The short answer: Nickel alloys — Inconel, Monel, Incoloy, Hastelloy, Alloy 20 and the rest — are chosen for corrosion resistance and strength at elevated temperature, and they arrive from fabrication with free iron, grease and metallic particles on the surface that corrode first. Passivation submerges the part in an acid bath with chemistry set for the alloy, removes those contaminants without changing the finish or dimensions, and lets the alloy perform as engineered. Harrison has passivated nickel alloys for decades, to ASTM A967, ASTM A380 or your specification, on components of all sizes, in Houston and on-site.

Why nickel alloys are passivated

Steel tooling, fixtures, grinding and shop handling embed free iron in a nickel-alloy surface, and welding and heat treatment leave oxides. In chloride, acid, sour or high-temperature service those sites corrode before the base alloy. Passivation removes the contaminants so the alloy's own passive surface forms uniformly. Heat tint and scale are pickled first where present.

Alloys we passivate

Inconel 600, 625, 718, X-750 and 800 · Monel 400 and K-500 · Incoloy · Hastelloy grades (see Hastelloy passivation) · Alloy 20 (20Cb-3) · Nickel 200 series · Kovar and Alloy 42 · other nickel-based alloys on request. Chemistry and parameters are set for the alloy family — nickel-chromium, nickel-copper and nickel-iron alloys do not all respond to the same bath.

Process and verification

Pre-cleaning; immersion or circulation in the passivation bath; deionized-water rinse; drying; verification and a certificate of conformance naming the specification and method.

Typical components

Reactor internals, heat-exchanger tubes and bundles, valve bodies and trim, pump components, gas-turbine and aerospace hardware, cryogenic and gas-system components, and electronic and vacuum parts. Large fabrications are handled in Houston with four overhead cranes and 15,000 lb material-handling capacity; installed equipment is passivated on-site across the Houston area and the Gulf Coast.

For electropolishing of nickel alloys see nickel alloy electropolishing; for mechanical polishing certified as low as 4 µin Ra, chemical cleaning and oxygen cleaning, see nickel alloys.

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