In addition to aluminium and titanium alloys, the magnesium alloys comprise the group of lightweight alloys which have the highest practical importance in structural applications. The WE43 alloy with the addition of rare earth elements and yttrium is used mainly for the sand mould castings for the aerospace industry. The castings for aerospace industry have complicated shapes and varying wall thickness, as a result of which they often have casting effects such as misruns, micro-shrinkages and cracks. The frequency of defect occurrence in the complicated shape casting may exceed 50%. The defects are repaired by means of welding and pad welding. Such practice is often used in foundries. The paper presents the results of repair evaluation of the WE43 alloy castings in the as-cast state by means of the TIG welding. The welding tests have been performed on the joints bevelled to “I”, “Y” and “V” and the technological repair guidelines have been formulated. The defect has been repaired and the non-destructive and structural tests have confirmed that the technology is correct. The WE43 alloy should be welded and pad welded with maximum linear arc energy of 3.0 kJ/cm, straight beads, with filler metal of a similar chemical composition, in the as-delivered state.