Influence of pH and flow on the polarisation behaviour of pure magnesium in borate buffer solutions

The influence of pH and flow on the polarisation and impedance behaviour of pure Mg was investigated in 0.6 wt% NaCl borate buffer solutions at pH 6.7, 7.6, and 9.3 using a rotating electrode. The existence of flow prevented the accumulation of the corrosion product and promoted uniform corrosion, leading to an increase of the anodic current density and a decrease of the impedance regardless of the pH of the bulk solution. The influence of the pH did not obviously appear under the static condition, whereas, under the dynamic condition, the anodic current density at pH 6.7 and 7.6 was higher than that at pH 9.3. This result suggests that pH near the surface can be buffered at the pH of bulk solution by borate buffer with the acceleration of ion diffusion. (C) 2008 Elsevier Ltd. All rights reserved.