A continuing challenge in materials design is the achievement of high operational efficiency through improvements in performance criterion, particularly its service life-time characteristics. Benzotriazole (BTAH) has now been in use for many years for the protection of copper and copper alloys against various forms of corrosion. In this review, the chemistry of BTAH and theories regarding its mode of action are summarized. Also, a survey of the reported work in both clean and polluted environments is documented. More interestingly, the adverse effect of BTAH on the corrosion of Cu and Cu alloys in sulfide polluted environments is introduced.

A review of the effects of benzotriazole on the corrosion of copper and copper alloys in clean and polluted environments

The corrosion behavior of oxygen-free copper in an anoxic 0.1 M NaCl + 5 × 10 ―4 M Na 2 S solution was studied using electrochemical impedance spectroscopy, scanning electron microscopy equipped with a focused ion beam, X-ray photoelectron spectroscopy and micro X-ray diffraction. The corrosion film grew as a coherent, compact crystalline layer with a nonuniform thickness. The growth kinetics obeyed a parabolic law consistent with control by a diffusion process. Once a coherent layer was established, film growth kinetics appeared to be controlled by Cu + ion diffusion through the film. At shorter times before a coherent film was established, SH- diffusion in solution exhibited a considerable influence on the growth rate.

https://iopscience.iop.org/article/10.1149/1.3478570/pdf

Kinetics of Corrosion Film Growth on Copper in Neutral Chloride Solutions Containing Small Concentrations of Sulfide

The conversion of a Cu 2 O film on copper to Cu 2 S in aqueous sulfide solutions has been followed using a combination of electrochemical techniques and in situ Raman spectroscopy. Oxide films were electrochemically grown in alkaline solutions and their composition and morphology determined using Raman spectroscopy and scanning electron microscopy. Although corrosion potential measurements indicate that the aqueous sulfide solution rapidly penetrates the porous Cu 2 O layer, the oxide-to-sulfide reaction appears to proceed chemically at the oxide/solution interface rather than via the galvanic coupling of Cu oxidation to Cu 2 S and Cu 2 O reduction to Cu. In situ Raman spectroscopy confirms that the sulfide formed is Cu 2 S, and cathodic stripping voltammetry shows that the reaction is initially rapid and then proceeds at a constant rate until the conversion is complete. Comparison of the amounts of oxide initially present and sulfide eventually formed demonstrates that the conversion is 100% efficient. These studies are part of a larger project to determine the important corrosion processes on copper high-level nuclear waste containers exposed to anoxic aqueous sulfide containing groundwaters.

The Electrochemical Response of Preoxidized Copper in Aqueous Sulfide Solutions

Long-term corrosion of copper in a dilute anaerobic sulfide solution

The assessment of the corrosion performance of containers (waste packages) for the disposal of high-level nuclear waste has been underway for more than 20 years. A review of the rationale behind disposal site selection, container design, materials selection for fabrication, and the bases for the development of corrosion models is discussed.

Assessing the Corrosion Performance of High-Level Nuclear Waste Containers

The mechanism and kinetics of Cu corrosion in anoxic aqueous chloride solutions containing sulfide (10−3 mol/L) have been investigated electrochemically and under natural corrosion conditi...

Sulfide film formation on copper under electrochemical and natural corrosion conditions

Electrochemical and surface analytical techniques are being used to determine the mechanism and kinetics of Cu corrosion in the presence of sulphide, with the primary goal of developing a mixed potential model for Cu corrosion under disposal conditions. Corrosion potential (Ecorr) measurements indicate the formation of copper sulphide films is rapid leading to rate control by the cathodic reduction of water. Impedance spectroscopy suggests the anodic charge transfer process is rapid leading to film growth limited by diffusive transport. Experiments are underway to determine the current-potential relationships necessary in the development of a mixed potential model.

Corrosion of Copper Nuclear Waste Containers In Aqueous Sulphide Solutions

Using a variety of electrochemical and surface analytical techniques, the mechanism and kinetics of Cu corrosion in anoxic, aqueous, sulphide-containing environments are being investigated. Under these conditions ([S]total = 10 −4 to 3 ×10 −3 mol/L), the anodicgrowth ofa film (XRD identifies Cu 2 S/Cu 1.8 S as major/minor phases, respectively) is supported by the cathodic reduction of water thereby destabilizing the copper surface. For more oxidizing conditions, the subsequent growth of a partially passivating film is observed. Electrochemical impedance spectroscopy (EIS) and cyclic voltammetry at rotating disc electrodes show film growth occurringwith negligible dissolution and under partial SH - transport control. Current-potentialrelationships as a function of [S]total give Tafel slopes of ∼ (40 mV) −1 suggesting reaction occurs via a 2step process: Aninitial rapid adsorption of SH - leading to an equilibrium surface concentration, followed by a rate determining electron transfer to form a sulphide film. It is proposed thatfilm growth propagates via transport of Cu I through the film to the solution interface. The primary goal of this research is the development of a mathematical model which can be used to assess the performance of copper nuclear waste canisters in granitic repositories.

https://www.cambridge.org/core/services/aop-cambridge-core/content/view/S1946427400638204

J. Smith

Papers

Sulfide film formation on copper under electrochemical and natural corrosion conditions

Corrosion of Copper Nuclear Waste Containers In Aqueous Sulphide Solutions

The Electrochemistry of Copper in Aqueous Sulphide Solutions