FabDigitFabDigit

Hard Chrome Plating

Electroplating & electroless plating · Electrolytic bath

Hard chrome is a thick engineering chromium deposit for wear, low friction, and dimensional restoration.

CNC machiningHigh cost $$$$Conductive
Quote a part with Hard chromeCompare electroplating & electroless plating
Hard Chrome Plating on a machined part

What is Hard chrome?

AMS 2406 and ASTM B177 govern common aerospace and engineering applications.

How it works

The part is made cathodic in a chromic-acid electrolyte and chromium deposits directly on activated metal. The process has poor cathode efficiency and poor throwing power, so robbers, shields, conforming anodes, and careful racking are needed. Edges burn or build heavily while recesses remain thin. Deposits are normally ground or honed after plating to restore size and surface finish. Electrical contact locations and anode spacing are planned around the significant wear surfaces.

Why specify it

  • 850–1050 HV typical hardness
  • 10–500 µm engineering thickness (wear to salvage)
  • Low adhesive friction and good galling resistance
  • Restores worn shaft and bore dimensions

Where it falls short

  • Poor throwing power causes severe thickness variation
  • Microcracked deposits are not a perfect corrosion barrier
  • Grinding adds cost and risk of overheating
  • Hexavalent chromium chemistry is tightly regulated

Hard chrome at a glance

Hard chrome is strongest on surface hardness (73 of 100), at a high cost.

Corrosion protectionFair40 / 100
Surface hardnessVery good73 / 100
Cosmetic qualityFair45 / 100
LubricityGood65 / 100
Relative costHigh78 / 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.

Hard chrome key numbers

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

Thickness10–500 µm0.39–20 mil
Hardness850–1,050 HV
Salt spray24–96 h
Max service temp.400 °C752 °F
Thickness
10–50 µm for wear surfaces; 100–500 µm for salvage, then finish-ground.
Hardness
850–1,050 HV — Typical hard chromium microhardness range.
Corrosion (salt spray)
24–96 h per ASTM B117 to red rust on steel, 25–50 µm unsealed microcracked chrome (typical) — Hard chrome is microcracked and is selected for wear, not as a barrier; a nickel underlayer gives a chrome system its corrosion life.
Electrical
Conductive
Colours
  • silver
Appearance
Bright to matte silver-gray; final appearance follows grinding or polishing.

Where Hard chrome 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. Hard chrome 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 41Electroless nickel — corrosion 70, hardness 68Nickel plate — corrosion 51, hardness 55Gold plate — corrosion 68, hardness 39Hot-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-PTFEType II anodizePowder coatZinc plateZinc-nickelDLCTiN PVDTin plateCadmium plateE-coatCerakoteWet paintHot-dip zincNitridingHVOF coatingHard chrome — corrosion 40, hardness 73Hard chrome
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 41Electroless nickel — corrosion 70, hardness 68Nickel plate — corrosion 51, hardness 55Gold plate — corrosion 68, hardness 39Hot-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 & POWDERPowder coatZinc plateHard chrome — corrosion 40, hardness 73Hard chrome
Anodize & conversionPlatingPaint & powderHard coatings

Specifications for Hard chrome

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
AMS 2406
Plating, Chromium, Hard Deposit · SAE
Drawing-specified hard chromium—Hard chromium deposit with thickness and final dimensions controlled by the drawing. · Drawing-specified thickness; hardness at least 700 HV; adhesion or grinding integrity; hydrogen-embrittlement control.Active
ASTM B177
Standard Guide for Engineering Chromium Electroplating · ASTM · alternative
———Active

Test and related methods: ASTM B850 (Standard Guide for Post-Coating Treatments of Steel for Reducing the Risk of Hydrogen Embrittlement).

Drawing call-out

HARD CHROME PLATE PER AMS 2406, 0.0020 IN MIN BEFORE GRIND; FINISH GRIND TO Ø25.000 ±0.005 mm AND Ra 0.4 µm; MASK THREADS

Pattern: HARD CHROME PLATE PER AMS 2406, <FINAL THICKNESS>, [PLATE THICKNESS BEFORE GRIND], [GRIND TO DIMENSION], [HYDROGEN-RELIEF REQUIREMENT], [MASKING]

Which materials take Hard chrome?

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

Material familyVerdictNotes
Steel
YesPrimary engineering substrate.
  • High-strength grades require hydrogen-embrittlement controls.
Aluminum
With carePossible with specialized preparation; not the first-choice aluminum wear coating (use Type III).
Brass
With carePossible but uncommon; nickel underplate is often used.
Copper Alloy
With careCan be plated for wear or salvage; hydrogen and adhesion need review.
DMLS / SLM
With careSteel AM wear parts can be hard-chromed after porosity and grind-stock review.
Nickel Alloy
With carePlateable with qualified activation.
Stainless Steel
With careRequires strong activation and often a strike.
Titanium
LimitedRequires specialized activation; rarely specified.
FDM
NoFused-filament polymers are incompatible with this process.
Magnesium Alloy
NoNot a practical hard-chrome substrate.
MJF
NoPolymer powder-bed prints are incompatible with this process.
Polymer
NoOrganic polymers cannot take this inorganic metal-finishing process.
SLA
NoPhotopolymer prints are incompatible with this process.
SLS
NoPolymer powder-bed prints are incompatible with this process.
Zinc Alloy
NoDie-cast zinc is not a hard-chrome substrate.

How Hard chrome is applied, and what it does to the part

  1. 1Pregrind
  2. 2Clean
  3. 3Mask and rack
  4. 4Activate
  5. 5Hard chromium plate
  6. 6Embrittlement-relief bake when required
  7. 7Finish grind or hone
  8. 8Inspect
DimensionsProvide grinding allowance; never assume the as-plated 10–500 µm deposit will meet final cylindricity or size.
Build-up per side10–500 µm — Plate oversize, then grind or hone; local as-plated buildup is highly nonuniform.
MaskingUsually needed. Mask all nonfunctional surfaces, threads, edges prone to burning, and areas that cannot accept post-grind stock.
ElectricalConductive
Temperature limit400 °C (752 °F) continuous
AppearanceBright to matte silver-gray; final appearance follows grinding or polishing.
Added lead time5–10 working days on top of the bare part

Design rules for Hard chrome

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

  1. Provide post-plate grinding stock.As-plated hard chrome is not dimensionally uniform.
  2. Radius sharp edges.Current crowding causes nodules and burning.
  3. Identify significant surfaces only.Shielding and auxiliary anodes must focus current.
  4. Specify hydrogen relief.High-strength steel is susceptible after cleaning and plating.

Hard chrome versus the alternatives

Finishes engineers weigh against Hard chrome, and when each wins.

FinishCorrosionHardnessCosmeticCostThicknessChoose it when
Hard chrome
this page
407345$$$$10–500 µm—
Electroless Nickel Plating
Hard chrome vs Electroless Nickel Plating →
706855$$$5–75 µmwhen uniform coating without finish grinding is more important
Nickel-PTFE Composite Plating
Hard chrome vs Nickel-PTFE Composite Plating →
725745$$$$10–25 µmwhen low friction and corrosion protection outweigh maximum hardness
CorrosionHardnessCosmeticLubricityEconomy
Hard chromeElectroless Nickel Plating

The radar overlays Hard chrome with Electroless Nickel Plating, its most common alternative — chosen when uniform coating without finish grinding is more important. Scores in the table are 0–100 across every finish in the catalog.

Cost, lead time and compliance

Relative cost

Hard Chrome Plating is a high-cost finish ($$$$): more expensive than about 84 % 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 time5–10 working days
RoHSCompliant
NotesThe metallic chromium deposit is not hexavalent chromium, but conventional baths contain regulated Cr(VI) and require strict controls.

What Hard chrome is used for

  • Hydraulic rods
  • Engine liners
  • Mold components
  • Bearing journals
  • Dimensional salvage

Hard chrome — frequently asked

how thick is hard chrome plating

Common wear deposits are 10–50 µm. Salvage deposits of 100–500 µm are normally ground back to final size.

how hard is hard chrome plating

Hard chromium is typically about 850–1050 HV. That hardness supports wear resistance, but the microcracked layer is not a perfect corrosion barrier.

hard chrome vs decorative chrome

Hard chrome is usually 10–500 µm and is deposited for wear and dimensional restoration. Decorative chromium is a very thin topcoat, commonly under 1 µm, over bright nickel.

does hard chrome cause hydrogen embrittlement

Yes, pretreatment and electroplating can introduce hydrogen into high-strength steel. Relief baking must begin promptly under AMS 2406, ASTM B850, or the controlling drawing.

why is hard chrome ground after plating

Chromium has poor throwing power and builds heavily at edges, so as-plated size is not uniform. Grinding or honing converts the oversize deposit into the required diameter and surface finish.