Spray pyrolysis of thin adhesion-promoting ZnO films on ZnMgAl coated steel

The presented work focuses on the effect of the deposition of zinc oxide layers by means of spray pyrolysis on the electrochemical and adhesive properties of ZnMgAl-alloy coated steel (ZM). Films were spray coated from aqueous solutions onto substrates at a bulk temperature of 553 K. Film coated substrates were characterized by field emission scanning electron microscopy (FE-SEM), X-ray photoelectron spectroscopy (XPS), and Raman spectroscopy as well as cyclic voltammetry. Even at small thickness values, the deposited ZnO films show a homogeneous coverage. XPS data revealed the existence of surface carbonate and hydroxyls groups. Peel-tests at high water partial pressure showed that the peel force of epoxy adhesives could be increased from 50 N/m to about 200 N/m based on the ZnO thin film deposition. Finally, cyclic voltammetry revealed an effective inhibition of electrochemical reactions at the electrolyte/oxide interface attributed to the as-deposited ZnO-films. •ZnMgAl-alloy coated steel was spray coated with ZnO films.•Spray pyrolysis led to homogeneous coverage at low film thickness.•Film deposition rate was 29 nm/s.•Structure-property relationship could be established.•Significantly improved adhesive properties are achieved at film thicknesses (