High Quality Content by WIKIPEDIA articles! Alloy 20 is a nickel-chromium-molybdenum stainless steel alloy developed for applications involving sulfuric acid. Its corrosion resistance also finds other uses in the chemical, food, pharmaceutical, and plastics industries. Alloy 20 resists pitting and chloride ion corrosion and its copper content protects it from sulfuric acid. Alloy 20 is not a SS but a nickel alloy (ASTM).