Alloy 20 is a nickel–chromium–molybdenum alloy developed for applications involving sulfuric acid. Its corrosion resistance also finds other uses in the chemical, food, pharmaceutical, power generation, 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 stainless steel but a nickel alloy (ASTM). Alloy 20 is often chosen to solve stress corrosion cracking problems, which may occur with 316L stainless. Alloy of the same name with the designation "Cb-3" indicates Columbium stabilized.

Composition

• Nickel, 32–38%
• Chromium, 19–21%
• Carbon, 0.06% maximum
• Copper, 3–4%
• Molybdenum, 2–3%
• Manganese, 2% maximum
• Silicon, 1.0% maximum
• Niobium, (8.0 X C), 1% maximum
• Iron, 31–44% (balance)

Other names

• UNS N08020
• DIN 2.4660
• CN7M
• Carpenter 20 CB-3^TM
• AL 20^TM
• Carlson Alloy C20^TM
• Nickelvac 23^TM
• Nicrofer 3620 Nb^TM, also known as VDM® Alloy 20^[1]

Specifications

• ASTM B729, B464, B366, B463, B473, B462
• ASME SB729, SB464, SB366, SB473, SB462
• ANSI / ASTM A555-79
• EN 2.4660
• UNS N08020
• Werkstoff 2.4660
• Castings are designated CN7M