Effect of a Uniform Magnetic Field on Corrosion of Ni-Al Bronze in 3.5 wt% NaCl

Following the observation of enhanced corrosion of parts of a seawater-immersed permanent magnet motor made from Ni-Al bronze, a laboratory study of the effect of uniform magnetic field on the corrosion of this alloy in a 3.5 wt% NaCl solution has been performed. The results have been compared with measurements of enhanced convection with a rotating disc electrode. The largest effect of the magnetic field was an enhancement of the anodic current density of 52% in a field of 800 mT. This enhancement was equivalent to that resulting from gentle stirring with the rotating disc electrode with diameter 10 mm at 20 rpm. The increase in corrosion current varied with the magnitude of both the magnetic field and the initial corrosion current, and increased with both. The effect can be explained in terms of the Lorentz force, and modeling was performed to quantify the flow induced in the electrolyte by this force.