Technology analysis for chrome-free coating processes

Electroplating is a very important and economically established process for applying thin metallic layers to metal and plastic parts. Chrome layers in particular, with their high hardness, are very popular for corrosion protection and for optical reasons in the sanitary area and in the household. Unfortunately, chromium-containing sewage and exhaust gases pollute the environment and increase the risk of lung cancer. But there is still almost no alternative to chromium (VI) oxide (chromium trioxide) in electroplating for technical and economic reasons.

At the instigation of Germany, chromium trioxide has been listed as a dangerous substance (SVHC = substances of very high concern) in the so-called European REACH regulation (REACH = registration, evaluation, approval and restriction of chemical substances) since 2013. This stipulates that approval permits are required for use. The “sunset date” indicates the date from which a chemical substance may no longer be used or placed on the market according to REACH without the corresponding authorization. In the case of chromium trioxide, this was September 21, 2017. The aim of the process was to get coaters to implement chromium-free alternative technologies. But comparable alternative technologies can only be found in rudiments.

Results
In the project, the various possibilities for establishing chrome-free alternative technologies were recorded and the development status presented. The coating qualities to be achieved for the individual processes were evaluated and roughly compared in terms of their economic efficiency. In addition, an assessment of the use of resources and the sustainability of the processes was given. In a patent search, some essential property rights to alternative coating processes could be recorded.

image: Sol-gel technology as a replacement for chromium VI compounds (source: EPG)