Inhibition of copper aqueous corrosion by non-toxic linear sodium heptanoate: mechanism and ECAFM study

Research on non-toxic inhibitors is of considerable interest for replacing classical molecules containing sulphur, nitrogen or an aromatic function, l ike benzotriazole (BZT) in copper corrosion. This paper reports a study of the conditions and mechanism of copper corrosion inhibition by linear sodiu m heptanoate, with a formula of CH3-(CH2)(5)-COONa. Stationary electrochemical measurements (voltamperometry, chronopotentiomet ry) have established that sodium heptanoate is a good 'green' inhibitor wit h the optimum conditions of 0.08 M NaC7 at pH 8. In addition, the in situ e lectrochemical AFM technique (ECAFM) has proved that the inhibition is due to the formation of a layer, mainly constituted by a copper heptanoate, Cu( CH3-(CH2)(5)-COO)(2). Studies of the passive films by ECAFM allow us to observe in situ the morph ology of the films and the change in function of several electrochemical pa rameters, without the ordinary surface preparation necessary for ex situ te chniques, which may damage the layer. (C) 2001 Elsevier Science B.V. All ri ghts reserved.