r i n g t h e t e n - y e a r e x p o s u r e of t h e s t e e l s p e c i m e n s a r e given in T a b l e I. F i g u r e 1 i s a g r a p h i c a l r e - p r e s e n t a t i o n of t h e a v e r a g e c o n c e n t r a t i o n of SO a t e a c h t e s t s i t e . 2 The A. S. T . M . c o r r o s i v e n e s s i n d e x (5,

6)

w a s d e r i v e d b y ex;)tislng : r ~ i ? r l s t e e l s a m p l e s a t s i t e s a c r o s s C a n a d a a n d U. S , A., n l e a s u r j n g t h e m a g n i t u d e of c o r r o s i o n p r o d u c t s lorme,cl a f t e r a s i \ - e n t i m e on e a c h s a m p l e a n d e x p r e s s i n g t h e a m o u n t of c o r r o s i o n ~ v i t h r e l a t i o n t o s i m i l a r s a m p l e s e x p o s e d a t S t a t e College, Pa., v:hich w e r e taken a s b e i n g unity. T h e A.S. T.M. i n d i z c ~ s f o r the s i t e s u s e d in t h i s p r o g r a m m e a r e a s follows: H a l i f a x ( m a r i n e - i n d u s t r i a l ) H a l i f a x ( m a r i n e - r u r a l ) M o n t r e a l T r a i l Ottawa

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S a s k a t o o n

-

0.

6

N o r m a n Wells

-

0. 03

As a n e x a m p l e , the i n d i c e s show t h a t Halifax ( m a r in e - i n d u s t r i a l ) i s

127 t i m e s m o r e c o r r o s i v e than N o r m a n Wells a f t e r one y e a r of e x p o s u r e .

MATERIALS T E S T E D

S t e e l s of t h r e e c o m p o s i t i o n s w e r e s e l e c t e d and g r o u p e d a s low carbon, low c a r b o n c o p p e r - b e a r i n g , a n d low a l l o y c o p p e r - n i c k e l - b e a r i n g . T h e s e s t e e l s w e r e d e s i g n a t e d a s A3, Aq, a n d A5, r e s p e c t i v e l y .

T a b l e I 1 g i v e s t h e c h e m i c a l c o m p o s i t i o n of t h e s e t h r e e s t e e l s .

RESULTS

T h e r e s u l t s of the c o m p l e t e t e n - y e a r t e s t p e r i o d f o r t n e t h r e e s t e e l m a t e r i a l s h a v e been c o m p i l e d in t h e Appendix. The weight l o s s , c o r r o s i o n r a t e , and t h i c k n e s s l o s s v a l u e s a r e inciuded.

B a r g r a p h s showing the c o r r o s i o n r a t e s a f t e r e a c h

c o r r o s i o n p e r i o d f o r the s t e e l m a t e r i a l a t t h e e i g h t c o r r o s i o n s i t e s a r e shown in F i g u r e 2. C o r r o s i o n r a t e s h a v e d e c r e a s e d s i g n i f i c a n t l y on a l l the s t e e l s a t all c o r r o s i o n s i t e s e x c e p t N o r m a l Wells, w h e r e t h e a m o u n t of c o r r o s i o n even a f t e r ten y e a r s i s v e r y s m a l l .

C o r r o s i o n v s , t i m e g r a p h s f o r t h e t h r e e s t e e l s at e a c h t e s t s i t e a r e shown m F i g u r e

3.

S a n l p l e s e x p o s e d a t t h e Halifax : m a r m e - i n d u s t r i a l s i t e s u f f e r e d t h e g r e a t e s t a m o u n t of c o r r o s i o n and t h o s e a t N o r m a n W e l l s the l e a s t . T h e c o r r o s i o n r a t e c u r v e s of t h e i o x ~ c a r b o n and low c a r b o n c o p p e r - b e a r i n g m a t e r i a l s show only a s l i g h t d i f f e r e n c e in c o r r o s i o n r a t e s a t e a c h of the eight t e s t s i t e s .

F i g u r e s 4,

5,

and

6

show t h e c o r r o s i o n r a t e c u r v e s of e a c h type of s t e e l a t t h e e i g h t c o r r o s i o n s i t e s . At t h e enci of the t e n - y e a r period, t h e s l o p e of t h e c u r v e s f o r t h e t h r e e m a r i n e s i t e s is s t e e p e r than t h a t f o r the o t h e r s i t e s . T h e c u r v e s f o r t h e low c a r b o n and the c o p p e r - b e a r i n g s t e e l s a t t h e Ottawa s i t e do n o t follow t h e s a m e p a t t e r n a s t h o s e f o r the o t h e r n o n - m a r i n e s i t e s . T h i s s i t e m a y have u n d e r g o n e a change in c o r r o s i v e n e s s d u r i n g the t e s t p e r i o d .

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T a b l e I11 g i v e s t h e a v e r a g e c o r r o s i o n r a t e in m i l s p e r y e a r b e t w e e n t h e fifth and t e n t h y e a r f o r t h e t h r e e s t e e l m a t e r i a l s . T h e a v e r a g e c o r r o s i o n r a t e f o r the c o p p e r - n i c k e l s t e e l a t S a s k a t o o n i s o m i t t e d f r o m T a b l e I11 a s a n e g a t i v e r e s u l t w a s i n d i c a t e d ; h o w e v e r , f r o m t h e v a l u e s f o r t h e o t h e r two m a t e r i a l s t h e c o r r o s i o n r a t e e x p e c t e d would b e l e s s t h a n 0.01

8

r n i l s p e r y e a r . Weight l o s s r e s u l t s m a y n o t i n d i c a t e t h e e x t e n t of l o c a l i z e d pitting; f o r t h i s r e a s o n v i s u a l examinatiol-1 of d e s c a l e d s a m p l e s w a s u n d e r t a k e n . E x a m i n a t i o n showed t h a t c o r r o s i o n h a d o c c u r r e d u n i f o r m l y o v e r t h e e n t i r e s u r f a c e with t h e u n d e r s u r f a c e a t t a c k e d m o r e s e v e r e l y t h a n t h e u p w a r d s u r f a c e ( 7 ) . No e x c e s s i v e pitting w a s n o t e d a t a n y of t h e e d g e s . R e s u l t s frorrl v i s u a l e x a m i n a t i o n c o n f i r m t h e w e i g h t l o s s r e s u l t s a s to e x t e n t of c o r r o s i o n . F i g u r e 7 shosvs t h e d e s c a l e d u p - w a r d s u r f a c e of t h e c o p p e r - n i c k e l - b e a r i n g s t e e l f r o m t h e v a r i o u s c o r

-

r o s i o n s i t e s . T h e c r o s s - s e c t i o n s of t h e c o r r o d e d s t e e l s a m p l e s t a k e n f r o m t h e N o r m a n W e l l s , Ottawa a n d H a l i f a x m a r i n e - i n d u s t r i a l s i t e s a f t e r t e n y e a r s of e x p o s u r e a r e shown in F i g u r e s 8 , 9, a n d 10. T h e s e t h r e e s i t e s r e p r e s e n t t h e r a n g e of c o r r o s i o n e n c o u n t e r e d in t h i s p r o - g r a m m e . V e r y l i t t l e c o r r o s i o n h a s t a k e n p l a c e on a n y 01 t h e s a m p l e s f r o m N o r m a n W e l l s ( F i g u r e 8), a l t h o u g h i t i s e v i d e n t t h a t t h e lolver e x p o s e d s u r - f a c e h a s b e e n a t t a c k e d t n o r e s e v e r e l y t h a n t h e u p p e r e x p o s e d s u r i a c e . Tli.:, a m o u n t of c o r r o s i o n on t h e Ottawa s a m p l e s ( F i g u r e 9 ) i s c o n s i d e r

-

a i ~ l y trlorc t h a n 'chat on the s a m p l e s f r o m N o r m a n W e l l s . T h e low c a r b o n and low c a r b o n c o p p e r - b e a r i n g m a t e r i a l s h a v e c o r r o d e d m o r e t h a n t h e c o p p e r - n i c k e l - b e a r i n g m a t e r i a l . T h e m e t a l s u r f a c e s h a v e b e c o m e p i t t e d , c a u s i n g s o m e l o c a l d e c r e a s e in c r o s s - s e c t i o n .

F i g u r e 10 s h o w s t h e sn3cjunt of c o r r o s i o n a t the H a i i i a x m a r i n e - i n d u s t r i a l s i t e a f t e r t e n y e a r s of e x p o s u r e . T h e c r o s s - s e c t i o n s of the low c a r b o n and low c a r b o n c o p p e r - b e a r i n g s t e e l s f r o r n t h i s s i t e i l l u s t r a t e t h e c o n s i d e r a b l e r e d u c t i o n in t h i c k n e s s o f t h e s e s a n l p l e s c o m p a r e d with t h o s e e x p o s e d a t t h e o t h e r two site:; ( F i g u r e s 8 a n d 9 ) . Comparing the c o p p e r - n i c k e l - b e a r i n g s t e e l e x p o s e d a t H a l i f a x m a r i n e - indl.istria1 s i t e with t h e o t h e r two s i t e s ( F i g u r e s 6 anrl 9 ) it i s o b v i o u s t h a t c o n s i d r : r a b l e pitting h a s o c c u r r e d b u t t h e t h i c k n e s s of tn:s r i ~ a t e r i a l h a s n o t d e c r e a s e d n e a r l y a s m u c h a s t h e t h i c k n e s s of tht: iow c a r n o n o r lolv c a r b o n c o p p e r - b e a r i n g m a t e r i a l s .

(9)

DISCUSSION

The c o r r o s i o n r a t e c u r v c s f o r t h e low c a r b o n a n d the low c a r b o n c o p p e r - b e a r i n g m a t e r i a l s show only a s l i g h t d i f f e r e n c e in r a t e s a t e a c h of t h e e i g h t t e s t s i t e s . T h e c h e m i c a l c o m p o s i t i o n of the two m a t e r i a l s i s v e r y s i m i l a r e x c e p t t h a t t h e low c a r b o n m a t e r i a l c o n - t a i n s 0.090 p e r c e n t c o p p e r a n d t h e low c a r b o n c o p p e r - b e a r i n g m a t e r i a l c o n t a i n s 0.205 p e r c e n t c o p p e r . D.M. Buck found a t t h e t u r n of the c e n t u r y t h a t s m a l l a d d i t i o n s of c o p p e r g r e a t l y influt,nit-cl the c o r r o s i o n r e s i s t a n c e of s t e e l . T h e m o r e r e c e n t w o r k s of Hudson a n d S t a n n e r s

( 8 )

a n d L a r a b e e and C o b u r n

( 9 )

s u b s t a n t i a t e t h e s e e a r l i e r f i n d i n g s . L a r r a b e e and C o b u r n found t h a t t h e g r e a t e s t c h a n g e s in c o r r o s i o n with s m a l l c h a n g e s i n c o p p e r c o n t e n t a r e c a u s e d by a n i n c r e a s e i n c o p p e r f r o m 0 . 0 1 t o 0.04 p e r cent. T h i s c h a n g e w a s found t o d e c r e a s e t h e t h i c k n e s s l o s s by c o r r o s i o n t o a p p r o x i m a t e l y 2 0 m i l s o v e r a 1 5 . 5 - y e a r p e r i o d a t K e a r n y , N. J. I n c r e a s i n g t h e c o p p e r c o n t e n t f r o m 0.10 t o 0 . 2 4 p e r c e n t only d e c r e a s e d t h e c o r r o s i o n l o s s by a b o u t 1 . 9 m i l s o v e r t h e s a m e p e r i o d . Evidently, t h e r e s i d u a l c o p p e r p r e s e n t in t h e low c a r b o n s t e e l w a s s u f f i c i e n t to c a u s e i t to b e h a v e in a s i m i l a r m a n n e r to a c o p p e r - b e a r i n g s t e e l . A low c a r b o n s t e e l without r e s i d u a l c o p p e r would be e x p e c t e d t o h a v e a h i g h e r c o r r o s i o n r a t e t h a n t h e m a t e r i a l t e s t e d . C o r r o s i o n r a t e v s . t i m e c u r v e s show t h a t t h e m e t a l l o s s d e c r e a s e d rapicily o v e r thc f i r s t two y e a r s , a n d then a p p r o a c h e d a m o r e c o n s t a n t r a t e w i t h i l l c r e a s i n g t i m e . T h e s l o p e of t h e c o r r o s i o n t i i n e c u r v e b c t w c e n t h e f i f t h and t e n t h y e a r i n d i c a t e s t h e e f f e c t i v e n e s s of t h e c o r r o s i o n l a y e r in p r o t e c t i n g thc st.eel f r o m f u r t h e r c o r r o s i o n (7, 10). T h e c o p p e r - n i c k e l - b e a r i n g s t e e l i o r r i ? e d a p r o t e c t i v e f i l m which k e p t t h e c o r r o s i o n r a t e a f t e r five y e a r s t o q u i t e low v a l u e s , e s p e c i a l l y in r u r a l a n d i n d u s t r i a l a t m o s p h e r e s . A s m a y b e e x p e c t e d , the t h r e e m a r i n e l o c a t i o n s h a v e t h e h i g h e s t c o r r o s i o n r a t e s b e t w e e n t h e f i f t h and tenth y e a r ; i n d i - c a t i n g t h a t c o r r o s i o n p r o d u c t s f o r m e d in c h l o r i d e a t r l l o s p h e r e s o f f e r l e s s p r o t e c t i o n t h a n t h o s e f o r m e d in o t h e r e n v i r o n m e n t s . T h e h i g h e s t c o r r o s i o n r a t e f o r t h e coppe:--nicrkel-bearing s t e e l b e t w e e n t h e fifth a n d tenth y e a r w a s only

(1.28

rrij1.s a y e a r , c o m p a r e d with 2.72 m i l s a y e a r f o r t h e sarlle m a t e r i a l . a n d l o c a t i o n a f t e r t h e f i r s t y c a r of e x p o s u r e . T h i s w a s a l-l~arirl;: s i t e ; t h e r u r a l and i n d u s t r i a l s i t e s had c o n s i d e r a b l y l o w e r v a l u e s .

(10)

T h e c o r r o s i o n r a t e s on t h e low c a r b o n a n d low c a r b o n c o p p e r - b e a r i n g m a t e r i a l h a v e d e c l i n e d c o n s i d e r a b l y when c o m p a r e d t o the r a t e s d u r i n g i n i t i a l y e a r s ; h o w e v e r , t h e r a t e s f o r t h e s e s t e e l s s t i l l r e m a i n c o n s i d e r a b l y h i g h e r t h a n t h o s e f o r t h e c o p p e r - n i c k e l - b e a r i n g s t e e l . T h e s u p e r i o r c o r r o s i o n r e s i s t a n c e of t h e c o p p e r - n i c k e l - b e a r i n g s t e e l is c l e a r l y e v i d e n t when F i g u r e s 7 and

9

a r e c o m p a r e d . CONCLUSIONS 1. A f t e r t h e i n i t i a l y e a r s of e x p o s u r e , c o r r o s i o n r a t e s d e c r e a s e d s i g n i f i c a n t l y f o r a l l s t c e l m a t e r i a l s a t e v e r y c o r r o s i o n s i t e e x c e p t N o r m a n Wells, w h e r e t h e c o r r o s i o n r a t e s w e r e low e v e n f r o m t h e s t a r t of the t e s t s . 2. T h e r e s i d u a l c o p p e r c o n t e n t of t h e low c a r b o n s t e e l m a t e r i a l w a s s u f f i c i e n t t o d e c r e a s e i t s c o r r o s i o n r a t e . 3 . T h e c o p p e r - n i c k e l - b e a r i n g s t e e l f o r m e d a n a d h e r e n t , p r o t e c t i v e o x i d e f i l m which m a i n t a i n e d t h e c o r r o s i o n r a t e s a t low v a l u e s a f t e r f i v e y e a r s 1 e x p o s u r e . T h i s w a s p a r t i c u l a r l y n o t i c e a b l e a t t h e r u r a l a n d i n d u s t r i a l s i t e s , 4. The t h r e e m a r i n e l o c a t i o n s h a v e t h e h i g h e s t c o r r o s i o n r a t e s b e t w e e n t h e fifth and t e n t h y e a r . 5. The c o r r o s i o n p r o d u c t f o r m e d u n i f o r n l l y o v e r the s u r f a c e s of a l l s a m p l e s , but thc l o w e r e x p o s e d s u r f a c e s w e r e a t t a c k c d m o r e s e v e r e l y t h a n t h e u p p e r e x p o s e d s u r f a c e s . R E F E R E N C E S 1. Gibbons,

E.

V. A s s o c i a t c ConlmitCee on C o r r o s i o n R e s e a r c h a n d P r e v e n t i o n S u b - C o m r n ~ t t e e C , "The C o r r o s i o n Behaviour of M a j o r A I - c h i t e c t u r a l a n d S t r u c ~ u r a l M e t a l s in C a n a d i a n A t n i o s p h e r e s : Surnrnar y of Two- y e a r R e s u l t s , National R e s e a r c h Councll,

Ottawa, F e b r u a r y 19 59.

2. Gibbons, E. V. C o r r o s i o n 17, " A t r n o s p h e r i c C o r r o s i o n T e s t i n g 01 M e t a l s in Canada!' (19 6 1 j, ! ! 8t - 32Ot.

(11)

3. F o r a n ,

M.

R., Gibbons, E. V., a n d Wellington, J. R. " T h e M e a s u r e m e n t of A t m o s p h e r i c S u l p h u r Dioxide a n d C h l o r i d e s ; ' C h e m i s t r y in Canada, 10, (19 58), p. 3 3 -41. 4. Gibbons,

E.

V. "Outdoor E x p o s u r e S i t e s of t h e N a t i o n a l R e s e a r c h Council1' C h e m i s t r y i n Canada, 12, (1960), p.44-48. 5. L a r r a b e e , C. P. a n d E l l i s , 0 . B. I 1 P r o g r e s s r e p o r t of s u b g r o u p of S u b c o m m i t t e e VII, on c o r r o s i v e n e s s of variou:; a t m o s p h e r i c t e s t s i t e s a s m e a s u r e d by s p e c i m e n s of s t e e l and z i n c , A, S. T. M e P r o c e e d i n g s 53, (1953), p. 194-197. 6. L a r r a b e e , C. P. and E l l i s , 0, B. " R e p o r t of s u b g r o u p of S u b c o m m i t t e e VII, on c o r r o s i v e n e s s of v a r i o u s a t m o s p h e r i c t e s t s i t e s a s m e a s u r e d by s p e c i m e n s of s t e e l a n d zinc. A . S . T.M. P r o c e e d i n g s 59, (1959), p. 183-201.

7. Copson, H. R. I 1 T h e o r y of M e c h a n i s m of R u s t i n g of Low Alloy S t e e l s in ~ t m o s ~ h e r e : ' A. S.

T.

M., P r o c e e d i n g s , 45, (1945), p554-580.

8. Hudson,

J.

C. a n d S t a n n e r s , J. F. J o u r n a l I r o n a n d Steel, 180, (1955), p. 271-284.

9. L a r r a b e e , C.

P.

a n d Coburn, S. K. F i r s t I n t e r n a t i o n a l C o n g r e s s on M e t a l l i c C o r r o s i o n , London, B u t t e r wor th' s S c i . Publ. ( 1 9 62), p. 276-285.

10. Copson, H. R. t'Long-Ti:ne A t m o s p h e r i c C o r r o s i o n of Low-Alloy S t e e l s ,

"

A . S . T . M . P r o c e e d i n g s , 60, (1960), p.650-665.

(12)

T A B L E I

AVERAGE AMOUNT O F SULPHUR DIOXIDE I N T H E ATMOSPHERE

AT EACH T E S T S I T E FROM 1 9 5 4 - 19 64 S i t e No. L o c a t i o n MgSO / d m 2 / d a y 3 Halifax M o n t r e a l T r a i l Ottawa Y o r k Redoubt S a s k a t o o n E s quimalt N o r m a n W e l l s

(13)

T A B L E I 1 C H E M I C A L C O M P O S I T I O N O F T H E S T E E L S T E S T E D L o w c a r b o n ( A 3 0 . 0 9 0 0 . 2 9 0 . 0 0 2 0 . 0 6 4 0. 0 1 3

-

0. 035 L o w c a r b o n c o p p e r - b e a r i n g ( A 4 ) 0 . 2 0 5 0 . 3 2 0 . 0 0 2 0. 060 0 . 0 1 4

-

0 . 0 4 8 L o w a l l o y c o p p e r - n i c k e l - b e a r i n g ( A 5 ) 0 . 7 3 8 0 . 7 8 0 . 0 2 1 0 . 1 2 4 . 0 . 0 9 5 0 . 6 8 0 0 , 0 3 2 T A B L E 111 A V E R A G E M I L S P E R YEAR P E N E T R A T I O h T B E T W E E N F I F T H A N D T E N T H Y E A R S a s k a - M o n - H a l i - H a l i - N o r m a n E s q u i - M . a t e r i a l O t t a w a t o o n t r e a l fax** f a x * W e l l s m a l t T r a i l - L o w c a r b o n ( A 3 ) 0 . 2 9 4 0 . 0 1 8 0. 1 3 0 1. 3 3 6 0 . 4 5 8 0. 042 0 . 2 0 0 0. 1 2 0 L o w c a r b o n c o p p e r - b e a r i n g ( A 4 ) 0 . 2 8 2 0. 0 1 8 0. 142 1. 1 6 2 0 . 4 7 0 0. 032 0 . 1 9 2 0 . 0 8 6 L o w a l l o y c o p p e r - n i c k e l - b e a r ing ( A 5 ) 0 . 1 0 6

-

0 . 0 4 6 0 . 2 8 0 0. 1 8 6 0 . 0 2 2 0. 1 2 4 0 . 0 2 0 L*. -E m a r i n e - i n d u s t r i a l

**

m a r i n e - r u r a l

(14)

F I G U R E

1 A V E R A G E A M O U N T O F S U L P H U R D I O X I D E I N T H E A T M O S P H E R E

A T E A C H T E S T S I T E F R O M 1 9 5 4 - 1 9 6 4

(15)

ATMOSPHERIC CORROSION RATES FOR THREE TYPES OF STEEL

A 3

Low Carbon

Steel

I

Year Exposure

A 4

Copper Bearing

Steel

U

2 Years Exposure

A 5

Copper

-

Nickel Bearing

Steel

B€l

5

yea^

Exposure

10 Years Exposure

OTTAWA

SASKATOON

MONTREAL

HALIFAX

MAR1 N

E

l

NDUSTRlAL

(16)

ATMOSPHERIC CORROSION RATES FOR THREE TYPES OF STEEL

HALIFAX MAR1 NE RURAL

ESOU

IMALT

i

1 i

--+

.--..--I---+

I

'

4.-.-

I

j

! I

I

I &---

4.-

1

i

_I I

_I

I 1 I 1

NORMAN WELLS

TRAIL

FIG

2 (Cont'd)

I "._ ___._"I__

_

-

-- -- -- -.--

(17)

CORROSION

VS TIME CURVES

FOR

THREE TYPES OF STEEL

o

Low Carbon Steel

Copper Bearing Steel

@

Copper -Nickel Bearing Steel

NORMAN

WELLS

SASKATOON

0

2

4

6

8

10

0

2

4

6

8 1 0

Time. years

Time ,years

0

2

4

6

8

10 Time, years

MONTREAL

Time ,years

(18)

CORROSION VS

TIME

CURVES

FOR THREE TYPES OF S T E E L

OTTAWA

TRAIL

"0

2

4

6

8

10 Time, years

"0

2-

4 6 8

10 Time,

years

HALIFAX MARINE RURAL

HALLFAX

MAR1

N

E

l NDUSTRIAL

-0

2

4

6

8

10 Time,

years

-0

2

4

6

8 1 0

Time,

years

(19)

CORROSION VS

TIME CURVES FOR

LOW

CARBON

STEEL AT VARIOUS CANADIAN CORROSION SITES

0

1

2

3

4

5

6

7

8

9 1 0

Time,

years

(20)

CORROSION VS TIME CURVES FOR COPPER

BEARING S T E E L AT VARIOUS

CANADIAN

CORROSION SITES

0

0 '1

2

3

4

5

6 Time,

years

(21)

CORROSION

VS

TIME

CURVES FOR COPPER-

NICKEL BEARING STEEL AT

VARIOUS CANADIAN

CORROSION

SITES

-

. O

1

2

3

4

5

6

7

8

9

10 Time, years

(22)

Ottawa

M o n t r e a l (31 Halifax (Marine Industrial)

($1

Mag.

IX

(23)

Halifax (Marine R u r a l ) ( 5 ) Norman W e l l s

6)

Trail (8)

Mag.

lX

(24)

Steel material exposed ten years

at Norman W e l l s Mag. 18%

(25)

Steel material exposed ten

years at Ottawa M a g .

10X

(26)

Steel material exposed ten y e a r s

at

Kalidax

(marine indue tr ial)

Mag.

POX

(27)

APPENDIX

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