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Electroless Nickel Plating

Electroplating & electroless plating · Electroless (autocatalytic)

Electroless nickel is an autocatalytic nickel-phosphorus coating with nearly uniform thickness on complex geometry.

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Electroless Nickel Plating on a machined part

What is Electroless nickel?

Engineers specify it for corrosion protection, wear, dimensional control, and salvage of precision metal parts.

How it works

After cleaning and activation, parts enter a heated aqueous bath containing nickel ions and sodium hypophosphite. The reducing agent deposits nickel and phosphorus without external current, and the fresh deposit catalyzes continued growth. Because current density does not control deposition, recesses and outside edges receive similar thickness when solution exchange is adequate. High-phosphorus deposits favor corrosion resistance and are nonmagnetic as plated; mid-phosphorus balances hardness and corrosion; low-phosphorus deposits are harder and more wear resistant but less corrosion resistant.

Why specify it

  • Uniform 5–75 µm buildup on complex shapes
  • About 450–550 HV as plated; suitable heat treatment can approach 1000 HV
  • High-phosphorus classes provide strong barrier corrosion resistance
  • Coats metal additive-manufactured geometry without electrical contact

Where it falls short

  • Blind passages still require bath circulation and drainage
  • Heat treatment can distort parts and reduce corrosion performance
  • Aluminum needs zincate or equivalent activation
  • Not sacrificial on steel; pores or edge damage can drive local corrosion

Electroless nickel at a glance

Electroless nickel is strongest on corrosion protection (70 of 100), at a premium cost.

Corrosion protectionVery good70 / 100
Surface hardnessGood68 / 100
Cosmetic qualityGood55 / 100
LubricityLow30 / 100
Relative costPremium60 / 100
CorrosionHardnessCosmeticLubricityEconomy

Each score is 0–100 against every finish in this catalog. Corrosion comes from salt-spray life (ASTM B117, log scale) and hardness from the finish layer's Vickers or pencil hardness; cosmetic, lubricity and cost are FabDigit's engineering assessment. Economy on the radar is the inverse of cost.

Electroless nickel key numbers

Typical values from the governing specifications and shop practice; bars are this finish against the highest value among electroplating & electroless plating finishes.

Thickness5–75 µm0.2–3 mil
Hardness450–1,000 HV
Salt spray100–1,000 h
Max service temp.250 °C482 °F
Thickness
10–25 µm for dimensional work; 25–50 µm for wear or corrosion; ASTM B733 SC4 allows up to 75 µm.
Hardness
450–1,000 HV — Common deposits are about 450–550 HV as plated; controlled heat treatment can produce approximately 900–1000 HV.
Corrosion (salt spray)
100–1,000 h per ASTM B117 to red rust on steel; ≈ 100 h at 12 µm, ≈ 1,000 h at 25 µm high-phosphorus (typical) — ASTM B733 sets no salt-spray hours — porosity governs. Phosphorus class, thickness and heat treatment move the figure by an order of magnitude.
Electrical
Conductive
Colours
  • silver
Appearance
Uniform semi-bright to bright silver-gray; high-phosphorus deposits may be slightly less bright.

Where Electroless nickel sits among all finishes

Surface hardness (Vickers, log scale) against corrosion protection (salt-spray hours, log scale) for every coating FabDigit offers, one cloud per finish group. Electroless nickel is highlighted; hover a dot for its name or open the full map.

02550751000255075100Corrosion protection (0–100)Surface hardness (HV, log scale, 0–100)Plating — 19 finishesHard coatings — 17 finishesAnodize & conversion — 8 finishesPaint & powder — 7 finisheshard, low corrosion protectionhard and protectiveprotective, softsoft, little protectionType II anodize — corrosion 71, hardness 54BSA anodize — corrosion 71, hardness 52Type I anodize — corrosion 71, hardness 49Hard anodize — corrosion 71, hardness 61PTFE hard anodize — corrosion 71, hardness 61Nitriding — corrosion 55, hardness 73PEO — corrosion 70, hardness 74Sherardizing — corrosion 83, hardness 56Brass plate — corrosion 35, hardness 44Bronze plate — corrosion 40, hardness 49Cadmium plate — corrosion 70, hardness 26Copper plate — corrosion 32, hardness 39Decorative chrome — corrosion 64, hardness 71Electroless copper — corrosion 20, hardness 41Nickel plate — corrosion 51, hardness 55Gold plate — corrosion 68, hardness 39Hard chrome — corrosion 40, hardness 73Hot-dip zinc — corrosion 90, hardness 42Nickel-PTFE — corrosion 72, hardness 57Silver plate — corrosion 55, hardness 39Solder plate — corrosion 42, hardness 9Tin plate — corrosion 34, hardness 0Zinc plate — corrosion 60, hardness 30Zinc-nickel — corrosion 86, hardness 60Cerakote — corrosion 83, hardness 27E-coat — corrosion 83, hardness 15Epoxy coat — corrosion 83, hardness 15Powder coat — corrosion 83, hardness 14Wet paint — corrosion 59, hardness 10AlCrN PVD — corrosion 58, hardness 93AlTiN PVD — corrosion 52, hardness 94CrN PVD — corrosion 62, hardness 83DLC — corrosion 55, hardness 93MoS2 PVD — corrosion 20, hardness 26TiAlN PVD — corrosion 50, hardness 93TiCN PVD — corrosion 40, hardness 92TiB2 PVD — corrosion 40, hardness 94TiN PVD — corrosion 45, hardness 87WC/C PVD — corrosion 48, hardness 77ZrN PVD — corrosion 52, hardness 90CVD alumina — corrosion 70, hardness 85CVD TiCN — corrosion 38, hardness 92CVD TiN — corrosion 45, hardness 87Multilayer CVD — corrosion 62, hardness 88HVOF coating — corrosion 78, hardness 77Plasma spray — corrosion 60, hardness 68Plastic chrome — corrosion 72, hardness 71Electroless plastic — corrosion 58, hardness 39Clear coat — corrosion 20, hardness 12Soft-touch — corrosion 20, hardness 5PLATINGHARD COATINGSANODIZE & CONVERSIONPAINT & POWDERNickel plateNickel-PTFEType II anodizePowder coatZinc plateZinc-nickelHard chromeDLCTiN PVDTin plateCadmium plateE-coatCerakoteWet paintHot-dip zincNitridingHVOF coatingElectroless nickel — corrosion 70, hardness 68Electroless nickel
02550751000255075100Corrosion protection (0–100)Surface hardness (HV, log scale, 0–100)Plating — 19 finishesHard coatings — 17 finishesAnodize & conversion — 8 finishesPaint & powder — 7 finishesType II anodize — corrosion 71, hardness 54BSA anodize — corrosion 71, hardness 52Type I anodize — corrosion 71, hardness 49Hard anodize — corrosion 71, hardness 61PTFE hard anodize — corrosion 71, hardness 61Nitriding — corrosion 55, hardness 73PEO — corrosion 70, hardness 74Sherardizing — corrosion 83, hardness 56Brass plate — corrosion 35, hardness 44Bronze plate — corrosion 40, hardness 49Cadmium plate — corrosion 70, hardness 26Copper plate — corrosion 32, hardness 39Decorative chrome — corrosion 64, hardness 71Electroless copper — corrosion 20, hardness 41Nickel plate — corrosion 51, hardness 55Gold plate — corrosion 68, hardness 39Hard chrome — corrosion 40, hardness 73Hot-dip zinc — corrosion 90, hardness 42Nickel-PTFE — corrosion 72, hardness 57Silver plate — corrosion 55, hardness 39Solder plate — corrosion 42, hardness 9Tin plate — corrosion 34, hardness 0Zinc plate — corrosion 60, hardness 30Zinc-nickel — corrosion 86, hardness 60Cerakote — corrosion 83, hardness 27E-coat — corrosion 83, hardness 15Epoxy coat — corrosion 83, hardness 15Powder coat — corrosion 83, hardness 14Wet paint — corrosion 59, hardness 10AlCrN PVD — corrosion 58, hardness 93AlTiN PVD — corrosion 52, hardness 94CrN PVD — corrosion 62, hardness 83DLC — corrosion 55, hardness 93MoS2 PVD — corrosion 20, hardness 26TiAlN PVD — corrosion 50, hardness 93TiCN PVD — corrosion 40, hardness 92TiB2 PVD — corrosion 40, hardness 94TiN PVD — corrosion 45, hardness 87WC/C PVD — corrosion 48, hardness 77ZrN PVD — corrosion 52, hardness 90CVD alumina — corrosion 70, hardness 85CVD TiCN — corrosion 38, hardness 92CVD TiN — corrosion 45, hardness 87Multilayer CVD — corrosion 62, hardness 88HVOF coating — corrosion 78, hardness 77Plasma spray — corrosion 60, hardness 68Plastic chrome — corrosion 72, hardness 71Electroless plastic — corrosion 58, hardness 39Clear coat — corrosion 20, hardness 12Soft-touch — corrosion 20, hardness 5PLATINGHARD COATINGSANODIZE & CONVERSIONPAINT & POWDERNickel platePowder coatZinc plateElectroless nickel — corrosion 70, hardness 68Electroless nickel
Anodize & conversionPlatingPaint & powderHard coatings

Specifications for Electroless nickel

The documents a drawing cites to define this finish, with the Type / Class rows that apply. Each links to a page explaining the standard.

StandardType / ClassThicknessRequirement / testStatus
ASTM B733
Standard Specification for Autocatalytic (Electroless) Nickel-Phosphorus Coatings on Metal · ASTM
SC0—No minimum thickness specified · Thickness as agreedActive
SC1≥ 5 µmLight service · Thickness and adhesion
SC2≥ 13 µmMild service · Thickness and adhesion
SC3≥ 25 µmSevere service · Thickness, adhesion, and agreed performance tests
SC4≥ 75 µmVery severe service · Thickness, adhesion, and agreed performance tests
Type 1—Low-phosphorus nickel deposit · Phosphorus content
Type 2—Medium-low-phosphorus nickel deposit · Phosphorus content
Type 3—Medium-phosphorus nickel deposit · Phosphorus content
Type 4—High-phosphorus nickel deposit · Phosphorus content
Type 5—Very-high-phosphorus nickel deposit · Phosphorus content
Classes 1–6—As-deposited or specified heat-treatment condition selected for substrate, adhesion, hardness, or dimensional stability · Heat-treatment records and applicable adhesion or hardness test
AMS 2404
Plating, Electroless Nickel-Phosphorous · SAE · alternative
Class 1—No post-plating thermal treatment except required hydrogen-embrittlement relief. · Default substrate minimum: ferrous 38.1 µm; aluminum 25.4 µm; copper, nickel, cobalt, titanium, and beryllium 12.7 µm. · Thickness, adhesion, corrosion resistance where applicable, deposit composition when specified, and embrittlement control.Active
Class 2—Thermally treated at 450–800 °F (232–427 °C) to harden the deposit. · Same substrate-linked thickness defaults unless otherwise specified. · Deposit hardness of at least 800 HK100, thickness, adhesion, and applicable corrosion and embrittlement tests.
Class 3—Thermally treated at 375 ± 15 °F (191 ± 8 °C) for 1–1.5 h to improve adhesion on non-heat-treatable aluminum and beryllium alloys. · Same substrate-linked thickness defaults unless otherwise specified. · Thickness and adhesion after the specified thermal treatment.
Class 4—Thermally treated at 250 ± 10 °F (121 ± 6 °C) for 1–1.5 h to improve adhesion on heat-treatable aluminum. · Same substrate-linked thickness defaults unless otherwise specified. · Thickness and adhesion after the specified thermal treatment.

Drawing call-out

ELECTROLESS NICKEL PLATE PER ASTM B733, SC2, TYPE V, 0.0005–0.0008 IN THICK; MASK THREADS; NO POST-PLATE HEAT TREATMENT

Pattern: ELECTROLESS NICKEL PER ASTM B733, TYPE <1–5>, SC<0–4>, CLASS <1–6>

Which materials take Electroless nickel?

Verdict per material family, with the grades that behave differently. Each family links to its datasheets in the material library.

Material familyVerdictNotes
Brass
YesReadily plated after cleaning and activation.
Copper Alloy
YesGenerally plateable after cleaning and activation.
Stainless Steel
YesRequires activation to prevent passive-film adhesion failure.
Steel
YesCommon engineering substrate; pretreatment and porosity control are critical.
  • Bake high-strength steel when required by the governing specification.
Aluminum
With careNormally requires zincate activation.
  • High-silicon castings may need specialized pretreatment.
DMLS / SLM
With carePorosity must be sealed or controlled before immersion processing.
Titanium
With careRequires specialized activation; adhesion must be qualified.
Zinc Alloy
With careNeeds a protective strike and porosity control.
Magnesium Alloy
LimitedPossible with qualified pretreatment but not a routine cycle.
Polymer
LimitedOnly after etch, catalysis, and a conductive seed on plateable resins.
SLA
LimitedOnly qualified metallization resins.
FDM
NoNot a standard electroless-nickel substrate.
MJF
NoPorous nylon is not a standard EN substrate.
SLS
NoPorous nylon is not a standard EN substrate.

How Electroless nickel is applied, and what it does to the part

  1. 1Clean and degrease
  2. 2Acid activate
  3. 3Zincate aluminum if applicable
  4. 4Autocatalytic nickel-phosphorus deposit
  5. 5Rinse
  6. 6Optional heat treatment
  7. 7Inspect thickness and adhesion
DimensionsAdd the full specified thickness per coated side; unlike electrolytic nickel, edge buildup is generally close to flat-surface buildup.
Build-up per side5–75 µm — Deposit grows outward by approximately the specified coating thickness on every exposed surface.
MaskingUsually needed. Mask threads, bearing fits, sealing lands, and holes whose final size cannot accept full-thickness buildup.
ElectricalConductive
Temperature limit250 °C (482 °F) continuous
AppearanceUniform semi-bright to bright silver-gray; high-phosphorus deposits may be slightly less bright.
Added lead time3–7 working days on top of the bare part

Design rules for Electroless nickel

What to decide on the drawing before the part goes to the finisher.

  1. Specify phosphorus class and thickness.Low, mid, and high phosphorus deposits trade hardness against corrosion resistance.
  2. Mask precision threads and fits.The full coating thickness builds on each exposed side.
  3. Provide drain and circulation paths.Stagnant solution can produce thin or rough deposits in blind cavities.
  4. State any post-plate heat treatment.Temperature changes hardness, adhesion, magnetism, and corrosion behavior.

Electroless nickel versus the alternatives

Finishes engineers weigh against Electroless nickel, and when each wins.

FinishCorrosionHardnessCosmeticCostThicknessChoose it when
Electroless nickel
this page
706855$$$5–75 µm—
Electrolytic Nickel Plating
Electroless nickel vs Electrolytic Nickel Plating →
515578$$5–25 µmwhen bright decorative appearance or rapid edge buildup is preferred
Nickel-PTFE Composite Plating
Electroless nickel vs Nickel-PTFE Composite Plating →
725745$$$$10–25 µmwhen lower friction is required
CorrosionHardnessCosmeticLubricityEconomy
Electroless nickelElectrolytic Nickel Plating

The radar overlays Electroless nickel with Electrolytic Nickel Plating, its most common alternative — chosen when bright decorative appearance or rapid edge buildup is preferred. Scores in the table are 0–100 across every finish in the catalog.

Cost, lead time and compliance

Relative cost

Electroless Nickel Plating is a premium-cost finish ($$$): more expensive than about 70 % of the finishes FabDigit quotes.

Finishing is priced per part with a lot minimum, from FabDigit's own China-side rates cross-checked against US job-shop pricing. The exact figure appears on the instant quote once the part is uploaded.

Lead time and compliance

Added lead time3–7 working days
RoHSCompliant
NotesNickel is restricted in some skin-contact applications and bath chemistry requires controlled waste treatment.

What Electroless nickel is used for

  • Precision pump impellers
  • Plastic injection molds
  • Industrial valves
  • Complex sensors
  • Metal additive-manufactured parts

Electroless nickel — frequently asked

electroless nickel vs electrolytic nickel

Electroless nickel deposits nearly the same 5–75 µm thickness on edges and recesses because it uses chemical reduction. Electrolytic nickel is less uniform and builds fastest at high-current-density edges, but it can deliver a brighter decorative surface.

how hard is electroless nickel plating

Typical nickel-phosphorus is about 450–550 HV as plated. A suitable heat treatment can raise it to roughly 900–1000 HV, although corrosion performance may decline.

high phosphorus vs mid phosphorus electroless nickel

High-phosphorus EN is commonly selected for barrier corrosion resistance and is normally nonmagnetic as plated. Mid-phosphorus balances corrosion and hardness, while low-phosphorus EN is harder and more wear focused.

can you electroless nickel plate aluminum

Yes, but aluminum normally needs controlled cleaning, etching, desmutting, and zincate activation before nickel deposition. The drawing should identify the alloy and critical fits because 10–25 µm per side is common, with ASTM B733 allowing up to 75 µm.

does electroless nickel build up threads

Yes; every exposed thread flank receives approximately the specified deposit thickness. Internal threads and precision gauges are usually masked or machined oversize to accept 5–75 µm per surface.