Stress corrosion cracking of carbon steel in ammonia

The authors discuss how stress corrosion cracking (SCC) growth of carbon steel in ammonia increases with the stress intensity factor and follows approximately the square root of the exposure time. The reduction of crack growth rate with time is mainly caused by crevice corrosion attack in the outer part of the crack. SCC of carbon steel in ammonia is prevented by cathodic polarization. With high anodic polarization, SCC occurs in ammonia with 2000 ppm water and in ammonia without oxygen. Coupling to zinc, aluminum, and magnesium anodes gives cathodic protection and prevents SCC. Aluminum and zinc metal spray both prevent cracking.