API 571 Certification (Corrosion & Materials) Practice Test

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Among the following, which alloy offers the best resistance to sulfuric acid corrosion?

316L SS
Alloy C-276
CS
Alloy B-2

The correct answer is: Alloy B-2

Alloy B-2 stands out as having excellent resistance to sulfuric acid corrosion, making it ideal for applications where exposure to such conditions is frequent. This nickel-molybdenum alloy exhibits exceptional resistance to both reducing and oxidizing environments, specifically against highly concentrated sulfuric acid. Alloy B-2 is engineered to minimize susceptibility to pitting and crevice corrosion, which can be problematic in many other materials, particularly at elevated temperatures and aggressive concentrations. Its composition allows it to remain stable and maintain strength in corrosive acidic environments, making it a preferred choice for equipment and piping used in corrosive service. While 316L stainless steel is known for its good corrosion resistance in many environments, it does not match the performance of Alloy B-2 in sulfuric acid conditions. Similarly, Alloy C-276 offers significant corrosion resistance but is more effective in reducing environments rather than in strong acids. Carbon steel (CS) is generally unsuitable for sulfuric acid service due to rapid corrosion and deterioration in such environments. Therefore, Alloy B-2 is regarded as the material of choice for the best protection against sulfuric acid exposure.