Sacrificial anodes protect metallic parts of a vessel against electrochemical corrosion by corroding in place of the metal they are intended to protect. The appropriate anode material depends largely on the operating area and therefore on the salinity and electrical conductivity of the water. The material and size of the structure being protected and the design of the cathodic protection system must also be taken into account.
Zinc or suitable aluminium anodes are commonly used in salt water. Aluminium is generally the preferred choice in brackish water, where zinc anodes can be prone to passivation. Magnesium anodes are normally used in pure fresh water because their higher driving voltage can provide the required protective current despite the lower conductivity. Magnesium may also be used under certain brackish-water conditions, depending on conductivity and the design of the cathodic protection system. Aluminium anodes can likewise be formulated for different salinities; the aluminium anodes offered by TOPLICHT are specified for use in salt, brackish and fresh water.
The range includes long and oval hull anodes made from zinc, aluminium and magnesium. Depending on the version, they are fitted with undrilled steel or aluminium mounting straps for attachment to steel or aluminium hulls. As sacrificial anodes are gradually consumed in service, their condition and electrical connection should be checked regularly and the anodes replaced in good time. Further information on selecting anodes and galvanic corrosion protection can be found in the TOPLICHT guide “Care & Maintenance of Ships”.
