THE ALUMINUM ELECTROLYTIC CONDENSER 



61 



corrosion occurs, going up in some cases 20 or 30 times, but this 

 current again decreases and approaches the original value. The 

 capacity likewise increases when corrosion occurs, but this merely 

 lowers the impedance of the condenser which, in most cases, is not 

 objectionable. The performance of a condenser that has corroded 

 and continued to operate satisfactorily is shown in Fig. 15. The 

 curves on the chart show how the leakage current,' capacity and 

 resistance varied during continuous operation on a 65-volt d.c. 

 circuit over a period of two years, both before and after the anodes 

 were attacked by corrosion. 



TIME IN DAYS 



Fig. 15 — The performance of a condenser, the anodes of which were attacked by 

 corrosion after 62 days of operation at 65 volts direct current 



Under certain conditions it is possible for the products of corrosive 

 action to cause short circuits within a condenser, not by bridging 

 from the positive to the negative plates because the corrosion product, 

 aluminum oxide, is a non-conductor, but by accumulating between 

 the plates and forcing the positive plates out of position into contact 

 with the negative. 



Also if corrosion occurs on the positive terminals eating through 

 the supports one of the plates may drop and cause a short circuit. 

 These possibilities of trouble are minimized by suitable design, and 

 can be cleared up when they occur by removing the electrodes from 

 the solution and repositioning or removing the deranged anode 

 plates. 



