Electroless nickel (EN)

Electroless nickel is a nickel-phosphorus alloy deposited chemically, without electric current, so thickness stays uniform within about ±10% on edges, bores and recesses. Typical coatings are 0.0002–0.001 in (5–25 µm). As-plated hardness is about 500–600 HV, rising to about 850–1,000 HV after heat treatment. High-phosphorus EN gives the best corrosion resistance; low-phosphorus the best hardness and wear.

Add it to a part

Applies to: Steel, stainless steel, aluminum, copper and brass; powder metal after sealing
Adds: 5 days
Cost: Moderate

Colors

Bright to semi-bright nickel
Black electroless nickel on request

Specs

Electroless nickel (EN) specifications
Thickness	0.0002–0.001 in (5–25 µm) typical; up to 0.003 in (75 µm)
Uniformity	About ±10% of thickness on all wetted surfaces
Phosphorus content	Low 1–4%, mid 5–9%, high 10% and up
Hardness	About 500–600 HV as plated; 850–1,000 HV after about 750 °F (400 °C) heat treat
Service conditions	ASTM B733 SC0–SC4 by thickness
Magnetism	High-phosphorus EN is non-magnetic as plated

Call out on the drawing

ASTM B733 (Types I–V, SC0–SC4, Classes 1–6)
AMS 2404
AMS-C-26074 (formerly MIL-C-26074)
ISO 4527

Materials it suits

Common on

Questions

Electroless nickel vs electrolytic nickel?

Electroless nickel deposits evenly on every surface, including holes and internal features, and can be heat-treated to high hardness. Electrolytic nickel builds up on edges and thins in recesses, but costs less and is brighter for decorative work. Use EN for precision and function.

How hard is electroless nickel?

About 500–600 HV (roughly 48–55 HRC) as plated. A bake at about 750 °F (400 °C) precipitates nickel phosphide and raises it to about 850–1,000 HV (roughly 65–69 HRC), comparable to hard chrome.

High-phos vs mid-phos electroless nickel?

High-phosphorus (10% and up) has the best corrosion and chemical resistance and is non-magnetic as plated. Mid-phosphorus (5–9%) is the general-purpose default with good hardness and brightness. Low-phosphorus (1–4%) is hardest as plated and best for wear.

Can electroless nickel be applied to aluminum?

Yes, after a zincate pretreatment. It is common on aluminum connectors, heat sinks and precision parts for solderability, wear and corrosion. Full hardening bakes would soften heat-treated aluminum, so aluminum parts get a low-temperature adhesion bake instead.