Task and function of sacrificial anodes
Sacrificial anodes are used for cathodic protection in a maritime environment: they are made of a more reactive metal than the components to be protected. As a result, they corrode preferentially and absorb electrical currents before sensitive alloys of the OMC drives are attacked. This considerably extends the service life of technical components.
Electrochemical corrosion in the maritime environment
In water, different metal potentials create an electrochemical environment. Without protection, this leads to
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Crevice or pitting corrosion on drive parts
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erosion on outboard housings or underwater surfaces
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Damage to shafts, bearings or couplings
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Damage to hull or drive mountings
Effective cathodic protection by sacrificial anodes minimizes this damage.
Materials & types: Zinc, aluminum
Sacrificial anodes for OMC drives are usually made of:
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Zinc: proven in classic saltwater environments
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Aluminum: lightweight, durable solution - even in mixed conditions
The electrochemical properties of these materials effectively protect the more sensitive alloys in the OMC system.
Areas of application for OMC drives
Sacrificial anodes are specifically installed where components are exposed to direct water contact:
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Outboard housing
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Underwater parts of the drive
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Shaft axles & propeller areas
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Hull contact surfaces near the drive
Targeted anode placement maximizes protection and corrosion prevention.
Selection criteria: Material, water type & application
The following criteria are decisive when selecting OMC sacrificial anodes:
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Water type:
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Salt water: preferably zinc or aluminum
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Brackish water: aluminum is often more suitable
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Fresh water: aluminum can also be effective
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Size & surface: adapted to flow and current
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Mounting type: bolt or screw connection suitable for the OMC component
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Compatibility: with the alloy of the component to be protected
Only correctly dimensioned and material-compatible anodes ensure lasting protection.
Installation & replacement for OMC systems
Important installation instructions:
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Clean contact surfaces: free from oxidation and dirt
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Corrosion-resistant fastening elements: marine-grade screws/nuts
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Positioning: close to the components to be protected
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Regular replacement: as soon as ≥ 50 % of the anode material has been sacrificed
Proper installation and timely replacement extend the protective effect and reduce consequential damage
Visual inspection & service life
Regular visual inspection includes:
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Degree of wear of the anode before and during the season
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Cleaning the contact surfaces before installation or replacement
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Checking adjacent components for corrosion
Early replacement ensures optimum protection.
Risks in the absence of protection
Without suitable sacrificial anodes, the following damage can occur:
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Corrosion on drive components
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Material erosion on underwater surfaces
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Damage to shaft axles, bearings or couplings
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Increased maintenance costs
Targeted cathodic protection significantly reduces such risks.
