API 571 Certification (Corrosion & Materials) Practice Test

Which stainless steel is known to be highly resistant to CO2 corrosion?

1. Duplex Stainless Steel

2. 410 Stainless Steel

3. 300 series Stainless Steel

4. Alloy 600

The correct answer is: 300 series Stainless Steel

The 300 series stainless steel, particularly types like 304 and 316, is well-regarded for its corrosion resistance, including its ability to withstand CO2 corrosion in various environments. This is largely due to the presence of a higher percentage of nickel and chromium, which enhances the passive film that protects the steel from aggressive agents such as carbon dioxide. In environments where CO2 is present, such as in certain oil and gas applications, the protective oxide layer on the stainless steel helps inhibit the formation of corrosion products, effectively maintaining integrity. This protective film minimizes the risk of localized corrosion, pitting, and stress corrosion cracking, all of which can be exacerbated by the presence of CO2. In contrast, the other choices presented have varying levels of resistance to CO2 corrosion. Duplex stainless steels have a different balance of microstructure and might be suited for specific applications but generally do not exhibit the same level of resistance as the 300 series in CO2 environments. Alloy 600, while resistant to some forms of corrosion, is not specifically known for CO2 resistance. Lastly, 410 stainless steel, which is a martensitic stainless steel, tends to be less resistant to corrosion overall and is not the preferred choice in environments with significant CO2