How to assess whether a coating is mechanical galvanizing or something else?

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hi, I have an italian customer who produces hardened fasteners has always protected them by the means of hot dip centrifuged process. now he is suffering competition from german and hollandaise companies that sell a steel faucet they declare is hot dip galvanized but in fact looks very smooth, regular coating, dark grey matte finish and approx 85 microns in thickness. furthermore, the first microscopic analysis revealed a way too regular coating thickness and layer, with no presence of the usual alloy layers. Can anybody help me with suggesting how to assess what kind of coating is that? (it is zinc based, that's for sure)
thanks a lot
Mario Ubiali
Italy

Mario Ubiali
- Brescia, Italy

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In may be mechanical galvanizing, or possibly thermal diffusion (sort of a successor to Sherardizing) or maybe even a zinc-rich dip-spin coating, Mario. Unfortunately, the person or company who is offering a different coating always knows more about it than the outsider and is always a step ahead. This means one will usually comes off poorly if they try to demonstrate their knowledgble of someone else's coatings.

For that reason I think the best approach in these cases is to test which one is superior in some way. And there is certainly nothing wrong with you deciding what those tests should be to present hot dip centrifuged coatings in the best light.

If you think the other coating is softer, prescribe a scribe test with a hardened knife. If you think your coating has greater salt spray resistance, try that. Better freedom from stick-slip when torquing up, try that. If you think the other coating is not easily strippable, try that. I know you are already very familiar with hot dip galvanizing, but go to some of the trade association websites and read the advantages again and see if you can formulate tests where hot dipping will come out on top. Good luck.

Ted Mooney, P.E.
finishing.com
Brick, New Jersey