Inhibitoren der Korrosion 26 Die Struktur der bei der Korrosion von Kupfer in Gegenwart von 2-Aminopyrimidin (Sauerstoff, NaCl, pH 4,1, 22 °C) aufgebauten Schutzschicht/ Corrosion Inhibitors 26 The Structure of the Protecting Coating Formed During the Corrosion of Copper (Oxigen, NaCl, pH 4.1, 22 °C) in the Presence of 2-Aminopyrimidine

Abstract

Abstract The analysis of the protective coating produced during the corrosion of copper in the presence of 2-aminopyrimidine (2-AP) is consistent with the composition [Cu1+-2-AP-Cl]n. The individual units form a three-dimensional macro-structure via chloride bridging and hydrogen bonding. The assignment of the structure was supported by NMR, IR, UV and magnetic susceptibüity measurements and an X-ray investigation using the Debye- Scherrer powder method. The thermal behaviour of the coating was studied by massspectral and DTA (differential thermal analysis) methods. Radiochemical experiments were carried out using active copper samples (i.e. containing 64Cu), or using added 64CuCl and 64CuCl2 in the corrosion of non-active copper both in the presence and absence of added 2-AP. The results elucidate the exchange reactions at the copper surface between dissolved and metallic components. The equilibrium between Cu2+ and metallic copper on the one hand and 2 Cu1+ ions on the other is central to the problem, as is also the dissociation of the [Cu1+-2-AP-Cl]n complex. The concepts here developed were confirmed by studies of the autoxidation of CuCl and CuO in the presence and absence of 2-AP.