Hybrid Functional Coatings: A Cost-Effective Coating Innovation
The field of industrial coatings is ever-changing, with new methods and options becoming available each year. The coating industry depends on research to advance the science behind protecting metal substrates, and this research has unveiled innovative new approaches. One of the most recent developments in the field is that of an engineered thin-film coating for aluminum and titanium substrates, offering a low-cost alternative to existing coating methods while providing superior corrosion and wear resistance.
The Cirrus Hybrid™ Coating Technology
Presented as part of the National Association for Surface Finishing (NASF) SURFIN annual tradeshow and technical conference in June, 2018, the Cirrus Hybrid™ coating technology represents a cost-effective step forward for professional finishing operations.
Developed by researchers at the New Zealand-based Cirrus Materials Science, Ltd., Cirrus Hybrid is an electrodepositing technology that provides a thin-film coating for industrial coating operations, particularly in coating light metal substrates like titanium and aluminum. The coating bonds tightly to the substrate, and offers excellent wear resistance and protection against corrosion. Electrical and thermal performance is also superior, especially as compared to existing coating technologies. In laboratory tests, this low-cost coating solution has demonstrated substantial environmental and occupational health advantages over traditional coating technologies like primer-and-paint, electroless nickel, and anodizing processes. The Hybrid film is considered relatively non-toxic and non-hazardous, negating the need for advanced hazard mitigation systems in the coating process.
The Hybrid Coating Process
As the name suggests, Cirrus Hybrid coating technology is actually a hybrid of two other coating methods: anodization and electrodeposition. Advances in both of these processes led to the development of the Hybrid thin-film coating, allowing coating service providers to control pore size, wall thickness, and film thickness by adjusting coating bath chemistries and operating parameters.
For aluminum alloy substrates, the Hybrid process begins with traditional anodizing, which creates a tightly-aligned surficial nanotube structure. The structure forms an ideal surface to accept the next step, that of deposition of an electro- or electroless interlock metal layer, which is typically nickel. Finally, a finish layer of nickel or another metal like gold, copper, tin, or chromium completes the coating process. The result is a thin film that demonstrates superior corrosion and wear resistance. In corrosion resistance testing, the film was able to withstand 500 hours of neutral salt spray and 75 hours of acid salt spray exposure. By controlling the anodized and interlock layers, corrosion resistance can be customized to suit the unique needs of the substrate’s end user.
The process for titanium requires several additional steps, and further research is needed to improve results, according to PCS. In preliminary testing of one coating protocol, there was poor adhesion between the metal substrate and the anodized layer, possibly due to the presence of oxide layers. In a subsequent coating protocol, researchers anodized the titanium substrate, removed any oxide buildup, then anodized again and annealed the substrate before electrodepositing the finishing layer. This protocol shows great promise, but additional testing and development is needed. For now, however, Cirrus Hybrid represents a major industrial coating innovation, providing a cost-effective and environmentally sound solution to metal substrate finishing processes used throughout industries.