Effect of the relative velocity between ship hull and seawater on the performance of sacrificial cathodic protection

Abstract

Purpose

The purpose of this paper is to study the effect of the relative velocity between ship hull and seawater on the rate of zinc consumption and degree of cathodic protection during sacrificial cathodic protection of steel hulls using zinc anodes.

Design/methodology/approach

The rate of zinc consumption under different relative velocities was determined by the loss in weight technique while the degree of cathodic protection of the ship hull at different distances from the anode was determined by measuring the cathode potential of the hull cathode against a silver/silver chloride reference electrode.

Findings

Within the present range of conditions, the rate of zinc consumption (R) was found to increase with increasing the relative velocity according to equations: R=3.9×10⁻⁴ Re^0.0126; for Re<3,500, and R=7.36×10⁻⁶ Re^0.5; for Re>3,500, where Re is the Reynolds number. The degree of cathodic protection represented by the hull (cathode) potential at a given distance from the anode was found to decrease slightly with increasing the relative velocity.

Originality/value

The present results would make it possible for the designer of sacrificial cathodic protection systems to assess the amount of zinc required to protect the ship hull under certain operating conditions more accurately than the situation where the effect of the relative velocity was not considered.

Citation

Sedahmed, G.H., Farag, H.A., Hassan, M.A. and Hassan, I. (2010), "Effect of the relative velocity between ship hull and seawater on the performance of sacrificial cathodic protection", Anti-Corrosion Methods and Materials, Vol. 57 No. 2, pp. 70-74. https://doi.org/10.1108/00035591011028032