Inorganic Corrosion Inhibitors in Acid Solution'

In dilute hydrochloric acid with excess potassium nitrate as a depolarizer, iron, zinc, and cadmium dissolve at, or nearly at, a maximum rate controlled by the rate of con-vection and the speed of diffusion of the hydrogen ion. The dissolution rates of these metals may be reduced to comparatively small values by addition of dichromate, molyb-date, or tungstate. With very pure iron and zinc the dissolution rate in the presence of dichromate can be reduced still more by the addition of a soluble fluoride. While none of the solutions used are highly protective, the experiments described arc of aid in inter-preting the mechanism of inhibition