Development of superhydrophobic coatings on AISI 304 austenitic stainless steel with different surface pretreatments

In the context of increasing industrial importance of superhydrophobic surfaces, three different pretreatments on an austenitic stainless steel surface have been tested to be coated with a silane-based solution containing SiO2 nanoparticles, in order to obtain superhydrophobic surfaces. The pretreatments are (i) an acetone degreaser, (ii) this one followed by a hot air treatment and acid pickling, and (iii) the previous one followed by an alkaline etching. Pretreated surfaces have been characterized by X-ray photoelectron spectroscopy, tapping-mode atomic force microscopy and contact angle measurements. After the three pretreatments, a solution of methyltrimethoxysilane and tetraethoxysilane in white spirit solvent and 1% of SiO2 (% by wt.) has been used to prepare a superhydrophobic coating on them. The hydrophobicity of the developed coatings has been studied using water contact angle measurements (static angles and advancing and receding angles). Besides, scanning electron microscope has been used to study the coatings. The results show that different tailored surfaces can be obtained in stainless steels using these pretreatments, obtaining surfaces that exhibit different physicochemical characteristics that may condition the formation of superhydrophobic coatings on them.