Hydrophobic polyvinyl butyral/polytetrafluoroethylene composite coating on 5052 aluminum alloy: Preparation, characterization, and anticorrosive properties

To enhance the corrosion resistance of metal, the current investigation employed polyvinyl butyral (PVB) as the intermediate bonding layer and polytetrafluoroethylene (PTFE) as the hydrophobic surface layer to prepare a PVB/PTFE composite coating on the surface of 5052 aluminum alloy (5052AA) through a simple dipping and pulling method. The optimum preparation process, microstructure, surface characteristics and anticorrosion properties of the PVB/PTFE/5052AA were characterized and analyzed by means of field emission scanning electron microscope (FESEM), confocal laser scanning microscope (CLSM), contact angle measuring instrument and electrochemical techniques. The findings showed that the optimal preparation process involved a PVB dosage of 0.7 g, a PTFE mass fraction of 20 %, and a sintering temperature of 150 °C. The surface of PVB/PTFE/5052AA presented a morphology of interwoven nanobelts, with a water contact angle (WCA) of 133.8° ± 0.4°, indicating the transformation from hydrophilic to hydrophobic. Furthermore, the composite coating exhibited good chemical stability, mechanical robustness, and its surface could be transformed from hydrophobic to superhydrophobic after tape peeling. Electrochemical studies revealed that the low-frequency |Z| value of PVB/PTFE/5052AA was higher than 108 Ω·cm2, and the phase angle was close to −90° over a wide frequency range. Moreover, after being immersed in NaCl solution for 48 h, the water absorption of the composite coating remained at a low level of about 2.7 %. These results demonstrate that PVB/PTFE is a promising composite coating with broad application potential.