For cathodic protection of oil tankers carrying inflammable liquids, galvanic anodes are used. In the ballast tanks, gas-air mixtures from crude oil and other petroleum products are explosive when the gas-air ratios are in the dangerous range, and incentive sparks are produced, by impact. During the butterworthing and the installation of the anodes, there are sources of ignition by accidental incentive sparking such as caused by impact due to dropping tools or anode materials on rusted steel.
In order to examine the possibility of explosion caused by the impact of various galvanic anode materials on steel plate, Mg, Al and Zn alloys with impact energy of 200 or 1, 000 ft-lb were dropped on rusted steel plate in an atmosphere of 5.3vol %LPG-air mixture. The test results obtained are as follows:
1) Mg alloy produced incentive sparks and explosion 11 times out of 20 at both energies of 200 and 1, 000 ft-lb.
2) Al alloy and Zn alloy produced no sparking.

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Considerable interests have been aroused in the use of Pb-Pt and Pb-Pd bielectrodes counting for expensive Pt electrodes and corrodible lead dioxide ones.
In this study anodic polarization curves of these electrodes were measured by a potentiostat. The results obtained were as follows:
In the case of the Pb electrode in NaCl solution, the anodic current density took a minimum value at 1.4V, a maximum at 1.6V and another minimum at 1.75V, then increasing in proportion to the anodic potential, while for the anodic current density in Na₂SO₄ solution an ever increasing curve was obtained with increasing anodic potential. On the other hand, with the Pb-Pt bielectrode, only one minimum was seen between 0.6 and 0.9V, while with the Pb-Pd bielectrode the behavior curve was remarkably different indicating a steeper increase of the current density at -0.23V and a passive state between 0.8 and 1.1V. The anodic current between -0.2 and 0V probably derived from dissolution of palladium and above 0V oxygen evolved.
The electronic deflection revealed no annular pattern, thus suggesting non-crystalline deposit on the electrode surface in sodium sulfate solution.
So far as we studied, the Pb-Pd bielectrode has been proved to withstand the process of electrolysis in artificial sea water.

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