Evaluation of characteristics for microwave-assisted polymer coating of the steel substrate

Abstract

Abstract Polymeric barrier coatings are one of the most sought-after methods for protecting metallic parts from corrosion and for ensuring a glossy appearance. In this work, pure polyester barrier coating was applied on a steel substrate using a microwave-assisted curing process with an experimental design based on L9 Taguchi orthogonal array. It included three key factors, viz. voltage, powder output from the spray gun and microwave power with three levels of each. The heat required for curing was achieved through electromagnetic-thermal energy conversion with the aid of a graphite susceptor. A multi-physics numerical study was carried out to identify the magnitude of temperature attained at different levels of microwave power and irradiation time. This was used to build the microwave curing set-up. The impact of parametric variation of the microwave-assisted process on the gloss was quantified. In addition, an assessment of dry film thickness, corrosion resistance, and impact strength was performed. Taguchi analysis reveals that out of three factors used, microwave power has the most significant impact on the gloss units. The desired level of impact strength was achieved for all samples, with the exception of the one coated with the factor combination of the least levels. Corrosion resistance for specimens was measured to be 240 h using a standard salt spray test. Specimen prepared with larger power input showed lesser blistering. The results substantiate the feasibility of a microwave-assisted process route for the industrial coating process.