Robust network-like superhydrophobic magnesium hydroxide surface via cathodic electrodeposition with xanthan gum

Abstract

Economic cost of raw materials has become an important limiting factor for the further application of superhydrophobic surface. Magnesium hydroxide is an innocuous, antibacterial, eco-friendly, and especially cheap material. Superhydrophobic surface fabricated with magnesium hydroxide was safe, environment friendly, and of very low cost. However, magnesium hydroxide superhydrophobic surfaces prepared through traditional electrodeposition method was always fragile and easy to peel off substrate, due to the discontinuous platelet-like structure which led to weak mechanical property. In this work, we electrodeposited a robust network-like magnesium hydroxide layer on iron substrate under the structure direction of xanthan gum which formed network with helical conformation at low temperature and proper pH value in aqueous solution. Electrodeposition factors such as concentrations of xanthan gum and glucose, bath temperature, pH value of electrolyte and current intensity were studied. The magnesium hydroxide layer fabricated at the optimum condition (0.5 mol/L magnesium nitrate, 4 mg/L XG, 4 mg/L glucose, 2.6 pH value and 35 mA at 15°C for 20 min) was with network-like structure, and exhibited excellent superhydrophobicity (water contact angle, 153.56° sliding angle, 2.2°) and self-cleaning property after stearic acid modification. The robust layer kept superhydrophobic until 600 mm abrasion length facing 1000 grit SiC sandpaper under 100 g weight, and with detachment less than 5% after cross hatch tape adhesion test. The layer also demonstrated good long-term immersion stability, and was still superhydrophobic with 48 h immersion in 3.5 wt% NaCl aqueous solution at room temperature. The inhibition efficiency of the layer reached 99.03%, due to its extremely high corrosion resistance (Rct = 2.87 × 105 Ω/cm2, Rf = 2.53 × 106 Ω/cm2). The introduced method of electrodepositing robust network-like MH layer made the further application of low-cost superhydrophobic surface with magnesium hydroxide possible.