CHEMICAL CONVERSION COATING of ALUMINUM
H&W offers two alternatives for chemfilm, or aluminum conversion coating – chromate and non-chromate (RoHS-compliant). Both produce no measurable build-up and provide terrific corrosion resistance. Thickness of the film can range from 0.000001 to 0.000004 inches based on the time, temperature, and concentration of the prepared solution. The coatings are conductive with the electrical resistance increasing with heavier coatings. The chromate conversion coating option is known for superior bonding in paint and adhesive applications.
When first applied, these coatings produce a thin, soft, gelatinous film. Curing of the coating can be at room temperature or accelerated by baking up to 140 degrees F. Our chromate option produces a color from pale yellow to light brown depending upon the aluminum alloy. Our non-chromate option produces an iridescent, faintly blue to tan, appearance.
H&W’s chemfilm coatings are applied following existing standards, both military and customer created.
ZINC PHOSPHATE CONVERSION COATING of STEEL
Phosphating of metals is one of the most important surface treatment methods for steel. Treatments are used for corrosion protection together with paints, to assist in cold-forming processes, for corrosion protection together with oils and waxes, and for stand-alone corrosion protection. H&W offers zinc phosphate applications, which are often specified by the military and defense sectors, especially for equipment that might be exposed to severe environmental conditions. Cleaning is paramount prior to coating and it can have a significant effect on the growth rate of the phosphate coating, its thickness, and the crystal size.
The color of the zinc phosphate coating lies between light and dark gray. Standards that we follow yield either a fine-grain coating or heavy-grain, determined by the application. Heavy-grain is usually chosen for its ability to retain rust preventive oils and waxes since it acts as an absorbent substrate. Fine-grain has a finer crystal structure and is typically used as a base for paint or other organic coatings.