Atmospheric corrosion behaviour of stainless steels in eight Canadian atmospheres: summary of ten years' results

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Atmospheric corrosion behaviour of stainless steels in eight Canadian

atmospheres: summary of ten years' results

NATIONAL RESEARCH COUNCIL CANADA

DIVISION O F BUILDING RESEARCH

ATMOSPHERIC CORROSION BEHAVIOUR O F STAINLESS S T E E L S IN EIGHT CANADIAN ATMOSPHERES

- -

SUMMARY

O F T E N YEARS' RESULTS

R. J. C. MacDonald, Atlas S t e e l s Company, Welland, O n t a r i o and

E. V. Gibbons, Division of Building R e s e a r c h , National R e s e a r c h Council, Ottawa, O n t a r i o

A joint r e p o r t of the Atlas S t e e l s Company and

the Division of Building R e s e a r c h , National R e s e a r c h Council

I n t e r n a l R e p o r t No. 331 of the

Division of Building R e s e a r c h

OTTAWA J u l y 1966

P R E FA CE

A study was undertaken by the NRC A s s o c i a t e Committee 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 to obtain i n f o r m a t i o n on the a t m o s p h e r i c c o r r o s i o n behaviour of different a r c h i t e c t u r a l m e t a l s a t v a r i o u s locations a c r o s s Canada. The f i r s t group of m e t a l s w a s s e l e c t e d f o r e x p o s u r e i n 1953. Although i n f o r m a t i o n of t h i s n a t u r e is frequently needed f o r design and maintenance p u r p o s e s no s u c h s i m i l a r c o - o p e r a t i v e study had b e e n p r e v i o u s l y undertaken in Canada which involved the 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 organizations.

T h e s p e c i m e n s of the different m e t a l s w e r e exposed a t eight outdoor s i t e s a c r o s s Canada. T h e o v e r - a l l p r o g r a m included s e v e r a l metal and o r g a n i c coatings applied to s t e e l s u b s t r a t e s . T h i s r e p o r t d e s c r i b e s the 1 0 - y e a r p e r f o r m a n c e a t the d i f f e r e n t s i t e s of t h r e e s t a i n l e s s s t e e l s . One r e p o r t h a s a l r e a d y b e e n i s s u e d that d e s c r i b e s the p e r f o r m a n c e of t h r e e aluminum a l l o y s and

aluminum b i m e t a l l i c couples. Other r e p o r t s covering the 10 - y e a r r e s u l t s on other m e t a l s will be i s s u e d l a t e r .

T h e s p e c i m e n s of s t a i n l e s s s t e e l w e r e f u r n i s h e d by the Atlas S t e e l s Company, Welland, 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 sing t h e i r p e r f o r m a n c e and compiling t h i s r e p o r t . T h i s p a r t of the study w a s under the d i r e c t i o n of D r . R. Osadchuk with the a s s i s t a n c e of Mr. R. J. C. MacDonald. T h e a r r a n g e m e n t s f o r e x p o s u r e and examination of s p e c i m e n s , and s o m e o v e r

-

a l l

coordination of the p r o g r a m w e r e c a r r i e d out under the d i r e c t i o n of Mr. E. V. Gibbons of the Division of Building R e s e a r c h .

T h e Division is indebted not only to the Companies who have c o - o p e r a t e d i n making this study p o s s i b l e , but a l s o to those who have contributed i n the provision and s e r v i c i n g of c e r t a i n

e x p o s u r e s i t e s . Ottawa

July 1966

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

ATMOSPHERIC CORROSION BEHAVIOUR O F STAINLESS STEELS IN EIGHT CANADIAN ATMOSPHERES

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SUMMARY

O F TEN YEARS' RESULTS

R. J. C. MacDonald, ~ t l a s S t e e l s Company, Welland, O n t a r i o and

E. V. Gibbons, Division of Building R e s e a r c h , National R e s e a r c h Council, Ottawa, Ontario

This work was initiated i n 1953 by the A s s o c i a t e Committee on Corrosion R e s e a r c h and P r e v e n t i o n (A. C. C. R. P. ) of the National R e s e a r c h Council ( N. R. C. ) with the objective of obtaining r e l a t i v e a t m o s p h e r e c o r r o s i o n r e s u l t s f o r various m e t a l s in typical Canadian a t m o s p h e r e s . Details of the p r o g r a m w e r e planned by Sub-committee "C" of the A. C. C. R. P. and c a r r i e d out a t the outdoor exposure s i t e s o p e r a t e d by the Division of Building R e s e a r c h of N. R. C.. Atlas S t e e l s Company, being the m a j o r s t a i n l e s s s t e e l p r o d u c e r in Canada, p a r t i c i p a t e d i n this p r o g r a m by s e l e c t i n g and supplying the s t a i n l e s s s tee1 s p e c i m e n s used.

T r i p l i c a t e s h e e t panels of the following m e t a l s and alloys w e r e included i n the f i r s t group selected. They have been exposed a t eight s i t e s a c r o s s Canada for f o u r different t i m e p e r i o d s : ! Aluminum Alloys (supplied by Aluminium L a b o r a t o r i e s Limited)

( a ) Alcan 3 s - H - 1 4 (b) Alcan 57s-H- 34 ( c ) Alcan 6 5 s - T - 6

(d) Alcan 3 s - H - 1 4 aluminum alloy r i v e t e d to c o p p e r , zinc o r mild s t e e l with 2 s r i v e t s .

2. S t e e l Alloys (supplied by Steel Company of Canada Limited) ( a ) Low alloy r e s i d u a l

( b ) C o p p e r b e a r i n g ( c ) Copper -nickel alloy

3. S t a i n l e s s S t e e l Alloys (supplied by Atlas S t e e l s Company) ( a ) Type 302

(b) Type 316 ( c ) Type 430

4 . Magnesium Alloys (supplied by Dominion Magnesium Limited) ( a ) AZ80X alloy

( b ) ZK61X alloy

5. Rolled Zinc (supplied by Consolidated Mining and Smelting Company of Canada Limited)

The a t m o s p h e r i c e x p o s u r e s i t e s w e r e : S i t e No. 1 Location Ottawa, O n t a r i o 2 Saskatoon, Saskatchewan 3 Montreal, Quebec 4 Halifax, Nova Scotia

5 York Redoubt, Nova Scotia

6

N o r m a n Wells, Northwest T e r r i t o r i e s

7 E s q u i m a l t , B r i t i s h Columbia 8 T r a i l , B r i t i s h Columbia

The panels w e r e r e m o v e d a f t e r one, two, five and t e n y e a r e x p o s u r e t i m e s .

Additional m e t a l s that w e r e s e t out a t the s i t e s i n subsequent y e a r s included s p e c i m e n s of c o p p e r , muntz m e t a l , lead alloys and monel. Also exposed w e r e m e t a l coatings o n s t e e l of s p r a y e d zinc and s p r a y e d aluminum ( s e a l e d and unsealed), aluminized s t e e l , cadmium-plated s t e e l , and four types of

galvanizing. Two s e r i e s of o r g a n i c paint s y s t e m s applied to s tee1 to evaluate different s t e e l p r i m i n g paints have a l s o b e e n exposed. With the paint s y s t e m s i t was the usual p r a c t i c e to

r e - e x p o s e the panels f o r a n additional p e r i o d a f t e r e a c h l a b o r a t o r y examination until f a i l u r e of the coating had o c c u r r e d .

The A. C. C. R. P. was disbanded i n 1960, but the t e s t p r o g r a m was continued through the Division of Building R e s e a r c h . The p e r f o r m a n c e of the different m e t a l s , c o m p r i s i n g the f i r s t group, a f t e r one, two, and five y e a r s of e x p o s u r e have b e e n r e p o r t e d ( 1 , 2 ) . The examination and evaluation of the s t a i n l e s s s t e e l s p e c i m e n s a f t e r e a c h e x p o s u r e period w a s c a r r i e d out by Atlas S t e e l s Company. T h i s r e p o r t s u m m a r i z e s the behaviour of the s t a i n l e s s s t e e l s p e c i m e n s a f t e r ten y e a r s of exposure.

DESCRIPTION O F MATERIAL

T h r e e types of s t a i n l e s s s t e e l s w e r e s e l e c t e d for the p r o g r a m and given the following code designation.

A - 8 - S t a i n l e s s

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302 A-0

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S t a i n l e s s - 316 A-9 - S t a i n l e s s

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430

T h e s e t h r e e types of s t a i n l e s s s t e e l s w e r e s e l e c t e d o v e r the o t h e r numerous types available b e c a u s e they r e p r e s e n t e d the most commonly used g r a d e s for a r c h i t e c t u r a l applications at the t i m e the t e s t p r o g r a m w a s initiated.

In g e n e r a l , s t a i n l e s s s t e e l s c a n be divided into t h r e e g r a d e s based on t h e i r s t r u c t u r e s ; (1) Austenitic ( 2 ) F e r r i t i c and ( 3 ) Mar tensitic. The g e n e r a l c h a r a c t e r i s t i c s of t h e s e g r a d e s a r e a s follows:

1. Austenitic G r a d e s (302, 316)

T h e s e a r e the 18 p e r cent c h r o m e

-

8 p e r cent nickel s t e e l s . Type 302 i s the b a s i c composition g r a d e and i s widely known a s 18-8.

T h e s e g r a d e s c a n be hardened only by cold working; heat t r e a t i n g only tends to soften them. They a r e non-magnetic

i n the annealed condition, but s o m e may become slightly magnetic a f t e r cold working.

The p r o p e r t i e s of t h e s e s t e e l s a r e controlled by the perceritage of c h r o m i u m , nickel, c a r b o n and manganese in

t h e i r a n a l y s i s . Chromium i s the most i m p o r t a n t f a c t o r in d e t e r - mining r e s i s t a n c e to c o r r o s i o n and oxidation. Nickel, c a r b o n , and manganese i n c r e a s e the stability of the austenite s t r u c t u r e .

In g e n e r a l a l l of the 18- 8 types show equally good r e s i s t a n c e to c o r r o s i o n and in m o s t environments the 200 s e r i e s ( c h r o m e , nickel- manganese) have c o m p a r a b l e p r o p e r t i e s .

Type 316 w a s developed a f t e r i t w a s found that 18-8 types pitted and failed in contact with s a l t w a t e r . An addition of 2 to 3 p e r cent molybdenum to the b a s i c 18- 8 a n a l y s i s provided a n a u s t e n i t i c s t e e l with 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 to s e a w a t e r and many o t h e r types of c h e m i c a l c o r r o d e n t s .

2. F e r r i t i c G r a d e s (430)

T h e s e s t a i n l e s s g r a d e s contain c h r o m i u m but no nickel. They can be hardened to s o m e extent by cold working but not by heat t r e a t m e n t . They a r e always magnetic.

Of the f e r r i t i c s t e e l s , type 430 can be used in many applications a l m o s t interchangeably with the a u s t e n i t i c 18- 8 types. T h e f e r r i t i c s t e e l s a r e r e s t r i c t e d , however, to a n a r r o w e r r a n g e of c o r r o s i v e conditions than the austenitic g r a d e s . Among the f e r r i t i c s t e e l s , type 430 h a s the b e s t combination of c o r r o s i o n r e s i s t a n c e , useful mechanical proper t i e s , good formability, and low cost.

3. M a r t e n s i t i c G r a d e s

T h e s e s t a i n l e s s g r a d e s contain c h r o m i u m and with few exceptions no nickel. They c a n be hardened by h e a t t r e a t m e n t and a r e always magnetic. T h e s e s t e e l s develop maximum

c o r r o s i o n r e s i s t a n c e only in the fully h e a t - t r e a t e d condition. S u r f a c e F i n i s h

T h e t h r e e types of s t a i n l e s s s t e e l s t e s t e d in t h i s c o r r o s i o n p r o g r a m had the following s u r f a c e finishes.

Type 302 ( A - 8 ) - 2B Type 316 (A-0) - 2B Type 430 ( A - 9 ) - 4B

T h e s e f i n i s h e s , 2B and 4B, r e p r e s e n t the finishes most frequently used f o r a r c h i t e c t u r a l applications.

It should be noted that a l l t e s t s p e c i m e n s w e r e given a n a i r anneal a s no bright annealing f a c i l i t i e s w e r e available a t that time. Annealing in a n a i r a t m o s p h e r e r e s u l t s i n a c h r o m i u m depletion of the s u r f a c e l a y e r s which a d v e r s e l y affects c o r r o s i o n r e s i s t a n c e . In the c a s e of the type 430

s p e c i m e n s they w e r e given a 4B finish which i s a ground finish. As a r e s u l t the chromium-depleted upper l a y e r s would be removed by grinding thus the type 430 was exposed in i t s most advantageous

F i n i s h 2B i s a m i l l finish which i s applied by cold rolling. It h a s a bright s u r f a c e a p p e a r a n c e and i s g e n e r a l l y used for c u r t a i n walls and i n d u s t r i a l , c o m m e r c i a l , and t r a n s

-

p o r t a t i o n equipment.

F i n i s h 4B i s a mechanically polished finish. It h a s a b r i g h t , l u s t r o u s a p p e a r a n c e and i s the most commonly used f i n i s h f o r a r c h i t e c t u r a l t r i m , and r e s t a u r a n t , kitchen, and

s a n i t a r y equipment. Chemical Analysis

The initial c h e m i c a l analysis of the t h r e e types of s t a i n l e s s s t e e l s tested i s given in the following table. ( T h e s e a n a l y s e s a r e typical of c u r r e n t p r a c t i c e with the possible exception of Type 3 16. The carbon content of Type 316 i s now held to a 0. 08 maximum. T h i s should not influence the p r e s e n t t e s t but would have to be c o n s i d e r e d i f weldments w e r e involved. )

ANALYSIS, PERCENT

E l e m e n t Type 302 Type 430 Type 316 - Mn S i Cr C P Ni S Mo x previously -- 1. 24 0 . 4 3 0.41 0 . 4 1 18.78 16.62 0 . 1 2 0 . 1 1 0.029 0.030 8.6Ox 0 . 7 5 0.018 0.025 0. 23 r e p o r t e d a s 6.80% TEST SITES

A d e s c r i p t i o n of the eight t e s t s i t e s o p e r a t e d by the Division of Building R e s e a r c h f o r the p r o g r a m i s given below:

Site 1 - Ottawa

This s i t e i s located on the e a s t e r n o u t s k i r t s of the City of Ottawa 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 .

Site 2 - Saskatoon

T h i s is a r u r a l s i t e located on the c a m p u s of the U n i v e r s i t y of Saskatchewan on the o u t s k i r t s of Saskatoon. Site Montreal

This is an i n d u s t r i a l s i t e located on the roof of the C. N. R. building in the Point St. C h a r l e s D i s t r i c t .

S i t e 4 - Halifax

T h i s is a m a r i n e - i n d u s t r i a l s i t e located on the roof of the F e d e r a l building i n the downtown a r e a - two blocks f r o m the h a r b o u r .

Site 5 - York Redoubt

T h i s is a r u r a l - m a r i n e s i t e , located on the Atlantic c o a s t approximately s e v e n m i l e s f r o m Halifax. It i s a t a n elevation of 100 f e e t and 300 feet f r o m the ocean.

S i t e 6 - Norman Wells

T h i s is a f a r n o r t h e r n s i t e located in the Mackenzie R i v e r Valley approximately 90 m i l e s south of the A r c t i c C i r c l e . Site 7

-

E s q u i m a l t , B. C. (Rocky Point)

T h i s is a m a r i n e s i t e located o n the s o u t h e a s t e x t r e m i t y of Vancouver Island, about 15 miles f r o m the City of Victoria. It is a t an elevation of 50 f e e t and a p p r o x i m a t e l y

1500 f e e t f r o m the ocean. S i t e 8 - T r a i l , B. C.

T h i s is a s e m i - r u r a l s i t e located a t Birchbank in the Columbia R i v e r Valley s i x m i l e s n o r t h of the City of T r a i l

T h e s i t e s a r e n e a r weather stations of the Meteorological Division of the Department of T r a n s p o r t . Weather r e c o r d s a r e

thus available with r e s p e c t to precipitation, t e m p e r a t u r e , h o u r s of sunshine, wind velocity and d i r e c t i o n during the periods of

exposure. Although considerable t i m e and e f f o r t h a s been devoted to a s e a r c h f o r a suitable method to m e a s u r e a t m o s p h e r i c chlorides

in the Halifax a r e a , no e n t i r e l y s a t i s f a c t o r y way h a s a s yet been developed. The lead peroxide method was used to m e a s u r e the sulphur dioxide content of the atmosphere. This instrument does not m e a s u r e the v o l u m e t r i c concentration of SO2 in the a t m o s p h e r e d i r e c t l y , but p r e s e n t s an integrated m e a s u r e of the sulphur dioxide

"activity" during a period of exposure. T h i s i n s t r u m e n t w a s well suited to m e a s u r e the r e l a t i v e l e v e l s of SO2 a t the exposure s i t e s when m e t a l s w e r e under t e s t . It h a s been found that the sulphur dioxide pollution i s g r e a t e s t at the Halifax m a r i n e - i n d u s t r i a l s i t e , followed by Montreal, T r a i l , Ottawa, York Redoubt, Saskatoon, Esquimalt, and Norman Wells in that o r d e r . The a v e r a g e sulphur dioxide content, m e a s u r e d by the lead peroxide method, f o r the different e x p o s u r e periods a t each s i t e is given in Table 9. EXPERIMENTAL PROCEDURES

( a ) G e n e r a l

F o u r - by six-in. panels of the t h r e e alloys, s t a i n l e s s 302, 316, and 430 w e r e cut f r o m r e g u l a r 16-gauge s h e e t s (0.062 in. ).

T h e s e panels w e r e identified with punched holes using a template according to the d i r e c t i o n s provided by Sub-committee

"C"

of the A. C. C. R. P.

.

T h i s template is shown in F i g u r e 1.

T h e panels w e r e then d e - b u r r e d , d e g r e a s e d , passivated, weighed and s e n t to the Division of Building R e s e a r c h , Ottawa,

f o r distribution to the v a r i o u s s i t e s .

Eight panels of each alloy w e r e a s s i g n e d to s i t e s 1 to 7; duplicate panels w e r e removed a f t e r e a c h t i m e period. In the c a s e of the T r a i l s i t e twelve panels of each alloy w e r e assigned; t h r e e panels w e r e removed a f t e r each exposure period.

T h e panels w e r e mounted during 1953 and 1954 on the outdoor exposure r a c k s . The s p e c i m e n s w e r e held in place by p o r c e l a i n i n s u l a t o r s at 30 d e g r e e s to the horizontal and facing south.

After exposure periods of one, two, five and t e n y e a r s , specimens w e r e removed f r o m the t e s t s i t e s and s e n t to the

Division of Building R e s e a r c h , Ottawa, where the s a m p l e s w e r e examined, photographed and condition r e c o r d e d , then sent to Atlas Steels Company for cleaning and detailed examination and evaluation. The specimens w e r e removed according to the following plan.

One-year exposure

-

Lot #1 panels Two-year exposure - Lot #2 panels F i v e - y e a r exposure

-

Lot #3 panels T e n - y e a r exposure - Lot #4 panels

SPECIMEN CLEANING AND EXAMINATION PRO CEDURES

The extent of c o r r o s i o n of the s t a i n l e s s s t e e l specimens w a s determined by the l o s s i n weight of the panels after being

cleaned by a standardized procedure. Observations w e r e made a s to the appearance of the panels and extent of pitting. No m e a s u r e m e n t s of pit depth w e r e made.

The cleaning procedure employed consisted of b r i s k scrubbing with a stiff b r i s t l e b r u s h and a mild a b r a s i v e for

approximately one minute. In the c a s e of the specimens f r o m the the Halifax m a r i n e s i t e it was s o m e t i m e s n e c e s s a r y to use a s t a i n l e s s s t e e l knife on the edges of the specimens to r e m o v e the c o r r o s i o n products.

In o r d e r to e n s u r e that no undue l o s s of metal w a s o c c u r r i n g during the cleaning procedure, blank panels of the t h r e e grades of s t e e l w e r e cleaned side by side with the actual specimens. No corrections w e r e applied to the weight l o s s e s .

Fcllowing the scrubbing procedure the specimens w e r e rinsed in hot w a t e r , distilled water and finally i n absolute alcohol and then a i r d r i e d and weighed.

EXPERIMENTAL RESULTS

Lot #1 specimens which included duplicate panels of e a c h of the t h r e e g r a d e s of s t e e l f r o m e a c h of the eight s i t e s w e r e removed f r o m t e s t a f t e r one y e a r exposure time. The weight l o s s r e s u l t s a r e given in Table 1 (A, B, C).

S o m e of the p a n e l s showed a weight gain and t h i s c a n p r o b a b l y be a t t r i b u t e d to a n e r r o r i n weighing o r insufficient cleaning.

F i g u r e 2 gives a g r a p h i c c o m p a r i s o n of the c o r r o s i o n r a t e s of the t h r e e types of s t a i n l e s s s t e e l s a f t e r one y e a r e x p o s u r e . Owing to the s m a l l l o s s of m e t a l t h i s g r a p h gives the c o r r o s i o n r a t e i n m i l s p e r y e a r x 1000.

F o r a l l t h r e e t y p e s of s t e e l the Halifax i n d u s t r i a l s i t e g i v e s the w o r s t c o r r o s i o n r a t e with type 430 having the l a r g e s t weight l o s s and type 31 6 the b e s t a t this s i t e . Type 302 exhibits the b e s t o v e r - a l l c o r r o s i o n r e s i s t a n c e followed by t y p e s 430 and 316.

Lot #2 p a n e l s w e r e r e m o v e d f r o m t e s t a f t e r two y e a r s e x p o s u r e . T h e weight l o s s r e s u l t s a r e given i n T a b l e 2 (A, B, C); F i g u r e 3 shows a plot of the c o r r o s i o n r a t e s .

H e r e again types 302 and 430 a r e q u i t e s i m i l a r e x c e p t f o r the Halifax i n d u s t r i a l s i t e w h e r e type 430 shows a g r e a t e r weight l o s s . Type 316 shows the l e a s t c o r r o s i o n r e s i s t a n c e a t a l l the s i t e s except the Halifax i n d u s t r i a l s i t e w h e r e i t is the best.

One o t h e r point about the t w o - y e a r r e s u l t s is the poor showing of type 316 a t the Montreal s i t e . Although t h e s e s p e c i m e n s had b e e n r e c h e c k e d a t the t i m e , i t is b e l i e v e d t h a t t h e r e is a definite e r r o r i n weighing i n t h i s c a s e . Lot #3 p a n e l s w e r e r e m o v e d f r o m t e s t a f t e r five y e a r s e x p o s u r e . T h e weight l o s s r e s u l t s a r e given i n T a b l e 3 ( A , B , C ) ; a g r a p h i c c o m p a r i s o n of the c o r r o s i o n r a t e is shown in F i g u r e 4. T h e r e s u l t s show t h e t h r e e types of s t a i n l e s s s t e e l s a s being quite s i m i l a r i n c o r r o s i o n behaviour. Type 430 again s h o w s the g r e a t e s t weight l o s s a t the Halifax i n d u s t r i a l s i t e and type 31 6 the l e a s t .

L o t #4 p a n e l s w e r e r e m o v e d f r o m t e s t a f t e r t e n y e a r s e x p o s u r e . T h e r e s u l t s f o r t h e s e s p e c i m e n s a r e given i n T a b l e 4 and F i g u r e 5.

H e r e also the t h r e e types of s t e e l s a r e quite s i m i l a r in their c o r r o s i o n behaviour, and once again type 430 shows the l a r g e s t weight loss at the Halifax industrial s i t e and type 316 the s m a l l e s t .

Comments on the appearance of the c o r r o s i o n specimens before cleaning a r e available f o r most of the specimens and a r e included in Tables 1 to 4.

F i g u r e s

6,

7 and 8 show the four lots of s t a i n l e s s s t e e l f r o m each exposure s i t e after cleaning. In these photographs

only specimen 1 of each lot i s shown; in the c a s e of A - 0 m a t e r i a l the specimen i r o m s i t e 7 i s missing. Comments on the appearance of each of the specimens in the photographs a r e given in Tables 5, 6, and 7.

Samples exposed at s i t e s 4 and

6 w e r e selected f r o m

each type of s t e e l a f t e r the t e n - y e a r exposure period for confirma- tory chemical analysis. These r e s u l t s a r e given in Table 8. T h e r e a r e no significant differences f r o m the original analysis except in the c a s e of s t a i n l e s s 302 f r o m the Halifax industrial site. Here t h e r e i s a significant d r o p in the chromium content f r o m 18.78 to 18. 21 p e r cent.

A metallographic examination of these s a m e s a m p l e s ,

f r o m s i t e s 4 and 6 a f t e r the ten-year period was a l s o made along with a blank which had not been exposed at any of the s i t e s . Micro-

photographs of these s a m p l e s a r e given in F i g u r e s 9.10 and 11. F r o m these r e s u l t s it is s e e n that the c o r r o s i o n of the t h r e e types of s t e e l i s a general c o r r o s i o n r e s t r i c t e d mainly to the s u r f a c e of the panels. No evidence of intergranular attack was found.

F i g u r e s 12 to 19 show graphically the c o r r o s i o n behaviour of the three types of s t a i n l e s s s t e e l s v e r s u s t e s t s i t e .

DISCUSSION O F RESULTS AND RE COMMENDATIONS

-

The high levels of SO2 in the atmosphere a t the Halifax industrial s i t e (situated on the roof of the F e d e r a l Building),

provides a v e r y s e v e r e exposure condition. The level i s influenced by the smoke f r o m the chimney nearby that s e r v e s this building.

Under this unusual environment a l l t h r e e types p e r f o r m e d exceptionally well with s t a i n l e s s 31

6

being l e a s t affected. The a v e r a g e sulphur dioxide content of the a t m o s p h e r e a t e a c h s i t e f o r e a c h e x p o s u r e period i s given in Table 9 . F r o m this table the behaviour of the t h r e e d i f f e r e n t types of s t a i n l e s s s t e e l s a t the Halifax i n d u s t r i a l s i t e can be p a r t l y attributed to the high sulphur dioxide content of the a t m o s p h e r e . A l i s t i n g of the eight s i t e s in o r d e r of d e c r e a s i n g c o r r o s i o n r e s i s t a n c e i s a s follows: 1. Norman Wells 2 . Saskatoon 3. Ottawa 4. T r a i l 5. Montreal

6.

Esquimalt 7. York Redoubt 8. Halifax - Site

6

-

Site 2 - Site 1 - Site 8 - Site 3 - Site 7 - Site 5 - Site 4

It i s obvious when this listing i s c o m p a r e d with T a b l e

9

that sulphur dioxide alone does not account f o r the c o r r o s i o n of the s t a i n l e s s s t e e l .

One f u r t h e r observation about the c o r r o s i o n r a t e s i s that a l l t h r e e types of s t a i n l e s s s t e e l showed a d e c r e a s e in c o r r o s i o n r a t e a f t e r the o n e - y e a r e x p o s u r e period. This d e c r e a s e i n the

c o r r o s i o n r a t e with t i m e i s s t a n d a r d f o r most m a t e r i a l s , a t l e a s t up to the point w h e r e spalling o r flaking of the m a t e r i a l o c c u r s . T-i'he d e c r e a s e in the c a s e of the s t a i n l e s s s t e e l s i s due to the protective oxide coating which f o r m s on s t a i n l e s s s t e e l whenever i t i s exposed to an oxidizing a t m o s p h e r e . Once f o r m e d , the oxide slows down f u r t h e r c o r r o s i o n . In the r e s u l t s r e p o r t e d h e r e t h e r e a r e t h r e e exceptions to this r u l e of d e c r e a s i n g c o r r o s i o n r a t e : the 430 type s t a i n l e s s a f t e r the 10 - y e a r period a t the two Halifax a r e a s i t e s and at the E s q u i m a l t site. T h e s e d i f f e r e n c e s a r e quite s m a l l , however, and can be attributed to spalling of the oxide f i l m o r e r r o r s in weighing.

Type 430 s t a i n l e s s s t e e l p e r f o r m e d v e r y favourably a t s e v e r a l t e s t s i t e s . As mentioned previously t h e s e s p e c i m e n s had a ground 4B finish which would r e m o v e any chrome-depleted s u r f a c e l a y e r s r e s u l t i n g f r o m a i r annealing. The t e s t r e s u l t s f o r the 430 s t a i n l e s s s t e e l in what was r e f e r r e d to a s i n d u s t r i a l

o r s e m i - r u r a l s i t e s should not be taken a s the b a s i s f o r recommending the use of Type 430 in downtown o r highly i n d u s t r i a l i z e d a r e a s .

S t a i n l e s s s t e e l p r o d u c e r s c u r r e n t l y r e c o m m e n d type 430 f o r indoor a r c h i t e c t u r a l p u r p o s e s only.

This work h a s pointed out the i m p o r t a n c e of and n e c e s s i t y for c a r e f u l documentation and standardized weighing

and cleaning p r o c e d u r e s of a l l long- r a n g e c o r r o s i o n testing p r o g r a m s .

It i s unfortunate that quantitative evaluation of the extent of pitting w a s not followed in the c a s e of the s t a i n l e s s s t e e l s p e c i m e n s a s this m u l d give a complete p i c t u r e of the p e r f o r m a n c e of the s t a i n l e s s s t e e l s p e c i m e n s .

In view of the r e s u l t s obtained f o r the s t a i n l e s s s t e e l s , i t i s recommended that consideration be given to o t h e r c o r r o s i o n testing p r o g r a m s on Atlas alloys w h e r e the principal application involves u s e in an a t m o s p h e r e w h e r e c o r r o s i o n would be expected.

CONCLUSIONS

1. T h e r e s u l t s f o r the s t a i n l e s s s t e e l u s e d in this p r o g r a m show that the t h r e e types a r e quite s i m i l a r in t h e i r c o r r o s i o n

behaviour. All t h r e e types showed good c o r r o s i o n r e s i s t a n c e in

a r u r a l cold and d r y c l i m a t e .

2. Type 302 s t a i n l e s s s t e e l shows the b e s t o v e r - a l l c o r r o s i o n r e s i s t a n c e to typical Canadian a t m o s p h e r e s .

3 . Type 31

6

s t a i n l e s s s t e e l i s definitely s u p e r i o r under a d v e r s e conditions s u c h a s the Halifax i n d u s t r i a l m a r i n e t e s t s i t e .

4. Type 430 s t a i n l e s s s t e e l , although showing the l e a s t o v e r - a l l c o r r o s i o n r e s i s t a n c e , did p e r f o r m favourably a t s e v e r a l t e s t s i t e s .

5. All t h r e e types of s t a i n l e s s s t e e l show a d e c r e a s e in t h e i r c o r r o s i o n r a t e s a f t e r the one - y e a r e x p o s u r e period. T h i s d e c r e a s e i s s t a n d a r d f o r m o s t m a t e r i a l s , a t l e a s t up to the point w h e r e spalling o r flaking of the m a t e r i a l o c c u r s .

6 .

_{It should be noted that in a l l c a s e s the weight l o s s e s} a r e quite s m a l l and it i s difficult to make any r e a l distinction between the t h r e e a s to p e r f o r m a n c e .

7. The high l e v e l of a t m o s p h e r i c s u l p h u r dioxide a t the Halifax i n d u s t r i a l s i t e m a k e s i t the m o s t a g g r e s s i v e e n v i r o n m e n t with r e g a r d to the o v e r - a l l p e r f o r m a n c e of the t h r e e s t a i n l e s s s t e e l s .

8. T h e s t a i n l e s s a p p e a r a n c e of types 302 and 316 with 2B f i n i s h is r e t a i n e d although dulled s o m e w h a t a f t e r the t e n - y e a r p e r i o d of e x p o s u r e .

9. S t a i n l e s s 430 s p e c i m e n s with #4 f i n i s h f r o m the Halifax i n d u s t r i a l s i t e even a f t e r cleaning a r e v e r y black. F r o m the o t h e r s i t e s the 430 s p e c i m e n s a r e quite b r i g h t and l u s t r o u s , r e t a i n i n g much of t h e i r o r i g i n a l f i n i s h a f t e r cleaning. E v e n b e f o r e cleaning t h e i r a p p e a r a n c e is quite good except f o r staining.

R E F E R E N CES

( 1 ) The C o r r o s i o n Behaviour of Major A r c h i t e c t u r a l and S t r u c t u r a l Metals i n Canadian A t m o s p h e r e s

-

S u m m a r y of Two Y e a r R e s u l t s . NRC, A s s o c i a t e Committee 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 , Ottawa, 24 F e b r u a r y 1959. ( 2 ) Gibbons, E. V. A t m o s p h e r i c C o r r o s i o n T e s t i n g of Metals i n

Canada. National R e s e a r c h Council, Division of Building R e s e a r c h , R e s e a r c h P a p e r No. 124, Ottawa, June 1961, NRC 6260.

TABLE 1 (A)

ONE YEAR RESULTS O F STAINLESS S T E E L ALLOY TYPE 302 (A-8) -

@ S I T E NO. 1 1 2 2 3 3 4 4 5 5 6 6 7 7 8 8 S

-

SITE LOCATiON - Ottawa Ottawa Saskatoon Saskatoon Montreal Montreal Hal if

ax

(Industrial) Halifax (Indust rial) Halifax (Rural) Halifax (Rural) Norman W e l l s Norman Wells Esquimalt Esquimalt T r a i l T r a i l T r a l l SPEC. NO. 1 2 1 2 1 2 1 2 1 2 1 2 1 2 1 2 3

---

ORIGINAL WEIGHT (GMS) 195.398 199.447 196.877 199.316 196. 870 199.111 198.327 198.096 197.215 199.426 194.443 194.791 197.443 195.955 196.754 200.377 196.393 COMMENTS

.

-

AVERAGE CORROSION RATE

(MILS PER YEAR) ,00015 .00039 ,00031 .02100 .0007 1 .00055 WEIGHT AFTER CLEANING (GMS) 195. 397 199.446 196.874 199.314 196. 870 199.107 198.182 197.975 197.209 199.423 194.442 194.793 197.440 195.951 196.782 200.387 196.392 WEIGHT DIFFERENCE (GMS)

-.

001

-.

001

- .

003

-.

002 ,000

-.

004

-.

145

-.

121

-.

006

-.

003

-.

001

+.

002

-.

003

-.

004

+.

028

+.

010

-.

001

TABLE 1 (B)

ONE YEAR RESULTS O F STAINLESS STEEL ALLOY TYPE 316 (A-0)

SPEC. ORIGINAL WEIGHT AFTER WEIGHT AVERAGE

LOCATION NO. WEIGHT CLEANING DIFFERENCE CORROSION COMMENTS

(GMS) (GMS) (GMS) RATE (NnLS

f

ER YEAR) 911.905 ,000 ; 00031 2 2 3 3 4 4 5 5 6 6 7 7 8 8 8 Saskatoon Saskatoon' Montreal Montreal Halifax (Industrial) Halifax (Industrial) Halifax (Rural) Halifax (Rural) Norman Wells Norman Wells E squimalt E squimalt T r a i 1 T r a i l T r a i l 1 2 1 2 1 2 1 2 1 2 1 2 1 2 3 206. 305 206.795 202.652 204.154 205.485 206.210 207.377 207.455 210.707 210.004 200.640 205.052 205. 806 205.947 208. 234 206. 302 206.791 202.647 204.151 205.421 206.125 207.377 207.446 210.705 209.996 200.636 205.046 205.798 205.938 208.228

-.

003 -.. 004

-.

005

-.

003

-.

064

-.

085

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000

-.

009

-.

002

-.

008

-.

004

-.

006

-.

008 .. ,009

-.

006 .00054 ,00062 .01156 .00070 .00078 .00078 .00118

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TABLE 3 ( A J

SITE NO.

FIVE YEAR RESULTS O F STAINLESS STEEL ALLOY TYPE 302 _{-- - -- - -} (-4 -8)

---

WEIGHT AFTE

L' LEANING

(GMS)

---

= --=- -- -- - - ---- r , ILS PER YEAR - - -- - - - -

1 Ottawa 1 9 7 . 9 l Q 197.555 Saskatoon 196.498 199.094 196.638 197.285 199.275 192.9'75 200. 874 194.456 196.256 192.945 199.570 198.570 200.030 196.115 193.474

--

_ r r -

-

-_

Di.11. s t a i n l e s s c o l o u ~ ,

I

no pitting I f 1 1 I ? Dull s t a i n l e s qli ht s t a i n s anJZplttfng

I

Brownish stains,

I

slight pitting E l I, t

Black & brown stains,

much pitting

I

Dull stainless, brown

stains, , and piping

Bright s t a i n l e s s finish, slight stain

Silvery -white, slight pitSjng, s c r a t c h e s

Slight stain on edges

Slight pittiiig, s t a i n on

SITE NO. 1 1 2 2

3

3 4 4

5

5

6

6

7 7 8 8 8 SITE LOCATlON Ottawa Ottawa Saskatoon Montreal Montreal Halifax

,

(Industrial) Halifax (Industrial) Norman Wells Norman Wells Esquimalt Esquimalt TraiI T r a i l T r a i l TABLE 3 (B)

FIVE YEAR RESULTS O F STAINLESS STEEL ALLOY TYPE 316 (A-0)

- .~ ~ -- ORIGINAL WEIGHT (G MS)

-I---

-- ---=- =*-- WEIGHT AFTER

---- -

-

----

--

AVERAGE CORROSlON RATE L M L S PER YEAR'L .00005

--

---

COMMENTS

Dull stainless colour, no

,, pitting ,,

Dull stainless, slight s t a i n s and pitting

I I 1 1

Brownish stains, pitting

1 1 II

Brcwnish black stai-ns, much pitting

1 1 I I

Dull stainless, slight s t a i n s and pitting

I t f I

Bsight stainless, no pitting

1 1 1 1

Silvery-white, slight pitting

Silvery-white, s c r a t c i e s s l i ht pitting

Slight stain on edges, no pitting

I I 1 1

Slight ssain or. edges, slight pitting

SlTE LOCATION Ottawa Ottawa Saskatoon Saskatoon Montreal

I

Montreal Halifax (Industrial) Halifax (Industrial) Halifax(Rura1) Halifax(Rura1) Norman Wells Norman Wells

I

E squimalt Esquimalt Trail Trail Trail Notes- 1.c'

I

TABLE 4 (A)-

TEN YEAR RESULTS O F STAINLESS STEEL ALLOY TYPE 302 (A-8)

---.- SPEC. NO. 1 2 1 2 1 2 I 1 2 1 2 1 2 1 2 1 2 3 = Int --

-

.- ORIGINAL WEIGHT (G

m)

-

199.417 199.953 195.185 199.913 193.116 198.378 197.412 194. 19.5 194.770 194.611 194.972 195.330 197.129 198.293 197.565 197.952 196.199 trference col

---

WEIGHT AFTER CLEANlNG (GMS) WEIGHT DIFFERENCE (GMS)

AVERAGE

CORROSION RATE

(MILS-PE

R

Y

EARL -

---

COMMENTS

Dull, slight brown stain, Inter -

ference colour

Dull stainless colour, stalns on edges, I. C.

Dull, slight brown stains Dull stainless steel colour Dull, stained, pitted, black edges, I. C.

Brownish, stained, I. C.

I

Greyish, stained, pitted, black

'edges, I.. C.

Black & dark grey staining,

pitted, I. C.

Dull, brown stain on edges

1

~ u l l stainless colour, stained

brown edges, I. C. Bright stainless finish, slight stain

Bright, slightly pitted, I. C.

I

'

Silvery -white, brown stains on

edges

1 I I I 1 I

Silvery-white, grey stains on edges

1 1 I 1 1 1

G r e brown stains around edg&.

TABLE _--4 (B)

TEK YEAR RESULTS O F STAINLESS STEEL ALLOY TYPE 316 (A-0 )

f

l

SITE

-

GR=[I-

WKG

H

T

A

F

T

E

R

I

W

~

2 Saskatoon 2 Saskatoon NO. 1 2 1 2 W ElGHT (G MS) CLEANING (GMS) DIFFERENCE (GMS) CORROSION RATE

(MILS PER YEAR)

----

COMMENTS

Dull, brown stain, pitted, I. C.

Dull, stained, pitted Dul.1, slight brown stain Daull, stained, pitted

Halifax (Industrial) Halifax (Industrial) Halifax (Rural

I 5 I

Halifax (Rural) 2

I 1

205.927

I

205.920

-..

007

Stained, black edges, pi.tted, I, C . Black edges, g r e y i s h brown stains, pitted, I. C.

Dull, slight brown stains,

1

slight pitting

Dull, brown stains, slightly pitted

1

6

1

Norman Wells

I

1

1

203.150

1

203.155

1

+.005

I

I

Dull, slightly pitted

I

Bri ht s t a i n l e s s colour, slight s t aBning 6 Norman Wells

I ) I

E squimalt

I I

213a004

I

212.994

I

Esquimalt

I I

214Q

Brown spots & g r e y specks,

pitted 2

-.

010

1

.00015 214. 169

-.

009 8 8 8 Dull, g r e y s t r e a k s , pitted G r e y s t r e a k s , pitted Dull, g r e y s t r e a k s , brown stains, pitted White s i l v e r y l u s t r e , s m a l l black dots 211.312 , T r a i l 209.943 T r a i l 207.820 T r a i l 206.975 209.942 207. 807 206.972 2 1 i . 311 t e r f e r e n c e colour

-.

001

TABLE 4 (C)

TEN YEAR RESULTS O F STAINLESS STEEL ALLOY TYPE 430 (-4-9) _{-. --- - - - -- --}

3

1

Montreal 1 2 Halifax (Rural)

I

Halifax (IndustrS al) Halifax (Industrial) Halifax (Rural)

I

1 2 Esquimalt E squ imal t Norman Wells Norman Wells T r a i l 1 2 T r a i l T r a i l 1. C. = Interferenc

A_____

.-- . ~ . - - - A . ~.-. ORIGINAI WEIGHT (GMS) - - ~ - 188. 25'7 186. 139 189. 196 191.421 191.811 192.113 191. 529 189.136 186. 851 191.258 192.624 191.566 190. 808 191. ,328 188.422 190. 299 184.776 : cclour

-

-

- -

-- =

-

. -. --. -WEIGHT AFTER CLEANING ( G M ) WEIGHT DIFFERENCE (GMS)

---

AVERAGE CORROSION RATE (Mi 1

s

p e r y e a r ) -COMMENTS -. -- I

Dull, slight brown stain, I. C ,

Dull, stair1 on edges, I. C . Dull, slight brown stain Dl111 stainless colour, slight s t a i n

Dull, slight stain, slight pitting

Greyish, brownish -grey stain, pitted

1

Black spalling oxide, pitted.

Black and dark g r e y staining, pitted.

Sl ~ g h t brown staining, slight

pitting

Dull, slight stdlning Bright, slightly stained

1

Bri.ght, slightly stained

Silvery, r u s t s t r e a k s , I. C.

Silvery, brown s t r e a k s , I. C.

I Silvery l u s t r e , slight brown

stains

Brown stains on edges, I. C . Silvery lustre, milky hlotclles, stains

TABLE 5 - continued

VISUAL APPEARANCE O F STAINLESS STEEL (302) SAMPLES A -8

MATERIAL AFTER CLEANING

Appearance

_-

Dull stainless s t e e l colour, silvery -white and slight brown stains, irrterference colour, (silvery-white blotches on r e v e r s e side).

Dull g r e y colour, light s i l v e r - g r e y blotches, slight brown stains, (milky-white blotches and dark brown stains on back) Dull

grey colour, dark g r e y and slight brown s t a i n s especially

along edges, slightly pitted, (silver-grey s t a i n s on back). Dull g r e y colour, pitted, greyish-white blotches, black and dark g r e y s t a i n s along edges.

Dull stainless s t e e l colour, dark g r e y and light brown s t a i n s along edges, interference colour, ( m o r e s t a i n s and greyish brown spots on back).

Bright s t a i n l e s s s t e e l finish, slight brown stains, (silver-white blotches and g r e y s t a i n s on back).

Silvery-white appearance, dark g r e y and brown s t a i n s and spots especially along edges, ( m o r e r u s t stains, silver-grey s t a i n s on back).

Silvery-white appearance, grey -brown s t a i n s along edges, (milky -white s t a i n s on back).

Dull stainless steel colour, very slight brown and g r e y s t a i n s

I

along edges, interference colour.

Dull stainless steel colour, slight brown stains, a few s i l v e r y - white blotches.

Dull g r e y colour, slight brown and g r e y staining, interference

I

i

colour.

Dark g r e y colour, pitted, brown and greyish -black s t a i n s

especially n e a r edges, bluish interference colour, ( m o r e stalning

and milky white spots on back).

₁

Dull stainless steel colour, brown s t a i n s along edges, (brownish- I

g r e y spots and bluish I. C. on back).

Bright stainless s t e e l finish, slight brown s t a i n s

Silvery -white appearance, slight brown s t a i n s n e a r edges, (milky -

white s t r e a k s on back).

TABLE 6

VISUAL APPEARANCE O F STAINLESS STEEL (316) SAMPLES A - 0 MATERIAL AFTER CLEANING

I

I

Lot Spec.

X I N O - I

Appearance Blank 1 1 1 1 I 1 1 1

Bright, slightly stained, top left c o r n e r

-

pits Bright, slightly stained

Bright, slightly stained, s c a t t e r e d pits Greyish stains, s c a t t e r e d pits

Dull grey, dark g r e y stains, pitted Bright, slight!y stained, pitted D ~ l l , stained, slightly pitted Missing

Dull, brown and dark g r e y stains, pitted

Bright, stained, pitted Brownish stains, pitted

Dull., dark g r e y stains, pitted

Dill, black edges, g r e y and brown stains, pitted Bright, slightly stained, pitted

Bright, g r e y stains, slightly pitted Bright, slightly pitted and stained

Bright, top left c o r n e r pitted and stained

Dull, slightly stained and pitted Dull, greyish stains, slightly pitted Dull, greyish, stained and pitted

Dull grey, black edges, dark and light g r e y s t a i n s and pitted Dull, greyish stains, pitted

Bright, slightly stained Dull, pitted

Dull grey, dark g r e y stains, pitted, brown edges

Dull, greyish, stained and pitted

Dull, slight brown stains, slightly pitted Du.11, greyish, stained

Dull grey, dark g r e y stains, black edges, pitted Dull, brownish stains, slightly pitted

Dull, sli-ghtly stained, pitted Dull, slightly pitted

TABLE 7

VISlJAL APPEARANCE O F STAINLESS STEEL (430) SAMPLES A-9 MATERIAL AFTER CLEANING

Site

1

Lot

1

Spec.

1

- - Appearance

3

No.

I

No. ( No.

1

I

I

!

S

Bright stainless s t e e l metallic lustre, shiny

Brrght shiny stainless steel metallic lustre, very slight filmy-

white stains

!

Bright shiny stainless s t e e l metallic lustre, very slight filmy-

1

white stains

Bright stainless steel colour, pitted, black spalling oxide specks, Bright stainless s t e e l finlsh, slight brownish-grey staining

I

black edges (heavy ~ o a t i n g of dark brown and black oxide on back)

(

E

Bright stainless s t e e l finish, still quite shiny, slight filmy-white

1

stains

1

Silvery bright stainless s t e e l finish, somewhat shiny, brown 1

r u s t spots especaally along edges, interference colours on edges t Silvery bright stainless steel finish, slight brown stains n e a r

\

edges, slight interference colour.

,

1 !

\

Bright stainless steel metallic l u s t r e , slight brown and filmy- $

white stains, shiny

4

V

Bright stainless steel finish, somewhat shiny, slight brown and

_i

filmy white stains :

Bright stainless s t e e l finish, somewhat shiny, slight pitting,

slight brown m d filmy-white stains

1

Bright stainless steel colour, pitted, blazk spalling oxide in patches

!

and specks, black edges (heavy coating of dark brown and black 3

1

oxide on back.).

Bright stainless steel finish, slight brownish-grey staining in I spots and along edges, interference colours, (extensive brownish -

1

g r e y staining and i n t e r f e r e n i e coloura on back). ?

i Bright stainless s t e e l metallic lustre, shiny, very slight filmy- G white stairiag.

Bright stainless s t e e l metallic lustre, shiny, brown r u s t spcts

and interference colours, slight filmy-whi.te stains

I

_t

Bright stxinless metallic lustre, shiny, slight brownish-grey

TABLE 7

-

continued

VISUAL APPEARANCE O F STAINLESS STEEL (430) SAMPLES A-9 MATERIAL AFTER CLEANING

Appearance

Bright stainless s t e e l metallic lustre, shiny, slight brownish- grey stains along edges, interference colour, slight filmy-white stains.

Bright stainless steel metallic lustre, shiny, slight brown and filmy-white stains.

Bright greyish stainless s t e e l colour, slight pitting, slight brown and milky-white blotches especially n e a r bottom edge. Bright greyish stainless steel colour, pitted, black spalling oxide in patches and specks, black edges, (heavy coating of dark

brown and black oxide on back). Site - No. 1 2 3 4

Bright s t a i n l e s s s t e e l finish, brownish-grey spots and s t a i n s along edges, slight pitting.

Bright metallic stainless s t e e l lustre, shiny.

Silvery bright stainless s t e e l finish, extensive r u s t s t r e a k s on edges and interior, interference c olours.

Silvery stainless steel finish, brownish-grey s t a i n s along edges, interference colours.

Greyish stainless steel colour, somewhat shiny, slight brownish g r e y s t a i n s along edges, interference colours

Greyish stainless steel colour, somewhat shiny, very slight brown staining

Dull greyish stainless s t e e l colour, greyish-brown, and fllmy stains n e a r edges, interference c. olours

Dull greyish colour, pitted, black and dark brown oxide specks especially along edges

Bright stainless steel finish, somewhat shiny, slight pitting, slight brown stains and interference colour n e a r edges, slight Bright stainless steel finish, shiny, v e r y slight brown staining Bright s i l v e r - g r e y stainless finish, shiny very slight brown Bright silver -grey stainless finish, shiny, v e r y bright stain along Lot - No. 3 3 3 3 Spec. - No. 1 1 1 1

TABLE 8

CHEMICAL ANALYSIS O F STAINLESS STEELS AFTER TEN YEARS -- EXPOSURE

CHEMICAL

ANALYSIS

?PERCENT

& Ni 8. 56 8. 51

-

0.71 0.71 12.84 12.84 Mo

-

-

-

-

2.35 2.35 C r 18.93 18.21 16.70 16.71 17.06 17.04 S i 0.48 0.47 0.39 0.39 0.38 0.39 I Material and Site No.

A - 8

SS 302 Site

#6

Site #4 C 0.11 0.11 Mn 1.30 1.28

-

-A - 9 SS 430 Site #6 Site #4 A - 0 SS316 Site

#6

Site #4 0.45 0.47 1.94 1.92 0.07 0.08 0.07 0.065 P 0.024 0.026 S 0.019 0,018 0.0.30 0.030 0.026 0.026 0,017 0.018 0.020 0.019

TABLE 9

AVERAGE SULPHUR DIOXIDE CONTENT OF ATMOSPHERE AT EACH EXPOSURE SITE

(Reported a s Mg S03/day/100 sq crn lead peroxide)

EXPOSURE ONE YEAR TWO YEARS

0.49 0.27 2.22 12.83 0.50 0.008 0.05 0%' SlTE Ottawa

-

1 Saskatoon-2 Montreal -3 Halifax

-

Industrial

-

4 Halifax

-

Rural -5 Norman Wells E s q ~ i m a l t -7 Trail

-

8 0.52 0.33 2. 19 14.67 0.51 0.02 0.06

0.8/

FIVE YEARS 0.50 0.20 1.99 9.55 0.33 0.022 0.06

0.7+

TEN YEARS 0.52 0.15 1.69 6.48 0.28 0.009 0.05

0 . 6 8

FIGURE 1

-

TEMPLATE FOR SPECIMEN IDENTIFICATION

The template used to identify the panels exposed at the various s i t e s is shown below. The template is notched at the upper left hand corner. The metal designation

is obtained from the l e t t e r s around the outside edge and the vertical numbers 1 to 0 on t h e right hand s i d e of the panel. The row of numbers on the bottom designate the s i t e number ( 1 to 0). Lot and specimen numbers a r e also shown.

3/16"

"ti

0

0

0

0

0

0

0

0

I

STAINLESS

-

3 0 2

BLANK

SITE

#4

-

HALIFAX, INDUSTRIA&

S I T E #6

-

NORMAN WELLS

FIGURE 9

-

ELECTROLYTIC ETCH,

10%

O m L I C ACID, 3 0 SECONDS, 6 VOLTS

STAINLESS

-

316

BLANK

SITE

#4

-

HALIFAX, INDUSTRIAL

SITE

#6

-

NORMAN WELLS

FIGURE 10

-

ELECTROLYTIC ETCH. lo0% OXALIC ACID. 30 SECONDS, 6 VOLTS

500X

STAINLESS

-

4 3 0

BLANK

S I T E #4

-

HALIFAX, INDUSTRIAL

S I T E

#6

-

NORMAN WELLS

FIGURE

11

-

ELECTROLYTIC ETCH, 10% OXALIC ACID, 3 0 SECONDS,

6

VOLTS

FIGURE _-- 14

ATMOSPHERIC CORROSION O F STAINLESS STEELS A T S[TE NO. 3 (MONTREAL)

EXPOSURE TIME (YEARS) 0.005-

E

₂

0.004- C3 V rn

8

Ll b 0.003-

9

5

0.002- 0.001-

--

- -

I

- -- --

--I---

--

-

Stal1lle4s Steel Type 302 A-A

Stainless Steel Type 316 M

Stainless Steel Type 130

-

-

-

-

-

---

1

I 1 I

- - L

1 1 I 1

2

5

A 10

d

d

d