Aluminum Decay

[philzero44]

I found this when I took of the plywood motor mount.

Is this Electrolysis.

 

[tashasdaddy]

Re: Aluminum Decay

exactly and trapped salt water. edges of plate should have been sealed.

 

[Bob_VT]

Re: Aluminum Decay

Welcome to iboats! You have visited the right place.

That is evidence of a galvanic reaction from the bolts that were in those holes. You caught it in time. Are there other areas that need attention?

Prevention - Sand it down lightly and epoxy coat the metal behind the wood. You can use gluvit or regular epoxy but get it all coated. When you re-install a piece of wood coat each screw/bolt with grease or 3m4200 where it passes through the metal. If you use washers that contact the aluminum then use plastic between the washer and the metal.

 

[sschefer]

Re: Aluminum Decay

Tashasdady- right on. The fix is to sand it down with some 36 grit production paper to clean up the zinc residue, replace the hardware with 18-8 Stainless and before insterting the hardware, coat it with a zinc based anti-seize compound. The anti-seize compound will become the sacraficial lamb and not your aluminum. 3M 4200 should only be used if this is transom and you are passing through wood. Then you would want to be sure to get some sort of sealant between the wood and the aluminum.