Influence of Angle of the Line of Magnetic Force on the Dissolution of Copper, Zinc and Brass in Nitric Acid Solution

Abstract

The effect of direction of the magnetic force on dissolution of copper, zinc and brass (Cu/Zn=6/4) were examined. Their sample plates were dissolved in a 5cm³ nitric acid solution and their dissolution rates were determined. Corrosion potential and corrosion current density also were determined by use of polarization curves. The specimens were examined by using an X-ray diffractometer to determine the crystal plane of prefered dissolution which were expressed in terms of the texture coefficient. On copper and brass, inhibition effects were enhanced with increasing magnetic flux densities. Inhibition was considered to be due to the formation of oxidation film. The relation between dissolution rate and angles of line of magnetic force was obtained as follows: U₁=U₀/sin|(90°-θ)|, (θ=0-45°, 135°-225°, 315°-360°) and U₁=U₀cos|(θ-90°)|, (θ=45°-135°, 225°-315°), where θ was angle of line of magnetic force, U₀ was dissolution rate at θ=90° and U₁ was dissolution rate at other angles. It was considered that dissolution rate was not related to angle of the line of magnetic force, but was related to magnetic flux densities on a vertical component of metal surface. Corrosion potential shifted negative and corrosion current densities decreased with increase in magnetic force. Corrosion of the planes of metal surface was also affected. On zinc, corrosion rate, corrosion potential and corrosion current density hardly underwent the effect of magnetic field. It seemed that the solution was starred due to generation of hydrogen gas.