Cathodic protection survey

A cathodic-protection survey checks the corrosion-control system protecting a ship’s underwater hull and ballast tanks: the sacrificial anodes and any impressed-current cathodic protection, ICCP. The surveyor measures anode wastage and remaining life, inspects ICCP anodes, reference electrodes, and the controller, and reads hull-to-water potentials to confirm the steel sits in the protective range, around minus 800 millivolts against silver/silver chloride. Spent anodes or a misset ICCP system leave bare steel to corrode and accelerate wastage that later shows up as thickness loss at the special survey. The survey is run during dry-docking, in-water survey, or ballast-tank inspection.