Sacrificial Anodes for Protection of Seawater Pump Caissons Against Galvanic Corrosion

Corrodium developed sacrificial anodes that control themselves by electronic circuit boards. Applications are protection of stainless steels and protection against galvanic corrosion. Such anodes have been installed in (fresh water) sandbed filters, seawater coolers, water inlets and seawater liftpumps. This paper will present the protection of seawater liftpumps and caissons against galvanic corrosion. Under protection leads to severe galvanic corrosion of the caisson, over protection leads to hydrogen embrittlement of the duplex stainless steel pump or riser. The circuit board controls the ideal protection potential under alternating circumstances. Examples of alternating circumstances are changes in water flow, temperature, salinity and fouling or scaling. The electronics have no internal resistance, and no threshold voltage, meaning the aluminium anodes can deliver full current, if required. In this case the ideal potential is 200-300 mV against a Zinc reference electrode. The power for running the electronics is generated by the aluminium anodes themselves. The benefits related to normal sacrificial anodes are that alternating conditions do not lead to under or overprotection. The benefits related to ICCP are more robustness, no maintenance and no cables or power supplies are required. The anodes are installed as 'plug and play', similar to a normal bracelet anode. Logged data and CP measurements of aluminium self controlling anodes on offshore seawater liftpumps will be presented.