Galvanizing buildup on MIG wire weld areas

A. This problem is seen frequently by galvanizers everywhere.
It is not as a result of the steel changing during the galvanizing process, but the raised portion is actually a thicker coating over the weld.
The thickness of galvanizing varies with several factors, but the most influential is the chemistry of the steel.
When fabricators use a different chemistry of steel in the weld filler wire to the base material, often even a different grade of steel, this different thickness of coating results.
To avoid it there's really only one solution - change weld filler wire to match the base steel.
Faced with this problem and fabricators doing less critical work (not load bearing for example), I have often asked if they change wire when changing to weld a different grade of steel and got a blank look. "uh no, should I?" sort of reply. But why would you weld one grade of steel with a wire of another grade?
The galvanizer can do little to control the problem, but most actually do what they can. That is to micro alloy the zinc with Nickel. Running Nickel in the zinc, to about 0.05% Ni, will reduce but not eliminate the problem.
So when this is likely to be a problem, ask the galvanizer. "Do you have Nickel in your zinc? How much?".

A. Thomas,
The first thing I would do is contact my welding goods supplier and ask about some low silicon wire, 0.05% Si. This wire is made to weld very low silicon steels and may simply invert the issue. Another option is looking at your welding process and see if it is worth it to you to change your process for it. I did see that you can get 0.30% Si wire, however, it was submerged arc welding wire.

Perhaps someone can confirm as to whether shaving off the excess galvanizing on the weld is likely to reduce the protection afforded. I would think it would not due to the fact you are shaving the coating down to the same thickness.