Dry cleaning of metal surfaces by a vacuum arc

The cathode spots of a vacuum arc have ‘smart’ properties such as preferential attack against oxides and selective removal of them. Recently they have been used for cleaning and roughening of metal surfaces before coating or surface modification. Based on a simplified model of the energy balance at the cathode spot, the author investigated the removal rate of an oxide layer as well as the roughening of the surface. The current density at the cathode spot affects the removal rate and the surface roughness. A theoretical analysis reveals that the removal rate increases proportionally to the arc current and decreases inverse proportionally to the thickness of the oxide layer. The surface roughness is predicted to decrease with the increase of the current density. A novel apparatus has been developed to remove metallic oxides on a metal surface in a manner friendly to the environment. By using a convenient cleaner cup, a local area to be treated can be cleaned quite easily in a short time.