API 571 Certification (Corrosion & Materials) Practice Test 2025 - Free Practice Questions and Study Guide

In phosphoric acid environments, the selection of a suitable material is crucial to ensure resistance to corrosion. Among the options provided, 316L stainless steel is known for its enhanced corrosion resistance properties due to its molybdenum content, which helps to improve resistance to pitting and crevice corrosion when exposed to chlorides and acidic conditions.

Although 304L stainless steel has some resistance to many acids, its lack of molybdenum makes it less effective in environments like phosphoric acid, which can be more aggressive. C-0.5Mo LAS (Low Alloy Steel) may not provide adequate resistance to acidic corrosion, especially in higher concentrations of phosphoric acid. Alloy C-276 is renowned for its impressive corrosion resistance to a variety of corrosive environments, including hydrochloric acid and sulfuric acid, but it may not be as favorable in phosphoric acid as 316L stainless steel, which is specifically designed for such applications.

Thus, 316L stainless steel is the most suitable choice due to its balance of strength, formability, and resistance to corrosion in the specific conditions presented by phosphoric acid environments.