bubbling paint

[ad heeney]

hi mates
i noticed this morning when starting the motor the paint around a deck-wash kit we had put in ,was starting to bubble looks like rust on a car i don't know the name but don't like one bit boat only two years old. how do we go about fixing or prevent it from getting any worse. thats the only place i could find it looking allover the boat hit it on the head quick,is there a fix regards rob

[wayno60]

Rob,
So i take it we are talking alloy....sounds like the where the paint has been broken, the salt water has gotten in under the paint and started to corrode the alloy. if you want to nip it in the bud and your pretty handy with a spray pak sand back the effected area and touch up or just spray the area with a product called Inox, its like wd40 or even fish oil in a spray can....

[wags on the water]

Rob,

Use the search feature here and use keywords such as "oxidisation" "galvanic corrosion" or the best one is "duralac". There are a number of ways your problem can be fixed. I'd be contacting the company who installed your deckwash and be giving them a mouthful for allowing this corrosion to start. Holes drilled through, and screws/bolts in painted aluminium should be coated in duralac to stop/slow the corrosion process.

Hope it helps.

[gr hilly]

wags has given you very good advice i would have the hair on the back of my neck standing up when i spoke to the company who stuffed up the job.glynn

[black runner]

You will need to take it out, sand back the bubbling paint and feather the good paint, prime all bare ally with aluminium etch primer followed by original colour touch up/spray. Refit using Sikaflex to seal around the cutout and fastenings or Duralac for the fastenings.

Cheers

[WalrusLike]

I am sure you blokes are right but I dont get why it is so.

Bare aluminium doesnt rust through... it oxidises (rusts) just at the surface then the oxidised layer forms a barrier so there it stops.

How come painting it changes that? Youd think that paint can only make it harder for O2 to get in... and if it does then the initial rust should stop further deterioration.

Whats wrong with this picture? (there must be something in the above wrong, else it wouldnt continue to get worse....)

[wags on the water]

I am sure you blokes are right but I dont get why it is so.

Bare aluminium doesnt rust through... it oxidises (rusts) just at the surface then the oxidised layer forms a barrier so there it stops.

How come painting it changes that? Youd think that paint can only make it harder for O2 to get in... and if it does then the initial rust should stop further deterioration.

Whats wrong with this picture? (there must be something in the above wrong, else it wouldnt continue to get worse....)


All your questions will be answered if you use the SEARCH function here and read the countless pages on oxidising paintwork or galvanic corrosion. It really gets on my nerves to repeat my dramas with oxidising paintwork (on a brand new boat!) time and time again.

The Search feature is on the forum for a reason.

[Mr__Bean]

Very simply put...aluminium will not corrode in salt water, stainless steel screws will not corrode in salt water.

But put them together in salt water and they react together, like a wet cell battery does.

The salt water provides the electrolyte in the minature battery cell you have just created, the most noble metal (the aluminium) corrodes away beneath the paint in an increasing manner.

The paint continues to bubble as new metal is corroded away by the electrolyte.

This can be only be prevented by total sealing of the two different metals from the salt water, something that is very difficult to achieve.

As mentioned by others, there are compunds to use (Duralec) to reduce the occurence but even with duralec it is difficult to prevent the corrosion in all applications.

Sealing with sikaflex is another method, but make sure you seal the back of the srews as well as the salt water residue will attack the hull from behind.

When installing any stainless steel fasteners through painted aluminium boats that are to be used in salt water this prevention must be afforded, preferably use both methods, seal around the appliance and duralec all fasteners (including the nut on the back).

Sadly most boat bit installers just drill the holes and bang in a screw, couldn't give a hoot that your pride and joy will corrode away in about 18 months time.

- Darren

[ad heeney]

hi mates
thanks for the imformation be on to them on tuesday
thanks again boys

[White Pointer]

G'day,

Previous contributors have given you the guts on the problem and causes and some good product solutions to use for the fix.

Please also include TEFGEL as an alternative to DURALAC. I don't sell the stuff but have used it for a year in stainless to aluminium screw threads and it doesn't harden. Very pleased with the results.

It might be worthwhile asking the original boat manufacturer to supervise this repair. It may also be worthwhile checking the condition of other sealers to the fuel tank and cell and pressurising the hul to test for leaks.

Regards,

White Pointer

[bennyboy]

After 2 years you have to start expecting bubbling around some fittings, a deck wash pump is probably located out of the way and doesn't get the same attention other parts of the boat get when washing. The salt sits around the break in the paint and screws and the paint bubbles.

After two years you really don't have a case to complain to the person who fitted it if they used duralac or similar product. They only slow the process they don't stop it. If the area isn't washed and I mean washed and wiped over with a sponge and rag it happens alot earlier.

Alot of people wash their boats with a hose and don't use a sponge, particually in the hard to get at places, who washes their car with just a hose? you don't get the salt and dirt off just by hosing it.

My advice is to sand it back, touch up the paint, re apply duralac to the screws and look for other areas where it could be starting and attend to those areas too. When you wash the boat use a boat wash product that disolves salt better and pay particular attention to fittings. Make sure your boat dries out in the sun before putting it away or putting a cover over it. At the end of the day all boats need ongoing maintainance. If you live close to the coast I would expect to spend 1 day a year removing stainless fittings and maintaining them if you want a painted boat to look great for years to come.

[Mr__Bean]

hi mates
thanks for the imformation be on to them on tuesday
thanks again boys

How did you go?

-Darren

[ad heeney]

How did you go?

-Darren
Darren mate got in touch with them had a few words they supplied all of the gear to help fix the problem , paint, silkaflex, durlac even sand paper so didn't have to spend a cent was pleased with that , thanks mate for your help, onyah rob

[wags on the water]

A little bit of good news then....Thanks for the update.