Raised Welds
We often get asked why some welds appear raised up after galvanizing. During fabrication, the weld might have been ground smooth, hoping for a nice finish, then after galvanizing, the weld appears as if it has raised up about half a millimeter.
A weld like this, well ground smooth, can appear to raise up during galvanizing.
And then looks like this...
Why? How does the steel grow?
It doesn't. The extra thickness is zinc, and it happens only on the weld because it is of a different steel chemistry than the parts welded.
The thickness of the coating in galvanizing is dependent on several factors, one of them the steel chemistry. If the weld filler material (mig wire, welding rods etc) is different to the steel being welded, this phenomenon occurs, with what looks like a raised weld. It is only the coating thats thicker.
How to avoid it?
Use weld filler that's the same as the base metal. Its possible to get a flush weld, like that shown below.
Here a ground flush weld has not "raised", and even the grinding marks are visible after galvanizing.
