Anodizing, conversion & passivation · finish comparison
Magnesium Chemical Conversion Coating vs Plasma Electrolytic Oxidation
Magnesium Chemical Conversion Coating and Plasma Electrolytic Oxidation are both anodizing & conversion coatings finishes; pEO resists corrosion better.
Magnesium Chemical Conversion Coating
Anodizing & conversion coatings · $$$
Magnesium conversion coating reacts with magnesium alloys to improve corrosion resistance and paint adhesion with minimal buildup.
Plasma Electrolytic Oxidation
Anodizing & conversion coatings · $$$$
Plasma electrolytic oxidation, also called micro-arc oxidation, creates a thick ceramic oxide on aluminum or magnesium using high-voltage micro-discharges.
When to choose which
Choose Mag conversion
Mag conversion is the pick when its strengths below matter more than PEO's.
- Thin 0.5–5 µm film limits dimensional change
- Improves primer and paint adhesion
- Provides temporary corrosion protection to reactive magnesium
Choose PEO
Choose PEO when a thicker ceramic wear and dielectric layer is required.
- Commercial systems span roughly 10–150 µm
- Local ceramic phases can measure about 700–2,000 HV
- Treats both aluminum and magnesium alloys
What the numbers say
- PEO resists corrosion better.
- Mag conversion is the lower-cost option ($$$).
- Mag conversion is the thinner coating (0.5–5 µm), so it disturbs tight fits less.
- Mag conversion is semi-conductive; PEO is insulating.
Scores side by side
Each score is 0–100 against every finish in this catalog. Corrosion is derived from salt-spray test duration and surface hardness from the finish layer's Vickers hardness where a measured figure exists; a finish that leaves the base metal's own surface is not rated for hardness. Cosmetic, lubricity and cost are FabDigit's engineering assessment. Scores and typical figures are screening data, not matched side-by-side tests or service-life rankings; ASTM B117 is a controlled salt-fog method, not a field-life prediction.
| Score | Mag conversion | PEO |
|---|---|---|
| Corrosion resistance | 42 Fair | 70 Very good |
| Surface hardness / wear | — — | 74 Very good |
| Cosmetic quality | 25 Low | 35 Fair |
| Lubricity | 12 Minimal | 20 Low |
| Cost | 42 $$$ | 78 $$$$ |
Key numbers
| Property | Mag conversion | PEO |
|---|---|---|
| Thickness | 0.5–5 µm | 10–150 µm |
| Surface hardness | — | 700–1,500 HV |
| Electrical | Semi-conductive | Insulating |
| Colours | clear, gold, brown, gray | white, gray, dark gray |
| Relative cost | Premium ($$$) | High ($$$$) |
| Added lead time | 4–8 working days | 7–15 working days |
| RoHS | Conditional | Conditional |
| Instant quote | On request | On request |
Bold marks the side that is ahead on a row where more (or less, for cost and lead time) is better. Ranges are the typical specification window; the drawing call-out fixes the class.
Which materials take each finish
| Material family | Mag conversion | PEO |
|---|---|---|
| Aluminum | No | Yes |
| Magnesium Alloy | Yes | Yes |
| DMLS / SLM | Limited | With care |
| Titanium | No | Limited |
| Zinc Alloy | No | Limited |
Specifications and drawing call-outs
Mag conversion
- AMS-M-3171 — Magnesium Alloy, Processes for Pretreatment and Prevention of Corrosion on
- SAE AMS 3171 — Magnesium Alloy, Processes for Pretreatment and Prevention of Corrosion on
CHEMICAL TREAT MAGNESIUM PER SAE AMS-M-3171 / AMS 3171, CHROME-FREE CONVERSION, PRIME WITHIN 8 HOURS; DO NOT SUBSTITUTE HAE ANODIZE
PEO
No governing public specification — called out by name and thickness.
PLASMA ELECTROLYTIC OXIDATION PER APPROVED PROCESS SPECIFICATION FD-PEO-001, 50 ± 10 µm, SEALED, FINAL HARDNESS 900 HV0.05 MIN; MASK THREADS
Mag conversion vs PEO — frequently asked
What is the difference between Mag conversion and PEO?
Magnesium Chemical Conversion Coating and Plasma Electrolytic Oxidation are both anodizing & conversion coatings finishes; pEO resists corrosion better. Mag conversion is the lower-cost option ($$$). Mag conversion is the thinner coating (0.5–5 µm), so it disturbs tight fits less.
When should I use Mag conversion instead of PEO?
Conversely: choose PEO when a thicker ceramic wear and dielectric layer is required.
Is Mag conversion or PEO cheaper?
Mag conversion is the lower-cost finish ($$$ against $$$$ for PEO) among the finishes FabDigit quotes. Both are priced per part with a lot minimum; the exact figure appears on the instant quote once the part is uploaded.