Aluminum Chemical Conversion Coating (Chrome-Free and Trivalent Chromium)

Reaction Formulas for Aluminum Chemical Conversion Coating (Chrome-Free and Trivalent Chromium)

Characteristics of Aluminum Chemical Conversion Coating (Chrome-Free and Trivalent Chromium)

Aluminum chemical conversion coating forms a dense film on the aluminum surface through a chemical reaction, improving corrosion resistance, paint adhesion, and conductivity. Both environmentally friendly chrome-free and trivalent chromium treatments are available, and the process is adopted in fields requiring high reliability such as aerospace, transportation, and electronics.

1. Forms a strong, uniform oxide film on the aluminum surface that effectively prevents corrosion and maintains performance over long-term use.

2. Improves adhesion with paints and adhesives, preventing peeling and bonding failures.

3. Offers a choice between chrome-free treatment (no hexavalent chromium) and low-electrical-resistance trivalent chromium treatment, accommodating applications that require conductivity.

Types of Aluminum Chemical Conversion Coating (Chrome-Free and Trivalent Chromium)

Type	Characteristics
Trivalent Chromium Conversion Coating	Forms a film using trivalent chromium compounds without hexavalent chromium. Excellent corrosion resistance and paint adhesion; also suitable for applications requiring low-resistance conductivity
Chrome-Free Conversion Coating	Contains no chromium at all; forms a film using titanium or zirconium compounds. A thin film of about 100nm ensures corrosion resistance and paint adhesion. Compliant with environmental regulations (RoHS).

Equipment and Available Sizes for Aluminum Chemical Conversion Coating (Chrome-Free and Trivalent Chromium)

*Jigs and treatment tanks can be custom-made in-house by our maintenance department. We can also accommodate rush jig requirements.

Advantages and Disadvantages of Aluminum Chemical Conversion Coating (Chrome-Free and Trivalent Chromium)

Advantages	・Greatly improves adhesion as a base for painting or bonding ・Combines corrosion resistance with environmental friendliness ・Adopted in high-reliability applications such as aerospace and electronics
Disadvantages	・The film is thin and, on its own, not suited to high-durability applications ・Chrome-free coatings in particular are sensitive to process conditions and require careful control ・Uneven processing or color variation may occur depending on the base material

Film Properties of Aluminum Chemical Conversion Coating (Chrome-Free and Trivalent Chromium)

Property	Chrome-Free (Zr-based) Trivalent Chromium
Structure	Zr oxide + Al oxide layer Cr(III) compound + Al oxide layer
Corrosion Resistance	Corrosion resistant Higher corrosion resistance than chrome-free
Film Thickness	Very thin (tens to a few hundred micrometers)
Adhesion	Well suited as a paint base, with good paint adhesion
Appearance	Colorless film Base material color to pale milky white

Compatible Materials

Aluminum in general

Applications and Case Examples of Aluminum Chemical Conversion Coating (Chrome-Free and Trivalent Chromium)