It has been known for some time that Monel is susceptible to intergranular stress corrosion cracking in fluosilicic acid. It was surprising, however, to find “K” Monel bolts breaking in transgranular fashion in hydrofluoric acid vapor. The diagnosis that these failures were stress corrosion cracking was confirmed by reproduction of the cracking in the laboratory. Several similar case histories are reviewed and a number of qualitative laboratory experiments on the stress corrosion cracking of Monel and some other high nickel alloys in hydrofluoric acid environments are described. The number and path of the cracks is influenced by composition, cold work, heat treatment, stress, time and conditions of exposure. Cracking is most prone to occur where corrosion rates are high, such as in moist, aerated vapor. This suggests that hydrogen may play a part in the cracking. Means of avoiding the cracking are discussed. 3.5.8
Stress Corrosion Cracking Of Monel in Hydrofluoric Acid★
HARRY R. COPSON—Dr. Copson, head of the Corrosion Section of the Research Laboratory, The International Nickel Co., Inc., Bayonne, N. J., has been chairman of the Corrosion Division of The Electrochemical Society and general chairman of the society’s 1953 New York meeting. In 1949 he was chairman of the AAAS Gordon Research Conference on Corrosion and in 1946 was awarded the Dudley Medal of the ASTM. Active on many corrosion committees, author of many papers he has a BS from University of Massachusetts (1929) and PhD in physical chemistry from Yale (1932). He has been active in corrosion research since 1934.
C. F. CHENG is an engineer in the Large Steam Turbine-Generator Department, General Electric Company, Schenectady, New York. Previously he spent nine years with The International Nickel Company, where he was in charge of their technical office in China and reassigned in 1950 to their Research Laboratory. His other associations include U. S. Steel Export Co., Republic Steel Corporation and Wah Chang Refining and Smelting Co. He received a degree in chemical engineering from Massachusetts Institute of Technology in 1940.
