THE RECHROMING PROCESS
1 Stripping, pickling, grinding and polishing
The old chrome is removed by dipping the part in a solution of sulphuric acid and glycerine, then passing a low-voltage but high-amperage current through it. This can take several hours. It’s then ‘pickled’ in hydrochloric acid to remove any remnants of grease, rust and other contaminants. The rear is shot-blasted, if necessary. Next, the surfaces to be rechromed are ground to flawless perfection using increasingly fine grades of abrasive paper. Finally, the surfaces are polished using mops of varying sizes.
2 Wiring up
Good electrical contact with the component is essential. It’s often possible to attach copper wire in such a way that ‘wiring marks’ aren’t visible after rechroming. In some cases, though, it’s necessary to solder wire to a hidden area on the component.
3 Cleansing
Typically, Cranbourne Chrome soaks the part in a caustic cleaning solution, cleans it abrasively with a detergent, rinses it in water, deep-cleans it in a cyanide electro-cleaner, rinses it again, neutralises it in a sulphuric acid solution and rinses it yet again.
4 Nickel coating
A coating of copper is often applied before nickel plating. In many cases, though, comprehensive nickel plating alone is sufficient. The component is dipped in a solution of nickel sulphate, nickel chloride and sulphuric acid, plus bags of nickel metal chippings immersed in the solution. Very high quality nickel is essential, here. Electrical current – again low-voltage and high-amperage – is passed through the component, causing nickel from the solution and the chippings to be transferred to it.
5 Finished nickel coating
It generally takes between half-an-hour and three hours to achieve a sufficient coating of nickel. The component is then removed from the tank and rinsed thoroughly. This photograph shows the high quality of the nickel coating, before chroming.
6 Chrome plating
The chrome plating tank contains chromic acid, plus lead and tin anodes. The component is immersed in the tank, a current is passed through it and the chrome is attracted to the surface.
The process typically takes around three minutes.
7 Final results
A final rinse removes the deep coppercoloured solution. Refitting components to the car will be the reverse of disassembly… hopefully. Their shininess will show up old seals, gaskets and fasteners: try to find better ones if they’re ailing.