Hydrogen Blistering of Steel In Hydrogen Sulfide Solutions^⋆

Extensive damage to some refinery equipment has occurred owing to transmission through steel of the hydrogen formed during corrosion of steel by hydrogen sulfide solutions. Damage in the form of hydrogen blistering, fissuring and embrittlement of steel has been particularly severe in catalytic cracking gas plants. Laboratory investigations have been made of the relative influence of environmental factors on the rate and extent of hydrogen transmission through carbon steel. These studies include determination of the effects of concentration of important constituents such as hydrogen sulfide, low molecular weight organic acids, ammonia and hydrogen cyanide. Several other compounds were studied and found to be of minor importance. The laboratory method involved measurement of the volume of hydrogen which passed through to the opposite side of a thin wall of carbon steel. In certain hydrogen sulfide environments hydrogen transmission practically ceased after a short time. This behavior is ascribed to formation of a protective scale of iron sulfide. However, in certain alkaline solutions containing cyanide ion corrosion and a high continuing rate of hydrogen transmission occurred owing to formation of a ferrocyanide complex which prevented development of a protective scale. On the basis of the data obtained it is shown that rate of hydrogen transmission can be reduced greatly by indicated changes in chemical environment.