corrosion- ANY Dis-simalar metals contacting each other will cause "GALVANIC CORROSION" (ON ALUMINUM it shows as a white powder) Make sure when using bolts/washers/nuts you try to keep simalar metals touching each other for example- you DO NOT want a stainless steel washer or bolt against an aluminum part... A stainless steel bolt then an aluminum washer is ok- the only thing to corrode will be the washer NOT the aluminum part or boat.