The aim of the master’s thesis was to verify the possibilities of improving the corrosion resistance of magnesium substrates through a combination of plasma electrolytic oxidation (PEO) and subsequent sealing of the resulting porous layers using Mg–Fe layered double hydroxides (LDH). The theoretical part summarizes the properties of magnesium and its alloys, their corrosion behavior, and surface treatment options, including PEO coatings and the characteristics of LDH materials.
Experimentally, PEO coatings were prepared on the ZE41 magnesium alloy, onto which precursor layers were subsequently deposited and further processed to form MgFe-LDH. The preparation conditions were optimized.
The morphology and composition of the individual layers were analyzed using scanning electron microscopy with energy-dispersive spectroscopy (SEM-EDS), and their phase composition was determined by X-ray diffraction analysis (XRD). Corrosion properties were evaluated electrochemically using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).
The results showed that optimized LDH layers derived from a sulfate precursor (3 h) effectively seal the pores of the PEO coating and enhance the corrosion resistance of the Mg substrate in short-term tests (Ecorr -1450 mV, icorr 0,5 μA∙cm-2) compared to the unsealed PEO coating (Ecorr -1560 mV, icorr 4,27 μA∙cm-2). In contrast, under long-term exposure to the corrosive medium, the LDH/PEO system exhibited a decrease in corrosion resistance compared to the PEO coating alone (from Rp 25994 Ω∙cm-2 to 13478 Ω∙cm-2). This is likely due to structural degradation and the formation of defects facilitating ion transport. A negative effect may also be attributed to the low thickness of the LDH layers.