Fabrication of Ultrahydrophobic Epoxy Coating Modified by SiO2-PDMS for Corrosion Protection and Self-Cleaning

In this work, ordinary epoxy coatings were modified by hydrophobic nanoSiO2 and hydroxyl PDMS to construct ultrahydrophobic epoxy coatings for corrosion protection and self-cleaning of phosphatized Q235 carbon steel. Ordinary epoxy polymer coating was fabricated via polyaddition reaction between E44 (bisphenol A epoxy resin oligomer) and DDM (4,4-diaminodiphenyl methane). The microscopic morphologies of coatings showed that many SiO2 nanoparticles were presented on the surface of ultrahydrophobic epoxy coating. Through static water contact angle measurement, the modified epoxy coating displayed ultrahydrophobicity with a water contact angle of approximately 150°. However, adding too much nanoSiO2 caused cracks on the modified epoxy coating, which deteriorated the corrosion resistance of the coating. According to the corrosion test results, the modified coating added with 6.7 wt% hydrophobic nanoSiO2 and chemically modified with hydroxyl PDMS showed the best corrosion protection performance, which was reflected by the high impedance of approximately 109 Ω·cm2 after 50 d immersion in 3.5 wt% NaCl (aq.). Besides, the coating also presented good self-cleaning performance. The coating extracted from the slurry still remained clean without any contamination.