Oxidation Performance of ZrO2 Sol–Gel Coatings on P91 Steel in a High-Temperature Vapor Atmosphere

Abstract The aim of the present work was to evaluate the oxidation performance of ZrO 2 sol–gel coatings deposited on the P91 ferritic steel and exposed to a high-temperature–water vapor atmosphere. Sols were prepared from zirconium propoxide and an acetic/nitric acid mixture as a complexing/catalyst system. ZrO 2 coatings were obtained by dip coating varying the aging time between 0 and 21 days before sol deposition. The gelation process was investigated by rheological tests, pH measurements, and FTIR, whereas the coatings were characterized using ATR-IR, SEM, and XRD. Finally, the oxidation performance of the coatings was evaluated in an air atmosphere with 10 vol% water vapor at 650 °C for periods of up to 192 h. The obtained ZrO 2 coatings exhibited excellent oxidation performance for all the aging and exposure times evaluated. Despite this, residual oxide nodules were observed in some cracked regions of the coatings, with no significant influence on their oxidation resistance.