Contact mark. Intermittent marks adjacent to the weld line resulting from the electrical contact between the electrodes supplying the welding current and the pipe surface.
触点痕。由于供焊接电流的电极与管子表面间的电接触，致使在焊缝线附近产生不连续痕迹。
2
It and reversing current different is not to be, but with a anode intermittently stop, because the intermittent power supply current interrupted, cathode potential with time periodically change.