I am surprised to hear of number of boats affected. It seems this is a common failure mode. I have not done mine. I only discovered the problem when I spent a couple of days inside both of my forward lockers (lazarettes) doing the repairs on their floors. Really not that bad of a job with a tyvek suit and full face respirator. Prior to that I had never looked up, to the underside of the locker "ceiling" but I found the FRP "collar" at the top of the pipe split due to the pressure of the underlying rust. Since I had my angle grinder in hand I ground enough FRP away to see the extensive rust of the pipe and flange. I couldn't see any evidence of water intrusion, like salt crystals etc, and I am at a bit of a loss as to why this rusted so badly. I will definitely do a non-rusting repair. I don't believe this hawse pipe was structural in any way since there is only a single tab at the top and nothing tying it to the floor except the lower FRP collar. We all know that the floor of these lockers are under engineered for the loads imposed in pounding seas (e.g. tabbed only on the top so that loads tend to delaminate the plywood and un-protected from below from the moisture of the chain locker resulting in rot of the wood).
I just don't see the need to place anything made of mild steel (galvanized or not) on an ocean going boat. Like most of these things the cost of the materials is minuscule compared to the labor and grief involved in re-dos. Just my two cent worth.
Gary S. Silver
Amel SM 2000 #335