corrosion under lites

Chas · 05-17-2003, 03:35 PM

Well, I am over half ways done compounding the exterior of my Overlander, getting slowed down on the end caps. Yes, I am getting pooped! They are a bit harder to polish than the flat sides, have a different finish on them I guess from being formed and pressed into shape.

My question is, under the cast aluminum corner clearance lite mounts there seems to be some significant corrosion going on. I have seen it on the older ones, it can get bad enough to rot a hole in the skin. I removed the lite and the cast piece and I was able to wet sand it enough to get a decent polish on it so I guess i have stopped the corrosion for now. What can I do to protect it before putting it all back together? I guess it will come back?

Chas

**john hd** · 05-17-2003, 04:10 PM

chas

could the two types of aluminum be different enough to cause galvanic action, causing the corrosion between the light casting and the skin.

perhaps you could "insulate" it with a home made gasket.

an old inner tube might work.

john

nickcrowhurst · 05-18-2003, 02:10 AM

Chas, I agree absolutely with John's diagnosis and treatment. If I have the same problem with a small part where a gasket can't be installed, I use zinc chromate paste between the parts where they would otherwise touch. You can probably get this from a pharmacy, or a yacht chandlers, and it's the technique used in the building of aluminium masts on sea-going vessels, when dissimilar metal fittings are attached. If you can't get zinc chromate, dielectric grease or vaseline would be good, although john's gasket is the ideal. Good luck with the polishing. Nick.

Chas · 05-18-2003, 08:20 AM

Thanks for the tips,

I have a few pieces of leftover commercial rubber roofing material that I can make some gaskets out of. I guess I should remove the other three corner lights and do them also. I don't seem to have similar problems under any of the emblems or hardware mounts so I guess it could be worse. A lot of work but man does it shine!!

Chas

**john hd** · 05-18-2003, 08:57 AM

chas

it could be that no current is running through the emblems and other hardware.

just a thought.

john