Rusty Bolts

[j19]

I have a project where some of the bolts and nuts in beam-to-column shear connections and moment connections have a lot of rust on them. The steel has primer on it and it looks ok. This project has been under construction for about a year. Is there any information available regarding the effect of rust on bolts or how much rust should be allowed/expected?

Thanks.

 

[JAE]

In a year's time I wouldn't think that the bolts would have rusted to the extent that strength loss had occurred...unless there was some area of the building that was excessively exposed to water and air and significant damage was observed.

Check with AISC perhaps?

http://www.steel.org

 

[Guest102023]

They may be OK now, but project that corrosion rate over 10 or 30 years, and ask if they will still be OK.

 

[bridgebuster]

I agree with JAE. If the areas were primed they should be holding up. Can you clean up these connections and see if there is a problem? Quite often, rust can be decieving, i.e. it looks worse than it is.

 

[j19]

Here's a photo of one of the bolts. I'm note sure how many are like this so I'm not sure how feasible it will be to clean and prime them.

 

[Ron]

If the project is still under construction, then presumably the bolts will be only exposed for a while longer. What is showing in your photo is somewhat typical of exposure, but you wouldn't want it to start getting worse. You might clean and protect them while they get continued exposure and after that they should be OK.

 

[hokie66]

If that bolt has been taken from an in place connection, it is strange that it has an even coating of rust. Looks like it has just been sitting around. I assume that as black bolts were used, the steel structure is not to be exposed, in which case that amount of corrosion is not a problem unless there is an extended period when the building will not be enclosed.

 

[j19]

I'm going to find out how long the bolts have been in place, but the contractor is just starting to put up the siding and the roofing so that eventually all of the connections will be inside the building and not exposed to the weather.

 

[JAE]

That doesn't look too bad to me.

 

[rscassar]

Did you specify the bolts to be hot-dipped galvanized?

 

[apsix]

That doesn't look too bad to me.

Me neither

 

[MikeHalloran]

I don't like it.

I've seen fasteners that were under shelter for hundreds of years that looked better.

That one's been out in the rain. A lot.

I think I see pitting in the nut faces. ... which would be of no concern, except that I'd then expect pitting, or worse, of the bolt threads near/below the nut's faying surface.

I'm guessing that if you attempt to remove a few nuts for inspection of the bolts, some of the bolts will snap off at a much lower torque than you'd expect. Because of the rust, removing them turns both parts into scrap regardless, so you'll have to buy a few new ones anyway.

I hope I'm wrong.


Mike Halloran
Pembroke Pines, FL, USA