ASTM B366

Applies to: Factory-made wrought fittings in nickel and nickel-base alloys: Nickel 200/201 (N02200), Monel 400 (N04400), Inconel 600/625 (N06600/N06625), Hastelloy C-276 (N10276), Incoloy 825 (N08825), and other listed UNS alloys; corrosive chemical and high-temperature service above 800 °F (427 °C).

Does NOT cover: Nickel-clad or electroplated fittings; cast nickel-alloy fittings; austenitic stainless steel fittings (ASTM A403); copper-nickel fittings for marine service.

• Alloy UNS designation from B366 approved alloy list
• Heat treatment condition per alloy (annealed, solution annealed, or stress relieved)
• Chemical analysis verification per heat
• Hydrostatic test per governing construction code
• Dimensional compliance with ASME B16.9 for wrought buttwelding fittings
• Marking includes alloy UNS number, heat number, and manufacturer's mark

ASTM B366 covers wrought nickel-alloy fittings for the most demanding corrosive environments — concentrated acids, high-temperature oxidizing atmospheres, and chloride-rich media where even 316L stainless is inadequate. Engineers select the specific alloy based on the corrosion mechanism: Hastelloy C-276 (N10276) for HCl and wet chlorine; Inconel 625 (N06625) for seawater and sour gas; Monel 400 (N04400) for hydrofluoric acid; Incoloy 825 (N08825) for sulfuric acid.

Engineering note: Nickel-alloy fittings are expensive and have long lead times — typically 16–26 weeks for non-stock items. Early material requisition and vendor pre-qualification for heat treatment and chemical test traceability are critical for project schedule. Verify that fittings and pipe from different manufacturers are from compatible UNS grades and heat treatment batches before qualifying an isometric for hydrotesting.