ACTIVATIOX OF ELECTRICAL CONTACTS BY ORGANIC VAPORS 793 



The sort of erosion produced by the different types of ares is shown 

 in the somewhat conventionahzed sketches of Fig. 8. These sketches 

 represent cross-sections of the square mating areas (about 1.3 mm on a 

 side) of heavj^ type U relay palladium contacts. The contact contours 

 are drawni to scale after the metal transfer resulting from repeated arcs 

 with a total energy of 10^ ergs, using the values of Table II to convert 

 this energy into volumes of metal. The mounds and pits produced by 

 inactive anode arcs and by inactive cathode arcs are assumed to be 

 spherical segments, each having a height equal to half its radius. The 

 smooth erosion resulting from active arcs would have depths which do 

 not show up at all on the scale of this figure. For each electrode in each 

 of the four cases, the erosion is less than 2 per cent of the total volume 

 of the metal of the contact, and represents a fairly early stage in the ex- 

 pected contact life. The electrode separations at which arcs occur corre- 

 spond respectively to fields of 8 X 10^ 4 X 10^ and 0.5 X 10^ volts/cm. 

 The striking voltage is assumed to be 50 and the separations are drawn 



SEPARATION 



SCALE 



CATHODE S 



INACTIVE 

 ANODE ARCS 



^ANODE 



CATHODES 



INACTIVE 

 CATHODE ARCS 



; ANODE 



ACTIVE 

 ARCS 



Fig. 8 — Erosion produced by anode arcs at clean surfaces, bj^ inactive cathode 

 arcs and by active arcs of either type, the total energy in each case being 10^ 

 ergs. The electrode separations at which these arcs strike correspond to 50 volts 

 and are represented here on a greatly expanded scale. 



