Galvaneal weld issues

[gski]

We are currently welding (GMAW) 2 similar products from different suppliers. One is domestic (US) material, while the other is an import (Japan). The base metals are the same spec, but the galvaneal "coating" is giving us problems from a welding standpoint. The import material provides no issue, but the domestic produces porosity problems, as well as, leaking issues (welds must be leak-proof under pressure). A chemical analysis was done on the 2 materials. The zinc content in the domestic product is 10% - 12% higher than the import. The import has 0% silicon, while the domestic has .67% to 1.52%. (We are also using an ER70S-6 wire, which puts more silicon into the mix.) The question is: Are these elements (zinc & silicon) the reason for our issues. FYI...we have adjusted weld parameters and torch angles with very little improvement seen.

 

[stanweld]

You have pretty much hit the nail on the head re: silicon and zinc. For further info reference the American Galvanizers Association web page and call for technical assistance.

I believe that you will also find that the base carbon steel from the USA was fully silicon killed and that almost no silicon will be present in the Japanase product.

 

[gski]

Thanks, stanweld.

That's what I wanted to here.

 

[Wolfmantoo]

I have ran into the same problem with galvaneal sheet metal. Using it for compartments in firetruck bodies.
The solution we came to was to lightly sand the edges that were to be welded, this takes off the coating in the weld area and makes for a good weld. The coating burns off during the weld process and does cause the weld to have a significant amount of porosity otherwise.
If you are looking to have a rust proof area as well, you can always use a silicon based coating to take care of that.

 

[gski]

Thanks, Wolfmantoo.

 

[deanc]

See the following thread.
thread725-61369

 

[unclesyd]

When welding galvanized or in fact any metal have plenty of ventilation. I know a caution isn't probably needed, but I have a tendency to make them.

Some people are very sensitive to zinc fumes when welding. We used to call it Zinc Poisoning or Fume Poisoning.

My stepson just had a case several months ago from reworking brackets on some galvanized steel without a mask or good ventilation, in a hurry.