Magnesium

Magnesium anodizing forms a protective conversion coating that improves corrosion resistance, paint adhesion, and surface hardness on lightweight magnesium alloys.

Overview

Magnesium anodizing creates a controlled oxide or conversion layer on magnesium alloys, using electrochemical processes like Dow, HAE, or plasma electrolytic oxidation. The coating improves corrosion resistance, provides a good base for paint or adhesive bonding, and can increase surface hardness compared to bare magnesium. Typical coatings range from thin grey conversion films to thicker, more wear-resistant ceramic-like layers.

Use magnesium anodizing when you must protect magnesium castings or machined parts in corrosive or humid environments, or when you need reliable paint adhesion on a very light substrate. Expect limited cosmetic options: colors are usually grey to dark brown or black, not bright decorative finishes. Coating growth and porosity affect tight fits, so critical dimensions may need masking or post-processing. Some legacy processes use hexavalent chromium; many shops now offer RoHS-compliant alternatives with slightly different appearance and performance. Early design coordination with the finisher avoids surprises in fit, color, and corrosion life.

Common Materials

  • AZ31B
  • AZ91D
  • AM60B
  • ZE41A
  • Elektron 21

Tolerances

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Applications

  • Magnesium gearbox housings
  • Aerospace magnesium castings and forgings
  • Handheld electronics magnesium frames
  • Optical and camera magnesium housings
  • Automotive steering column and wheel cores
  • Medical equipment magnesium enclosures

When to Choose Magnesium

Choose magnesium anodizing when the base material is magnesium and you need corrosion protection, paint adhesion, or moderate wear resistance without adding weight. It suits small to medium production volumes where finish consistency, environmental exposure, and functional coating properties matter more than high-end cosmetics.

vs Aluminum

Pick magnesium anodizing over aluminum anodizing when extreme weight reduction is the driver and you are already committed to magnesium alloys. You accept more limited color options and slightly less refined cosmetic finishes in exchange for lower density and acceptable corrosion protection on magnesium parts.

vs Titanium

Choose magnesium anodizing over titanium anodizing when you need a low-cost, very lightweight structural part rather than premium strength and corrosion resistance. Magnesium with a good anodized or conversion coating works for moderate environments where titanium’s performance would be overkill and too expensive.

vs Zinc

Use magnesium anodizing instead of zinc-based finishes when the part itself is magnesium and you want an integral protective layer rather than a sacrificial metal deposit. This is appropriate when you need good paint adhesion and stable dimensions on magnesium castings or machined components rather than building up thicker zinc coatings.

vs Niobium

Select magnesium anodizing over niobium anodizing when you are finishing structural or enclosure components rather than chasing decorative interference colors. Magnesium coatings focus on corrosion protection, paint adhesion, and weight-critical applications, while niobium anodizing is mainly for specialty medical or decorative parts.

Design Considerations

  • Clearly identify magnesium alloy type on drawings so the finisher can choose a compatible anodizing or conversion process and predict final appearance
  • Call out masked areas and critical dimensions where coating growth cannot be tolerated, especially on tight bores, threads, and precision fits
  • Allow robust racking points or temporary holes so parts can be fixtured without touching critical surfaces during anodizing
  • Avoid deep blind holes and sharp internal corners that trap solution and cause uneven coating or pitting on magnesium
  • Specify performance requirements (salt spray hours, paint adhesion, hardness) rather than just a trade name, so shops can propose the most suitable magnesium process
  • Discuss environmental requirements early (chromate-free, RoHS, REACH) since they can restrict which magnesium anodizing chemistries are allowed