dissimilar metal protection

[jmy61]

Can anyone tell me if dissimilar metal protection is required between aluminum and clay masonry? If so, any suggestions for what to use? I am mounting aluminum plates to the face of exposed clay masonry walls. For aluminum embedded in conrete I have used black mastic (i.e. roof tar). For aluminum in contact with concrete I have used 2 layers of building felt as well as black mastic. Given that my walls are exposed and the plates are vertical, I believe the black mastic will be messy and possibly an eyesore.
Thanks for any recommendations you can give.

 

[Ron]

Your issue is not so much the dissimilar materials, but the potential for the clay masonry to entrap moisture behind the aluminum, thus exacerbating the corrosion. You should coat the aluminum, even if it is a light layer of asphaltic paint or mastic. Asphaltic mastic does not have to be "globbed" on to be effective. In fact, if you take asphalt mastic and cut it 1:1 with mineral spirits, then paint it onto the back of the aluminum plate, that should suffice.

 

[jmy61]

Thanks.