Conversion Coatings: Chem Film


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.


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.

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Conversion Coating at H&W Global meets or exceeds stringent military standards, including:

MIL-DTL-5541 Type I Class 1A & Class 3
MIL-DTL-5541 Type II Class 1A & Class 3
STP 58-405 (Code 210A)

Ask H&W Global
about Conversion Coatings:

How quickly can paint be applied after conversion coating a part?

After about 24 hours in room temperature.

Is it true that aluminum conversion coating can be used to repair an anodized surface?

Yes, this is true and is guided by the MIL-A-8625 spec.  The chemfilmed area has, however, only about half the corrosion resistance of the anodic coating.

Is conversion coating the same as electroplating?

No, conversion coating results from a chemical reaction process with the part surface and does not involve electrical current being applied to the part.  It is not an electrochemical process.

How thick is the conversion coating?

It can range between 0.000001 and 0.000004 inches as a general guideline.  It is very thin.

How may we help you?

Custom Masking
Custom Graphics
Laser Engraving
Threaded Inserts
Assembly, Kitting
Custom Packaging
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