--- In [email protected], "rigdent" <[EMAIL PROTECTED]> wrote: > > --- In [email protected], "Roger Millin" <roger.millin@> w > > Digging into my memory bank, I'm sure that you told me that your > > builder hadn't wanted to put any anodes on at all originally and that > > it was only after pressure from yourself that he grudgingly fitted > > some. In the light of that (penny-pinching?) attitude it is possible > > (if not probable) that he has fitted the cheapest anodes that he > > could get ('cos anodes are anodes, ain't they? ;-)) and that these > > could be of the less reactive type (ie those intended for brackish or > > salt water). If that is the case then they will stay in relatively > > good (un-eroded) condition in fresh water for some considerable time > > because (put simply) they aren't doing their job very well. > > Roger > > Well remembered Roger - almost > > Yes the boat was not fitted with anodes from new but once we declared > UDI from Gailey we had anodes fitted by another boatyard. Then when > we took the boat to yet another yard for re-blacking we were surprised > to find the 4 year old anode were in very good nick. That was when we > were told that anodes last a long while in our area. That was a year > ago and when we happened to be moored in some rather clear water I > checked again and they still look good. > > So I'm starting to wonder whether the anodes we fitted incorrectly > maybe over the old blacking which would isolate them from the hull. > > And given the competence that the place that fitted them has shown on > other jobs I wouldn't be surprised. > > Regards > > Terry >
This is not likely because on a steel hull they are normally welded on and if you try to weld through blacking you either get a fire of the anode falls off. Even if they tried to weld onto rust I still think the weld would have "taken" in sufficient places to make a good electrical connection with the hull - if it hadn't it would have fallen off. GRP/wood hulls require through bolts and internal bonding. What we really need now is a chemist to tell us a simple test to differentiate between zinc, aluminium and magnesium. Tony Brooks
