Long‐term polarisation and immersion for copper corrosion in high‐level nuclear waste environment

Abstract

Long‐term polarisation and immersion for copper corrosion were investigated in chloride‐containing sulphide solutions. Results showed that no active state exists for copper in sulphide‐containing solutions, whereas a typical active‐to‐passive transition exists in the second passivation region, indicating a hydroxyl activation effect on copper. After the sulphide passive film broke down, the pitting area was re‐passivated by hydroxide ions; however, if the chloride and sulphide concentrations were both high, then there was no second passivation and the copper would dissolve rapidly. The corrosion resistance and the film thickness both increased with increasing immersion time and an average corrosion rate of 51.2 µm/year was obtained in aerobic solution, which was much higher than in bentonite or under deoxygenated conditions. Moreover, several local corrosion pits appeared after 1‐year immersion and this would occur at the beginning of storage.

The Properties of Electrochemically-Grown Copper Sulfide Films

“…These observations, however, conflict with claims, [16][17][18] based on EIS measurements and Mott-Schottky analyses, that film growth was controlled by the transport of Cu + vacancies within a passive film, with a diffusion coefficient in the range of 10 −14 to 10 −15 cm 2 /s. These values, obtained for films ranging from ∼0.1 μm to ∼50 μm in thickness, are considerably lower than the diffusion coefficients measured for Cu + vacancies in various copper sulfides, which vary with the degree of non-stoichiometry, decreasing from ∼10 −8 cm 2 /s for chalcocite (Cu 2 S) to 10 −9 cm 2 /s for djurleite (Cu 1.96 S), to 10 −10 to 10 −11 cm 2 /s for anilite (Cu 1.75 S) and 10 −12 cm 2 /s for covellite (CuS).…”

“…Other authors have claimed that the film formed on Cu under electrochemical conditions in 2 × 10 −4 M SH − was passive in nature, [16][17][18] which ultimately led to Cl − -induced breakdown and pitting at very positive potentials. However, these claims were based on polarization curves recorded under stagnant conditions, while our results, recorded at a rotating disk electrode (RDE), 7 demonstrated that the current observed was due to film growth partially controlled by SH − transport, a situation which precluded the possibility of passivation.…”

Corrosion and Cavitation Erosion Behaviours of Cast Nickel Aluminium Bronze in 3.5% NaCl Solution with Different Sulphide Concentrations

“…Firstly, in the presence of sulphide, the corrosion potential, E corr , of the cast NAB moves forward in the negative direction and decreases with the increase of SC. This phenomenon is caused by the adsorption of HS − on the NAB surface [29,30], as also reported in other studies [13,29,30]. Secondly, both the anodic and cathodic branches of the polarisation curves change distinctly when the SC exceeds 50 ppm.…”

“…Other cathodic reactions will proceed in the presence of sulphide. In the solutions with SC higher than 50 ppm, the E corr decreases to approximately − 1.0 V. The cathodic branch of the polarisation curve indicates the occurrence of a charge transfer-controlled process, which corresponds to the following hydrogen evolution reaction [11,29,30]:…”

Susceptibility of copper to pitting corrosion in bicarbonate buffer solutions: Part I. Effect of chloride

“…Pitting is a common form of localized corrosion, and a major concern due to its unpredictability, ability to penetrate the bulk material, and self-sustaining nature. Many studies have been conducted on the properties of passive films, such as their structure, composition, and thickness and their role in pitting 4,8,[33][34][35][36][37][38][39][40][41][42][43][44][45][46] .…”