Multivariable analysis of electrodeposited silane based superhydrophobic coatings for corrosion protection of carbon steel

摘要

Superhydrophobic coatings are a field of great interest due to its many applications, including corrosion protection. Such films have been increasingly produced by coupling sol-gel processing with electrodeposition of silane precursors for the sake of its simplicity, controllability, variety of precursors, low toxicity, and low cost. However, despite of the method's sensitivity to process variables, current literature mostly reports univariate analysis, failing to provide their combined effect and relative importance on response variables. In order to fill this knowledge gap, this paper presents a screening design considering 11 independent variables, followed by a surface response design, to assess the water contact angle (WCA), film thickness, and impedance modulus of silane films electrodeposited onto carbon steel, under several conditions. Here, octyltriethoxysilane (OTES) was selected as one of the sol-gel precursors, since it presents a non-hydrolysable alkyl chain capable of providing low surface energy and consequently water repellence. Results pointed out pH and the ratio between the number of mols of OTES and tetraethoxysilane (TEOS) as key factors for achieving higher WCAs, while pH and the volumetric percentage of water in the deposition solution were the most relevant variables for film thickness. Improved deposition conditions led to WCAs and film thicknesses above 157 degrees and 70 mu m, respectively, while monitored impedance modulus at 0.01 Hz in NaCl 3.5 wt% solution were superior to 10(6) Ohm cm(2), even after 48 h of immersion.