This invention relates to a method for gas metal arc welding of coated steels, and a shielding gas therefor, in which the method comprises: (a) forming an arc between a consumable wire electrode and a coated steel workpiece; (b) maintaining a substantially constant arc voltage between said consumable wire electrode and the coated steel workpiece; (c) feeding the consumable wire electrode through a welding torch contact tube into said arc; (d) transferring metal from the consumable wire electrode to the coated steel workpiece; and (e) shielding the arc with a gas mixture consisting essentially of: (i) from 6 to 10 volume percent carbon dioxide; (ii) from 6 to 10 volume percent helium; and (iii) the balance argon.