Optimization studies and characterization of advanced geopolymer coatings for the fabrication of mild steel substrate by spin coating technique

Abstract

Advance inorganic fly ash – metakaolin- phosphatic geopolymer has been developed via greener approach and deposited on mild steel substrate using spin-coating method, to improve the substrate-matrix interaction. The present research investigates the effect of incorporation of metakaolin and phosphate to geopolymer matrix to assess the performance of coating and optimization of spin coating parameters are performed as well to achieve maximum adhesion strength. XRD, FTIR, and SEM studies coupled with energy dispersive spectroscopy (EDX) have been carried out for determination of mineralogical phases, bonding interactions, substrate–matrix interface, and microstructural and chemical analysis.Results indicated that spin coating method produced well-ordered thin geopolymeric coating (thickness 13-20 micrometres), therefore spin coating deposition is the simplest way to obtain thin coatings of visibly thick materials. Maximum adhesion strength of material with substrate is 2.5M.Pa. which is obtained at optimized water to precursor ratio 0.5 at 500rpm spinning speed. It is concluded that new inorganic phases (originated from mutual contribution of phosphate, metakaolin and fly ash) like sodium iron aluminium phosphate, aluminium phosphate and sodium iron phosphate were responsible for good adhesion of material to the substrate and then related properties. The developed and optimized method can be used to produce homogeneous coating of heterogeneous geopolymer material on low carbon steel to indorse its advanced applications.