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How to Differentiate Two parts Having Dacromet and Geomet Coating?

October 3, 2008

If one bolt is having Dacromet coating and another one is having Geomet coating and both are having same silver colour then how to differentiate Dacromet coated bolt from Geomet coated bolt.

Prashant Jadhav
employee - India

October 8, 2008

One approach would be to contact Metal Coatings International. Dacromet is based on the reaction of hexavalent chromium with monomers and zinc and aluminum flake. It will therefore test positive for hex chrome using the GMW 3034 or ISO 3613 [affil. link] test. (I wouldn't rely on spot tests.) Geomet is based on organosilane technology and will test negative for hex chrome. Or you could ask your supplier to tell you what they are putting on the parts in the way of a certification.

Tom Rochester
CTO - Jackson, Michigan, USA
Plating Systems & Technologies, Inc.
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October 21, 2008

You can put a couple of drops of NH4OH on the bolt, wait 30 seconds. If the part is Dacromet the NH4OH should turn yellow. Now the caution is if the coating is not cured properly this may not work. The most sure way would be to run an X-ray to get the elemental analysis and look for chromium.

David J. Wolf
David J. Wolf
Medina, Ohio

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