The level of reduction of the DC voltage component across an anodizing or electroplating tank may serve as a measure of efficiency of depolarization caused by a particular pulse waveform. The spectacular reduction from 40-70 VDC, when hard coating with straight DC, down to 12-14 VDC, when hard coating with DC+AC, is an impressive demonstration of how large the voltage difference can be. In the latter case, DC+AC is generated by a resonant anodizing power supply (RAPS), that superimposes a nearly sinusoidal AC voltage of industrial frequency over the DC voltage. The generated alternating current is so high that it reverses the DC during a portion of each period, and wipes out free oxygen and free hydrogen liberated on the electrodes during the rest of the cycle. In pulse plating, the tank voltage reduction is less conspicuous. Anodizing, therefore, can be considered as a 'magnifying lens* for testing the efficiency of different pulse-generating devices. Use of a RAPS, in this case, can be considered an attractive opportunity for effective pulse plating.
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