Sacrificial Anode
Block of zinc or aluminium attached to the hull that corrodes preferentially, protecting steel; used in addition to or instead of ICCP.
In practice
Inspected and renewed at each drydock; anode wastage indicates protective current was active.
Regulatory detail & full definition
Block of a more electrochemically active metal — typically zinc, aluminium, or magnesium — attached to the hull or in tanks, that corrodes preferentially to the surrounding steel. Sacrificial anodes are the older but still widely-used cathodic protection method, often supplementing ICCP in tanks and shielded hull areas. Anode mass and distribution are sized per DNV-RP-B401 to deliver the required protective current over the design life (typically 5 years). Inspection and replacement are routine drydock items; in-service anode wastage gives an early signal of coating breakdown.
Related
Source: DNV-RP-B401
High confidence
Editorial confidence: how we grade.