Cathodic protection continued sacrificial anode

The sacrificial anode system consists of burial of anodes in the electrical proximity of the tank. The anodes are made of magnesium or aluminum, which are less noble than the steel tank. This enables the flow of current from the sacrificial anode (A1 or Mg) to the cathodic steel tank. Over a period of time, the anodes are consumed and hence replaced with new anodes in order for continued corrosion protection of the tank. 

The anticorrosion protection of offshore platforms subjected to difficult operating conditions is an especially responsible task. Apart from the continuous strongly corrosive interaction of sea water, periodical phenomena are also encountered, such as storms, earthquakes, hurricanes, pressure of ice floats, and other phenomena increasing the corrosion hazard. These interactions cause stress and fatigue corrosion and other forms of corrosion attack. In such conditions, special protective coating systems are applied to protect the objects, coupled with cathodic protection realized by the use of sacrificial anodes or an external power sup-... 

A single sacrificial anode attached to one end of a pipe can normally, and in freshly piped seawater, protect the internal surfaces of a pipe only up to 2-3 diameters in depth and installation of a continuous strip anode may be required. In stagnant seawater, however, even 12-50 mm (0.5-2 inches) nominal diameter stainless steel (e.g. Type 304) and copper pipes can obtain effective cathodic protection after an initial polarization period, which can vary between four days, for 5 cm (2 in) diameter stainless steel pipe, and 186 days for 12mm (0.5 inch) diameter copper pipe, by a single sacrificial anode fitted to one end to a depth of approximately 6 m (20 ft). 

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