Investigation of Ti/Al2O3 + TiO2 and Ti + TiO2/Al2O3 + TiO2 hybrid coatings as protection of ultra-light Mg-(Li)-Al-RE alloys against corrosion

Marcin Staszuk; Daniel Pakuła; Łukasz Reimann; Małgorzata Musztyfaga-Staszuk; Robert Socha; Tomasz Tański

doi:10.1038/s41598-022-23452-x

Investigation of Ti/Al₂O₃ + TiO₂ and Ti + TiO₂/Al₂O₃ + TiO₂ hybrid coatings as protection of ultra-light Mg-(Li)-Al-RE alloys against corrosion

Sci Rep. 2022 Nov 12;12(1):19363. doi: 10.1038/s41598-022-23452-x.

Authors

Marcin Staszuk¹, Daniel Pakuła², Łukasz Reimann³, Małgorzata Musztyfaga-Staszuk⁴, Robert Socha^{5

6}, Tomasz Tański²

Affiliations

¹ Department of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego Street 18A, 44-100, Gliwice, Poland. marcin.staszuk@polsl.pl.
² Department of Engineering Materials and Biomaterials, Silesian University of Technology, Konarskiego Street 18A, 44-100, Gliwice, Poland.
³ Materials Research Laboratory, Silesian University of Technology, Konarskiego Street 18A, 44-100, Gliwice, Poland.
⁴ Welding Department, Silesian University of Technology, Konarskiego Street 18A, 44-100, Gliwice, Poland.
⁵ Institute of Catalysis and Surface Chemistry PAS, Niezapominajek Street 8, 30-239, Kraków, Poland.
⁶ Centrum Badań i Rozwoju Technologii dla Przemysłu S.A., Ludwika Waryńskiego 3A, 00-645, Warszawa, Poland.

Abstract

Low corrosion resistance is a significant problem of magnesium alloys, particularly ultra-light magnesium-lithium alloys. Surface treatment is one way to improve their corrosion resistance. The paper presents the results of tests of Ti/Al₂O₃ + TiO₂ and Ti + TiO₂/Al₂O₃ + TiO₂ coatings obtained in a hybrid process combining PVD and ALD methods and ALD coating of Al₂O₃ + TiO₂ type obtained on AE42 (Mg-4Li-2RE) and LAE442 (Mg-4Li-4Al-2RE). Structural studies were performed using scanning and transmission electron microscopy (SEM and TEM), atomic force microscopy and EDS and XPS spectroscopic methods. Potentiodynamic tests and electrochemical impedance spectroscopy EIS in 0.05 M NaCl solution were performed to determine the electrochemical properties of the tested materials. Moreover, tests of surface wettability and tribological properties using the ball-on-disc method were performed. Based on the analysis of anodic polarisation curves and Tafel analysis, it was found that the Ti + TiO₂/Al₂O₃ + TiO₂ coating showed the best potentiodynamic properties on both substrates. In particular, on the magnesium-lithium substrate, the value of the polarisation resistance of this hybrid coating is R_pol = 14 × 10³ Ω × cm², and the value of the corrosion current is j_corr = 0.4 µA/cm². For the uncoated LAE442 substrate, the polarisation resistance is R_pol = 1.05 × 10³ Ω × cm², and the corrosion current value is j_corr = 5.49 µA/cm². This improvement is due to the synergistic effect of the combined PVD and ALD technologies. The study confirmed the impact of hybrid coatings on improving the anti-corrosion and tribological properties of ultra-light magnesium alloys.