Bottom Paint Haloing
"Haloing" of bottom paint is sometimes observed on boats with bonding systems that are in poor condition or are providing overprotection of the bronze components. It's most prevalent with vessels using black or other dark-colored bottom paint and is more common with certain brands containing higher amounts of copper. If found on your boat, inspect your bonding system connections (if you have one) to ensure they are clean, tight, and corrosion free. Another good idea is to conduct a corrosion survey to ensure proper galvanic protection is being provided.