HYDROPHOBIC SURFACE OF Zn-Al-WO3 HOT DIPPED GALVANISED COATING MODIFIED WITH DIFFERENT MOLARITY OF STEARIC ACID

Abstract

Hot dip galvanizing is the oldest and most cost-effective corrosion resistance method for steel, acting as both a physical barrier and a sacrificial effect. Galvanised steel, on the other hand, corrodes when exposed to harsh environments over time. Thus, increasing the hydrophobicity of galvanised steel can reduce corrosion rates and increase service life. The purpose of this study is to investigate the effect of stearic acid on the formation of a hydrophobic structure of Zn-Al-WO3 on mild steel. Hot dip galvanizing was used to coat the Zn-Al-WO3 on mild steel. The coated sample was surface treated with stearic acid in varied molarities ranging from 0.002 to 0.05 M. The surface treated coating was analyzed using scanning electron microscopy (SEM), field emission scanning electron microscopy (FESEM) equipped with energy dispersive X-ray (EDX), water contact angle (WCA), and atomic force microscopy (AFM). The corrosion resistance after surface treatment was assessed using the potentiodynamic polarization method in a 3.5% NaCl solution. The results demonstrate that the 0.008 M stearic acid had a greater WCA at 122.29o with a surface energy of 10.42 mJ.m-2. This 0.008 M stearic acid also provided the best surface roughness and corrosion rate, with minimum values of 21.30 nm and 0.707 mmyr-1, respectively. This study found that 0.008 M is the ideal concentration of stearic acid for modifying the hydrophobic surface and can be employed for Zn-Al-WO3 galvanised coating.