In the paper a technique of surface treatment, micro-beam plasma-arc scanning, is reported. Surfaces of metals were melted by micro-beam plasma-arc and then self-quenched by the underlying substrates. The effects of surface treatment on the microstructure, wear and corrosion resistance of metals were investigated. The high self-quenching rates resulted in the refinement of microstructure, extended solubility of alloying elements, and even the formation of an amorphous structure. Wear and corrosion resistance of many alloys, particularly ferrous alloys, were improved. Reasons responsible for the effects are discussed. (C) 2003 Kluwer Academic Publishers.