Influence of the coating type in the electrode life in spot welding

The influence of the coating type in the electrode life in spot welding of pure Zn (GI) and Zn-Fe alloy (GA) coated IF (interstitial free) steels was evaluated. The electrode life was estimated and the behavior of the Zn of the coating in the steel/electrode contact surface during electrode life was determined using SEM/EDS analysis. The electrode life in the welding of GA steel was greater than in the welding of GI steels. The results showed that in the GI coating, the layer, probably, is melted. A part of this melted layer penetrates into the electrode and the rest moves to the electrode/steel contact in the beginning of the electrode life. With the increase in the number of welds, the Zn do not tend to move to the border, due to the reduction of current density and the electrode wear caused by its contamination. The GA coating did not present displacement of the Zn from central area to the periphery of the spot weld during the electrode life, attributed to the high fusion point of the coating.