Introduction to Zinc Nickel Alloy Plating
By: Andy Scheer Burbank Plating Service Corp.
Cadmium Plating has long been used by the automotive, aerospace and marine industries for its superior corrosion protection. However, cadmium is a heavy metal. Cadmium is known to be a toxic heavy metal and is considered a carcinogen. The European Union End Of Life Vehicle Directive (ELV) banned the use of Cadmium along with other heavy metals in the automotive industry in the fall of 2000. RoHS, another regulation restricts the presents of certain substances including Cadmium. The handling, grinding or welding of Cadmium Plated parts expose individuals to this heavy metal. These facts and other regulations throughout the world have increased concerns about the impacts of Cadmium on humans and the environment. Industries are motivated to find alternatives to Cadmium Plating.
Zinc Nickel Alloy Plating is an exceptional Cadmium Plating Alternative. Burbank Plating Service has been applying Zinc Nickel Plating for 15 years. It is comprised of between 5-15% Nickel with the balance being Zinc. The plating is then chromated with clear, yellow or black chromates and then sealed.
Zinc Nickel Alloy Plating significantly exceeds other types of coating in these three main areas:
- It offers greater corrosion protection. Salt Spray Tests consistently show that Zinc Nickel Plating is at least 2 to 3 times more resistance to corrosion than Cadmium Plating and even more compared to zinc plating. 1000 hours of salt spray testing consistently shows no red rust. We have had test parts exceed 2000 hours without any formation of red rust. Check out this YouTube video, which shows the results of one of these salt spray tests on bolts. You can search for zinc nickel plating vs. zinc plating or use this link https://www.youtube.com/watch?v=N2QWsdv8drE.
- It provides more wear resistance in moving parts. A hard, thin-film Zn-Ni coating has a consistently smooth finish that increases wear resistance both through its hardness and by producing a surface that virtually eliminates irregularities, reducing both friction and opportunities for abrasion. On the Vickers hardness scale, parts coated with Zn-Ni reach 450, compared to less than 150 for zinc-coated parts.
- It limits thermal stress to parts subjected high temperatures Tests show, for example, that components coated with Zn-Ni retain their corrosion resistance despite exposure to thermal stresses in temperatures up to 200°C
Automotive manufacturers and their component suppliers have been pioneers in adopting Zn-Ni coatings. They have begun applying them to the undersides of hoods and other engine-compartment structures to protect them from the heat, as mentioned earlier. They also coat fasteners used in wheel wells and other exposed areas of vehicles requiring increased abrasion and corrosion protection. This extends the life and appearance of those parts and reduces warranty claims. Almost all OEM brake calipers use Zinc Nickel Plating.
Many aerospace components manufacturers are switching away from Cadmium Plating to Zinc Nickel Plating. Boeing has been one of the pioneers in the transition from Cadmium to Zinc Nickel.
Zinc Nickel Plating provides superior corrosion protection without any of the environmental impacts of Cadmium Plating. Cadmium Plating may end up being a thing of the past.