Under some conditions, copper and copper alloys are either immune from corrosion or undergo slow uniform corrosion, generally considered a favourable situation, because predicting the damage incurred by the metal during a period of uniform corrosion is relatively straightforward. However, under conditions leading to surface passivation of Cu, localized corrosion might occur in the presence of aggressive oxidants. Therefore, the susceptibility of Cu to localized corrosion must be considered carefully to avoid unpredictable failures in Cu-based structures. Understanding the pitting probability of Cu is important for various applications, including the use of Cu-coated containers for the permanent disposal of used nuclear fuel. In this study, the pitting probability of Cu in chloride-containing solutions crudely representing the groundwater that might be found in a deep geologic repository (DGR) was investigated using electrochemical techniques and statistical analysis. The probabilities of both pitting and repassivation of Cu were found to increase with increasing [Cl-]. The surface morphologies of copper electrodes in the same solution were also evaluated using scanning electron microscopy (SEM). The passive film on the surface of the copper electrode with the highest breakdown potential (Eb) was found to be more protective than that on the electrode with the lowest Eb

Copper (Cu) and stainless steel 316L are widely used for biomedical applications, such as intrauterine devices and orthopedic/dental implants. Amino acids are abundantly present in biological environments. We investigated the influence of select amino acids on the corrosion of Cu under naturally aerated and deaerated conditions using a phosphate-free buffer. Amino acids increased the corrosion of Cu under both aeration conditions at pH 7.4. Cu release was also significantly (up to 18-fold) increased in the presence of amino acids, investigated at pH 7.4 and 37°C for 24 h under naturally aerated conditions. Speciation modelling predicted a generally increased solubility of Cu in the presence of amino acids at pH 7.4. 316L, investigated for metal release under similar conditions for comparison, released about 1000-fold lower amounts of metals than did Cu and remained passive with no change in surface oxide composition or thickness. However, amino acids also increased the chromium release (up to 52-fold), significantly for lysine, and the iron release for cysteine, while nickel and molybdenum release remained unaffected. This was not predicted by solution speciation modelling. The surface analysis confirmed the adsorption of amino acids on 316L and, to a lower extent, Cu coupons.

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The pitting corrosion, passive film morphology, and surface composition of copper were studied in chloride-containing bicarbonate buffer solutions using multielectrode arrays and single electrodes. Cu was shown to be susceptible to pitting in 0.01 and 0.1 M Cl¯, but to experience active dissolution in 1 M Cl¯. The passive film morphology and composition were investigated using the single-electrode setup. Surface analyses showed the presence of pits in both 0.01 and 0.1 M Cl¯ buffer solutions. The results indicated the dependency of passive film morphology and composition on both charge density and applied potential.

Copper and copper alloys have found applications in various industries. One of the main reasons Cu and its alloys are utilized widely is that they have sufficient corrosion resistance in key environments, such as seawater and anoxic solutions; however, localized corrosion processes might occur in the presence of aggressive anions, oxygen, or an increase in solution pH. In critical applications of Cu, the susceptibility of Cu to localized corrosion, specifically pitting, must be carefully considered, as it could lead to material failure. In this study, the pitting probability of Cu in unary (sulfate) and binary (sulfate + bicarbonate) solutions was investigated using electrochemical techniques in conjunction with statistical analysis. We determined pitting probabilities based on two different defining criteria for pitting susceptibility, one based on the probability that the corrosion potential, Ecorr, could exceed the passivity breakdown potential, Eb, and the other, a more conservative approach, based on the likelihood that Ecorr would be greater than the repassivation potential, Erp. The pitting probability of Cu did not change significantly with sulfate concentration at pH 8 but was found to increase with increasing [SO42−] up to 0.005 M at pH 9 and then to decrease with a further increase in [SO42−].

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