Letter 34012

Electroplating ABS  

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I am a high school student starting an investigation on the electroplating of ABS using nickel electrodes. I have the following substances: Carbon particle (Aquadag), sulphuric acid. etc. but i did not know more substances required and the concentrations of this substances to use. and also I don't know the procedure of the experiment. many thanks on your help.

Thanks.

Nduka o.
student - Edinburgh, Scotland, UK

The principle of metallising ABS is: coat ABS with a metal you need to etch it in a mixture of CrO3 and sulphuric acid. This dissolves out some of the butadiene on the surface and creates "keyholes" in the surface where the metal can grip. It also chemically attacks the molecular structure of the ABS making the surace more hydrophilic, so there are some chemical bonds formed. The etched plastic is then washed and neutralised in (say) sodium metabisulphite. This reduces the hexavalent chromium to the safer trivalent form. The parts are then thoroughly rinsed to remove all traces of chromium salts. The etched parts are then activated and allowed to absorb a mixture of tin and palladium salts; the tinis hydrolysed to form a very thin layer of gel that holds in the active palladium ions. The palladium then reduces the metal ions of what you want to use as the coating material. The samples are then put into an electroless metal plating bath, such as copper or nickel and allowed to get coated. Once they are totally covered in this metal they can be thickened by conventional electrolytic plating. Some of the chemicals are very harmful and if you are at school, the process should only be done under supervision. If you are serious about wanting to do it, try contacting a electroplating chemical supply house and ask for their system for plating plastics. They will then give you the full process method and all the details you will require.

Trevor Crichton R&D practical scientist - UK

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