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Highlights: [•] The cathodic dissolution of pure Al and AA6061 aluminum alloy is measured. [•] Cathodic dissolution of Al occurs with a stoichiometry of 4.62±0.22 OH−/Al3+ over several orders of magnitude of cathodic current. [•] Cathodic dissolution of SiO2 observed at high cathodic current. [•] Mg2+ species precipitated on the surface perhaps in the form of MgSiO3. [•] Al n [Fe m ,Mn1−m ]Si phases serve as local cathodes forming “trenches” around the intermetallic particles. [ABSTRACT FROM AUTHOR]

The origins of the second anodic current peak in polarization curves of AISI430 (UNS S43000) stainless steel in deaerated 0.1 M sulfuric acid (H2SO4) have been investigated by potentiodynamic polarization and atomic emission spectroelectrochemistry (AESEC). The elemental dissolution rates of Fe, Cr, Ni, Cu, and Mn were measured in real time during linear potential sweep voltammetry, revealing the formation and dissolution of a copper-rich corrosion product layer. The deposition and subsequent dissolution of this copper layer is proposed to be the main cause of the second anodic current peak. The negative current loop observed after the first anodic peak is attributed to the cathodic reduction of H+ ion on the copper-enriched layer. Other factors such as the oxidation of the adsorbed H atoms on the copper-enriched layer and the presence of chromium-impoverished grain boundaries are shown to have a negligible effect on the second anodic current peak. [ABSTRACT FROM AUTHOR]

Abstract: Atomic emission spectroelectrochemistry (AESEC) was used to quantify simultaneously the rates of Sn dissolution and SnO2 film formation for Sn and Sn coated steel in carbonate solution at pH 11.2. The technique is demonstrated by applying different potentiostatic treatments (variable potential and time) and measuring the amount of oxide formed and Sn dissolved during the treatment, and subsequently measuring the open circuit dissolution rate following the treatment. It is observed that the degree of passivation is a strong function of potential and time. Cathodic and low potential anodic potentiostatic treatments lead to a dissolution–precipitation mechanism that does not significantly passivate the surface. The stability of the passive film was investigated as a function of the quantity of oxide generated. [Copyright &y& Elsevier]

Abstract: The polarization behaviour of zinc in alkaline solution has been investigated using atomic emission spectroelectrochemistry. By independently measuring the oxidation rate of zinc (electrical current) and the rate of Zn2+ dissolution (partial elemental current) it is possible to calculate the amount of insoluble zinc cations produced at any instant. Assuming the insoluble cations are present as a zinc oxide film, the growth of this film as a function of potential and time was determined. On the basis of kinetic evidence, it was found that at least three forms of zinc based oxide/hydroxide films form during polarization experiments. Type I oxide formation occurs when the metal/electrolyte interface becomes locally saturated with Zn2+ ions. Type II oxide forms on the metal surface underneath the film of Type I oxide but has little inhibiting effect on zinc dissolution. Type III oxide is produced in much smaller quantity and results in a transition to the passive state. This may be due to a potential induced transition of Type II→Type III oxide. [ABSTRACT FROM AUTHOR]

Abstract: Atomic emission spectroelectrochemistry (AESEC) was used to monitor the release of Al from 99.99% aluminum (1199 alloy) and Al, Mg, and Cu from 2024 Al alloy in 30g/l NaCl electrolyte as a function of pH. The cathodic dissolution of Al was demonstrated and attributed to an increase in the pH at the interface due to the water reduction reaction. The dissolution of Mg was also observed but was a more complex function of current probably depending on the interfacial pH and the Al dissolution rate. The detachment of copper-rich particles was observed as very rapid spectroscopic emission transients (peak width<10ms). [Copyright &y& Elsevier]