Section 139.13 - Cathodic protection(a) The requirements in paragraph (b) of this section apply to discharges resulting from a vessel's cathodic corrosion control protection device, including but not limited to sacrificial anodes and impressed current cathodic protection (ICCP) systems.(b) Spaces between any flush-fit anode and backing must be filled to remove potential hotspots for biofouling organisms.(c) The vessel operator must consider using, but is not required to use, less toxic metals when selecting sacrificial anodes.