Zinc plating

Zinc plating electrodeposits a thin layer of zinc on steel, typically 0.0002–0.0005 in (5–12 µm), which corrodes sacrificially to protect the base metal. A trivalent passivate in clear, yellow or black, plus an optional sealer, extends salt spray life. It is the lowest-cost plated finish for fasteners, stampings and machined steel parts, specified to ASTM B633 by service condition and type.

Add it to a part

Applies to: Carbon and low-alloy steels, including stampings, fasteners, springs and sealed powder metal parts
Adds: 3 days
Cost: Low

Colors

Clear / blue-bright
Yellow iridescent
Black

Specs

Zinc plating specifications
SC1 (mild)	0.0002 in (5 µm)
SC2 (moderate)	0.0003 in (8 µm)
SC3 (severe)	0.0005 in (12 µm)
SC4 (very severe)	0.001 in (25 µm)
Passivate types	Type V clear and Type VI colored (non-hexavalent); Types II and III are chromate
Hydrogen embrittlement	Relief bake per ASTM B850 for parts at 31 HRC or harder

Call out on the drawing

ASTM B633 (SC1–SC4, Types I–VI)
ASTM F1941 (fasteners)
ISO 2081 / ISO 4042 (fasteners)
ASTM B850 (hydrogen embrittlement relief)

Materials it suits

Common on

Questions

How long does zinc plating last in salt spray?

It depends on thickness, passivate and sealer. Clear trivalent alone typically reaches roughly 24–72 h to white corrosion in ASTM B117, and colored passivates or sealers push that to 120 h or more; red rust comes later. State the hours to white and red corrosion you need on the drawing.

Does zinc plating cause hydrogen embrittlement?

It can in hardened steel. ASTM B633 calls for an embrittlement relief bake per ASTM B850 on parts at 31 HRC or harder. Springs, hardened fasteners and clips need the bake started within a few hours of plating.

Zinc plating vs zinc-nickel?

Zinc-nickel, with 12–16% nickel, lasts several times longer in salt spray, commonly 720 h or more to red rust, and holds up better after heat exposure, at a higher price. Use plain zinc for indoor and mild service and zinc-nickel for automotive, outdoor and high-corrosion parts.

Is zinc plating RoHS compliant?

Yes, with trivalent (non-hexavalent) passivates, ASTM B633 Types V and VI. Older Type II yellow chromate contains hexavalent chromium and is restricted.