Corrosion inhibitors 26. Pt. 1

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]sub(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 susceptibility measurements and an X-ray investigation using the Debye-Scherrer powder method. The thermal behaviour of the coating was studied by mass-spectral 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]sub(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. (orig.)