Etching Mechanism of a Rotating Steel Disk Electrode in 49-54 mass% Ferric Chloride Solutions

Abstract

The effect of rotation rate upon potential and etch rate of steel is examined utilizing a rotating steel disk electrode. Being based upon these experiments, etching mechanism is discussed.
The principal ingredient of etchants is FeCl₃. The concentrations of FeCl₃, FeCl₂ and free HCl are 49 to 54 mass%, 1.9±0.1 mass% and 0.09±0.02mol/kg (molality), respectively. The temperature of the etchants is maintained at 70°C and the rotation rate of the steel disk is set at 400-4900rpm. The etch rate is obtained from the weight loss.
The etch rate and the square root of rotation rate are in proportionate relations at any concentrations of FeCl₃. The mechanism that anodic and cathodic reactions are controlled by mass transfer process is proposed.