Abstract: Method of one side spot welding of a metallic auto body construction containing vaporizable coatings or ingredients, the construction having overlapping metal plys, comprising: impinging a plasma column on a selected spot of one side of the construction, the plasma column being generated by passing a plasma gas at a predetermined flow rate through an electrical arc created by a predetermined electrical current path; shielding the plasma column in an inert gas containing at least 5-35% by volume of oxygen, the shielded plasma column melting at least the metal on one ply at the spot while the oxygen increases the fluidity and wetablility of the melted metal and reduce its surface tension allowing any vaporization of the ingredients to quiescently escape through the molten metal; and ceasing plasma arc impingement for allowing the molten metal to solidify and complete the spot weld.