DEVELOPMENT OF ZINC–ALUMINUM–TITANIUM NANOCOMPOSITES SUPPORTED ON BIO-WASTE ACTIVATED CARBON FOR COATING MILD STEEL AISI 1015

Abstract

Metal nanoparticles have been used in the past to coat mild steel against corrosion due to their outstanding mechanical and corrosion resistance properties. However, metal nanoparticles when used to coat mild steel without solid support or host matrix have shown some deficiencies such as micro cracking and pull-out of coatings from their substrates because of their inherent high surface energy which tend to make them coalesce to one another. Therefore, it is essential to trap these nanoparticles on a solid support when used for coating to help them stay away from each other for improved protection efficiency of nanomaterial coatings. This investigation was carried out on the development of zinc-aluminum-titanium (Zn–Al–Ti) nanocomposite supported on biowaste based activated carbon for coating of mild steel AISI 1015. Preparation of activated carbon from groundnut shell with percentage carbon yield of 50.04% was undertaken by chemical activation process, using ZnCl 2 as activating agent at optimized process conditions of 600 °C, 1.32 hours and 3, representing the activation temperature, activation time and impregnation ratio respectively. A quadratic model was developed to correlate the activation process parameters to the response (percentage yield) and it was observed that the activation temperature with F-value of 2413.99 had the most significant effect on the yield among the other process variables. Zn–Al-Ti metal nanocomposites supported groundnut shell activated carbon (GSAC) coatings were developed by hosting the metal nanoparticles on the GSAC, starting with Zn metal nanoparticles at three different mixture ratios of 75:25 %wt, 50:50 %wt. and 25:75 %wt. The GSAC/Zn-Al-Ti sample formulated at mixture ratio of 50:50 %wt. which gave the least average crystallite size of 35.24 nm was then loaded into epoxy resin at four different ratios of 1:1, 2:1, 3:1 and 4:1 and coated on mild steel. Porosity and micro hardness tests were carried out on the coatings. The least percentage volume of porosity of 0.5% was achieved with the 2:1 ratio coating while the maximum micro hardness value of 157 HV was recorded with the 4:1 ratio coating. Optimum resistance to the corrosion of mild steel coupon in 1M HCl was achieved using ratio 2:1, having recorded the least charge transfer resistance (R ct ) of 42.51 KΩcm and protection efficiency of 98.73%. 3