Ni-Cr-Mo alloy having improved corrosion resistance

Abstract

An alloy having a combination of good corrosion resistance in sulfuric acid and resistance to localized attack in chloride-bearing, gas scrubbing systems has a composition in weight percent of 22.0% to 24.0% chromium, 15.0% to 16.5% molybdenum, up to 1.5% iron, 0.14% to 0.46% copper, 0.1% to 0.4% aluminum, up to 0.010% carbon, up to 0.3% cobalt, up to 0.5% manganese, up to 0.10% silicon, up to 0.015% phosphorus, up to 0.010% sulfur, and the balance nickel plus impurities.

1 . An alloy with good resistance to concentrated sulfuric acid and chloride-induced pitting consisting in weight percent essentially of 22.0% to 24.0% chromium, 15.0% to 16.5% molybdenum, up to 1.5% iron, 0.14% to 0.46% copper, 0.1% to 0.4% aluminum, up to 0.010% carbon, up to 0.3% cobalt, up to 0.5% manganese, up to 0.10% silicon, up to 0.015% phosphorus, up to 0.010% sulfur, and the balance nickel plus impurities.  
   
   
       2 . A method of improving corrosion resistance in sulfuric acid and chloride induced pitting in an alloy having a composition consisting in weight percent essentially of 22.0% to 24.0% chromium, 15.0% to 16.5% molybdenum, up to 1.5% iron, 0.1% to 0.4% aluminum, up to 0.010% carbon, up to 0.3% cobalt, up to 0.5% manganese, up to 0.10% silicon, up to 0.015% phosphorus, up to 0.010% sulfur, and the balance nickel plus impurities comprising adding copper to the alloy thereby forming a modified alloy, the copper being added in an amount so that 0.14 to 0.46 weight percent copper is present in the modified alloy.