Electroplating onto ABS plastic for a science project

A. The principle of metallising ABS is: to coat ABS with a metal you need to etch it in a mixture of CrO3 and sulfuric 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 surface 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 tin is 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 an 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.

A. Hi, Stacey.

ABS can be metallized in many different ways, just like so many other organic materials. But an important reason that ABS is used in the first place, instead of other plastics, is precisely because we can dissolve the butadiene and create keyholes to obtain outstanding adhesion to a degree we can't achieve with other plastics. Further, the etching is just a surface phenomena; we're not turning the whole block of plastic into a sponge, just its very outer surface.

Please try to explain your own situation because when the question is cast in the abstract we soon find ourselves misunderstanding each other, answering questions that weren't asked, and failing to provide the info you need. As I say, I don't know whether I answered your question or not. Thanks.

Regards,