Optimization of multiple outputs of electric arc spray coating parameters for EN AW 7020-T6

Electric arc spray coating (EASC) is a method used to protect aluminum materials from corrosion, but there is no optimization in the literature using Al99.99 coating wire for EN AW 7020 alloy. The presented study aims to optimize the EASC process parameters (voltage, amperage, spray distance, and number of passes) for EN AW 7020-T6 aluminum samples. The experimental design of selected factors was made with Taguchi L 9 (3 4 ) orthogonal array and the aftermath of optimum values for coating were obtained with the TOPSIS multicriteria decision-making method. Output parameters respectively; pull-off strengths of coating were determined in compliance with the ASTM D4541 standard, the coating thicknesses were measured with a 3D profilometer, and the porosity values for cross-section were analyzed by optical microscope according to ASTM E2109 standard. After determining the optimum parameters, the substrates were coated and the crystallographic analysis of the coated samples was performed by XRD technique and electrochemical corrosion potential values were determined by galvanostat/potentiostat device in 3.5% NaCl solution. In exfoliation corrosion (EXCO) tests performed according to ASTM G34-1 standard, EXCO damage was detected on the surfaces of uncoated samples and graded as EA. In the EXCO tests with coated samples, no corrosion damages were observed on the coatings and they were rated with an N grade. The Al99.99 coating significantly improved the EXCO resistance of EN AW 7020-T6, reducing the corrosion rate by almost 100%. EXCO tests with uncoated and coated samples proved that the Al99.99 coating acts as a barrier to protect the substrate. Optimized Al99.99 coating offers a promising solution to improve the corrosion resistance of EN AW 7020-T6 aluminum alloys and extend their service life in harsh environments.