Alloy A20 (ASTM A 265, B 366, B 463, B 464, B 471, B 472, B 473, B 474, B 475, UNS N08020 NACE MR0175) is an iron-nickel-chromium-based austenitic superalloy renowned for its exceptional resistance to acid attack, particularly sulfuric acid. It exhibits outstanding resistance to general corrosion, pitting, and crevice corrosion in environments containing chlorides, sulfuric, phosphoric, and nitric acids. The addition of niobium stabilizes the alloy against sensitization and consequent intergranular corrosion.

Commonly known as Carpenter 20, 20Cb-3®, Incoloy® alloy 20, or simply alloy 20 stainless steel, this alloy is highly regarded for its robust properties. Equivalent grades to standard Alloy 20 (UNS N08020, WERKSTOFF NR. 2.4660, AFNOR Z2NCUD31-20AZ, EN NiCr20CuMo, JIS SUS 304, BS 304S31, GOST 08Х18Н10) further highlight its versatility and widespread use in various industrial applications.

Key characteristics of Alloy 20 include:

– Exceptional resistance to corrosion by both hot and cold sulfuric acid.
– Excellent resistance to chloride stress corrosion cracking.
– Impressive mechanical properties and ease of fabricability.
– Minimal carbide precipitation during welding, ensuring structural integrity.

These qualities make Alloy A20 a preferred choice where resistance to corrosive environments and durability are paramount.