The objectives of this study were to reduce the corrosion rate and increase the cytocompatibility of AZ31 Mg alloy. Two coatings were considered. One coating contained MgO (MAO/AZ31). The other coating contained Cu2+ (Cu/MAO/AZ31), and it was produced on the AZ31 Mg alloy via microarc oxidation (MAO). Coating characterization was conducted using a set of methods, including scanning electron microscopy, energy-dispersive spectrometry, X-ray photoelectron spectroscopy, and X-ray diffraction. Corrosion properties were investigated through an electrochemical test, and a H2 evolution measurement. The AZ31 Mg alloy with the Cu2+-containing coating showed an improved and more stable corrosion resistance compared with the MgO-containing coating and AZ31 Mg alloy specimen. Cell morphology observation and cytotoxicity test via Cell Counting Kit-8 assay showed that the Cu2+-containing coating enhanced the proliferation of L-929 cells and did not induce a toxic effect, thus resulting in excellent cytocompatibility and biological activity. In summary, adding Cu ions to MAO coating improved the corrosion resistance and cytocompatibility of the coating.

The pitting corrosion of some stainless steel alloys (preoxidized at different conditions) in 3.5% NaCl solution was studied. The alloys are: one ferritic (15.05% Cr) (alloy1) and two austenitic stainless steel alloys (17.9% Cr,7.08% Ni) (alloy2) and (20.45% Cr, 8.3% Ni) (alloy3). Potentiodynamic anodic polarization and galvanic current-time measurements were used in these investigations. The susceptibility of the alloys to pitting corrosion decreases with the increase of chromium content of the alloy and with the presence of nickel in the alloy. The preoxidation of the alloys in different media improves their resistance to pitting corrosion in NaCl solution. The resistance to pitting corrosion for the investigated alloy increases according to the order: no oxidation < oxidation in air < oxidation in molten alkali nitrates < oxidation in molten alkali carbonates. This resistance to pitting corrosion may be due to the formation of a protective oxide film on the alloys' surface. The composition of this film greatly depends on the chemical composition of the alloy, on the condition of the preoxidation process, and on the temperature.

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