As one of the leading electroplating companies in the UK, EC Williams was one of the electroplating manufacturers that had to adapt to the fall of cadmium plating services. Back in the 1950’s and 1960’s, cadmium was a very popular material to use for electroplating. Now however, there are very few electroplating companies that are allowed to offer cadmium plating – but why?
Cadmium plating was always the number one choice of plating for engineers looking for corrosion protection. The aerospace industry in particular was a sector that relied heavily on cadmium plating for its components.
Cadmium plating is an electrolytic process which involves depositing a layer of cadmium onto the surface of a substrate. This type of plating offers both corrosion protection and sacrificial protection. When cadmium is applied as a coating on steep components or other metals, the coating will corrode preferentially. As a result the substrate itself will remain undamaged – even if the coating is scratched. Cadmium coatings are usually applied with a thickness of between 5 and 20µm. Its own corrosion rate is often around one fiftieth of that of steel.
The Fall of Cadmium Plating
Environmental concerns surrounding cadmium plating now means that it features on both REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals) and RoHS (Restriction of Hazardous Substances) regulations. These regulations heavily restrict the use of cadmium to a handful of industries and applications.
Cadmium plating cannot be freely provided by any electroplating company anymore without special permissions. The aerospace and defence industries are generally the only two sectors still using cadmium plating whilst being heavily regulated.
Research into the health impact of cadmium revealed that the substance is highly toxic to humans. It is now classed as a carcinogenic which means that extensive safety measures are required in order to be able to work with it.
As a result of the above, cadmium has become increasingly hard to offer as a plating service and as a result, electroplaters and their clients have saught alternatives. Cadmium replacements are pivotal when it comes to electroplating. As a popular choice for metal surface protection, a replacement that offered the same resistance and strength was quickly needed when cadmium became harder to source. Luckily, a safer alternative has fast become one of the most popular choices for engineers seeking corrosion protection; zinc-nickel.
The Not-so New Alternative: Zinc Nickel
Although zinc nickel plating is a relatively new choice for those who previously used cadmium plating, the coating choice is certainly not a new invention for the electroplating industry and manufacturers. Zinc nickel has been popular since the mid 1980’s having been developed for use in the automotive sector to coat some of their most vulnerable components.
The aerospace sector (which was the main industry relying on cadmium) is the sector in which zinc nickel plating is probably less acquainted with.
Zinc is the sacrificial element within the coating, however when in use independently, it will corrode too easily. By adding nickel, zinc’s activity slows down significantly, which allows the other benefits of the plating to be reaped. Alongside providing excellent corrosion protection, zinc nickel offers fantastic coverage and thicknesses (10-20µm). The protective coating offers great adhesion and can also be painted on top of.
Other benefits include:
- Good natural lubricity
- Easier to source
- Zinc nickel does not set up a galvanic cell in an aluminium environment
With all of the above taken into consideration, the aerospace industry is now successfully in use in many different industries and applications including the aerospace and defence industries, the automotive sector, and the marine industry.
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If you have found this blog helpful, you may wish to read our previous blog: A Guide To Copper Electroplating