Surface Finish · Chemical Treatments
Chromate Conversion (Alodine / Chem Film)
Corrosion protection that stays conductive — the EMI-grounding finish for aluminum.
Process specifications
| Parameter | Value |
|---|---|
| Process group | Chemical Treatments |
| Coating thickness | 0.5–4 µm |
| Tolerance impact | Negligible (<4 µm) — no compensation needed; safe on finished tolerances, threads and EMI gasket faces. |
| Corrosion rating | 168 h salt spray (MIL-DTL-5541, Class 1A). Specifiable to AMS 2473 (general purpose) or AMS 2474 (low electrical resistance, Class 3) when the drawing calls an AMS standard instead of MIL. |
| Appearance | Golden-iridescent (Class 1A) or nearly colorless (Class 3); thin enough that the machined texture shows through. |
⚠ Not suitable for
Wear surfaces (the film is soft and microns thin — it abrades off); decorative applications expecting uniform color (iridescence varies); long outdoor exposure without a paint topcoat; non-aluminum metals.
Works on these materials
Typical applications
- Avionics and electronics enclosures needing EMI grounding
- Aerospace aluminum hardware per MIL-DTL-5541, AMS 2473 or AMS 2474
- Primer base under wet paint or powder coat
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