In the chromate conversion process, the metal surface of a part is converted to a superficial layer containing a complex mixture of chromium compounds. The chromate film is soft when freshly formed, but once dried and aged, the film becomes more abrasive resistant. Chromate conversion coatings provide excellent corrosion resistance. Paint, lacquer, and organic finishes bond exceedingly well to chromate conversion coatings. In addition, the chromate coatings prevent loss of paint adhesion due to under film corrosion.

Chromate conversion films vary in color depending on the chemical being used and the base metal being coated. Colors range from clear, to light iridescent, to gold. Greater corrosion protection is provided with formulations that give a golden color, as these coatings tend to be thicker. A varied appearance may be obtained when the base metal is non-uniform (i.e., welds in wrought materials and castings).

Major Industry Specifications Chromate Conversion: MIL-DTL-5541F

Type I – Compositions containing hexavalent chromium

Type II – Compositions containing no hexavalent chromium

Class 1A - For maximum protection against corrosion, painted or unpainted

Class 3 - For protection against corrosion where low electrical resistance is required

MIL-STD-171 MIL-S-5002

We now supply MIL-DTL-5541F finishing to meet the RoHS Directive.

T&T aoffers a non-hexavalent chromium-based processes! Type II Trivalent chromate is the RoHS(Restriction of Hazardous Substances) compliant. It ranges in color from clear, to a blue-ish tint.