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The adhesion or welding mechanism of an Ag-60Pd alloy during extremely short arcs on closure is investigated. The effect of oxygen on the adhesion is also examined under nonarcing conditions in an ultrahigh vacuum. The adhesion force and contact resistance are simultaneously measured under the conditions of a 10-g contact force, l-min contact duration, and 30-s contact interval. An Ag-60Pd alloy as well as Ag and Pd-Si alloy electrodes, whose surfaces are cleaned by Ar ion bombardment, are discharged by an R-C circuit in various atmospheres. It has been found that neither anode nor cathode arcs adhered the Ag-60Pd alloy over the voltage range of 50-400 V, which corresponded to arc energies of 300-10 000 ergs. The main cause of increase in adhesion is due to the surface cleaning effect of the short arc. The reason why adhesion in air is prevented by a cathode arc is considered to be due to surface oxidation because of the arc extinction before physical closure of the contacts.