Steel to Aluminum Connection 6

[MiketheEngineer]

This may not be the best forum but one thing I know - you guys have seen it all and respond quickly.

I have a primed steel to aluminum connection on interior of building. So it will always be dry. I have no trouble with the connection design - but now the owner is worried about corrosion or galvanic action or whatever.

I don't believe this to be a problem - at least for the next 100 years or so. Your thoughts please.

 

[dhengr]

Mike:
Galvanic action of dissimilar metals, it is; and if you eliminate the electrolyte (water) you probably do eliminate most of the problem, but not the potential (that’s not a pun). I think we used some thick bodied paints, or some such, which acted as a separating layer in the joint, between the two different metals, if the joint design will allow this. But, then you still have the bolt issue, stainless? Maybe ...Connecteng... will chime in here, he will have seen this problem more recently than I have.

 

[Ron]

Steel and aluminum are not particularly good combinations, even when apparently dry. Aluminum is particularly prone to developing condensation from the ambient humidity, so you will likely have an electrolyte present whether it appears to be the case or not.

Once the first passivation layer of the aluminum develops, you have an inherent moisture absorptive layer that will allow the galvanic process to continue.

Isolate them as best you can.

 

[msquared48]

Not to be ridiculous here, but I would consider a sacrificial zinc if it can be placed in a location that is unobserved, yet open to maintenance.

Mike McCann
MMC Engineering
Motto: KISS
Motivation: Don't ask

 

[connectegr]

My experiences have been similar to Ron's. Unless you are in Arizona, condensation will occur on bare interior metals. And it does not take much to begin the corrosion process.

http://www.FerrellEngineering.com

 

[CTW]

I always specify that the steel be painted with 3 mils dry film of inorganic zinc. But I've seen others use epoxy mastic.

 

[a2mfk]

We've used a neoprene pad to separate the two before, cheap insurance.