In this article physicochemical and thermo-physical properties of slags obtained from CaO–CaF2–SiO2–Al2O3 based shielded metal arc welding electrodes were investigated. The extreme vertices design methodology was used to prepare twenty-one coating compositions. Multi-pass beads were applied on the P22 low alloy steel plate. The welding slag for each weld bead was collected. Experimentation's on welding slags have been performed to estimate the weight loss, density, specific heat, enthalpy, thermal conductivity and diffusivity. X-Ray Diffraction (XRD) and Fourier transformation infrared spectrometry (FTIR) was performed to analyses the different phases present in slag. Thermogravimetric Analyzer (TGA) and hot disc apparatus have been used to characterize the slag's thermal properties. The regression analysis has been used to study the effect of coating constituents on the slag properties. The obtained output of properties has been further optimized using multi-response optimization. © 2019 Elsevier Ltd and Techna Group S.r.l.