Influence of chloride and sulphate content on the performance of aluminium based galvanic anodes

Aluminium-based alloys are widely used in seawater as galvanic anodes. Conversely, their use in soil is not recommended as they tend to passivate when chloride content is low. However, there are chloride contaminated soils where the use of aluminium anodes may be of interest. The aim of this research is to evaluate the effectiveness of aluminium galvanic anodes in low chloride solutions, in presence of sulphates. The research followed two phases: electrochemical characterisation of anodes through potentiodynamic polarisation tests in solution and galvanic coupling tests in soil saturated with chloride and sulphate solutions. The potentiodynamic tests showed that pitting potential decreased as chloride concentration increased; sulphate ions exhibited a passivating effect or increased nobility. The results have also been analysed by statistical methods. In galvanic coupling tests, anodes showed an acceptable working potential also at the lowest tested chloride concentration.