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

In-situ Grazing Incidence X-Ray Diffractometry (in-situ GIXD) by means of c ommon laboratory equipment, in combination with a potentiostated three-elec trode cell, revealed the conversion film dynamics during the alkaline chlor ide pitting action on copper. Several hours of oxidation in the potential r ange of Cu(OH)(2) formation resulted in the formation of crystalline CuCl a nd Cu2O. The attack of chloride ions initially replaces the outer amorphous Cu(OH)(2) layer. forming soluble CuCl2. Then the chloride ions start repla cing the oxygen in the Cu2O layer, forming a CuCl phase. At transient times , only CuCl occurs before corrosion currents increase due to copper dissolu tion and crystalline Cu2O formation. Ultrasonic treatment shows that CuCl h as poor adhesion, whereas Cu2O crystals persist at the pitted copper surfac e. (C) 1999 Elsevier Science Ltd. All rights reserved.