Zinc

Zinc anodizing forms a thin zinc-oxide surface film for mild corrosion protection and paint adhesion on zinc parts, with limited wear resistance and color range.

Overview

Zinc anodizing is an electrochemical surface treatment that grows a thin oxide layer on zinc and zinc-alloy parts (often die cast). It’s used to improve short-term corrosion resistance, reduce surface reactivity, and provide a better base for paint or subsequent finishing.

Choose it when the part must stay zinc (cost, weight, casting details) and you need a cleaner, more stable surface than bare zinc without adding a thick metallic coating. Expect appearance variability on die castings due to porosity and alloy chemistry; cosmetic consistency usually requires tight control of casting quality and surface prep.

Tradeoffs: the oxide layer is typically thin and relatively soft compared with anodize on valve metals, so it’s not a good choice for high-abrasion surfaces. Dimensional change is small but not zero, and masking/racking points will be visible and should be planned into the design.

Common Materials

  • Zamak 3
  • Zamak 5
  • ZA-8
  • ZA-12
  • ZA-27

Tolerances

—

Applications

  • Die-cast electronics housings
  • Decorative knobs and trim
  • Consumer product covers and bezels
  • Small brackets and hardware
  • Painted zinc components needing better adhesion
  • Light-duty corrosion protection on zinc castings

When to Choose Zinc

Use zinc anodizing when the base material is zinc/zinc alloy and you need a thin, conversion-like oxide surface to stabilize the part and support paint or light corrosion protection. It fits prototype through production volumes, especially for die-cast components where adding thickness from plating is undesirable. Plan for some cosmetic variation and visible rack/mask areas.

vs Aluminum anodizing

Choose zinc anodizing when the part is already zinc (often die cast) and you can’t switch alloys without cost or redesign. Aluminum anodizing offers harder, thicker, more color-stable finishes; zinc anodizing is typically thinner with less wear resistance and less consistent cosmetics on porous castings.

vs Titanium anodizing

Choose zinc anodizing for zinc components needing a mild protective oxide and paint base. Titanium anodizing is mainly for stable interference colors and excellent corrosion resistance on titanium; zinc anodizing won’t match titanium’s durability or color control.

vs Magnesium anodizing

Choose zinc anodizing when you’re finishing zinc die-cast parts and want minimal dimensional impact. Magnesium anodizing/conversion processes are usually selected for magnesium’s high reactivity and often target stronger corrosion systems; zinc anodizing is generally lighter-duty.

vs Niobium anodizing

Choose zinc anodizing for functional surface stabilization on zinc parts at typical industrial costs. Niobium anodizing is usually a premium decorative process with predictable color control on niobium; it’s not a practical substitute for zinc hardware.

vs Tantalum anodizing

Choose zinc anodizing for zinc castings where cost and throughput matter. Tantalum anodizing is specialized (medical/chemical) with exceptional corrosion behavior; zinc anodizing is thinner and intended for light-duty protection and finishing prep.

Design Considerations

  • Specify the exact zinc alloy (e.g., Zamak 3 vs 5) and casting process, because chemistry and porosity drive color and uniformity
  • Call out acceptable cosmetic variation and where rack/mask marks are allowed; include a non-cosmetic contact point in the model/drawing
  • Avoid sealing critical mating surfaces without accounting for film growth; define masking areas for threads, press fits, and electrical contacts
  • Use generous edge breaks and radii to reduce burn/edge effects and improve finish uniformity on die-cast features
  • Provide a surface finish target (as-cast vs machined Ra) and note any post-cast machining, because mixed surfaces can anodize differently
  • If the part will be painted, specify the paint system and adhesion requirements so the shop can align pretreatment, anodize parameters, and sealing