*3.2. High Speed Imaging*

Figure 6 shows the high speed frames for the standard GMAW and CW-GMAW inside the grooves. As suggested by the electrical signals, it was possible to verify that the arc for the GMAW often attaches to the sidewalls, thus eroding it. The same author claims that the arc attachment was avoided when welding in constant current mode, since, in these sources, to maintain and almost constant melting speed, the voltage highly varies. Meanwhile, in CW-GMAW, the arc attachment was to the cold wire, which prevents sidewall erosion. In Figure 6a, one can discern that the arc is pinned to the rear (cold wire) and not to the sidewalls.

**Figure 6.** High speed frames, arc dynamic behavior inside the groove: (**a**) standard GMAW; and (**b**) CW-GMAW.
