Influence of surface pretreatments on composition, structure and corrosion performance of zirconium conversion coating applied to AA7075-T6Šekularac, Gavrilo (Avtor) Kovač, Janez (Avtor) Milošev, Ingrid (Avtor) surface pretreatmentetchingdesmuttingThe effect of chemical pretreatment of aluminium alloy 7075-T6 on the composition, morphology, and structure of zirconium conversion coatings (ZrCC) was investigated. Chemical pretreatments included: (i) alkaline etching and desmutting using commercial reagents, (ii) alkaline etching using sodium hydroxide, (iii) acidic etching using nitric acid, (iv) desmutting using a commercial reagent and boiling in deionised water, and (v) alkaline etching and desmutting using nitric acid. ZrCCs were deposited at room temperature from a 200 ppm H2ZrF6 solution of pH 4.8. A commercial SurTec® coating containing zirconium and trivalent chromium was used as a benchmark. The electrochemical behaviour was evaluated using potentiodynamic polarisation measurements and electrochemical impedance spectroscopy conducted over a minimum of 5 days and up to 15 days in 0.1 M NaCl. Corrosion resistance was further assessed through immersion testing. Microstructural characterisation was performed using scanning electron microscopy with energy-dispersive spectroscopy, X-ray photoelectron spectroscopy, and time-of-flight secondary ion mass spectrometry. The SurTec® pretreatment of AA7075-T6 activated the self-sealing of the subsequently deposited ZrCC, about 40 nm thick, which exhibited the highest degree of compactness and uniformity. This study showed a significant impact of surface chemical pretreatment on the microstructural and protective properties of ZrCCs deposited on 7075 alloy.IOP Publishing 20252025-11-18 12:48:48Neznano24177Združeno kraljestvosl© 2025 The Author(s).