Also known as Carpenter 20 and 20CB-3, Alloy 20 Bolts offer users a combination of nickel, chromium, molybdenum, and copper which provides good general corrosion resistance. Alloy 20 (2.4660) bolts are best suited for mid-range corrosion use – better than steel alloys but not at the level of high performance nickel based alloys like Hastelloy C276. Alloy 20 is a nickel alloy that was specifically designed to withstand the harsh environment of hot sulfuric acid but also performs well in a variety of other acids. Alloy 20 bolts are an ideal choice when you don’t need the corrosion resistance power and price-tag of high performance nickel alloys like Hastelloy C276; but you need something that will give you more protection than 316 stainless steel.
Resistance to Corrosion
Alloy 20 bolts perform well in hot sulfuric acid, particularly in terms of stress-corrosion cracking resistance in boiling sulfuric acid at concentrations ranging from 20% to 40%, as well as overall sulfuric acid resistance. Alloy 20 provides solid acid protection and will outperform Duplex or even Monel, however for high temperature and high concentration acids, Inconel or Hastelloy fasteners may be required. Furthermore, Alloy 20 bolts have good resistance to phosphoric and nitric acids.
Corrosion Resistant Characteristics:
Sulfuric acid protection is good between 20% and 40%.
Chloride has good stress corrosion cracking, pitting, and crevice corrosion resistance.
General corrosion prevention that is reasonable
In the as-welded condition, there is good intergranular corrosion resistance.
Mechanical Characteristics
- Elongation: 30% • Ultimate tensile strength: 80 ksi • Yield strength: 35 ksi • Density: 0.292 lb/in.3 • Electrical Resistivity (RT) 651 ohm-cir mil/ft
Temperature In addition to their corrosion resistance, Alloy 20 bolts can withstand moderately high temperatures, with mechanical strength maintained up to 1000°F.
Columbium is used to support Alloy 20 bolts during welding to prevent carbide precipitation. Furthermore, it provides intergranular corrosion resistance in the as-welded state.
Applications
- For flue-gas desulfurization, power plants use alloy 20 bolts.
- In mid-range corrosive chemical processing environments, Alloy 20 bolts are used to connect heat exchangers, mixing tanks, metal cleaning equipment, pickling tanks and racks, and piping.
- Alloy 20 bolts aid in the prevention of corrosion in the food and dye industries.
- Plastics and synthetic rubber manufacturers also use alloy 20 fasteners.
