Thanks for the information, I'll try these tests to rule it out but I forgot to mention that this stuff is heavy. I'm an aircraft engineer so although I've not welded mag I deal with mag and alu castings all the time. It's dark grey in colour but polishes up real bright, (nickel?) It's not like any ...

I've been given a part from a vintage stationary engine to repair. It's a casting which has broken due to being badly fited but I'm not entirely sure what metal it is and what process to repair it with. It is dark grey and very 'grainy' which along with its age leads me to believe its some sort of z...