Not Happy with Halos

By: Frank Lanier

QuestionDuring my last haulout, I noticed what looked like rings in my bottom paint around each of the bronze fittings below the waterline (through-hulls, strut, etc). What could be causing this? The bottom paint I’m using is black Pettit Trinidad SR.

Answer“Haloing” of the bottom paint is often observed on boats with bonding systems that are either in poor condition or are providing overprotection of bronze components. It’s most prevalent with vessels using black or other dark-colored bottom paint and is more common with brands containing higher amounts of cuprous oxide (such as your paint). Higher levels of copper coupled with the bonding system issues mentioned above can more easily lead to the establishment of a galvanic cell and flow of galvanic currents. If I see haloing during a survey haulout, I recommend two things. The first is to inspect all bonding system connections to ensure they are clean, tight and corrosion free. Next would be to have a corrosion survey conducted on the vessel to determine if proper galvanic protection is being provided.

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