In the vast majority of uses, particularly for large production, zinc plating is done using hexavalent chromium, which are also known as yellow chromates. This compound is a known carcinogen and is highly toxic, which is why many different industries and area of the world have already severely limited or even banned the use of high levels of hexavalent chromates.
The Chemical Composition
This is particularly common throughout Europe, where new options, including clear zinc plating, are used as an effective and efficient option to the traditional yellow chromate. The car industry throughout most parts of Europe uses this exclusively since the high hexavalent chromates are banned from use.
For practical comparisons, it is important to note that clear or blue zinc plating is much lower in hexavalent chromate, but they were originally less corrosion resistant. New technology has allowed metal finishers to develop a product largely free of the toxic hexavalent chromates as well as with a much higher corrosion resistance through different treatment options.
The RoHS Compatibility
The vast number of top metal finishing companies offering clear zinc plating have products for all types of zinc plating that will meet the RoHS standards. RoHS or the Restriction of Hazardous Substances outlines the parts per million (ppm) of restricted materials that can be found in manufactured products sold into other ROHS compliant countries. To meet with RoHS standards the maximum level of hexavalent chromium is less than 1000 ppm.
There are also other standards that may need to be considered for specific parts. These include WEEE or the Waste from Electrical and Electronic Equipment, which is more specific to recycling and recovery of these components. There is also the new REACH (Registration, Evaluation, Authorisation and Restriction of Chemicals), which is a European standard that will impact the ability to export to countries in the European Union.
As with any type of yellow zinc, the clear zinc plating can be used as part of the primer type of layer to boost corrosion resistance. Of course, with the treated surface these components easier to process, including painting or gluing of components that would not be possible without the coating.
With different thicknesses possible to meet specific requirements, this is a very good option for all types of applications. The finish is long-lasting and allows for customization of parts for easy identification, and also the use or export in countries around the world.