What product and preparation to stop pin-hole corrosion in the aluminium.

[Crocodile]

Hello All,

I have an older tinny with some corrosion pin-holes.
I did find stray sinkers from a previous owner.
Amazing how much water comes in via a 3mm hole, a veritable fountain when on the plane.
I am seeking advice on surface preparation and what product to use to prevent the pin-holes from growing and paint flaking from spreading.
Would scouring with scotch pad and then application of Duralac be a good solution.?
Scotch pad not steel brush as steel particles are left behind.
Is it possible to get a scotch pad tool that fits in an electric drill?

I am currently patching the holes with silicon which is easy and effective but not a long term solution.
If something like Duralac works I will epoxy an aluminium patch over the top.

thanks in anticipation.

[swof63]

Obviously best solution is welding up the holes, competent Ali welder should be able to sort out best solution. An alternative short term remedy to your silicon is JB Weld, a two part metal filler much stronger. Last lot I got was from Bursons.

Cheers

[scottar]

Get some sealed aluminium pop rivets and a tube of sika. Give it a good clean, a liberal dose of sika on both sides and rivet her up then a bit more sika over the top. I actually used a drill and drilled the hole out to get rid of the corroded metal and to make the hole the right size for the rivet when I did my last tinnie with a repair like this. 10 years later it was still there when I sold it

[Moonlighter]

My old tinny had a couple such pinholes.

i found that when i drilled them out, to get back to clean metal, they ended up the size of a 5c piece, so welding up was the best option. I also fillled some holes drilled in the transom with Selleys Nead It and it worked great, was still there 5 years later.

[Dan5]

By any chance has the inside been painted?

I've seen 1/2 doz tinny's over the years that were internally painted from the factory develop corrosion pin holes under the paint.....My Father in laws was the worst a 4.2 Clark punt it was like the surface of the moon just about with literally hundreds of corrosion pits everywhere........Just curious of wether or not yours is also painted.

[Crocodile]

Hello Dan5,

yes painted.
In few other place the paint has pealed and the ally is like new, I think it was the sinkers that started galvanic corrosion.
I understand products like JB Weld etc. but I would like to treat the surface first.
Keep the ideas coming.

[Dan5]

Yes the sinkers would have started it but I also think that when they paint they inside they don't do good enough prep work and just paint over bits of spatter and swarf then it starts from there and starts corroding.

[aussiebasser]

Once you've used silicone a welder is not going to want to weld them, and not much else will stick to them.

[alleycat]

I once had an ex hire boat from Jacobs well that I bought cheap, when I got it home the first time I found nearly 40 sinkers had been bounced out of hiding, it had a few patches and a few holes, I found selleys "nead it" was great as somebody else said, also liquid nails was good as well.

[Darren Mc]

A clean and strip disc from bunning's will work well to clean up any loose bits of corrosion. If the hole is still small enough after that i'd do the rivet repair like scottar suggested. If it's to big i'd weld up the hole grind it flat with a flap disc from bunning's and be done with it.

[the gecko]

jb weld or liquid metal

[Crocodile]

Hello All,keeping the water out is the easy part, any number of products will do that.The hard part is stopping the corrosion, what paint or etch or whatever to use?

[Fed]

Simply remove all possibility of galvanic corrosion or electrolysis and make sure you have a good bond between the outboard & the hull. (That's usually a given with motor bolts but we don't know what you have)

To the best of my knowledge bare tinnys don't grow holes unless there's an outside influence on them, happy to be corrected though.

[TheRealAndy]

jb weld or liquid metal

This.

Have also used sikaflex to glue patches on. Got a 70year old aluminium lifeboat at the yacht club that proves this works!

[Moonlighter]

Simply remove all possibility of galvanic corrosion or electrolysis and make sure you have a good bond between the outboard & the hull. (That's usually a given with motor bolts but we don't know what you have)

To the best of my knowledge bare tinnys don't grow holes unless there's an outside influence on them, happy to be corrected though.

I agree with that assessment for base unpainted alloy boats.

A properly prepared, etch primed, undercoated and painted alloy boat will also stay corrosion free, especially if you take care of it by washing down and repairing chips in the paint and mianitaining it.

There are clear sealing products like Nyalic that will also do the job, the top half of my Surtees is done in Nyalic and no signs of any corrosion wherever it is on the surface. Easy to repair this stuff too. But it is not cheap.

The only other thing ive seen used on marine alloy is lanolin. On my last boat the underfloor tank was showing signs of developing pin hole corrosion so on the advice of the boatbuilder we cleaned it up and sprayed it with lanolin spray, it stayed looking good after that.