Blackening and bronzing are colour processes for metal that can be carried out by forming oxides and salts on the surface being treated – if they are metallochromic – and by applying dark-coloured electroplating metal alloys.
For outdoor use, they can be finished with wax or more costly advanced technologies; these techniques provide corrosion resistance after hundreds of hours of saline mist.
Finishes may be applied on copper alloys, as well as stainless steel, before galvanizing treatment with nickel, copper and brass plating.