API 571 Certification (Corrosion & Materials) Practice Test

Which alloys are particularly resistant to chloride stress corrosion cracking?

1. All grades of Copper Alloys

2. All 300 series Stainless Steel

3. 400 series Stainless Steel

4. Aluminum Alloys

The correct answer is: All 300 series Stainless Steel

The resistance of alloys to chloride stress corrosion cracking (SCC) is a critical factor for materials used in environments where chlorides are present, such as seawater or chemical processing environments. The 300 series stainless steels, particularly those containing higher nickel content, are known for their excellent resistance to SCC. This resistance is partly due to the protective passive film that forms on the surface of these alloys, which is particularly stable in the presence of chlorides. In contrast, the other materials listed have varying degrees of susceptibility to chloride SCC. Copper alloys, while generally resistant to corrosion, can still suffer from stress corrosion cracking under certain conditions. The 400 series stainless steels, typically ferritic and martensitic, are more susceptible to SCC due to their lower nickel content compared to the 300 series. Aluminum alloys can also be vulnerable to SCC in chloride environments, as their protective oxide layer may be compromised. Therefore, the 300 series stainless steels' composition and protective mechanisms make them particularly well-suited for applications in chloride-rich environments, significantly enhancing their ability to withstand stress corrosion cracking compared to the other options listed.