SOME GENERAL considerations about the usefulness of defining proper procedures for the performance of sinusoidal current measurements under the same conditions over broad frequency intervals are given, and useful hints for developing suitable software for driving computerized systems are outlined. The experimental applications concern the behaviour of the copper alloys 687, 706, and 715 exposed to artificial seawater at the three flow rates of 1.0, 1.5, and 2.0m/sec and at 40 deg C. Sinusoidal current measurements over the frequency range 0.08-2X10~4 Hz were performed under potential control using the four-wire technique and suitable software, which was able to optimize the current range so that the amplitude value of the potential difference between the reference and working electrodes was close to 5mV RMS for frequency values in the vicinity of 2X10~4 Hz. Results relating to long-lasting tests indicate that this procedure produces data free from systematic errors, the conditions Z_r(omega) >0 and Z_i(omega) <0 being always satisfied for omega I, and is valid for examining the behaviour of alloys having a high resistance to corrosion in their operating environments. Finally, the interphase capacitance is shown to be a valid parameter for monitoring the effectiveness of the protective film in restraining corrosion of the copper alloys 687, 706, and 715. For 706 and 715 alloys, the film is very sensitive to oxygen depletion and seawater velocity; on the other hand, for alloy 687, the experimental results show that the film is not impaired by oxygen depletion or seawater velocity.
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