Effects of electrolysis

[guidobaroni]

Hi again,
another topic for another question. We recently found a small spot of corrosion on the inner part of the hull on our 435, surely caused by electrolytic effects, enhanced by the face that the surface where this small "escavation" has took place has been for a while under salted water (few cm). The area I am referring is the one immediately forward the engine vane.
Any suggestions on how to face this issue and block the process (assuming that the original cause of the problem is not happening anymore). For example, aluminum soldering to fill the small hole, or marine plaster indicated for aluminum applications.
Thanks in advance for your kind reply.
Guido

[Dummy]

Several threads on the french part of the forum on these issues, you may get some rough idea using google translation.
However in a nutshell : if it's bad i.e. corrosion goes thru you need to drill a bigger and larger hole to get back to good uncorroded aluminium and weld. An aluminium expert welder would know this and fix it easily. If its only superficial, let's say less than 2 millimiters deep, cleaning, scrapping and putting some epoxy coating back should be enough.
Stagnant water is indeed not good.
I know some owners have digged holes in this area, in some of the bilge frames around the engine to avoid any "emprisonned" water. The only drawback, in case of an oil leak or a poor operation during maintenance including filter changes, oil would spread further...

[gael]

Effects of electrolysis

Message de guidobaroni » 14 Jan 2014, 15:33
Hi again,
another topic for another question. We recently found a small spot of corrosion on the inner part of the hull on our 435, surely caused by electrolytic effects, enhanced by the face that the surface where this small "escavation" has took place has been for a while under salted water (few cm). The area I am referring is the one immediately forward the engine vane.
Any suggestions on how to face this issue and block the process (assuming that the original cause of the problem is not happening anymore). For example, aluminum soldering to fill the small hole, or marine plaster indicated for aluminum applications.
Thanks in advance for your kind reply.
Guido

Hi Guido,
I found the same problem inside a locker. The root cause was "just" an improper maintenance.
I had 3 spots with less than 2mm depth and few others less than 1mm.
The solution I have elected at the end is to fill them with a BELZONA compound ( epoxy & ceramic). You will find all details how to prepare the aluminium surface on their web site. Not cheap, but it works.
cheers
gael

[cybelle]

...and keeping nappies (couches) in all the 'compartments' where there are seacocks (vannes), and underneath the stern gland, engine, bilges, etc, helps ensure water doesn't travel and hide/stagnate unseen. At first it pays to check them often to see which ones need changing regularly and to track the source of water. A dry boat is a sweeter-smelling boat too.