Stress Corrosion of Type 304 Stainless Steel in Chloride Environments

The stress corrossion behavior of AISI Type 304 stainless steel was investigated as a function of the environmental variables, temperature, pH, cation species, and chloride concentration in concentrated solutions of MgCl₂, CaCl₂ and LiCl.

The time to failure at a constant stress, chloride ion concentration, and temperature increased in the order MgCl₂, CaCl₂, LiCl. The data indicate that the cation has an important effect on the stress corrosion behavior in chloride solutions. The influence of the cation species on the stress corrosion phenomenon may be explained by surface effects in which the adsorption of ions plays an important role.

For MgCl₂ solution boiling at 125 C the time to failure increases with increase in pH of the solution, whereas for the CaCl₂ solution boiling at the same temperature the pH has no perceptible effect.

It was established that temperature has a considerably greater effect on the time to failure at a given stress in MgCl₂ solutions than does the chloride ion concentration. This observation is borne out by practical experience in which exceedingly low concentrations of chloride have caused cracking in Type 304 stainless steels at high temperatures; cracking is difficult to produce in concentrated solutions of similar chlorides at low temperature