EFFECT OF RELATIVE HUMIDITY, HEATING RATE AND FILM THICKNESS ON THE CRACKING ONSET TEMPERATURES IN ZRCONA SOL GEL THINFILMS DERIVED ON 316L SS SUBSTRATE

In this research, a sol-gel dip coating process has been used to derive zirconia (ZrO2) nanostructured thin films on 316L stainless steel substrate, using zirconium acetate hydroxide as precursor. Microstructural features and phase crystallization of the synthesized thin films were characterized by Fourier transform-infrared spectroscopy (FT-IR), X-ray diffractometry (XRD) and scanning electron microscopy (SEM). FTIR in corroboration with X-ray studies confirm the crystallization of tetragonal (t-ZrO2) and monoclinic (m-ZrO2) zirconia phase at 700 °C and 900 °C temperatures, respectively. SEM studies showed that the cracking onset temperature decreased with increasing relative humidity and film thickness, while it increased with heating rate until 5 °C/min and then decreased. Electrochemical investigations on these parameters demonstrated that the 3-layered coatings in 25% relative humidity with a heating rate of 5°C/min had the strongest corrosion barrier performance on the 316L stainless steel.

Keywords:

Sol-gel , ZrO , thin films , 316L SS , humidity , corrosion behaviour