Preparation of super-hydrophobic and corrosion resistant colored films on chemically etched 304 stainless steel substrate

A colored super-hydrophobic surface on stainless steel substrate was achieved by means of chemical coloring on etched substrate combined with modification by fluorosilane. Effect of chemical etching with HCl and FeCl3, and of passivation treatment for the etched substrate by H2O2/HNO3 on coloring behavior, micro-structure, chemical composition, wettability, mechanical durability and corrosion resistance of the surface was studied using spectrophotometry, water contact angle measurements, SEM, XPS, micro-fretting tests, potentiodynamic polarization and corrosion morphology observation. Etching was found to slow coloring speed and make the end color shift to the anti-clockwise direction in CIE coordinate. An orange super-hydrophobic surface with water contact angle of 152.6° and sliding angel of 8.9° could be realized on the 20-min etched substrate via subsequent coloration and fluorosilane modification, which showed improved corrosion resistance and durability under fretting wear compared with ordinary colored film formed on non-etched substrate. In spite of leading to a slight decreasing of water contact angle, oxidation treatment by H2O2/HNO3 for the etched substrate before coloring could further improved corrosion resistance and fretting contact durability of the finally got colored surfaces with fluorosilane layers, and the enhancement effect brought by H2O2 was found to be more remarkable in comparison to HNO3.