This is a microsection showing stress corrosion cracking of an austenitic cast iron pump case. This alloy has been used extensively for large, single stage pump cases, but it is susceptible to SCC in warm seawater. Stress relieving can extend the life, but failures generally occur in 1.5 to 5 years, depending on local stresses. The solution to this problem is to use a superduplex stainless steel pump case to ASTM A995 grade 6A, if cast, or to use a fabricated case made from UNS S32760.