Chemical Conversion Coatings:

Chemical conversion coatings sometimes referred to as chromate conversion, chem film, Iridite or Alodine refer to a process of applying a thin barrier coating on the substrate to passivate aluminum alloys to slow the formation of corrosion. It is gelatinous film that has self-healing properties and improves paint adhesion on aluminum alloys and die castings. It can also be applied to zinc die castings.

Materials qualified under Mil-DTL-5541F produce coatings that range in color from clear to iridescent yellow or brown.

They are all electrically conductive and impart some measure of corrosion protection on the substrate.

Visual inspection may be difficult since breaks in the coating are not easily seen.

Type I is Hexavalent Chromate

Type II is ROHS compliant, hex free chromate.

Class IA coatings are intended to provide corrosion protection as a standalone coating and improve adhesion of subsequent operations such as paint on aluminum substrates.

Class 3 chemical conversion coatings are used as a corrosion preventative film where electrical contact is still required. Many times it is applied under masking operations prior to anodic coatings in accordance with MIL-A-8625-F.

The primary difference between Class IA coatings and Class three coatings is thickness.

Chromate conversion coatings are commonly used on parts in the:

aircraft industry

electronic cabinetry

aluminum stampings

electronic components

zinc die castings

aluminum die castings

Chromate Conversion, also known as Chem-Film, Irridite, or Alodine; this coating chemically reacts with the surface of the material to form a soft gelatinous film when first applied. After time the film hardens and becomes hydrophobic. Its purpose is to provide maximum corrosion protection to aluminum and act as a base for paint primers. Conversion coatings are typically very thin, around 0.00001".
























Anodize   Black Oxide   Chromate   Hard Coat
Anodize   Black Oxide   Chromate   Hard Coat
Nickel   Passivation   Tin   Zinc
Nickel   Passivation   Tin   Zinc
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