Electroplating uses electricity to turn dissolved ions into solid metal bonded to a surface. Bumpers sit in a vat of acid containing dissolved, positively charged nickel ions. A current is run through the solution, forcing negatively charged electrons from the bumper into each nickel ion, neutralizing it. The ions bond to the bumper, plating it with a very thin layer of solid metal. After the nickel is applied, robot cranes transfer the bumpers to tanks of chromic acid, where the same process adds a coating of chrome.