ANODIC PROCESSES ON IRON COVERED BY THIN, DILUTE ELECTROLYTE LAYERS .1. ANODIC POLARIZATION

A modified three-electrode electrochemical system was developed to inv estigate the anodic processes on pure iron covered by various thicknes ses of dilute electrolyte (10(-4) and 10(-3) M Na2SO4, thickness from 50 mum to bulk solution). The electrochemical techniques used included anodic polarization measurements, allied with the determination of co rrosion potential-time relationship during wet/dry periods. It is sugg ested that in many cases, and particularly when the thin layer of elec trolyte is relatively dilute (e.g. 10(-4) Na2SO4), passivation of the iron is a prevalent phenomenon. During the initial period of atmospher ic corrosion of iron, the establishment of a passive film is dependent on the composition, concentration and the thickness of the electrolyt e layer. In the early stages of atmospheric corrosion, and possibly du ring normal conditions, iron corrodes in the atmosphere in alternative passive and active stages, corresponding to changes in the external s tate (wet/dry) of the surface.