Potential‐pH equilibria and potentiodynamic polarization studies were used to confirm that formation of CuCl2− complexes in 1.0M normalNaCl and 0.1M normalNaCl solutions produces a range of potentials at which anodic dissolution of copper occurs without formation of oxide. The interaction of benzotriazole (1 g/l) with oxide‐free copper surfaces in the chloride solutions was studied by potentiodynamic polarization and potentiostatic techniques. Inhibition of the anodic dissolution reaction was obtained in near‐neutral pH solutions and at pH 3.0. Inhibition was ineffective at pH 1.0. The interaction of benzotriazole with oxide‐free surfaces, leading to inhibition, was potential‐ and time‐dependent. Also, a limiting potential was observed and predicted above which additions of benzotriazole are ineffective and above which existing inhibiting films cannot undergo spontaneous repair. The results confirm that benzotriazole can interact with oxide‐free surfaces to promote corrosion inhibition of copper. The characteristics of the inhibition behavior, including breakdown and pH effects, were consistent with an inhibiting film that formed by adsorption of neutral benzotriazole molecules onto the Cu surface, followed by the adsorption of a thin layer of cuprous benzotriazole in polymeric form.

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Pitting of single crystals of A1 and homogenized A1-Cu alloys has been studied on low index surfaces as a function of surface orientation and alloy content in 0.5M NaC1. The potentials at which pitting phenomena occurred were determined potentiodynamically using single-cycle pitting tests at a scan rate of 0.5 mV/s. Galvanostatic tests were used for pit density studies. The potential at which pits initiated (Epit) was determined, together with a pit transition potential (Ept~,) that appeared as an abrupt potential discontinuity on the decreasing potential scan and was shown to be related to pit repassivation events. The observations indicated that pitting behavior was anisotropic. Pitting densities were dependent on crystallographic orientation. Consistent with this, the pitting potential showed a small dependence on surface orientation in the order (Epit)~0el~ > (E,it){~H} > (Epit){111}, whereas Eptp was found to be independent of orientation. Walls of pits on A1 were composed of {001} facets with <001> step edges:The presence of alloyed Cu raised pitting potentials, reduced the dependence of Epit on surface orientation, and modified the pit morphologies. The dependence of pitting behavior on surface orientation and alloy concentration is discussed in terms of a kinetic model of pitting in which pits are Considered to initiate at the base of flaws in the surface oxide film.

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Thermodynamic data, together with equilibria involving 1-H-benzotriazole (BTAH) and cuprous benzotriazole species (CuBTA), have been used to construct aqueous S-pH diagrams for Cu-BTAH-H20 and Cu-BTAH-Cl-H20 systems. The diagrams are the first of their kind for BTAH-containing solutions and show the domains of stability of the CuBTA salt. They are in reasonable agreement with the reported major effects of multilayer CuBTA polymer films on the corrosion inhibition of copper. Some kinetic considerations are discussed and the overall results provide a basis for understanding the combined effects of E, pH, C1, and BTAH concentrations (activities) on corrosion inhibition of Cu.

A model is presented for estimating oxygen solubility in water and solutions of inorganic electrolytes (I) as a function of oxygen pressure P O 2 (atm), temperature T (K), and I. It is based on a thermodynamic analysis for water, where the molal concentration c aq of oxygen follows an equation of the form c aq ) P O 2 k and k is a T-dependent function (equilibrium constant) related to the chemical potential, entropy, and partial molar heat capacity of the gaseous oxygen (O 2 ) g and dissolved oxygen (O 2 ) aq species. In the presence of I, the oxygen solubility becomes (c aq ) I ) φc aq , where φ is a modifying factor < 1 that is dependent on I and its molal concentration C I . The decreasing molar heat capacity of (O 2 ) aq with rising T, which affects k, is discussed. The decrease in φ with increasing C I is related in a general way to the decrease in partial molar volume of the water.

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