Paint under zincs?
 

I am finishing up painting the bottom of my boat. Am I supposed to paint under the zincs that I am putting on my rudders? I think that I should not, so that I maintain a good contact between the rudders and the zincs. Is that right or wrong? I know not to paint the zincs themselves. I intend to use primocon and Micron CSC. Any comments?

Rich S.

Paint under the zinc to protect the rudder. If you don't you will have a problem. The zinc is just going to sacrifice it's life for the whole area (weakest link theory and all).

answer
 

Vyper340
I did some checking on the Web and the answer is unanimous -
Never paint under the zinc. The zincs job is to sacrifice itself, however it can't do that job if electrical current can not flow thru the various metal parts of the boat and then thru the zinc. The zinc must must have as good an electrical contact as possible with the metal it is being attached to.

Rich S.

In my experience (as an ex-naval engineer) the sacrificial anodes (zincs etc.) were always used on top of the protective coatings appiled to hull and other parts of the ship/boat. If you want a practical, real life example of this go take a look at any new boat and tell me if the surface under any of the zincs is bare. I even looked at my brand new boat to verify and found that on my K-planes that the zincs are attached over the painted surface of the K-plane. The same goes true for the sterndrives. Regarding the flow of electical current that is required as you found out, it is accomplished through the uncoated attachement of the zinc (anode) via the connecting bolt or screw. That is all that is required to establish a good current flow.

That's my .02. Good luck with whatever method you go with.

Vyper thanks for the info.

Um the more I know the less I know.
Now, naturally, the answer is no longer unanimous,
and I thought just for a few minutes there, that everyone
was going to agree on something :-)

Oh well, here is some more support for your position.
As the zinc shrinks, the uncoated section of the bronze
rudder is going to come into direct contact with seawater
and all the bad things it brings. So it seems like coating that
section is definitely a good idea. Perhaps the right answer is
just to make sure that the very center section, bolt plus a little
is clear of coating.?

Finally, I have to say that I have no standing here
at all, as an Infanty Airborne Ranger, what do I know about
water??! When I'm thirsty I like it!

Like vyper pointed out, look at any new outdrive or trim tabs. There is always paint surrounding the zinc areas. Electrical conductivity will occurr through the bolt or attachment hardware. The threaded area(or hole) is the only part that is to remain bare.