ANODIC PROCESSES ON IRON COVERED BY THIN, DILUTE ELECTROLYTE LAYERS .2. AC-IMPEDANCE MEASUREMENTS

Impedance measurements (a.c.) were performed on a planar two-electrode sample, covered with thin, dilute electrolyte layers (10(-4) and 10(- 3) M Na2SO4, of thickness 101-1188 mum). The results obtained in this investigation confirm that the initial process of atmospheric corrosio n for iron is the establishment of passivation. The establishment of i nitial passivation depends on the composition, concentration, and thic kness of the electrolyte layer on iron. It is shown that in the initia l stages of atmospheric corrosion, the corrosion rate is mainly contro lled by the anodic process, i.e. the passivation of the material. The ohmic resistance polarization is not very significant.