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• As-cast and extruded MgZn x Ca y alloys were characterized by XRD, SEM, TEM and SKPFM. • The corrosion resistance of studied alloys was lower in media with organic species. • Daily solution replacement underestimates the corrosion rate of the systems. • Extruded alloy reveals a slightly higher corrosion degradation rate. • As-cast alloys show localized corrosion while extruded alloy corrodes uniformly. The aim of the present study is to evaluate the effect of alloy processing and composition as well as the pH control and testing medium on the in vitro corrosion performance of Mg Zn Ca systems for biodegradable implants. The grain size and secondary phases were analyzed by optical microscopy, scanning electron microscopy, transmission electron microscopy, and X-ray diffraction. Scanning kelvin probe force microscopy (SKPFM) was used to analyze the Volta potential values of the second phases. The corrosion performance of the three alloys was evaluated by electrochemical and hydrogen evolution methods in α-MEM with and without organic species (i.e. complete and inorganic α-MEM). Two strategies were followed to evaluate the influence of the pH on the corrosion behavior: daily solution replacement and CO 2 flow based pH control. For all the materials, the organic medium accelerates the corrosion process. Constant pH maintained by CO 2 flow through the medium results in considerably higher corrosion rates for all alloys. The impact of pH is lesser on the as-cast alloys due to the barrier effect of the secondary phases, particularly pronounced in the Mg1Zn1Ca alloy which showed the lowest corrosion rate. The wrought Mg0.5Zn0.2Ca alloy that lacks the refined secondary phase network and exhibits high number of twins undergoes accelerated uniform corrosion under constant pH conditions. [ABSTRACT FROM AUTHOR]

PEO coatings, aside from their reasonable corrosion protection, also feature a porous microstructure that can serve as a repository for corrosion inhibitors. This study presents and investigates the high corrosion inhibition effect of sodium salt of decylphosphonate (DP) when incorporated into PEO coating on a magnesium substrate. The interaction of DP with both bare and PEO-coated magnesium substrates was studied to understand its corrosion inhibition mechanism. Additionally, a strategy to enhance the active anti-corrosion ability of the DP-containing system was suggested and examined. The findings provide new insights into the potential of surfactants as corrosion inhibitors for magnesium alloys. • DP can significantly reduce the corrosion of both Mg and PEO coating. • interaction of DP with both bare and PEO coating is investigated in detail. • degradation of both Mg substrate and PEO promotes the inhibition effect of DP. • an approach to enhance active inhibition properties of DP was proposed and examined. [ABSTRACT FROM AUTHOR]

Highlights • Three high effective corrosion inhibitors are proposed for pure Mg containing a high level of Fe impurity. • Suppression of Mg dissolution or cathodic hydrogen evolution are defined as inhibition mechanisms for the chosen inhibitors. • Complex(es) can be formed between cathodic inhibitor molecule and Fe2+/Fe3+ impeding the re-deposition of Fe onto Mg surface. Abstract Three sodium salts of organic acids (2,5-pyridinedicarboxylic, 3-methylsalicylic and fumaric) were studied as corrosion inhibitors for pure magnesium containing a high level (342 ppm) of Fe impurity. The inhibition effect of the three inhibitors was evaluated by means of hydrogen evolution, electrochemical and surface analysis techniques. Significant reduction in corrosion rate was revealed for of the tested inhibitors in pH neutral NaCl electrolyte. 2,5-pyridinedicarboxylate and fumarate showed the effects characteristic for mixed-type inhibitors, while 3-methylsalicylate performed more as cathodic inhibitor, complying with the iron re-deposition model, where the electrochemical activity of iron-rich particles was effectively inhibited. [ABSTRACT FROM AUTHOR]