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Zinc Plating

Electroplating & electroless plating · Electrolytic bath

Electrolytic zinc is a thin sacrificial coating for carbon steel hardware and parts.

CNC machiningSheet metalBudget cost $Conductive
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Zinc Plating on a machined part

What is Zinc plate?

ASTM B633 service conditions SC1 through SC4 specify 5, 8, 13, and 25 µm minimum thicknesses.

How it works

Clean steel parts are made cathodic in an acid or alkaline zinc electrolyte. Direct current reduces zinc ions onto the surface, after which a conversion coating and optional sealer improve corrosion performance. Current concentrates at edges and exposed faces, so recesses and thread roots receive less zinc than outside corners. Clear, yellow, olive-drab, and black are chromate or trivalent-passivate classes within zinc plating; black zinc is not a separate deposit.

Why specify it

  • Low-cost sacrificial protection for steel
  • SC1–SC4 provide 5, 8, 13, or 25 µm minimum zinc
  • Rack or barrel processing supports both precision parts and fasteners
  • Black, clear, yellow, and olive-drab post-treatments are available

Where it falls short

  • Electrolytic throwing power leaves recesses and thread roots thinner
  • Barrel processing can cause impact marks and thread nesting
  • Hydrogen embrittlement risk on high-strength steel
  • Not suited to prolonged high-temperature service

Zinc plate at a glance

Zinc plate is a middle-of-the-range finish; its best score is corrosion protection (60 of 100), at a budget cost.

Corrosion protectionGood60 / 100
Surface hardnessLow30 / 100
Cosmetic qualityGood55 / 100
LubricityLow25 / 100
Relative costBudget12 / 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.

Zinc plate key numbers

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

Thickness5–25 µm0.2–0.98 mil
Hardness40–100 HV
Salt spray96–300 h
Max service temp.80 °C176 °F
Thickness
ASTM B633 SC1 5 µm, SC2 8 µm, SC3 13 µm, and SC4 25 µm minimum
Hardness
40–100 HV — Zinc is soft; hardness is not normally a drawing acceptance criterion.
Corrosion (salt spray)
96–300 h per ASTM B117 to red rust on steel, 8–13 µm with chromate or trivalent passivate (typical) — ASTM B633 itself specifies hours to WHITE corrosion (12 h clear / 96 h coloured chromate); red-rust life scales with thickness.
Electrical
Conductive
Colours
  • clear blue
  • yellow iridescent
  • black
  • olive drab
Appearance
Bright to matte metallic zinc with the selected clear, colored, or black conversion finish.

Where Zinc plate 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. Zinc plate 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 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-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 & POWDERHot-dip zincZinc-nickelType II anodizePowder coatHard chromeDLCTiN PVDTin plateCadmium plateE-coatCerakoteWet paintNitridingHVOF coatingZinc plate — corrosion 60, hardness 30Zinc plate
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 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-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 & POWDERHot-dip zincPowder coatZinc plate — corrosion 60, hardness 30Zinc plate
Anodize & conversionPlatingPaint & powderHard coatings

Specifications for Zinc plate

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 B633
Standard Specification for Electrodeposited Coatings of Zinc on Iron and Steel · ASTM
SC1≥ 5 µmMild service · Thickness and adhesion per specificationActive
SC2≥ 8 µmModerate service · Thickness and adhesion per specification
SC3≥ 13 µmSevere service · Thickness, adhesion, and corrosion per specified type
SC4≥ 25 µmVery severe service · Thickness, adhesion, and corrosion per specified type

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

Drawing call-out

ZINC PLATE PER ASTM B633, SC3, TYPE V, CLEAR TRIVALENT PASSIVATE; 13 µm MIN; BAKE PER ASTM B850 WITHIN 1 H OF PLATING

Pattern: ZINC PLATE PER ASTM B633, SC<1|2|3|4>, TYPE <I|II|III|IV|V|VI>

Which materials take Zinc plate?

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

Material familyVerdictNotes
Steel
YesPrimary substrate.
  • High-strength grades require an embrittlement-control plan.
DMLS / SLM
With careSteel AM parts can be zinc plated after powder and porosity review; bake if strength requires it.
Aluminum
LimitedNot a standard aluminum finish; galvanic pairing with zinc is usually handled by plating the steel fastener instead.
Brass
LimitedRarely specified; brass already has useful corrosion behavior.
Copper Alloy
LimitedTechnically plateable but uncommon for sacrificial protection.
Stainless Steel
LimitedPossible with activation and strike layers, but generally not the preferred corrosion system.
Zinc Alloy
LimitedRedundant on a zinc die casting except as a thin passivate system.
FDM
NoFused-filament polymers are incompatible with this process.
Magnesium Alloy
NoIncompatible; zinc on magnesium is the wrong galvanic direction for the magnesium.
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.
Titanium
NoTitanium is not zinc plated.

How Zinc plate is applied, and what it does to the part

  1. 1Clean and degrease
  2. 2Acid pickle
  3. 3Electroplate zinc
  4. 4Rinse
  5. 5Apply conversion coating
  6. 6Seal if specified
  7. 7Bake high-strength steel when required
  8. 8Inspect
DimensionsAllow at least the specified local zinc thickness per side; use thread allowances and specify measurement locations.
Build-up per side5–25 µm — Nominal buildup equals local deposit thickness; edges may exceed and recesses may fall below the average.
MaskingUsually needed. Mask tight threads, electrical contact lands when passivate is unacceptable, and precision bores.
ElectricalConductive
Temperature limit80 °C (176 °F) continuous
AppearanceBright to matte metallic zinc with the selected clear, colored, or black conversion finish.
Added lead time2–5 working days on top of the bare part

Design rules for Zinc plate

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

  1. Choose rack plating for cosmetic or damage-sensitive parts.Barrel contact and part-to-part impact leave marks.
  2. Specify a service condition and passivate type.Thickness and supplementary treatment jointly control corrosion.
  3. Add thread allowance.Zinc builds on both flanks and can bind gauges.
  4. Require embrittlement relief for susceptible steel.Cleaning and electroplating can introduce hydrogen.

Zinc plate versus the alternatives

Finishes engineers weigh against Zinc plate, and when each wins.

FinishCorrosionHardnessCosmeticCostThicknessChoose it when
Zinc plate
this page
603055$5–25 µm—
Hot-Dip Galvanizing
Zinc plate vs Hot-Dip Galvanizing →
904232$$45–100 µmwhen a much thicker outdoor coating is acceptable
Zinc-Nickel Plating
Zinc plate vs Zinc-Nickel Plating →
866048$$5–15 µmwhen substantially longer salt-spray life is required
CorrosionHardnessCosmeticLubricityEconomy
Zinc plateHot-Dip Galvanizing

The radar overlays Zinc plate with Hot-Dip Galvanizing, its most common alternative — chosen when a much thicker outdoor coating is acceptable. Scores in the table are 0–100 across every finish in the catalog.

Cost, lead time and compliance

Relative cost

Zinc Plating is a budget-cost finish ($): cheaper than about 90 % 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 time2–5 working days
RoHSCompliant
NotesSpecify a hexavalent-chromium-free trivalent passivate for RoHS work; legacy yellow and olive-drab systems may contain hexavalent chromium.

What Zinc plate is used for

  • Steel fasteners
  • Automotive brackets
  • Construction hardware
  • Agricultural equipment parts

Zinc plate — frequently asked

zinc plating vs galvanizing

Electrolytic zinc is typically 5–25 µm and suits threads and precision parts. Hot-dip galvanizing is commonly tens of micrometres thick and gives longer outdoor life but can fill threads and distort thin work.

how thick is zinc plating

ASTM B633 defines minimum local thicknesses of 5, 8, 13, and 25 µm for SC1 through SC4. State the service condition rather than writing only zinc plate.

what is black zinc plating

Black zinc is ordinary zinc electrodeposit followed by a black conversion coating or passivate. It is a color and corrosion-treatment class, not a distinct base metal coating.

does zinc plating cause hydrogen embrittlement

It can on hardened or highly stressed steel because pickling and plating generate hydrogen. ASTM B850 practices use prompt relief baking, but the drawing must define the applicable treatment.

rack zinc plating vs barrel zinc plating

Barrel plating is economical for small robust parts but causes contact marks and thread nesting. Rack plating controls orientation and appearance better, while edge-to-recess thickness variation remains an electrolytic limitation.