Functionalization of Plasma Electrolytic Oxidation/Sol–Gel Coatings on AZ31 with Organic Corrosion Inhibitors

• Published in: Coatings (Basel) Vol. 14; no. 1; p. 84
• Main Authors: Pillado, Borja, Matykina, Endzhe, Olivier, Marie-Georges, Mohedano, Marta, Arrabal, Raúl
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 01.01.2024
• Subjects: Acids; Alloys; Chemical inhibitors; Chemical properties; Coatings; Composition; Contact angle; Corrosion and anti-corrosives; Corrosion inhibitors; Corrosion resistance; Corrosion tests; Electrochemical impedance spectroscopy; Electrolysis; Fourier transforms; Hybrid systems; Hydroxyquinoline; Immersion tests (corrosion); Infrared spectroscopy; Magnesium alloys; Magnesium base alloys; Oxidation; Oxidation resistance; Precursors; Prevention; Protective coatings; Rheological properties; Saline solutions; Sol-gel processes; Spectrum analysis; Structure; Water drops; Spain; France; United States > US; Japan; Germany
• ISSN: 2079-6412; 2079-6412
• DOI: 10.3390/coatings14010084

In this investigation, the sol–gel method is employed along with a corrosion inhibitor to seal a plasma electrolytic oxidation (PEO) coating, aiming to improve the long-term corrosion resistance of the AZ31 Mg alloy. Following an initial screening of corrosion inhibitors, 8-hydroxyquinoline (8HQ) is incorporated into the hybrid PEO/sol–gel system using two methods: (i) post-treatment of the PEO layer through immersion in an inhibitor-containing solution; (ii) loading the inhibitor into the sol–gel precursor. The characterization includes scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), ultraviolet-visible spectroscopy (UV-vis), and water drop contact angle measurements. The rheological properties of the inhibitor-loaded sol–gel precursors are assessed by measuring flow curves. The corrosion processes are evaluated in a saline solution through electrochemical impedance spectroscopy (EIS) and immersion tests with unscratched and scratched specimens, respectively. The results demonstrate the successful incorporation of the inhibitor for both loading strategies. Regardless of the loading approach, systems containing 8HQ exhibit the most favourable long-term corrosion resistance.