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Trivalent Chromate Conversion

Trivalent chromate conversion finishes (Cr³⁺) are a modern alternative to hexavalent-based (Cr⁶⁺) treatments for aluminum and its alloys, offering robust corrosion protection with reduced health and environmental risks. RIE Coatings can help you find Restriction of Hazardous Substances (RoHS) Directive-compliant trivalent solutions that meet your application requirements. 

What Is Trivalent Chromate Conversion?

Chromate conversion finishes, also known as Alodine, Iridite or chemical film in some industries, are widely used for protecting aluminum and its alloys and may also be applied to magnesium and zinc parts, particularly in the aerospace, defense, electronics and automotive sectors.

Two main types include trivalent chromate conversion finishes and hexavalent chromate conversion finishes, which are the traditional industry standard now being phased out due to health and environmental concerns. The process typically involves immersing, spraying, or brushing the part with a solution containing chromium compounds. 

The main distinction lies in the type of chromium compound — trivalent for newer processes and hexavalent for older ones. There is also a visual difference. Trivalent finishes are clear, while hexavalent finishes are known for their distinctive yellow or iridescent gold color. Some finishes may also vary by product chemistry, substrate or process.

Manufacturers in the aerospace, defense, electronics and automotive sectors rely on this process, using trivalent finishes to prepare parts for advanced bonding, adhesive applications or subsequent layers.

The Benefits of Trivalent Chromate Conversion

Trivalent chromate conversion finishes can:

  • Enhance corrosion resistance: Trivalent chromate conversion forms a passive layer that effectively protects aluminum substrates from oxidation and corrosion. In some cases, corrosion resistance is comparable to that of hexavalent chromate.
  • Promote paint adhesion: The microstructure of trivalent finishes improves paint and adhesive bonding, prolonging finish life and minimizing delamination.
  • Extend the life of metal components: Trivalent chromate conversion finishes provide ongoing passivation, which refers to the creation of a stable and less reactive oxide or chromate layer on aluminum. Even if the surface is scratched, the surrounding areas help inhibit corrosion, extending component life.
  • Protect conductivity: Trivalent chromate finishes maintain higher surface electrical conductivity than anodized finishes, making them ideal for connectors and grounding applications.
  • Help your organization reach environmental goals: Trivalent chromate conversion finishes are often regarded as an eco-friendly alternative to hexavalent chromate, which is toxic and carcinogenic. The use of hexavalent chromium is highly restricted under European Union (EU) RoHS and Registration, Evaluation, Authorization and Restriction of Chemicals (REACH) regulations, with only limited exemptions. Trivalent chromium compounds are subject to far fewer restrictions and are generally considered safer for people and the environment. 
  • Allow you to expand into more markets: RoHS-compliant trivalent finishes meet key international and EU requirements for electrical and electronic equipment, supporting access to regulated markets, and may also aid compliance with REACH and industry-specific standards.

Why Choose RIE for Hex-Free Trivalent Chromate Conversion Finishes?

RIE leads in advanced conversion finishes for aerospace, military and commercial clients. Our Albuquerque facility is ISO 9001:2015 and AS9100 certified and RoHS-compliant. 

Our hex-free trivalent chromate finishes fulfill MIL-DTL-5541 Type II requirements for Class 1A corrosion protection and Class 3 low electrical contact resistance. We tightly control pre-treatment and bath chemistries to achieve a 168-hour salt spray pass for Class 1A applications while supporting conductivity-sensitive Class 3 requirements.

Because trivalent chromium baths are more sensitive to metallic impurities than hexavalent chromium baths, they require careful control of additive balance and pH ranges. RIE’s technical know-how helps maintain that control so parts meet performance requirements.

RIE offers direct access to engineers so that you can solve your biggest challenges with a collaborative approach. We offer timely turnarounds and support in finding you the right metal finishing solution for your application. 

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Consult With an Engineer About Chromate Conversion Finishes

Speak with engineers who can help you find metal finishing solutions for your specific applications.

 

Call (320) 592-6325, contact us online or email us at info@riecoatings.com. We typically respond within a few hours with answers or within 24 business hours for quotes.

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