Hastelloy C-276 is a nickel-molybdenum-chromium alloy with the addition of tungsten, known for its exceptional resistance to a wide range of corrosive environments, including strong oxidizing and reducing acids, chlorides, and wet chlorine gas. It is one of the most versatile corrosion-resistant alloys available. The alloy is solid-solution strengthened and is not precipitation hardenable.

The nominal chemical composition is: nickel 57.0 percent (balance), molybdenum 15.0–17.0 percent, chromium 14.5–16.5 percent, iron 4.0–7.0 percent, tungsten 3.0–4.5 percent, cobalt up to 2.5 percent, and smaller amounts of carbon, manganese, silicon, vanadium, and phosphorus.

Key mechanical properties (typical, annealed condition):

● Tensile strength: 690–790 MPa

● Yield strength (0.2% offset): 280–355 MPa

● Elongation: 40–50 percent

● Hardness: 85–100 HRB

● Density: 8.89 g/cm³

Hastelloy C-276 offers outstanding resistance to pitting, crevice corrosion, and stress corrosion cracking in chloride environments. It resists a wide variety of aggressive chemicals including sulfuric acid, hydrochloric acid, nitric acid, phosphoric acid, acetic acid, and wet chlorine gas. The alloy is readily weldable and retains its corrosion resistance in the as-welded condition (no sensitization).

Common standards: ASTM B575 (plate, sheet, strip), B574 (bar, wire), B622 (seamless pipe and tube), B619 (welded pipe), B626 (welded tube), ASME SB-575, SB-574, SB-622, and NACE MR0175/ISO 15156 for sour service.

Typical applications include:

● Chemical processing: reactors, heat exchangers, distillation columns, and piping handling highly corrosive chemicals.

● Air pollution control: flue gas desulfurization (FGD) scrubbers and ductwork.

● Oil and gas: downhole tubing, flowlines, and components for sour gas (H₂S, CO₂, chlorides) at high temperatures.

● Pulp and paper: bleach plant equipment handling chlorine dioxide.

● Pharmaceutical and nuclear: equipment requiring high purity and corrosion resistance.

Comparison with other alloys: Hastelloy C-276 has higher molybdenum and tungsten than Inconel 625, giving it superior resistance to reducing acids and pitting. Inconel 625 has higher strength due to niobium addition. For less severe environments, Hastelloy C-22 offers similar performance with better thermal stability. For extremely oxidizing conditions, Hastelloy C-2000 or Alloy 59 may be considered.

Selection guidance: Choose Hastelloy C-276 for severe chemical service involving mixed acids, chlorides, and wet chlorine gas, especially where welding is required without post-weld heat treatment. For high-temperature strength rather than corrosion, select Inconel 625. For slightly better overall corrosion resistance and thermal stability, consider Hastelloy C-22.