Surface Morphological and Chemical Features of Anticorrosion ZrO₂–TiO₂ Coatings: Impact of Zirconium Precursor

• Main Authors: Irina Stambolova, Daniela Stoyanova, Maria Shipochka, Nelly Boshkova, Alexander Eliyas, Silviya Simeonova, Nikolay Grozev, Nikolai Boshkov
• Format: Article
• Language: English
• Published: MDPI AG 2021-06-01
• Series: Coatings
• Subjects: composite sol-gel coatings; corrosion performance; hydrophobic properties; surface morphology; oxide films
• Online Access: https://www.mdpi.com/2079-6412/11/6/703

Dense, highly textured, hydrophobic ZrO₂-TiO₂ (1:1) coatings with amorphous structure were prepared using the sol-gel method. Both organic and inorganic zirconium precursor salts were used. The present study dealt with the investigation of their protective ability in a selected model corrosive medium with chloride ions as corrosion activators. The coatings showed good anticorrosion performance during the test, which was demonstrated both by the weight loss method and potentiodynamic polarization curves. The samples were characterized by means of X-ray diffraction (XRD), Atomic Force Microscopy (AFM), contact angle measurements, Infrared spectroscopy (IRS), Scanning Electron Microscopy (SEM), Differential Thermal analysis (DTA-TG) and X-ray photoelectron spectroscopy (XPS). It was established that the extent of influence of some factors, like treatment temperature (T_tr) and type of zirconium precursor, was different. The PD curves of samples treated at 400 °C (A4 and B4, respectively) demonstrated an increased effect of the precursor in comparison to T_tr, since the application of organic Zr salt led to deterioration of the anodic passivation zones. Contrary to this, the coatings obtained from both the organic and inorganic Zr precursor salts with T_tr = 500 °C had similar corrosion efficiency, i.e., the influence of the precursor was minimized. All investigated coatings had no visible corrosion damage. It seems that some complex structural and surface parameters, such as amorphous dense structure, surface smoothness, hydrophobicity and the surface chemical composition (low hydroxyl groups content), were responsible for the increased anticorrosion properties of the composite films.