Black Marks on Steel in a new pre-engineered bldg.?

[BFstr]

Colleagues
Anybody know what these marks might be?
Are they black mold????
Thanks

 

[Heaviside1925]

OP,
My first thought (if you hadn't said mold) would be soot marks from an oxyacetylene torch.

 

[Tomfh]

Water staining from when the beams were laid on site.

 

[BFstr]

Tomfh (Structural),
May I ask water makes "black stains"? I thought water makes rust brownish marks?
Shall I do anything about it? Is it bad?

Thanks

 

[bones206]

I think it’s probably just dirty. These PEMB columns get transported on their sides and remain on their sides in lay down areas on site. Water can pool at a low point on the web and concentrate dirt in that area.

 

[RPGs]

Try to clean it (your hand, a paper towel, a wire brush) and see if you have loss of corrosion protection or section.