Fabrication of superhydrophobic surfaces with hierarchical structure through a solution-immersion process on copper and galvanized iron substrates

Superhydrophobic surfaces were obtained on copper and galvanized iron substrates by means of a simple solution-immersion process: immersing the clean metal substrates into a methanol solution of hydrolyzed 1H,1H,2H,2H-perfluorooctyltrichlorosilane (CF3(CF2)(5)(CH2)(2)SiCl3, FOTMS) for 3-4 days at room temperature and then heated at 130 degrees C in air for 1 h. Both of the resulting surfaces have a high water contact angle (CA) of larger than 150.0 degrees as well as a small sliding angle (SA) of less than 5 degrees. The formation and structure of the superhydrophobic surfaces were characterized by means of scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), X-ray photoelectron spectroscopy (XPS), and energy-dispersive X-ray spectrometry (EDX). SEM images showed that both of the resulting surfaces exhibited special hierarchical structure. The special hierarchical structure along with the low surface energy leads to the high surface superhydrophobicity.