Copper specimens were exposed to Sulfate-Reducing Bacteria (SRB) for 10 months under the conditions corresponding to the final disposal of high-level nuclear waste. In-situ electrochemical impedance spectroscopy (EIS) measurements were carried out to characterize the surface-environment interface after various times of exposure. The EIS results are interpreted in terms of the Point Defect Model (PDM), in order to obtain kinetic information on the formation of the Cu 2 S passive film. The standard rate constant and the rate constants for the surface reactions revealed that the Cu 2 S layer is a p-type semiconductor. The diffusion constant for cation vacancies in the barrier layer and the average bulk cation vacancy concentration in the barrier layer were found to be on the orders of 10 −13 cm 2 •s −1 and 10 22 cm −3 , respectively, i.e., both slightly higher than reported in literature for corresponding electrochemically developed Cu 2 S layers. The electric field strength was approximately 3•10 5 Vcm −1 at all measurement points. These results are presented and discussed in this work in the light of storage of high-level nuclear waste.

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In the present work, corrosion rates of API grade X65 pipeline steel in sodium chloride solutions with and without alternating currents (AC) at different direct current (DC) potentials were measured using weight loss analysis. The results show that the effect of AC is most pronounced near the open circuit potential; at more positive potentials the rates approach those of the ohmic drop / mass transport-limited DC rates. Correspondingly, at negative potentials the rates decrease. Surprisingly, it was found that at all potentials the AC corrosion rate was equal to the average AC current in the system. The data generated from weight loss experiments were compared with the results from a model for AC corrosion that was developed using a modified Butler-Volmer approach. The model considers the anodic and cathodic Tafel slopes, diffusion limited oxygen transport, interfacial capacitance and solution resistance. Both experimental and model results showed the importance of the interfacial capacitance on the rate of AC corrosion, especially at a frequency of 60Hz. The models were also used to explain the observation that the AC corrosion rate was equal to the average AC current in the system.

To analyze the effect of lithium and microstructure on the pitting corrosion behavior of aluminum alloys, three types of aluminum alloys were studied via scanning electron microscopy, transmission electron microscopy, electrochemical polarization, and by immersion tests coupled with in-situ observation of pitting and statistical analysis of pit depths measured by surface profilometry. It was found that, with increasing lithium content, the resistance to pitting corrosion was enhanced and the passive range was enlarged. In-situ observation revealed that the development of pitting corrosion exhibited three stages, including an initial slow nucleation stage (Stage I), a fast development stage (Stage II), and a stabilized growth stage (Stage III). Higher lithium content contributed to shorter time periods of Stages I and II, resulting in faster pitting evolution and a higher number of pits. However, the pits were generally shallower for the specimen with the highest lithium content, which is in agreement with the results of the electrochemical analysis.

Pitting corrosion is a possible mode of failure of the carbon steel overpack of the Belgian supercontainer concept for the isolation of high‐level nuclear waste (HLNW). However, no firm experimental data are currently available to estimate the probability of failure over the extended storage time (100,000 years). Extensive work shows that passivity breakdown results from the condensation of cation vacancies (CVs) at the metal/barrier layer (m/bl) interface, in response to the absorption of Cl− into oxygen vacancies at the surface of the barrier oxide layer. The CVs migrate across the bl to the m/bl interface where they condense, leading to the separation of the bl from the metal. The resulting blister prevents the growth of bl into the metal and dissolution results in blister rupture, marking a passivity breakdown event. Stabilization via differential aeration produces a potentially damaging, stable pit. We review our work on passivity breakdown and the nucleation of pits on P355 QL2 carbon steel in high‐pH aqueous media typical of concrete pore solution, with emphasis on the mechanistic aspects. We conclude that failure of the carbon steel overpack containing the HLNW over a storage horizon of 100,000 years is improbable.

Prediction of the accumulated pitting corrosion damage in aluminum-lithium (Al-Li) is of great importance due to the wide application of these alloys in the aerospace industry. The Point Defect Model (PDM) is arguably one of the most well-developed techniques for evaluating the electrochemical behavior of passive metals. In this paper, the passivity breakdown and pitting corrosion performance of AA 2098-T851 was investigated using the PDM with the potentiodynamic polarization (PDP) technique in NaCl solutions at different scan rates, Cl− concentrations and pH. Both the PDM predictions and experiments reveal linear relationships between the critical breakdown potential (Ec) of the alloy and various independent variables, such as a C l − and pH. Optimization of the PDM of the near-normally distributed Ec as measured in at least 20 replicate experiments under each set of conditions, allowing for the estimation of some of the critical parameters on barrier layer generation and dissolution, such as the critical areal concentration of condensed cation vacancies (ξ) at the metal/barrier layer interface and the mean diffusivity of the cation vacancy in the barrier layer (D). With these values obtained—using PDM optimization—in one set of conditions, the Ec distribution can be predicted for any other set of conditions (combinations of a Cl − , pH and T). The PDM predictions and experimental observations in this work are in close agreement.

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The Comments by Martino et al. 1 on the original manuscript 2 criticize our interpretation of the existence and properties of the Cu 2 S barrier layer of the passive film that forms on the surface of copper in SRB-bearing groundwater at 10°C. First, it is necessary to recognize that this discussion involves two forms of copper, which we refer to as "pure copper (P-Cu)" (nominally > 99.999%) and "oxygen-free phosphorous copper (OFP-Cu)". P-Cu has been used in the majority of our work [3][4][5][6] with only some of our later work employing OFP-Cu, 2 a point that does not seem to be appreciated by Martino et al. 1 On the other hand, the Shoesmith group appears to have concentrated exclusively upon OFP-Cu, at least in recent years. [7][8][9][10][11] This difference is of crucial importance in responding to the critique by Martino et al. 1