Fasteners and options for highly corrosive atmospheric environment 1

Use glass reinforced plastic washers to isolate SS bolts if compression allows. Otherwise, encapsulate with your favorite means. Dow Corning 734 silicone flows nicely to cover the galvanic couple to seal it. Epoxy and others work but aluminum is sensitive to crevice corrosion so brittle coatings that may break away from the surface can make things worse. Consider etching with phosphoric acid or similar prior to coating.

Grease tapes like Densyl tape also work and allow you to encapsulate the entire flange. Don't get lazy with surface prep, grease tapes benefit just like paint.

There are also hot melt coatings that are peelable and work quite well. The initial investment is quite high for the application tool. Supposedly the coating is reusable, though.

Thank you for your informative response. I have used Denso wax tape before on large flanges. But I am not familiar with epoxy, Dow Corning 734 silicone, or other products. Other than Dow Corning 734 silicone, would you recommend any specific product for encapsulation? Thank you.