Pitting corrosion has been observed in the internal of a tank after only one year of service in a petrochemical plant. The tank was protected by sacrificial magnesium anodes suspended from the roof. The corrosion occurred as a result of the failure of internal Cathodic Protection (CP) through the fast consumption and self corrosion of the magnesium anodes. The analysis of the tank content indicated an alkaline electrolyte with pH 10.5 at 60 °C and high conductivity.

The main objective of this paper is to study the magnesium anode corrosion behavior in the same solution as the tank by examining polarization behavior of the magnesium anode in the same solution and by simulating the entire CP system using the commercial boundary element analysis software. The possibility of using aluminum anodes in the tank solution was also investigated.

The High conductivity of the solution and relatively high temperature accelerate the self dissolution of magnesium anodes. Aluminum anodes are recommended as replacement for the magnesium anodes.

Subject
Galvanic anodes, Anode potential, Modeling, Cathodic protection, Magnesium anodes, Boundary element method, Anodic current, Magnesium, Carbon steel, Aluminum alloys, Conductivity, Electrolytes, Electrode potential
Keywords:
Sacrificial Cathodic Protection, Boundary Element Method
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2011
Association for Materials Protection and Performance (AMPP)
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