Class I Thickness : .0005″ min
Class II Thickness : .0003″ min
Class III Thickness : .0002″ min
Type I – as plated
Type II – with supplementary Chromate Treatment
Chromate is a type of conversion coating that is used as either the primary finish for aluminum or a supplemental coating over cadmium or zinc plating. Chromate conversion coating is widely used for corrosion protection, undercoat for paint and adhesive applications.
This application is commonly used in the aerospace industry, electronic cabinets and component parts. The overall thickness can range from 0.00001″-0.00004″ allowing for almost no dimensional change to the part. As an added advantage the cost can tend to be lower than other finishes.
Chromate comes in various colors including clear, gold and olive drab (OD).
Olive drab, or forest green chromate is the ultimate in commonly available conversion coatings, with neutral salt spray resistance in excess of 150 hours. This chromate is most commonly specified for military applications. It is generally not possible to apply to barrel plate work. The color and the corrosion resistance are due to the inclusion of an organic acid modifier to the chromate formula. Many customers find the color is not especially pleasing, but specify it for nonmilitary applications for its function, rather than its decorative, value.
Chromate conversion coatings are included in a great many specifications and are also covered in their own specification MIL-C-5541, although that specification applied exclusively to chromate conversion coatings on aluminum.