weld prep

snowman · Nov 12, 2005

How much of a difference does it make?

Now, dont think I dont grind away rust...but lets say it's just mill scale, how important is it to grind, wirebrush, clean the surface prior to welding?

For general welding, just stickin metal together, is it going to make a differnce? I'm not talking about anything that puts someones life in danger (automotive, etc).

-Jacob

SND · Nov 12, 2005

I think it makes little difference if you are Stick or Fluxcore welding. As long as its not covered in paint or oil its usualy ok. You don't want porosity. I think the flux is able to carry the mill scale and most of the other impurities out of the puddle.

Mig and Tig doesn't like mill scale and such impurities, its better to get it as clean as possible in this case.

snowman · Nov 12, 2005

Ok, I'm mig welding.

I know when I have a porous weld...but I just dont get em with the scale. Paint and rust, yes, it'll be porous...scale no, it seems to flow to the top in nice little pools, much like slag.

-Jacob

SLOEIT · Nov 12, 2005

Snowman, for non critical welding... Making a bike rack...getting the fence to stay up, etc...its not THAT big of a deal. Although for dirty stuff outside, id run flux core. At least for deeper penetration.

As for keeping a building up...it should be freshly ground, and brushed. Crud in welds is a nucleation point for cracks. And welding over most anything OTHER than the metal, will yield crud in the welds.

NK

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