Corrosion Protection of Structural Steel

[jar546]

For this project, 'pig iron' was ordered. It was ordered this way, no primer at all because of the fire-proofing material that is to be applied. When you have this situation, how do you deal with the sheets for the concrete deck above being in contact with the pig iron? The fire-proofing material being sprayed will not touch this portion and the dissimilar metals will still be in contact.

 

[steveray]

Are they actually dissimilar enough to cause an issue? Both ferrous....

 

[classicT]

What code section applies? I am not aware of one, so is this really a code issue?

 

[ICE]

Are they actually dissimilar enough to cause an issue? Both ferrous....

The zinc will react with the iron. The zinc will corrode and the steel pan deck in contact with the iron will not corrode any more than the iron.

ChatGPT:

 

[classicT]

Perhaps this is the applicable reference... I'd have to dig into AISI S100.

2021 IBC 2203.1 General​

Painting of structural steel elements shall be in accordance with AISC 360. Painting of open-web steel joists and joist girders shall be in accordance with SJI 100 and SJI 200. Individual structural members and assembled panels of cold-formed steel construction shall be protected against corrosion in accordance with the requirements contained in AISI S100. Protection of cold-formed steel light-frame construction shall be in accordance with AISI S240 or AISI S220, as applicable.

 

[steveray]

P shall be protected against corrosion in accordance with the requirements contained in AISI S100. Protection of cold-formed steel light-frame construction shall be in accordance with AISI S240 or AISI S220, as applicable.

I have a good AISI guy in CT if anyone needs one at some point...

 

[Paul Sweet]

Galvanic corrosion needs water, so if it is dry there won't be any corrosion. Even if the zinc coating sacrificed itself the steel deck wouldn't be corroded by the "pig iron" (actually steel) beams.

 

[Mark K]

Pig iron is not a term used by structural engineers. These members are referred to as steel.

When fire protection is your concern the steel beams you either spray fire proofing on to the steel beam, encase the steel beam within a fire proofing assembly, or encase the steel beam in concrete.

Experience has shown that corrosion between steel beams and metal decking is not a problem.

If there is a concern about corrosion the strategies are to either encapsulate the steel beam in concrete or use zinc rich primer on the steel beam.