Could it be that there is a slight difference in either the plates used in
the hull and the welding rod? Or even between the plates?
"chuck" wrote in message
ink.net...
Interesting.

I have a difficult time explaining your bubbles in terms of galvanic
currents, since they occur mainly where stuff has been welded on the
inside of the hull.

My first reaction is to think in terms of increased thermal mass in the
welded areas causing temperature differences.

Next thought is stresses on the hull at those spots causing "stretching"
of the paint surface, maybe allowing water in.

Sorry I can't do better than that.

Good luck.

Chuck