T&T: Making zincs last longer

[capteric36]

 Hello All,
 The first step in the process of making your 
boat's zincs last longer is to DISCONNECT all the 
bonding connections that are attached to 
underwater metal objects on your boat. You see 
bonding DOES NOT protect against galvanic 
corrosion, it PROMOTES it!
 The way it works is as follows. There needs to be 
current flow between dissimilar metals in an 
electrolyte (salt water in this case). That 
current flows from one metal object THROUGH the 
BONDING WIRE and then to the other metal in the 
electrolyte.
 If you disconnect the bonding wire the current 
path is broken and there can BE no galvanic 
corrosion of underwater metals as long as they are 
not in direct contact with each other.

 Thus you will still need the shaft zinc as the 
bronze propeller is directly attached to the 
stainless steel shaft. You may still need the 
zincs on any swim step or other metal object that 
is not made of only one type of metal, but your 
zincs now only protect the item they are attached 
to, and not every bronze through hull on your 
boat.

 Then you can actually enjoy the benefit of a 
galvanic isolator if you install one, as that 
device will only protect your boat from current 
flow arising from the difference in voltage 
between your shore power ground (green wire) and 
the water surrounding your boat ("hot marina").

 In my marina we had several people complaining 
about the need to replace the electrode pack in 
their LectraSan units every six months or even 
more often. After one of them followed my 
recommendations his unit needed no more 
replacement electrode packs.
 Then another boat did the same thing, with the 
same results.

 Remember that you need to RECONNECT the bonding 
system before your next insurance survey, as 
otherwise your surveyor will flag it as a problem. 
Thus just cutting the wires is NOT recommended.

 I know I'm wasting my time, but I just had to 
point these facts out one more time...

 My $0.02 worth.

Eric Thompson
S/V Procrastinator
South San Francisco
capteric36 at sbcglobal.net