Structural Steel Rust Industry Standard for Steel Exposed to Elements

[metzdmichael]

A previous structural steel subcontractor and general contractor fabricated steel on my project. The entire project got delayed by approximately six months and the delivered steel sat outside in the elements during this time. The new steel rusted, and had "above average industry standard" rust on the steel. This was mainly surface rust. When the new general contractor and structural steel subcontractor came on to erect the building, the inspector required all bolted connections be sanded to remove the rust for slip coefficient. My question is, what is the industry standard for allowable rust on beams and columns? I know with the project being delayed for so long and the beams sitting outside in the elements, that is not industry standard for time exposed to elements, what is the industry standard time for steel allowed to be exposed to the elements? Like two weeks? The project teams are arguing on the costs for who should be responsible for the sanding of the bolted connections.

 

[EdStainless]

So these were slip critical joints with special torque requirements?
If not then as long as the rust isn't flaking off why would it matter?



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P.E. Metallurgy, consulting work welcomed

 

[metzdmichael]

Yes they were slip critical bolted beam to column connections. The tops of the beams where nelson studs were added needed to be sanded down as well for proper weld connection. The rust wasn't specifically flaking off, only at some areas where the water had ponded on the steel. I've attached some photos of the steel and the mockup that was performed to determine the sanding method.

 

[EdStainless]

It makes me wonder if the sanded surface is smoother and has less friction.
What grit was used? I would have looked at 24 or maybe 32.
I have seen this done with grit blast or wire wheel.
There are wire wheels where the wires are 'flung' into the surface.
These remove anything soft but actually leave a texture.

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P.E. Metallurgy, consulting work welcomed