Chemical Conversion Coating

At a Glance

Chemical 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.

Elemental metals (except precious metals), including their alloys, usually spontaneously react with the medium to form compounds and return to their mineral state under normal conditions. This is the reverse process of metallurgy. This process is called metal corrosion. Sometimes this process does not go on and will stop very quickly, because at this time, the compounds formed by the metal and the medium accumulate on the metal surface, and this layer of dense metal compounds forms a "film". At this time, the metal seems to wear a coat that prevents further contact between the metal and the medium, especially if the compound is poorly soluble in water. The chemical conversion film is designed based on this principle.

Advantages of Chemical Conversion Coating

  • Anti-corrosion. Anti-corrosive chemical conversion coating is mainly used in the following two cases: Firstly, there are general anti-rust requirements for parts, such as anti-rust oil, etc. The conversion film is used as the bottom layer and can be applied when it is very thin. Secondly, the components have higher requirements for corrosion resistance, and the workpiece are not subject to external forces such as deflection and impact. The conversion film is required to be uniform and dense, and the thicker is preferred.

  • Wear-resistant. Abrasion-resistant chemical conversion coatings are widely used in areas where metal and metal surfaces rub against each other.

  • Insulating. Chemical conversion films are mostly poor conductors of electricity. Phosphate films have been used as insulating layers of silicon steel sheets. This insulating layer is characterized by a small duty factor, good heat resistance, and can reduce mold wear during punching.
  • Types of Chemical Nickel Plating

    Here at DH Machining, we offer various of high quality Chemical Conversion Coating surface treatment for CNC precision machined parts.

    Surface Treatment TypeMaterialThicknessColorReference Standard
    Chemical conversion coating / AlodineVarious types of aluminum alloy1 ~ 2μmClear, light blueMIL-DTL-5541 Type II
    Golden alodineVarious types of aluminum alloy1 ~ 2μmGoldenMIL-DTL-5541 Type II
    Chromium-free passivationVarious types of aluminum alloy1 ~ 2μmClear, light blueMIL-DTL-5541 Type II
    Oxidizing blue (black)Medium and low carbon steel & tool steel0.5 ~ 1μmBlack, blue blackMIL-DTL-13294D
    Oxidizing blue (black)Cast iron0.5 ~ 1μmBlackMIL-DTL-13294D
    Oxidizing blackVarious types of copper0.5 ~ 1μmBlackMIL-DTL-13294D
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