This article describes the common defects associated with arc welds in the weld metal and the heat-affected zone (HAZ) of the plate. These defects include porosity, incomplete fusion, hot cracks, lamellar tearing, undercut, rollover, and inclusions. The article details hydrogen-induced cracking and its mechanism as well as the control measures. It provides information on measurement of hydrogen in weld metal and presents a table that contain information on effect of welding processes and electrodes on hydrogen levels in welds.