A comparison between conventional macroscopic and novel microscopic scanning electrochemical methods to evaluate galvanic corrosion

The scanning reference electrode technique (SRET) has been used to examine corrosion in a galvanic 'Kelocouple' system, being that of an explosively b onded joint comprising a trimetallic sandwich of steel/aluminium/aluminium alloy. Quantitative results of local current densities in 4% sea water at r oom temperature have been obtained. These have been compared with results f rom two conventional macroscopic techniques for measuring galvanic current, namely zero resistance ammetry and polarisation curves. The SRET results w ere found to be at least an order of magnitude higher than the average resu lts obtained using the macroscopic methods. Comparison between SRET current densities and corrosion las obtained by the amount of aluminium in solutio n) showed good agreement. Whether attack predominated on the aluminium (nea rer the steel) or the aluminium alloy (further from the steel) depended on the concentration of the sea water. (C) 2001 Published by Elsevier Science Ltd.