riveted steel hull

Hello all. I have been working aboard a riveted, steel hulled sail boat for a couple of years now and we recently hauled out for a couple of months. During our time on the hard, what seemed to be a solid vessel began to deteriorate rather rapidly. She has only sailed salt water and has concrete ballast in her bilges, along with various chains and pipes (all steel) so we expected to find some issues. However, pits were continuously being discovered and welded. One formed a salt pyrimid on the exterior of the hull. Could this be due to the freshwater rinse of the rain we recieved so much of during our time on the hard?
Also, upon launching, we discovered weeps and some leaks in most of the seams around one particular panel. I have learned alot about riveted hull vessels during my time aboard, but am not sure about the integrity of a panel with so much salt water exposure around the rivets nor what will happen to these rusty and salt encrusted areas when we venture into the fresh water of the Great Lakes this summer. Lastly, I have been noticing an increased amount of a fine, white, cotton candy-like growth in some areas since we have been back in the water. Has anyone else experienced this? Is it salt related? Thanks in advance for any input or suggestions

Re: riveted steel hull

I would ask a marine surveyor.

Re: riveted steel hull

Ditto.. riveted steel hulls are not common enough that there's a standard way to deal with them or repair them.

I'd recommend strongly hauling the boat out again and having a surveyor go over it... for safety's sake if nothing else. He can do an inspection in the water, but he won't be able to check your hull as well, which is the number one thing to look at.

The "salt pyramid" you mention was probably formed by a slow drip of water from the inside of the hull carrying salt out... could be from fresh water leaking in from above or from a pool of salt water slowing coming out... but does it matter? You need to seal that up

Given what you mention about pits, you probably need to check the thickness of the whole hull and look for corrosion. Welding is a quick fix, but you may need to replace some plates, otherwise compromised steel could put you on the bottom, especially in the great lakes where every reef is pretty much solid rock.

If you don't have them, consider installing zincs in wet areas inside the hull too, to prevent corrosion from working its way out. Check them when you check the ones on the hull's exterior.

The cotton candy growth you mention probably is mold or fungus of some kind, which won't grow in salt water easily but if fresh water got inside and puddled somewhere it could cause that.

All in all, sounds like the boat needs more than a haul out and cleaning, it needs a check-up from a qualified professional.

Erik