Les anodes en aluminium pour la protection cathodique en mer^*

Sacrificial aluminum anodes for cathodic protection in sea water

Aluminium Péchiney

Abstract

The working potential of pure aluminum is not anodic enough to protect Steel in sea water. Alloying elements are used to activate aluminum. The activation mechanism results from stripping off the oxide film by alloying elements during dissolution of aluminum anodes. This, shifts the anode potential in the more active direction.

Because of weight and cost advantages, aluminum is the most commonly used sacrificial material, for cathodic protection of bare Steel in sea water. For cathodic protection of painted Steel which needs ten time less anodes, the weight advantage of aluminum is not so important and zinc is generally prefered. But aluminum Hydral anodes can be used, the fouling which coated aluminum anode doesn’t prevent them to protect Steel.

For buried sea lines, aluminum anodes can be used also, even when hot products are transported. Hot temperature and very low current density decrease aluminum anodes efficiency, but aluminum anodes do not passivate and still protect sea lines.