The protection of Cu-alloy condenser tubes by the electrolysis with mild steel anode in the sea water has been examined.
The results are summarized as follows:
(1) The electrolytic solution contains ferrous and ferric colloids, and furthermore the ratio of ferrous to ferric colloid varies with coulomb concentration.
(2) The current efficiency is about 90per cent (as Fe²⁺).
(3) The ferric colloid is effective for the protection of condenser tubes as well as ferrous colloid.
(4) The results of field test showed that homogeneous protection film was formed inside of the tubes by continuous injection of 0.01ppm as Fe.

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Operational amplifiers have been employed extensively in electrochemical measurement. This paper deals with a trial construction of a galvanostat for precisely controlling current during the tests for measuring the efficiencies of the galvanic anodes. This instrument consists of three main parts: (1) the very stable current-setting circuit in which a temperature-compensated zener diode and a precise potentiometer are used, (2) the high voltage-gain amplifier in which an OP amplifier and a power transistor are combined, (3) the regulated power supply in which two power modules are employed for the sake of easy construction. The test results showed that this instrument could control output current with the precision of ±0.2% for long period even under the condition that the ambient temperature changed by about 30°C. The theoretical amounts of electricity passed through the test cells could be measured with the precision of ±0.2%, this galvanostat being used. Consequently the efficiencies of the galvanic anodes might be determined accurately without the use of the copper coulombmeter. The electrical circuit and the simple interpretation for the circuit are presented.

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