Heater transfer pipes

[djm16]

I have these off as part of a head gasket replacement. One had been twisted near the water pump inlet. So by the time it was untwisted and the subsequent cracks in the copper brased up the brightwork was looking a little ugly. I was looking into making up some new ones from scratch, but the curves are too extreme for what O can manage. So I am cleaning up the old ones, filling up the dings and am going to get them replated. The question is, what are they plated with already? I thought it was nickel but it is not dissoving in dilute sulphuric, and it is a real sod to grit blast.