Alloy 20 is a nickel-iron-chromium austenitic alloy developed with the additions of copper and molybdenum for maximum resistance to acid attack, specifically sulphuric acid.
It has excellent resistance to generation corrosion, pitting and crevice corrosion in chemicals containing chlorides, sulphuric, phosphoric and nitric acids. This means it offers strong resistance to chloride stress corrosion cracking.
It also contains niobium for stabilization against sensitization and resultant intergranular corrosion. It excels in resisting corrosion to hot sulphuric acids.
Alloy 20 combines excellent corrosion resistance with elevated mechanical properties and relatively easy fabrication. Its stabilization also minimizes carbide precipitation during welding.
While it was originally designed for use in sulphuric acid related industries, Alloy 20 is now a popular choice in a variety of industries including the chemical, food, dye, pharmaceutical and plastics industries. In addition, this superalloy is used in heat exchangers, mixing tanks, metal cleaning and pickling equipment and piping.
The nickel content of Alloy 20 is on the border between a nickel alloy and stainless steel. It may also be referred to as alloy 20 stainless steel.