mmc wrote:
"Brian Whatcott" wrote in message
...

joost wrote:

Hi,

Last year when I hauled out my steel boat I found many paint blisters
on the bottom. When I opened them, clear grey steel came out
underneath. I then suspected a ground leak causing electrolysis to be
the problem. There was indeed a leak on the RF ground of the shortwave
radio, which I fixed by adding capacitors in the ground path.
According to my measurements then, no more ground leaks existed. I
scraped off all the blisters and repainted.

Today I was overwhelmed by a feeling of sadness when I discovered that
there is a whole bunch of new blisters at and below the waterline. The
question that I would like to ask is:

Are there other causes for this type of blistering than electrolysis?
The size of the blisters is about 5-25 mm.

Thanks,
Joost.


My guess: if you see ACTUAL steel under a blister, the primer/basecoat is
faulty. If you see primer/basecoat under the blister, the top coat is
faulty.

Brian W


I agree with Brian.
Might try an epoxy barrier coat where you need to treat blisters. What I do
is only wait the minimum recoat time before applying subsequent coatings
including bottom paint. I've heard this allows the new and last coats to
chemically bond and since I haven't had any problems doing it this way I'll
continue.




could be more unknown electrical leaks - esp if blisters are round.
Could also be 'salts' - we don't have products for it, but do have an
info page with links on it explaining it.
www.epoxyproducts.com/salt.html

paul oman
progressive epoxy polymers