In-situ grazing incidence X-ray diffractometry observation of pitting corrosion of copper in chloride solutions

Abstract

In-situ Grazing Incidence X-Ray Diffractometry (in-situ GIXD) by means of common laboratory equipment, in combination with a potentiostated three-electrode cell, revealed the conversion film dynamics during the alkaline chloride pitting action on copper. Several hours of oxidation in the potential range of Cu(OH) 2 formation resulted in the formation of crystalline CuCl and Cu 2O. The attack of chloride ions initially replaces the outer amorphous Cu(OH) 2 layer, forming soluble CuCl 2. Then the chloride ions start replacing the oxygen in the Cu 2O layer, forming a CuCl phase. At transient times, only CuCl occurs before corrosion currents increase due to copper dissolution and crystalline Cu 2O formation. Ultrasonic treatment shows that CuCl has poor adhesion, whereas Cu 2O crystals persist at the pitted copper surface.