Metal finishing.

[John Chambers]

Zinc coating is ok, my finisheres asked me to leave the stripped pistons in the calipers to save the bores when blasing and if you make a piece of wood the size of the bores and put that in they will not be plated either. On thing i would say is dont go for a nickel or dull nicker finish because the process of nickling (is that a word?) makes the caliper brittle and CAN lean to cracks, if the calipers arent first de-brittled. If you wanted a goldish finish then you could go for a lemon yellow finish, this is what the race boys use and is the ultimate in hard wearing posh looking finish, my set of four calipers blasted and plated cost £40 and the quality was great.

[bnissel]

Jim,
Looked up some info from plating company on WWW quote follows.
" Zinc gives sacrificial protection to the base substrate. Sacrificial protection allows the zinc coatings to be attacked preferentially to the base material by a corrosive element i.e. humidity. Unlike a paint coating that if scratched through to the steel allows the steel to rust, zinc will corrode in preference to the steel base.

To further enhance the corrosion resistance of the zinc coating a chromate conversion can be obtained which is also known as a passivate. This converts the surface of the zinc to a complex chromium compound. The colours obtained range from clear or blue, yellow iridescent or colour, olive drab and black. The protection can be further increased by the application of various seals and lacquers as well as dewatering oils.

The protection is related to the thickness of the zinc coating and the types of passivate applied and this is obtained usually from a customer specification. The surface area of component, applied current density, and time determines the thickness of plating.
We as a company regularly work to many specification standards and hold a large number of national standards or company specific standards. "

So be sure to specify the colour of the passivation. As the plating will probably be only 5 microns(you can specify)thick you do not have to worry about things fitting but avoid grit or bead blasting critical areas.

[sprocket]

I would like to thank everyone for replying to this question. I will give it great thought before I commit myself.

[Miket]

Sprocket

Don't waste your money on plating or powdercoating, spend time on preparation and paint with smooth Hammerite and let it cure for at least a month before fitting.

Mike