|MadSci Network: Chemistry|
Hi Jeff Chrome plating, (and most other types of plating) are part of a branch of chemistry known as "Reduction-Oxidation", or Redox for short. All redox reaction involve a transfer of electrons from one atom to another. If a substance is losing electrons, it is being "oxidised". If it is gaining electrons, it is being "reduced". Since plating involves moving electrons around, it is better known as 'electroplating'. Electroplating is generally performed by reducing metal ions to solid metal. Eg: Cu2+ + 2e- ---> Cu(s) (e- is an electron) In the case of chrome plating, the object to be plated is electrically connected to the negative terminal of a battery, or other DC power source. This is the source of electrons required for the reaction. The positive terminal is connected to an inert electrode (eg, platinum), and they are both inserted (not touching!) into an acidified dichromate solution. When the correct voltage is applied, the following reactions take place: Cr2O7(2-) + 14 H+ + 12 e- ---> Cr(s) + 7 H2O 2 H20 ---> O2 + 4 H+ + 4 e- The chromium solid (in the first reaction) is deposited onto the surface of whatever is attached to the negative terminal of the power source, and oxygen gas is produced at the inert electrode. There are a lot of good reduction/oxidation resources. You can start by looking in the MadSci library. Also have a look at How Electroplating Works. However, the best place to go is probably your local library. If you look under Dewey No. 537, you'll find chemistry textbooks, which usually have at least a whole chapter devoted to Redox and electroplating. Hope this helps! Jonathan Feldman, UWS Nepean email@example.com
Try the links in the MadSci Library for more information on Chemistry.