On 27 Feb 2005 07:32:34 -0800, "kese" wrote:

4. if your vessel is stationary there, not moving very often where u
will not scratch your underwater hull by those floating wood or
rubbish, then the coal tar expoxy will last for many years but i am not
sure it will last 30 years. if u do the blasting and follow the paint
scheme, then the underwater hull really may last for many years.
5. In my country many boat owners like to use coal tar because it is
cheaper then other new paint system.
hope this will help.

Yes, it does. I am not so concerned with the exterior of the hull, as
that is accessible and visible. I am concerned with buying a used
steel boat, and on the durability of coal tar epoxy as an interior
steel hull barrier coating. I have seen a few steel boats now in my
travels, and they are either pristine inside and maybe have a couple
of chips and rust weeps on the deck or topsides, or they are
acceptable on the exterior and absolute masses of rust and "orange
foam" on the inside.

I am persuaded that ureathane foam on hull interiors below the
waterline and in the bilges and surrounding tankage is a terrible
idea, because it can trap water low and you can't see the damage being
done by the dampness that never gets out of the bilges.

Preparation of the interior seems to be the key. I've seen 25 year old
steel boats with pristine coal tar epoxy bilges and carefully coated
structural elements that look factory new. Of course, seldom accessed
areas of GRP boats can go decades and look new with just a cursory
vinegar wipeout every so often.

But steel seems either/or: either it was coated correctly when built,
or it's heading for the scrapyard in a dozen years.

R.