To the best of my knowledge, wires are welded to structural steel for fireproofing purposes: they (the wires) will hold in place the concrete that will line the structural steel to protect it from fire.   
Is this your application? If so, you don't need to worry very much about it. I've done that work back in my days of erector engineer in the following manner:
1) the wires are tack welded to the steel with a bead, say, 5/8 to 3/4 of an inch long. 
2) the tack is given on only one side of the wire. A 12 gage wire is too thin to support two welds, one on each side.
3) use an E-6012 or 6013 low penetration electrode. E-6010 or 6011 have a strong penetration and will burn the 12 gage wire.
4) you say you'll use galvanized wires. Don't forget to burn with a torch the end of the wire that's gone to be welded. Don't weld directly on the galvanized surface. After the tack is complete and cool, paint it with a zinc rich paint.
5) is the structural steel galvanized also? In this case, you'll have to burn with a torch the surface on which the wire will be welded.

Vessel plates that will be insulated will receive wires that are tack welded in a similar manner.

Giovanni S. Crisi
Sao Paulo - Brazil

If you are desacribing the wire anchors like Giovanni mentioned, we routinely attach them to our fabricated steel for buildings and we use a 5/32" E7028 and it has enough heat to volitalize the galvanized coating off and produce a good weld without melting the wire completely away. Also like he mentioned, we weld the anchors only on one side and alternate sides from top to bottom whether we use the 10' lengths or single wire anchors. Typically we use the long lengths on columns (toes of the flanges and in the web) and the short individual anchors on beams.