Mailport: September 2012
Bottom Paint Woes
Please see the photos of my Downeaster 38’s hull bottom and prop (at right) after the boat was in the waters off City Island (Bronx), N.Y., from June 6 until Aug. 25. The bottom paint used was West Marine Bottomshield; Pettit Zinc Coat Barnacle Barrier 1792 was used on the prop. As you can see, the treatments were pretty much failures. Barnacles grew over the bottom and clustered on the prop in just a few months.
After lightly sanding the previous season’s prop zinc treatment, I sprayed on three coats of new Barnacle Barrier. The previous season, I had applied the coating to bare metal and had much better results: Barnacles were fewer in number and much smaller in size. I do not see why one cannot apply Barnacle Barrier to a lightly sanded pre-existing zinc coating and get the same results as applying it to bare metal.
Regarding the use of the Bottomshield: In the 30 years I have had this boat, I have never had the growth of barnacles all over the bottom, usually barnacles on the waterline and slime on the rest of the hull bottom. Paints used in the past were Woolsey, Interlux VC, Pettit Trinidad, Pettit Trinidad SR, and more recently Pettit Unepoxy. My results make the use of Bottomshield and Barnacle Barrier very questionable for this area.
Alcee Marie, Downeaster 38
City Island, N.Y.
While the Pettit-made West Marine Bottomshield (pre-2010) earned Recommended ratings in some past PS antifouling tests—even after 24 months (PS, October 2011)—test panels coated with the more recent formulations have not fared as well. Like many manufacturers, Pettit has reduced the copper content in some of its paints. Previous versions of the single-season Bottomshield were 46-percent copper, but the newer iterations contain only 29 percent. In the most recent report (PS, March 2012), it rated Fair after 14 months in Florida, meaning it was still repelling hard growth.
We also have seen year-to-year variability among antifouling paints of identical formulas (although not as significant as yours) in our tests. Pettit has several other paints that have done consistently well over the years. The copper-heavy Pettit Trinidad (76 percent) and Trinidad SR (70 percent) have proven more effective in recent panel tests, earning Good ratings after 14 months and Recommended ratings after 30 months. We suggest going with one of those, especially if they historically have done well for you.
Regarding the Barnacle Barrier: We’ve not yet field-tested it, but we’ve had good reports from readers who use it. According to their reports, applying it to bare metal—as the directions call for—allows for better adhesion and, therefore, better results.
Next: Measuring Epoxy Success