Conversion coating
Conversion coatings are coatings for metals where the part‘s surface is subjected to a chemical or electro-chemical process by the coating material which converts it into a decorative or protective substance. Examples include chromate conversion coatings, fluorozirconates, fluorotitanates, sol gels, phosphate conversion coatings, bluing, black oxide coatings on steel, and anodizing. They are used for corrosion protection, decorative color, adhesion promoters, and electrically conductive coatings.
Aluminum is one of the most common substrates to conversion coat. Historically this has been with chromate conversion coatings, although recent environmental regulations have led to much interest in finding replacements. Generally these coatings are measured by two military specifications, MIL-DTL-81706, and MIL-DTL-5574. There are two general classes in these specs Class 1 and Class III.
