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Exploring Three Hexavalent Chrome Alternatives: A Sustainable Approach to Wear Resistance

 

In the world of industrial coatings, hard chrome plating is well-known for its toughness, resistance to corrosion, and durability. But as we move towards more sustainable practices, with increasing environmental awareness and restrictions on hexavalent chrome, finding an alternative has left more than a few manufacturers in a lurch. Hard chrome plating serves a wide range of industrial needs, so no single alternative will do the trick. However, there are a lot of cutting-edge technologies being developed to try and fill this hole. For now, let's explore three currently available coating methods that stand as alternatives to hard chrome plating: thermal spray, physical vapor deposition, and electroless nickel plating.

Thermal Spray Coating

Thermal spray coating uses different types of combustion processes to apply wear and corrosion-resistant coatings comprised of a wide variety of metal and ceramic materials. It can be likened to spray painting with molten metal. As a hard chrome plating alternative, thermal spray coatings can be used to apply specialized carbide coatings, like our BTHC-0005™. It is harder than hard chrome and can be applied as thin as 0.005” to 0.050” thick. BTHC-0005™ can be removed and reapplied in most cases and is compatible with most base materials. It does have some geometrical limitations due to line-of-sight application. Therefore, thermal spray isn’t conducive to reaching into crevices like the dip of a hard chrome can. BTHC-0005™ coatings can typically be polished down to 1 Ra-in. Thermal spray hard chrome alternatives are ideal, but not limited to, outside diameters, especially rolls and hydraulic piston rods.

Physical Vapor Deposition (PVD) Coatings

Physical Vapor Deposition, also known as thin-film coating, uses a specialized vacuum to vaporize solid materials and deposit them onto the substrate. To apply a PVD chrome, parts will have to be small enough to fit inside the vacuum chamber and withstand temperatures up to 800 °F. It can be applied to most substrates that can withstand the vacuum temperature, which typically excludes aluminum. It can be applied in very thin ranges, 0.0001” to 0.0004”, and can achieve the same surface finish as the substrate. PVD coatings are ideal for small, intricate parts that need thin multi-faceted coating.

Electroless Nickel Coatings

Electroless nickel coatings are applied in a bath, like hard chrome plating. The hard chrome equivalent is typically a nickel phosphorus alloy and can be applied from 0.1 to 5 mils thick. It is more ductile than hard chrome, heat resistant up to 1600 °F, and can be hardened after application. It can be applied to most substrates but may need extra processing to ensure adhesion to substrates other than steel. Electroless nickel plating is ideal for anything that requires a similar coating method as hard chrome plating.

Navigating New Norms and Embracing Alternatives

As more and more governments begin to restrict hexavalent chrome, familiarizing yourself with these alternatives is the first step to navigating the new norm. These alternatives are more environmentally friendly and offer the same benefits and then some. If you're looking for a thicker coating or something for larger applications, thermal spray is the place to start. If you have small parts, with intricate geometries, start with PVD or nickel plating.

Whether manufacturing a new part that would typically have chrome plating or setting out to repair a worn one, these options are worth exploring. It's best to assess each situation individually to see which solution fits best. Getting advice from a coating expert can also help steer you in the right direction. 

Interested in learning more about a thermal spray hard chrome alternative?