Cr6+ reduction in welding fumes by nano composite coatings on stainless steel manual metal arc welding electrodes

A new manual metal arc welding electrode was developed using a nano composite coating on the core wire prior to flux coating. As fume formation rate (FFR) and hexavalent chromium (Cr(VI)) concentration in the welding fumes are trade off with each other, a concurrent method was attempted to reduce both. Al2O3 and TiO2 were used via nano coating as the arc stabilizers to reduce the fume formation rate and a tertiary material, a reactive metal oxide (ZnO) was coated to reduce hexavalent chromium concentration in the welding fumes. The collective behavior of all three materials brought out an effective reduction in both the fume formation rate and the Cr(VI) concentration in welding fumes. An effective reduction of Cr(VI) concentration in the welding fumes accounting to 47% with reasonable reduction in fume formation rate as well as other harmful constituents was achieved among the tested tertiary nano coated electrodes. The optimum combination of process parameters which favored the maximum reduction in Cr(VI) concentration in the welding fumes at the source was arrived using the Taguchi methodology of experimental design. The stability of the statistical model was verified and found adequate.