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The dissolution of magnesium (Mg) has been investigated with an electrochemical flow cell coupled to downstream analysis. The setup allows for polarization experiments and simultaneous determination of the amount of dissolved magnesium ions via inductively coupled plasma -mass spectroscopy (ICP-MS). Additionally, Mg dissolution was compared to hydrogen evolution measurements in the flow cell and also in standard beakers. Experiments were performed in unbuffered NaCl and in buffered solutions of various pH to determine the influence of the pH on surface film stability and Mg dissolution. In borate buffer (pH 10.5), Mg(OH) 2 was found to be more stable than in unbuffered electrolyte. In the flow cell, the negative difference effect (NDE) was absent for low anodic polarization currents in a neutral buffered solution, whilst high anodic polarization currents and unbuffered electrolytes favored its existence. In beaker experiments, strong NDE was observed in a pH 10.5 buffer, and also in pH 7 and 3 buffers, but only at higher applied currents where the buffering capacity was locally overwhelmed. These observations validate the importance of the pH in near surface regions with respect to the stability of Mg-surface films and subsequent NDE.

The electrolyte flow profile and reactive species concentration distribution are calculated for a Scanning Flow Cell (SFC) by means of finite element method numerical calculation using COMSOL Multiphysics software. In case of a simple one-step reaction with kinetic parameters close to those of the oxygen reduction reaction the applicability of conventional Koutecky-Levich (KL) analysis for the kinetic current calculations is proved. In addition, the influence of the cell geometry, particularly the angle between inlet and outlet tubes and the tube diameter, is investigated to guide the further optimization of the method. The applicability of the kinetic analysis is demonstrated experimentally on the example of oxygen reduction reaction.

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Corrosion inhibitors are added in low concentrations to corrosive solutions for reducing the corrosion rate of a metallic material. Their mechanism of action is typically the blocking of free metal surface by adsorption, thus slowing down dissolution. This work uses electrochemical impedance spectroscopy to show the cyclic oligosaccharide β-cyclodextrin (β-CD) to inhibit corrosion of zinc in 0.1M chloride with an inhibition efficiency of up to 85%. Only a monomolecular adsorption layer of β-CD is present on the surface of the oxide covered metal, with Raman spectra of the interface proving the adsorption of the intact β-CD. Angular dependent X-ray photoelectron spectroscopy (ADXPS) and ultraviolet photoelectron spectroscopy (UPS) were used to extract a band-like diagram of the β-CD/ZnO interface, showing a large energy level shift at the interface, closely resembling the energy level alignment in an n–p junction. The energy level shift is too large to permit further electron transfer through the layer, inhibiting corrosion. Adsorption hence changes the defect density in the protecting ZnO layer. This mechanism of corrosion inhibition shows that affecting the defect chemistry of passivating films by molecular inhibitors maybe a viable strategy to control corrosion of metals.