Rudder Assembly Pitting

[Steve]

Experiencing some aggressive pitting reaction along the last three inches of the aluminum rudder flanks (crusty green stuff around the lower bolts), only in the areas in touch with the water. We are in salt water and have on occasionally bottom painted this small area to avoid the slimmy stuff. My theory, which could be wrong, is galvanic reaction between either the boat and the rudder assembly (I don’t see any electrical connection possible) or simply localized SS bolts and aluminum flank reaction issue? Either way it’s ugly!Anyone experienced this before? Thanks in advance!Steve

 

[Alan Long]

I have too

I notice a similar problem with my 23.5 when the lower part of the metal rudder assembly was covered with bottom paint. I later found that you should never coat aluminum with cupric oxide based bottom paint. I started using the paint designed for outboard motor lower units on the aluminum part of the rudder assembly and that seems to work fine. Check Boats US or West Marine, the stuff I have is made by Tempo.Alan LongS/V Random Access

 

[Bob Iamello]

Aluminum Pitting

After reading your pitting problem, I was curious to see if I had experienced the same. What I noticed was some pitting. I too had used bottom paint. It probably is a chemical reaction between the bottom paint (which contains copper)and the Aluminum. after I pull the boat for the season, I'll be removing the bottom paint. Any idea what the correct paint is?