Abstract
The anodic dissolution current of iron at constant potential in acid solution decreases markedly by addition of a small amount of iodide ions into the solution. The transient fall in the dissolution current was recorded to follow the inhibition process of iron dissolution by iodide ions, and the following results were obtained.
The rate of the inhibition process by iodide ions is represented by
dφ/dt=Aexp(-Bφ)
where φ is the relative amount of inhibition in percentage, and A and B are constants independent of the potential. Parameter A is proportional to the concentration of iodide ions, while B appears to be almost independent of the inhibitor concentration. Parameter A, which represents a rate constant of the inhibition process, is calculated to be much larger in the case of perchloric acid than that in sulphuric acid. It is suggested that the adsorbability of matrix anions of the solution on the surface of iron is closely related to the rate of the inhibition process by iodide ions; the stronger the adsorbability of matrix ions, the smaller the rate constant A.
