A protection cover suitable for being placed between a spray nozzle and a metal part during a process of resurfacing the metal part, the protection cover including a side wall extending along a reference axis, the side wall including an inner surface and an outer surface, the side wall having a lower end and an upper end, the side wall being perforated by at least one lateral gas inlet port, the lower end of the side wall being perforated by a notch into which a portion of the metal part can be inserted, the upper end of the side wall being provided with an opening into which a portion of the spray nozzle can be inserted. The inner surface of the side wall includes at least one frustoconical portion.