Abstract
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.
