INDUSTRIAL A N D E N G I N E E R I N G C H E M I S T R Y
April 1950
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RECEIVED September 16, 1949. Presented before the Division of Petroleum Chemistry a t the 116th Meeting of the AM~RICAN CHEMICAL SOCIETY, Atlantic City, N. J.
Acid Corrosion Resistance of Tantalum, Columbium, Zirconium, and Titanium DONALD F. TAYLOR Funsteel Metullurgical Corporation, North Chicago, I l l . Tantalum, columbium, zirconium, and titanium were tested in a number of reagents, under identical conditions of solvent action, to determine their acid corrosion resistance, Corrosion rates show tantalum to be completely
resistant to all solutions tested; columbium had a high resistance against all these solutions except hot concentrated hydrochloric and sulfuric acids; zirconium and titanium were the least resistant of the four metals.
T
HE solubilities and resistance to corrosion of tantalum and of columbium have been reported (I,%’). These properties of zirconium and titanium have been discussed in a number of re-
Specimens of the metals in sheet form (”8 X 4 X 0,010 inch) were partially submerged in various reagents under the conditions and for the periods indicated in Table I. The strips were cut from clean, bright, rolled, ductile sheet. The reagents were not cent publications (3-6). The purpose of this paper is to present the results of a solubility study obtained by subjecting the four agitated or aerated. “eight losses are reported as corrosion rates metals to identical conditions of solvent action. The solutions in inches per year. The data for tantalum, columbium, and zirconium (Table I ) selected include those which present many of the severe corrosion are in general agreement with those shown in the “Corrosion problems in chemical industries. The term “corrosion resistance,” like the terms “speed,” Handbook” ( 2 ) . There was no apparent attack on the zirco“brightness,” “hardness,” and “strength,” is more significant nium by cold nitric acid or by cold dilute sulfuric acid, but exposure when a standard of reference is used. The solubilities of any metal to all other acids tested and to 10% ferric chloride caused varying depend on the nature of the corrosive medium and on temperadegrees of attack. The zirconium samples were rapidly dissolved by cold and by hot concentrated sulfuric acid and by aqua regia. ture and time of exposure. Many metals are resistant t o a few The attack by hot concentrated hydrochloric acid was rather secorrosive materials; a few are resistant to many materials, but no vere. metal is completely resistant to all corrosive materials even at orOf the four metals titanium was found to be the least corrosion dinary temperatures. The tantalum and columbium specimens represent typical proresistant to acids. Its best resistance is against nitric acid and duction materials. The titanium and zirconium specimens were aqua regia. Columbium has a high degree of resistance against all solutions prepared from magnesium reduced materials and are believed to tested except hot concentrated hydrochloric acid and hot concenbe typical of the metals t h a t are currently available. No analytrated sulfuric acid. Tantalum is completely resistant to all the ses were made to determine purity. solutions tested. I n no case was there exhibited any weight loss or any detectable change in appearance. RESISTANCE OF TANTALUM, COLUMBIUM, ZIRCONIUM, AND TABLE I. ACIDCORROSION All four metals are rapidly attacked by TITANIUM hydrofluoric acid. Temp., Solution O C. 19-26 HC1, 18% 19-26 HC1, Coned. 110 HC1, Concd. 19-26 HK03 Coned. 19-26 1HNds.ZHCl 50-60 lHiiOs.2HCl 19-26 &SO4 50% 19-26 HzSOa: Concd. 95-100 HzSOr 20% 145 HISOI’ Coned. 19-26 HsPOi, 85% 19-26 FeCls, 10% e Became brittle. b Tarnished. 0 Uneven corrosion.
Test Period, Days 36 36 7 36 35 1 35 36 4
30 36 36
Tantalum
Corrosion Rate, Inches/Year Columbium Zirconium 0.00000 0.00009~ 0.00012 0.00008 0.01875 0.004b 0.00000 0.00000 0.00002 Very soluble 0.001 Very soluble Not tested 0 . ooooe 0.00002 Very soluble 0.00002 0.00018 0.1W Very soluble 0.00002 0.00002 0.00000 0.00042
;
Titanium 0.0445 0.698 Not tested 0.00005 0.00021 Not t e8t ed 0.0021 0.0468 Not tested Very soluble 0.00675 0.00003
LITERATURE CITED (1) Balke, C. W., “Corrosion Handbook,” H. H. Uhlig, editor, p. 60, New York, John Wiley & Sons, 1948. (2) Ibid., p. 320. (3) Fontana, M. G., INU. ENC.CHERI., 40, No. 10, 99A (1948). (4) Gee, E. A., Golden, L. B., and Lusby, W. E., Jr., Ibid., 41, 1668 (1949). (5) Hutchison, G. E., and Permar, P. H., Corrosion, 5, 319 (1949). (6) Jaffee, R. I., J . Metals, 1, No. 7, 6 (1949). RECEIVED November 21, 1949.
