The influence of parameter settings on cathodic self-etching during aluminum welding

Cathodic self-etching is a mechanism that has been used for a long time to make feasible the GTA welding of aluminum, by cleaning the metal surface in real time. The use of power supplies with rectangular wave AC output has extended the efficiency of the phenomenon. The objective of this work is to gain further insight into this matter. A study of the influence of the power source output parameters and travel speed on cathodic etching and, consequently, on welding geometry and arc stability is presented. An experimental design based in the robust design technique was applied to make the number of experiments affordable. The obtained tendencies were confirmed by validation experiments and comparison with the results of other authors: The results suggest the beneficial effect of a short electrode positive duration and increasing travel speed on oxide cleaning. Too effective cathodic etching leads to arc instability during polarity reversal. The negative electrode amplitude and duration does not govern this aspect, yet they govern the bead geometry. Finally, a theoretical explanation of the phenomena is proposed.