Aluinium Decay

[Bros]

Oldboot is pretty right on what he says in that an anode would be useless.

If you pulled motors of most aluminium boats that have been on for while you would see this type of corrosion.

One way to prevent it would be to expose the whole surface to water (not a viable option) or totally seal the area to exclude all water as it is the lack of oxygen to generate the anticorrosive oxide film that causes the problem.

[Willdoe]

I agree with those suggesting a non-porous mounting board and Duralac. I believe the wood holding water was your problem. The corrosion doesn't look to bad, and welding to fill holes may introduce more problems. Other fillers will only be cosmetic and if covered by a board what is the advantage.

I once bought an outfit with a trailer that had steel stabaliser boards with felt cushions. It looked great until one day I rolled the boat over on the lawn and found pitting all over the area in contact with the felt. The welder made a mess of trying to build it up.

Willdoe

[TheRealAndy]

I am not convinced that sacrificial anodes on the interior of a boat will do a damn thing. Absence of corrosion is not proof that they are working.

There are all sorts of pepole in all sorts of trades that have interesting ideas ( i'm probably one of them).

I would sugest that washing your boat and putting sealer under all fasteners and attached hardware will be doing more than the anodes described.

There has to be at least a continuous film of water for a sacrificial anode to function..... have you unbolted your interior anodes and looked under them recently?

As long as aluminium is not compromised it can look after its self pretty well.
The two biggest compromises are intriduced dis-similar metals and traped moisture... often both in combination.

and that can occur every time you fasten anything to your boat. Aluminium is dis-similar to just about ever other metal so you need to seal up under every fastener and piece of hardware you bolt down.

Polyeurathane sealer, duralac, metal primer, or paint....all are better than nothing and all have theer advantages and drawbacks.

cheers

The industry standard method for measuring if an anode is working is to measure the current flow. So think about it this way, connect lead one of your multimeter to the tinnie, then conect the other lead to the anode. That is, put your meter between the hull and the anode. You will measure no current flow. Its pretty much like waving you multimeter around in the air.

There is ways to protect against hull corrosion in the air, the oil rigs do it. I do remember learning about it at uni, but buggered if I can remember now.