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Corrosion behaviour of monel metal in eight Canadian atmospheres: a
five year progress report
NATIONAL RESEARCH COUNCIL OF CANADA DIVISION OF BUILDING RESEAR CH
THE CORROSION BEHAVIOUR OF MONEL METAL IN EIGHT CANADIAN ATMOSPHERES - - A FIVE YEAR
PROGRESS REPORT
by
R. J. Law, International Nickel Company of Canada Limited, Toronto, Ontario and
E. V. Gibbons, Division of Building Research, National Research Council of Canada, Ottawa, Ontario
ANALYZED
A joint report of the International Nickel Company and
the Division of Building Research, National Research Council of Canada
Internal Report No. 356 of the
Division of Building Research
OTTAWA April 1968
PREFACE
A study was undertaken by the former Associate Cormn itt.e e
on Corrosion Research and Prevention of the National Research Council to obtain information on the corrosion behaviour of different architectural metals at various locations in Canada. It was a co-operative study involving metal suppliers, users and research
organizations. The first group of metals were selected for exposure in 1953.
The specimens of the different metals were exposed at eight outdoor sites across Canada. The over-all program included three types of steel, three stainless steels, two magnesium alloys, a rolled zinc, three aluminum alloys and rivetted galvanic couples of aluminum 35 alloy to zinc, copper and mild steel. More recently specim.ens have been exposed of monel, two lead alloys, copper, muntz metal and a number of different metal and organic coatings applied to steel substrates. Reports have been issued describing their performance after five and ten years of exposure.
This report describes the 5 -year behaviour of monel metal. The specimens of monel were furnished by the International Nickel Company of Canada, Toronto, who were also responsible for
assessing their performance and in compiling this report. This part of the study was under the direction of Mr. R. J. Law. The arrangements for exposure and examination of specimens, and SOITle over-all co-ordination of the program were carried out under the direction of Mr. E. V. Gibbons of the Division of Building Research.
The Division is indebted, not only to those companies who co-operated in making this study possible, but also to those who have contributed in the provision and servicing of certain of the exposure sites.
Ottawa April 1968
N. B. Hutcheon As sistant Director
THE CORROSION BEHAVIOUR OF MONEL METAL IN EIGHT CANADIAN ATMOSPHERES - - A FIVE YEAR
PROGRESS REPOR T
by R. J. Law,
International Nickel Corrrpany of Canada Lirrri.ted, Toronto, Ontario
and
E. V. Gibbons,
Division of Building Research,
National Research Council of Canada, Ottawa, Canada
Studies were started in 1953 by the for rn e r As sociate Committee on Corrosion Research and Prevention to dete r m in e the relative corrosion behaviour of different architectural rn e ta l s when exposed at different locations across Canada. The m e ta.l s for exposure were selected by the Cornrrritte e and set out at the outdoor test sites of the Division of Building Research of the National Research Council of Canada. The first rn e ta l s exposed included s p e ci.rnen s of a lUITlinUITl, and a lurn inurn coupled to copper, zinc and steel, three low alloy steels, three stainless steel alloys, two rria gn e s iurn alloys and rolled zinc. To complete the over-all prograITl, additional rna te r i.al s were exposed. Included were s p ec irn en s of copper, rnurrtz rn e ta.l, lead alloys, Monel, and a number of different rne tal and organic coatings on steel. The first group of metals mentioned has c omp le ted the ten year s of exposure
originally planned, and the results have been reported. Progress reports have been issued describing the performance of the other metals after five years of exposure. This report describes the five-year pe rf or-rna.nc e of the Monel rn e ta l sp ec im eris furnished by the International Nickel
Company of Canada LiITlited and set out in 1961.
The s pe cirrien s exposed were flat sheets, held in place by porcelain insulators at 30 deg to the horizontal, facing south. Twelve sp ec irn en s of each type of m etal were set out initially at each site; three s p e c i.rn e n s of each are r em ov ed after one, two, five and ten years of exposure. The sp e c irn en s were cut to size by the supplier, corner notched for orientation, identified by a drilled hole sys terri and weighed prior to
s h iprn errt to the sites. After each exposure period the appropriate lot was r ern ov ed and returned to D. B. R. for checking and photographing. The lot was then forwarded to INCO f01" cleaning, re-weighing and corrosion evaluation.
2
-DESCRIPTION OF MATERIAL
*
Monel nickel-copper alloy specimens were supplied by the International Nickel Cornpariy of Canada Lirn.ited and c or r e sp ond to a grade now designated as Monel alloy 400. Sp e c irrien s were 4 in. by 6 in. by .045 in., and were prepared fr om cold rolled
annealed and pickled strip, rn e chan.i.c a.lly polished on one side. This is a type of finish which has been used extensively in architectural applications, c on surn.e r products, and other iteITls for which a bright surface is a desirable feature. Sp ec irne n s were rn oun te d on the test racks with the polished surfaces facing upwards.
The chern.i.ca l c ornpo si.tion of Monel alloy 400 has the following riorn ina l analysis:
Nickel Copper Carbon Manganese Iron Sulphur Silicon
DESCRIPTION OF TEST SITES
66.0% 31.5% 0.12% 0.90% 1. 35%
o.
005% 0.15%The sites were provided with tubular racks and stainless steel
fr arn e s for rn ounting the sp ec irnen s , A c ornpl ete description of the test sites used has been published (l).
Site No.1, Ottawa - This site is located on the easterly city l irnits and can be classified as s ern iv r ur-al,
Site No.2, Saskatoon - This is a rural site located on the c arnpu s of the Univer sity of Saskatchewan on the outskirts of Saskatoon.
Site No.3, Montreal - This is an industrial site located on the roof of a CNR Stores building in the Point St. Charles district.
Site No.4, Halifax - This is a rna r ine-dndu s tr ia.l site located on the roof of a federal public building in the downtown area, two city blocks fr orn the harbour.
3
-Site No.5, York Redoubt - This is a approximately 7 miles from Halifax. 100 ft and 300 ft from the ocean.
rural-marine site, located
It is at an elevation of about
Site No.6, Norman Wells - This is a far northern site located in the Mackenzie River Valley approximately 90 miles south of the Arctic
Circle.
Site No.7, Esquimalt, B. C. This is a rural-marine site located at the southeast extremity of Vancouver Island, 15 miles from the
City of Victoria. It is at an elevation of 50 ft and approximately 1500 ft from the oc ean,
Site No.8, Trail, B. C. This is a semi-rural site located at Birchbank in the Columbia River Valley 6 miles north of the city of Trail.
In addition to meteorological data available from Department of Transport weather stations near the sites, the sulphur dioxide content of the atmosphere was determined, using the lead peroxide method. This rn e th od does not measure the volumetric concentration of sulphur dioxide (SOZ) in the atmosphere directly, but presents an integrated measure of the sulphur dioxide "activity" during a period of exposure. It was found that this instrument was well suited to measure the relative levels of SOZ at the exposure sites when metals are under test. The measurements were made on a monthly basis at each site. The results have been con-densed and the average levels during the five-year exposure of specimens
of monel metal are given in Table 1. Figure 1 is a graphic representation of the average concentration of SO at each test site.
Z
EXAMINA TION PR OCEDURE
Specimens from lot No. 1 (one-year exposure) and lot No. 3
(five- year exposure) were examined visually before and after being c Leaned ,
The cleaning procedure consisted of scrubbing the specimens lightly with a bristle brush using warm water and powdered pumice. Surface staining was readily removed by this treatment, so it was not necessary to resort to an acid dip. After being cleaned, specimens were rinsed thoroughly and wiped dry. An unexposed specimen lost an average of 0.015 gm when
subjected to this cleaning procedure, so recorded weight losses were corrected accordingly.
4
-The measure of the extent of corrosion was taken as the difference between the recorded original weights and the final weights of the specimens. Corrosion rates were calculated for the three different exposures and expressed in mils penetration per year.
OBSER VA TIONS
A considerable amount of tarnish or brown staining was observed on the specimens returned from exposure for one year; it was apparent largely on the under side of the specimens as they are mounted on the test racks. The condition was particularly noticeable on the specimens from the Halifax (marine-industrial) and Montreal
sites. When cleaned, specimens from Ottawa, Saskatoon, Halifax (rural), Norman Wells, Esquimault, and Trail showed little or no change from the original in the appearance of the top surface but a slight dulling on the under side. The specimens from Montreal showed slight dulling on the top surface, and more pronounced dulling on the under side. Specimens from the Halifax (marine-industrial) site were dull on both surfaces.
To some degree, dullness on the under side of specimens can be attributed to the original pickled finish.
Following exposure for five yea r s, uncleaned specimens again showed tarnish to a degree which varied from practically nil at Norman Wells, to severe tarnish, almost to a black colour, at the Halifax (marine-industrial) site. The tarnish was again generally most apparent on the under side of the specimens. After being cleaned, the specimens from the more aggressive sites at Halifax and Montreal
remained dull on both surfaces. Specimens from Norman Wells and also from Saskatoon retained the original bright polished top surface. Tables I I and III rate the behaviour of specimens following five years' exposure
at the different sites with respect to tarnishing before cleaning, and dulling after cleaning.
Table IV shows corrected weight losses in grams for Monel alloy 400 specimens removed from the eight atmospheric test sites after one, two and five years of exposure. Average weight losses are shown in Table V, together with equivalent penetration in mils per year. No local attack or pitting was observed on any of the specimens.
5
-DISCUSSION
A very high level of corrosion resistance was displayed by Monel alloy 400 at all test sites. As indicated in Figure 2, initially low corrosion rates tended to become even lower as the duration of exposure increased.
The Halifax (marine-industrial) site provided the most aggressive corrosive atmosphere; the Montreal site was next in
order of corrosivenes s , Comparison of observed corrosion rates with reports provided by the National Research Council of Canada on the average amount of SO in the atmospheres at the various sites suggests that this is the most i¥nportant characteristic in determining the
aggressiveness of the atmosphere. At very low levels of atmospheric S02' a marine location exerts some slight influence, as indicated by the similarity in rates between Esquimault (marine with very low SO ) and Ottawa (non-marine with low but appreciable SO). In this case,2 the virtual absence of S02 appear s to be offset by
ｴｨｾ
marine location. At Saskatoon and Norman Wells, which provide inland atmospheresthat are extremely low in S02' polished surfaces were virtually unchanged after five years' exposure.
REFERENCE
1. Gibbons, E. V. Outdoor Exposure Sites of the National Research Council Chemistry in Canada, Vol. 12, No.3, March 1960, p.44-48 (NRC 5593).
TABLE I
AVERAGE AMOUNT OF SULPHUR DIOXIDE IN THE ATMOSPHERE AT EACH TEST SITE FROM 1962-1966
2
Site No. Location Mg ofS0
3/dm /day 1 Ottawa 0.52 2 Saskatoon 0.10 3 Montreal 1. 39 4 Halifax 2.23 5 York Redoubt 0.29 6 Norman Wells 0.001 7 Esquimault 0.06 8 Trail 0.72
TABLE II
VISUAL INSPECTION, BEFORE CLEANING 5-YEAR EXPOSURE
Test Site Top Surface Under Side
1 Ottawa Very slight tarnish Quite tarnished
2 Saskatoon Very slight tarnish Slight tarnish
3 Montreal Tarnish Quite tarnished
4 Halifax (M-I) Completely tarnished; almost black; slightly worse, though uniform on top surface.
5 Halifax Slight tarnish Slightly more tarnish 6 Norman Wells As original Very slight tarnish 7 E s quimaul t Slight tarnish Slightly more tarnish
TABLE III
VISUAL INSPECTION, AFTER CLEANING 5 - YEAR EXPOSURE
Test Site Top Surface Under Side
1 Ottawa Very Slightly dull Slightly dull
2 Saskatoon As original Slightly dull 3 Montreal Quite dull Quite dull
4 Halifax (M -I) Dull Quite dull 5 Halifax Slightly dull Slightly dull 6 Nor m an Wells As original Slightly dull
7 Es quirn.ault Very slightly dull Slightly dull
TABLE IV
CORRECTED WEIGHT LOSSES (GRAMS) OF MONEL ALLOY 400 SPECIMENS EXPOSED FOR 1, 2, AND 5 YEARS
Test Site Spec. No. 1 Year 2 Years 5 Years
1 Ottawa 1 0.062 0.149 0.290 (semi-rural) 2 0.057 0.132 0.265 3 0.068 O. 133 0.268 2 Saskatoon 1 0.020 0.001 0.031 (rural) 2 0.020 0.007 0.037 3 0.007 0.002 0.022 3 Montreal 1 0.223 0.372 0.890 (industrial) 2 0.206 0.371 0.912 3 0.213 0.339 0.914 4 Halifax 1 0.675 1. 106 2.464
(marine- indus trial) 2 0.681 1. 250 2.481
3 0.624 1.047 2.476 5 Halifax 1 0.093 0.153 0.428 (rural-marine) 2 0.091 O. 165 0.404 3 0.091 0.163 0.418 6 Norman Wells 1 0.031 0.016 0.045 (rural) 2 0.014 0.017 0.035 3 0.002 0.015 0.046 7 Esquimault 1 0.059 0.082 0.206 (rural-marine) 2 0.069 0.076 0.213 3 0.064 0.082 O.182 8 Trail 1 0.039 O. 101 0.199 (semi-rural) 2 0.053 0.080 O. 183 3 0.049 0.108 0.207
TABLE V
AVERAGE WEIGHT LOSS (GRAMS) AND EQUIVALENT ｐｅｎｅｔｒａｔＱＰｾ
(MILS PER YEAR) OF MONEL ALLOY 400
SPECIMENS EXPOSED FOR 1, 2, AND 5 YEARS
Test Site No. 1 Year 2 Years 5 Years
GMS M. P. Y. GMS M.P. Y GMS M. P. Y 1 Ottawa 0.062 0.009 0.138 0.010 0.274 0.008 2 Saskatoon 0.016 0.002 0.003 0.0002 0.030 0.0009 3 Montreal 0.214 0.031 0.361 0.026 0.905 0.026 4 Halifax (M -I) 0.660 0.094 1. 134 0.081 2.474 0.071 5 Halifax 0.092 0.013 0.160 0.011 0.417 0.012 6 Norman Wells 0.016 0.002 0.016 0.001 0.042 0.001 7 Esquimault 0.064 0.009 0.080 0.006 0.201 0.006 8 Trail 0.047 0.007 0.096 0.007 0.196 0.006
3.0
0 -N E 0-
("t'\ 02. 5
Vl L.L. 0 C1l :E ,2. 0
0 0 ::J: I -ｾ :E1.5
ｾ 0x
0 a:::1.0
ｾ 0-0 <C ｾ -'0.5
, -' ｾ>
ｾ - ' N 0 Vl(1)
Ottawa
(5)
York Redoubt
(2)
Saskatoon
(6) Norman Wells
I--
(3)
Montreal
(7)Esquimalt
-(4 )
HaIi fax
(8)
Tr aII
(4 ) -ｾ -ｾ(3)
-ｾ-(8)
ｾ(1)
r---
-(5)
-( 2)ｾ
(6)
n
FIGURE
1
AVERAGE AMOUNT OF SULPHUR DIOXI DE IN THE ATMOSPHERE
AT EACH SITE FROM 1962-1966
3. 0
(I)
Ottawa
(5)
Halifax
(2)
Saskatoon
(6)
Norman Wells
(3) Montreal
(7)Esquimalt
(4 )
Halifax (M-I)
(8)
Tr ai I
(4 )- I
Note:
Average original specimen
LLI
