I don't know if anybody has experienced this sort of thing but I thought I'd try my luck. Everybody I talk to seems to have
different ideas. It is apparent to me that there are many degrees of understanding from patent mis- through to reasonably good but, so far, not complete. I've found info on the web - some good info - mostly very lengthy - but nothing which fits my case.
I have a problem with my lead keel - the anti-fouling blisters quite badly and comes off in patches. I had it ground back and
epoxied prior to a/f'ing - twice - but the same problem recurred. From what I can gather it could be due to electrolysis within
my own boat or electrolysis connected with my being on a marina and close to other boats.
I really cannot see how other boats on the marina can be a factor as I do not normally connect to shore power. The only time I
do use shore power, which is rare, is when using power tools on the boat, drill, soldering iron etc or when charging a battery. I normally charge bat's at home where I can keep an eye on the process. In view of this I find it hard to believe that the marina environment is a factor.
My boat (f****** I happen to like the stuff!) has a metal plate, presumably bronze, fitted flush into the underside of the hull and to which zincs are attached outboard. A couple of hefty bolts welded to this plate extend through the hull and the engine and batteries are wired ("grounded") to these.
There is also a hefty wire (more of which in a minute) running from a keel bolt (which shows no resistance to the other keel bolts - i.e. there's clearly good connection through the keel to the rest of the bolts) and back to the plate-bolts. The zinc on the plate is "working" - it wears out - but not at a great rate of knots. The engine etc, as far as I know & can tell, isn't rotting away !?!?! I also have a zinc mounted on the prop shaft and this "works" - not excessively. This is NOT electrically connected to the engine - it's "decoupled" at a flexible coupling which is not strapped across.
Now - this wire - keel to plate. I cannot be certain that, when I bought the boat, this was connected because I later found that the wire was chopped under a floorboard. When it was chopped I do not know - nor do I know whether it was done deliberately or not. I have since tried connecting it - disconnecting it - hanging a "guppie" over the side from the keel bolts and so on but have not been able to distinguish any effect on the blistering problem on the keel.
SO - what the heck should I do? I'm just having the keel re-painted from scratch - complete with burnishing and "treating" with various acids, potions and unctions. My current thinking is that I should isolate the keel - i.e. disconnect this wire and again see what happens following the paint job. If it is isolated - there's nothing for it to react with - save the (presumed) ironwork inside it - bolts etc.
All contributions will be gratefully receieved.
P.S. For those fortunate enough not to have come across me before - I'm a HE! The Auntie Podes thing is a pun.