In the last decades, several anodizing processes for Mg alloys have been proposed to achieve a good wear and corrosion resistance combination. In particular, Electro-Chemical Oxidation (ECO) showed an improved dense and compact anodized layer compared to other anodizing processes carried out above the dielectric breakdown voltage, such as Plasma Electrolytic Oxidation (PEO). However, the influence of the ECO treatment on the tribological behavior and cyclic mechanical performance of Mg alloys has not been investigated yet. This paper reports on the influence of ECO on dry sliding behavior (vs. 100Cr6 bearing steel (block-on-ring contact geometry)) and rotating bending fatigue performance of the rare earth (RE)-containing Mg alloy EV31A-T6, comparing it with both untreated EV31A-T6 and PEO-treated EV31A-T6, used as benchmarks. The ECO-treated alloy showed improved tribological behavior (critical load for coating failure one order of magnitude higher and coefficient of friction 40% lower than for PEO) and fatigue strength (no decrease for ECO-treated samples compared to the untreated alloy, while PEO-treated samples induced a 15% decrease) due to the increased compactness and lower defectivity of the anodized layer, induced by the minimization of destructive arc discharges during coating growth. In addition, the ECO treatment significantly improved wear resistance compared to the untreated alloy, avoiding, at the same time, the decrease in fatigue strength, which typically occurs after PEO. Therefore, the ECO process can be applied to improve wear resistance without decreasing the fatigue strength of high-performance components.

This study evaluates the effectiveness of a silica preceramic polymer for joining and coating Plasma Electrolytic Oxidated (PEO) aluminum components at temperatures below 200 °C. PEO aluminum slabs were coated and joined with a silica precursor polymer (Durazane1800, Merck, Darmstadt, Germany), both with and without the addition of 48 wt% silica nanoparticles, and cured at 180 °C for 4 h in air. Thermogravimetric analysis assessed the curing process and thermal stability, while X-ray diffraction confirmed the polymer’s conversion to amorphous silica after heating at 1200 °C. Resistance to humid environments was tested by soaking coated samples in tap water for a week, with no mass variation observed. Mechanical testing through tensile mode and tensile lap tests showed that adding 48 wt% silica nanoparticles significantly improved joint cohesion and nearly quadrupled mechanical strength. Fracture surfaces were examined using Field Emission Scanning Electron Microscopy, and composition analysis was performed with Energy Dispersion X-ray Spectroscopy. Crack detection was conducted using Computer Tomography with an in situ bending test setup to obtain the mechanical resistance of the PEO coating. The results indicate that the silica preceramic polymer is suitable for joining and coating PEO aluminum components, with silica nanoparticles enhancing mechanical strength and providing excellent thermal stability and resistance to humidity.