Stress Corrosion Cracking of Mild Steel in Ammonia Vapor Above Liquid Ammonia

The stress corrosion cracking (SCC) of mild steel in saturated ammonia vapor was studied by slow straining of a hollow specimen, which could be heated or cooled in relation to the temperature of the liquid. SCC was effectively prevented if the specimen was heated 1 to 2 C above the temperature of the liquid, but SCC did occur on the cooled specimen, where condensation took place. Water inhibition of the liquid ammonia (with 0.2% water) did not prevent SCC in vapor of a strongly cooled specimen, where condensation was rapid.