Finishes / Electroless nickel plating
Electroless nickel plating services
Electroless nickel (EN) is a nickel-phosphorus alloy deposited by a chemical reaction instead of electric current. Because no current is involved, the deposit builds at the same rate in bores, threads and corners as on flat faces. That even build is the main reason buyers choose it.
It is specified on valve bodies, pump parts, molds, housings and aluminum parts that need wear resistance, solderability or a hard surface with tight tolerances. The phosphorus content changes the result a lot, so it belongs on the RFQ along with thickness and any heat treatment.
- Aluminum 6061 substratebase
- Zincate pretreatunder 1 µm
- Electroless nickel, mid phosphorus12 to 25 µm
On aluminum the shop applies a zincate layer first so the nickel can bond. On steel the nickel goes straight onto the activated surface.
Typical values
Typical ranges, not promised. The spec on your drawing and the process control of the shop set the real numbers.
- Thickness
- 5 to 75 µm, 12 to 25 µm is common for wear and corrosion
- Thickness tolerance
- Often within about ±2 µm on a 25 µm deposit, including in bores
- Phosphorus
- Low 1 to 5%, mid 6 to 9%, high 10 to 13%
- Hardness as plated
- About 500 to 700 HV depending on phosphorus
- Hardness after heat treat
- About 850 to 1000 HV after a bake near 400 °C
- Magnetism
- High phosphorus is nonmagnetic as plated, low and mid are magnetic
- Variants
- EN with PTFE for lower friction, EN with boron nitride or diamond for wear
Specs buyers call out
Put the spec and its type, class or grade on the drawing. Shops quote against it, and approvals narrow the list.
- ASTM B733
- Autocatalytic nickel-phosphorus on metalType by phosphorus, service condition SC0 to SC4 by thickness, class by heat treatment
- AMS 2404
- Electroless nickel plating, aerospaceCommon on aerospace drawings, with class for heat treatment
- MIL-DTL-26074
- Electroless nickel coatings, militaryStill found on older defense drawings
- ISO 4527
- Autocatalytic nickel-phosphorus coatingsInternational equivalent used on European drawings
Base materials
Name the alloy and hardness on the RFQ. Preparation changes with the base metal, and some shops only run one family.
Suits
- Carbon and alloy steel
- Aluminum, with zincate
- Copper and brass
Needs care
- Stainless steel (needs a nickel strike first)
- Cast aluminum with porosity
- Hardened steel (relief bake)
Not typical
- Titanium (only a few shops)
- Lead, tin or cadmium bearing alloys
- Parts that cannot take the bath temperature near 90 °C
Hardened steel over 39 HRC
Electroless nickel carries less hydrogen risk than electroplating, but the acid activation before it does not. Steel over 39 HRC needs a relief bake after plating. Put ASTM B850 or your own requirement on the drawing, and if the EN is heat treated for hardness, ask whether that bake also covers the relief bake.
When to specify it, and when to look elsewhere
A good fit for
- Even thickness inside bores, threads and blind holes
- Wear surfaces that must stay within a tight tolerance
- Aluminum parts that need a hard, solderable surface
- Molds, valve parts and pump parts in mildly corrosive service
Look elsewhere for
- Low cost corrosion protection on simple steel parts: zinc or zinc-nickel is cheaper
- Heavy abrasive wear: hard chrome or a hard anodize may last longer
- Parts that flex a lot: thick EN can crack
- Heat treat on aluminum without checking the temper: the 400 °C bake softens most alloys
What to put on the drawing and RFQ
Six lines that decide whether quotes compare. Missing items come back as questions and add days.
- Spec and typeASTM B733 or AMS 2404 with type (phosphorus range) and class (heat treatment).
- ThicknessMinimum and maximum, or a nominal with tolerance. EN can hold a tight band, so give it.
- PhosphorusLow for hardness and wear, mid for general use, high for corrosion or nonmagnetic parts.
- Heat treatmentHardness target and the temperature limit of the base metal, above all on aluminum.
- MaskingMark every bore, thread or surface that must stay bare.
- Base metalAlloy and hardness. Stainless, cast aluminum and hardened steel need different preparation.
What moves the price
Shops price by load, lot and labor more than by the chemistry itself.
- Thicker deposits mean longer bath time, at roughly 10 to 20 µm per hour
- Heat treatment for hardness adds an oven cycle
- Masking bores and threads is hand work
- Aluminum and stainless need extra pretreatment steps
Questions buyers ask
About electroless nickel plating specifically. For how matching works, see the home page.
Which phosphorus level should I choose?
Low phosphorus gives the highest as-plated hardness and wear. Mid phosphorus is the general purpose choice. High phosphorus gives the best corrosion resistance in acidic or salt environments and is nonmagnetic as plated. If you are not sure, describe the service and ask the shops.
How even is electroless nickel thickness?
Very even compared with electroplating. A 25 µm deposit is often held within a few microns on faces, edges and inside bores, which is why it suits tight tolerance parts.
Can electroless nickel be plated on aluminum?
Yes. The shop applies a zincate pretreatment first. Name the alloy, since some cast alloys plate less evenly, and do not ask for the high temperature hardness bake unless the alloy can take it.
Does heat treatment make electroless nickel harder?
Yes. Baking near 400 °C can raise hardness to about 850 to 1000 HV. It also lowers corrosion resistance somewhat, so only ask for it when wear is the main need.
Is electroless nickel food safe?
Some food equipment specs accept high phosphorus EN. It depends on the standard your equipment has to meet, so name that standard on the RFQ.
Get quotes for electroless nickel plating
Send one RFQ with the drawing, base material, spec and lot size. We match it with up to 3 shops that run this finish on a line that fits your part, and reply within 24 business hours.
Send my RFQRelated guides
- Electroless Nickel Phosphorus Content: Choosing Low, Mid or High Phosphorus
- Zinc, Zinc-Nickel, Electroless Nickel, Anodize or Powder Coat: Matching the Finish to the Part
- Masking for Plating and Anodizing: Plugs, Tape and Lacquer Compared
- Hydrogen Embrittlement and the Relief Bake: What to Put on the Drawing