08 Aug WHY ZINC NICKEL ALLOY PLATING IS REPLACING CADMIUM
For a long time, cadmium plating saw a great deal of use, especially in marine and automotive applications. It provided excellent resistance to corrosion and lubricating properties. However, there are some definite drawbacks to using this heavy metal. For one, it has created a great deal of environmental concerns. Many companies have been seeking alternatives to cadmium (like zinc nickel alloy plating) for some time. In fact, zinc alloys are replacing cadmium in many industries today and here are some reasons why.
Cadmium is Discovered
In the early 1800s, cadmium was first discovered by a scientist in Germany named Friedrich Stromeyer. Stromeyer was asked by the German government to inspect zinc oxide from pharmacies. Back then, zinc oxide was used for a number of skin problems, and still sees wide use today.
When Stromeyer checked zinc oxide samples, he realized some pharmacies were actually selling zinc carbonate in the small German town of Hildesheim. In experiments, Stromeyer decided to heat the zinc carbonate until it became zinc oxide. When he did this, it should have created white oxide, but this material was a yellow orange color instead, so he checked for lead or iron contaminants and found none. In this part of Germany, a special metal was hidden inside the zinc carbonate and this is the reason the pharmacies were not heating it to turn it into zinc oxide. Stromeyer eventually isolated the metal causing the unnatural color and named it cadmium.
Today cadmium is produced from zinc carbonate by using a cyanide process, which creates a very toxic metal. However, it is extremely resistant to corrosion and an excellent conductor of electricity. In 1956, over 60 percent of all cadmium was used for coating iron or steel. However, over the years, this has decreased to as little as 7 percent in 2006, and materials like zinc nickel plating are seeing more and more use.
In Search of Alternatives
When the industry was looking for a viable replacement to cadmium, they tried zinc electroplate. However, this was not suitable for marine environments. In fact, in as little as three days, the material can start to show signs of rust.
Chromium alloys were tried but they were expensive. In addition, hexavalent chromium was being phased out for the same reasons as cadmium, and other chromium types did not offer the kind of protection needed for extreme environments.
Zinc nickel alloy plating has shown a great deal of promise when it comes to producing a corrosion resistant finish that is rust resistant. In fact, ever since Boeing came up with acid zinc nickel plating, this technology has gained popularity in almost all markets. Contact DeKalb Metal Finishing today to find out our Zinc Nickel plating can help you protect your parts.