Nikel Cadnium Plating

[pete376403]

The father of a friend used to build kids playground equipment (jungle gyms, etc) out of galvanised pipe (back in the days when kids were allowed to play on such things.
he spent the short period between retirement and death coughing his lungs out.

[Pixie]

I'd say cadnium is what he's after,that's the slightly yellow finish to all the nuts and bolts and small fittings on modern bikes,it's just a corrosion protection like zinc.

The yellow or blue tint is due to the chemical passivation method that is applied to zinc and cadmium plate after it is removed from the plating bath.
I think it is a chromate salt treatment.