Chromate conversion coating services
Chromate conversion coating — chem film on most drawings, Alodine by trade name — is a thin chemical layer grown on aluminium. It is specified for three different reasons: to slow corrosion, to give paint something to key into, and to protect the surface without insulating it.
Request a Quote| Surface preparation | Colors | Applicable materials | Thickness | Cosmetic availability | Visual appearance |
|---|---|---|---|---|---|
| As machined (Ra 3.2μm / Ra 126μin) | Clear/ slight yellow tint | Aluminum (7xxx series not recommended) | None | No | Machining marks are visible |
| Bead blasted (Glass beads #120) | Clear/ slight yellow tint | Aluminum (7xxx series not recommended) | None | Cosmetic on request | Machining marks are completely removed on "cosmetic" parts but may be visible on "non-cosmetic" parts |
Example of chromate conversion coated parts
As machined
Bead blasted
Design considerations for chromate conversion coating:
The layer is measured in fractions of a micron, so a chem-filmed part holds the tolerances it was machined to. Nothing needs masking for dimensional reasons.
It works on aluminium alloys. Steel and iron cannot take it directly — those need a different route, and an engineer will say so when the drawing arrives.
What is chromate conversion coating?
Chem film earns its place on three counts at once: it slows corrosion on aluminium, it gives paint a surface to key into, and it leaves the part electrically conductive. That combination is why it shows up on aerospace brackets, automotive housings and construction fittings rather than a thicker coating that would insulate them. Tell us on the drawing whether the part needs the hexavalent or the chromium-free chemistry and it will be quoted and certified against that.
How does chromate conversion coating work?
The part is immersed in a chromate bath, and the acid reacts with the aluminium surface to form a thin, adherent film. That film is what carries the corrosion resistance and the paint adhesion; the metal underneath is unchanged.
Metal Market offers chromate conversion coating for aluminum parts to improve functional properties. To find out more, contact sales@metal-market.in.
Here's how we apply chromate conversion coating:
Parts are cleaned and degreased to remove any contaminant
Parts are then rinsed to eliminate any residue of detergent
Aluminum parts are immersed in a tank containing the chemical solution
Parts are removed when a film of the desired thickness coats the surface
Parts are then rinsed again