Sacrificial anodes are fitted to a ship's hull to prevent corrosion. Seawater is highly corrosive due to its salt content, which acts as an electrolyte, facilitating the oxidation of iron (mild steel) and the formation of rust. Zinc anodes, being more reactive than steel, act as a sacrificial anode. They corrode preferentially, protecting the steel hull from corrosion. This is a form of cathodic protection.

• The anodes may have been manufactured from substandard material that does not possess the required electrochemical properties to act as a sacrificial metal.
• If the wrong type of material (e.g., aluminium or magnesium instead of zinc, or improperly alloyed zinc) was supplied or installed, the anodes may not function as intended.
• If the anodes are not electrically connected to the hull (e.g., due to improper installation or poor contact), they cannot provide cathodic protection.
• Incorrect placement of the anodes may leave sections of the hull unprotected, leading to corrosion in those areas.
• Poor-quality or damaged coatings on the hull can expose bare steel, which may corrode faster than the anodes can protect it.
• Stray currents from other sources (e.g., from shore connections, dock equipment, or adjacent vessels) may bypass the anodes and accelerate hull corrosion.
• The anodes require continuous exposure to seawater to create the necessary electrochemical reaction. If seawater flow is obstructed, the anodes may remain inactive.