Welding Problem

Q. I am TIG welding an electrolytic nickel-plated mild steel part to 321 stainless and we get pinholes in the weld unless we grind off the plating first. Is there electrolytic nickel-plating that is more conducive to welding?—F.J.

A. I am not an expert on TIG welding, but my thinking here is that the nickel plate oxidizes upon standing and prevents you from obtaining an adequate weld. Keep in mind that nickel forms an oxide on the surface that helps prevent further oxidation of the nickel layer. This oxide layer starts forming almost immediately after the plating process is complete. You do not mention in your question whether the welding is done immediately after the nickel-plating step or after a period of time. You might try dipping the nickel-plated part in a dilute nitric acid solution, rinsing and then welding. 
Another approach might be a Wood’s nickel strike prior to welding. Again, time between the strike and the welding step is critical.