Metal finishing Q&As since 1989

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Step by step Alocrom

I send components out to be Alocromed on a regular basis but I am unable to see with my own eyes what the process includes as our sub contractor is a few hours drive away, please could you explain in layman's terms the step by step process involved.

Christopher Grant
Production Engineer - Tewkesbury, England
2007

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You can probably get a technical data sheet from the Alochrom supplier and it will probably mention the steps. Usually the steps are alkaline non-etch clean, rinse, etch, rinse, desmut, rinse, Alochrom, rinse. Sometimes etching is skipped, sometimes there's a double etch-desmut.

Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2007

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2007

Further to Ted's response the common route (although nowhere near exclusive) for treatment for Alocrom (Alodine to the rest of the world) would be something like this:

1. Degrease (this may be a vapour-form degreasing or swabbing with non-chlorinated solvent)

2. Mild alkaline clean (this is usually a proprietary solution from one of many manufacturers)

3. Rinse

4. Etch/Deoxidise (this may be done out of either acid or alkaline solution, some deoxidisers are self de-smutting, others will require a de-smut)

5. Rinse

6. De-smut if necessary (this will depend on your etch/de-smut step)

7. Rinse

8. Alocrom to obtain the required features (whether it be coating weight, colour, corrosion resistance)

9. Rinse

10. Dry at a temperature below 50C (although I think it should be below 40C personally)

It is impossible to give times and temperatures for these processes as so many of them may be proprietary, plus I suspect your treatment house has been doing this process for a while and should have a reasonable understanding of the process.

Hope this goes some way to help give you an idea of the process.

Brian Terry
Aerospace - Yeovil, Somerset, UK