Surface treatment of metals and plastic
This document describes the best available techniques for surface treatment of metals and plastics. Substitution possibilities for EDTA, PFOS, zinc cyanide, copper cyanide and hexavalent chromium are mentioned.
The document also describes non-chemical alternatives to many processes
Hexavalent chromium compounds are included in SUBSPORT´s database of hazardous substances.
In this document the chemicals used in installation for surface treatment for metals and plastics using an electrolytical or chemical process are assessed in order to describe the best available techniques (BAT). SUBSPORT will only shortly mention the substitutions in the document. For more information please look in “Further information”. The document can be obtained for free from the link.
The following substitutions are mentioned:
Chelating agents such as EDTA and NTA are often used in degreasers and etchants used for printed circuit boards. They may be replaced by biodegradable ones – for example based on gluconic acid.
Perfluorooctans sulphonate is used as a foam suppressant and surfactant especially in the prevention of mists in hexavalent chromium electroplating and in alkali non-cyanide baths. The document mentions, that substitutes should be available for anodising, but no specific chemical is described.
Instead of using zinc cyanide solutions the best available technique is acid zinc. This gives an optimum energy efficiency and reduced environmental emissions. Where metal distribution is important alkali cyanide-free zinc is the best available technique. Some products may contain PFOS.
Copper cyanide is used in strike plating on steel and zinc die casts. It can be substituted by acid copper, which is the choice in Germany. Pyrophosphate copper can also be used, but has limited applications. No alternatives are found for brass and bronze.
For decorative chromium plating hexavalent chromium can be replaced by trivalent chromium. Sealers and phosphochromate finishers can contain hexavalent chromium. Many of these can be replaced with non-Cr 6 solutions based on for example silanes, zirconium and titanium.
It is not possible for SUBSPORT to evaluate the alternatives, as the information is not specified enough in the document.
Type of information supplier
Reference documents on best available techniques for surface treatment of metals and plastics. European Commission, August 2006.Type of publication and availability
Original document: click here
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