Effects of Lead Oxide Addition on the Electrochemical Properties of Alloy 600 in Aqueous 1 M Sodium Hydroxide Solution

Effects of lead oxide (PbO) addition on the electrochemical. properties of alloy 600 (UNS N06600) have been studied in aqueous 1 M sodium hydroxide (NaOH) solution at room temperature using surface analytical techniques and electrochemical methods. For the comparative study on the different roles of the surface layers in the electrochemical properties of alloy 600, two kinds of electrodes were potentiostatically prepared at the anodic. and cathodic potential peaks observed in cyclic voltammograms obtained in PbO-containing caustic solution:lead dioxide (PbO2) film-covered and Pb deposit-covered alloy electrodes. The crystal structures and morphologies of the two kinds of the surface layers were characterized by x-ray diffractometry and scanning electron microscopy. From the open-circuit potential (OCP) transients and galvanic current transients, it was inferred that Ni and Fe among alloy 600 constituents as anodic sites were dissolved selectively in caustic solution caused by the lower OCP value here there was no PbO2 film compared to that of PbO2 film-covered surface on the alloy. Based upon the experimental results, it was suggested that an enhanced dissolution of Ni and Fe in alloy 600 in caustic solution at room temperature was a consequence of PbO2-induced corrosion.