Rusting Bolt Heads

[Greenbrier]

Many of the lag-bolt type bolts in the engine compartment are showing a lot of corrosion. It is like white, powdery crystals ... with bits of rust. The bolt heads are all zinc galvanized ..... some are not corroded, many are. I keep everything very clean and polished ... so why is this and what can be done?? It looks like some form of conflict between different metal components .... it's on my '11 OB Thanks

[sixfifty]

well, i'm not qualified to speak about the "why," but i normally clean my engine compartment and spray it down with a good coat of s100 rust inhibitor a couple times a year. it's not rust free, but certainly better than doing nothing. amsoil makes a heavy-duty rust inhibitor (like paraffin) that i spray on the under carriage.