Development of water-repellent organic-inorganic hybrid sol-gel coatings on aluminum using short chain perfluoro polymer emulsion

摘要

The development of an organic-inorganic sol-gel coating system (thickness ～ 2 μm) on aluminum is reported. The coating uses glycidoxytrimethoxysilane (GPTMS) and methyltrimethoxysilane (MTMS) as silane precursors, crosslinked with hexamethylmethoxymelamine (HMMM) and followed by hydropho-bic modification using a water base short chain per-fluoro emulsion (FE). Such coating resulted in enhanced hydrophobicity with a contact angle of about 120° and sliding angle of 25° for a 20 μL water droplet. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements showed reduced corrosion upon coated substrates than the bare; correlated with both a higher degree of water repellency and formation of low permeable crosslinked sol-gel network. The structure of the coatings deposited was analyzed using Fourier transform infrared (FT1R) and X-ray photoelectron (XPS) spectroscopy, revealing replacement of hydrophillic surface hydroxyls groups with low energy per-fluoro groups.