Antifouling paint on bronze fittings

[Chris1956]

I have a bronze water inlet for my livewell. Each year I paint it with an ablative antifouling paint (copper based), when I paint the bottom. At the end of the season, the fitting has heavy barnacles on it, many times what the rest of the hull has.

The paint is compatible with bronze, and doesn't cite the need for a primer. Anyone know why the fitting appears to attract so many barnacles? The boat is used in saltwater, in NJ.

 

[alldodge]

My guess is electrolysis but maybe someone else has a better idea, maybe tpenfield or dingbat

I did find the interlux recommends interprotect 2000 as a primer (epoxy) to be put on props before any antifoul

 

[tpenfield]

There is a transducer antifouling (somewhere) or you could try cold galvanizing paint as well. I suspect the different metals are quickly depleting the AF paint that is on the bronze fitting.

 

[JimS123]

You can't put a copper based coating on bronze. You must first put an epoxy based barrier coat.

 

[Chris1956]

Jim and others, It is a fact that ships in the 19th century and earlier had copper plates on their hulls to help protect against barnacles. It is likely that is why the active ingredient in antifouling paint has been copper.

My bronze fitting could be one of several types of bronze, but all bronze is mostly copper. Silicone bronze, a common marine alloy, is 95% copper, for example.

One would think that copper-based paint on a mostly copper fitting would be OK, and would actually help the antifouling properties.

Are there any Chemists out there?

 

[JimS123]

Bronze is an alloy of copper. A "copper" plate on an antique ship was pure copper, with no other components. Copper in paint DOES improve the antifouling properties.

https://www.boatdesign.net/threads/barnacles-on-copper.49904/