Zinc to the Rudder?

[Steve]

Should I add a small zinc bullet to the H26 aluminum rudder lower support flanks where it meets the water?. Each year (5) I have to remove the rudder, all the stainless bolts, and sand and paint to make it look like new. The black paint peels and pitting is rather aggressive around the lower stainless steel bolts. We are moored in saltwater for 5-6 months. This year I used bottom paint on the lower 4 inches below the water line and have green very aggressive pitting around the lower two bolts.. What can (should) I do?

 

[Jim Bohart]

zinc won't help much

The problem isn't electrolysis as much as it is bi-metallic corrosion from the contact of SS. with Al. You can isolate the bolts with plasic washers, and sleeves to prevent the ss from contacting the al or replace the SS. bolts with aluminum.JB