Cure for cancer?

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Tinny Fleet

Well-known member
Joined
Mar 13, 2017
Messages
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Location
Florida and New England
LOCATION
Melbourne Beach
Gents:

The transom on a 70 something tinny is bubbling up through the paint in several places. The dreaded aluminum cancer. What is the cure?

Do I just wire brush the heck out of it, then fill with marine tex, sand and paint?
 
photo 1.JPGphoto 3.JPG

Finally got a couple pictures together.

This is an older boat that started to get cancer on the transom. By cancer I mean the aluminum started blistering underneath the paint.

In the pics you can see irregularities on the surface of the transom, that is because a few years ago I took a wire brush to the blisters and ground them down to bare aluminum and then some, then patched with Marine Tex, sanded and repainted.

Now you can see blistering at least on the edges of my "bodywork", and then some.

So, is there a way to stop the cancer spread? I don't want to go the new transom route, just too many other projects going on....

Thanks in advance!
 
You need to get the old wood OUT! On some model years, some manufactures used a plywood that corroded aluminum, even if allegedly sold as OK for use against metals. Or, what happened on Starcraft boats in particular, the wood wasn't sealed or treated and either a preservative in the wood, or exposure and wetting with saltwater, put some corrosive element (assuming a chloride) up against the aluminum and in time it leeched out ... attacking the aluminum and it turns into a cancer like that! Aluminum is VERY susceptible to chloride attack!

*Get the bad wood out ...

*Clean up w/ SS wire brush, removing ALL evidence of any "white residue"

*Scrub aggressively with liberally applied white vinegar - wipe off and allow to dry well

*Paint inside aluminum with zinc chromate etching primer

*Then fix/fill/repair any holes needed for cosmetic purposes

*Insert new wood (sealed!) transom
 

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