The Cooperative Inhibition Effects of Alkaline Earth Metal Ions and EDTA on the Corrosion of Pure Aluminum in an Alkaline Solution

The cooperative effects of alkaline earth metal ions and EDTA (ethylenediamine tetraacetic acid) on the corrosion inhibition of pure aluminum in 4 mol center dot L-1 KOH solution were investigated by hydrogen collection, polarization curve and electrochemical impedance spectroscopy (EIS). It was found that aluminum exhibits minimum corrosion rate in 4 mol center dot L-1 KOH solution containing 0.02 mol center dot L-1 EDTA, saturated Ca(OH)(2) and saturated Sr(OH)(2). EDAX analysis showed that alkaline earth metal ions and EDTA have no contribution to the formation of the surface film on aluminum. Therefore the inhibition effect may be caused by the adsorption of the inhibitor on aluminum surface. This fact indicates that these two ions act as interface inhibitors rather than inter-phase ones.