Research on non-toxic inhibitors is of considerable interest for replacing classical molecules containing sulphur, nitrogen or an aromatic function, like benzotriazole (BZT) in copper corrosion. This paper reports a study of the conditions and mechanism of copper corrosion inhibition by linear sodium heptanoate, with a formula of CH3-(CH2)(5)-COONa. Stationary electrochemical measurements (voltamperometry, chronopotentiometry) have established that sodium heptanoate is a good 'green' inhibitor with the optimum conditions of 0.08 M NaC7 at pH 8. In addition, the in situ electrochemical 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 morphology of the films and the change in function of several electrochemical parameters, without the ordinary surface preparation necessary for ex situ techniques, which may damage the layer.