It has been shown by means of a potentiostatic technique that both the anodic and the cathodic behaviour of steel are inhibited in an aqueous red lead slurry with 0.1 M sodium perchlorate as supporting electrolyte. The oxygen reduction on the cathode takes place at a slower rate in the slurry than in the pure electrolyte solution. According to scanning electron microscopy with microprobe analysis and Guinier X‐ray diffraction phase analysis, the layer formed on the cathode at about −1100 mV consisted of metallic lead deposited from solute lead species. At more negative potentials and unidentified phase appeared.