API 571 Certification (Corrosion & Materials) Practice Test

Which alloy shows greater resistance than regular carbon steel in sulfuric acid environments?

1. 316L SS

2. Low alloy steels

3. High Nickel Cast Iron

4. Alloy C-276

The correct answer is: 316L SS

The choice of 316L stainless steel as the alloy that shows greater resistance than regular carbon steel in sulfuric acid environments is rooted in its chemical composition and structure. 316L stainless steel contains significant amounts of chromium and nickel, which enhance its corrosion resistance compared to carbon steel. Additionally, the presence of molybdenum in 316L provides further resistance to pitting and crevice corrosion, particularly in chloride-rich environments. In sulfuric acid, carbon steel is prone to rapid corrosion due to the acidic nature of the environment, leading to material loss. Conversely, 316L's passivation layer, which forms in the presence of oxygen, helps protect the alloy from further attack, making it more suitable for such conditions. While low alloy steels might provide some resistance improvements over carbon steel, their performance in acidic environments is typically not sufficient to rival that of 316L. High Nickel Cast Iron does offer good corrosion resistance as well, but it generally does not outperform 316L in sulfuric acid. Lastly, Alloy C-276 is a highly corrosion-resistant nickel-molybdenum alloy, but in comparison to 316L, which is more widely used and has significant resistance, it is considered a specialty alloy for severe conditions and