ON THE ATMOSPHERIC CORROSION OF METALS WHICH ARE COVERED WITH THIN ELECTROLYTE LAYERS .1. VERIFICATION OF THE EXPERIMENTAL-TECHNIQUE

In this series of three papers new techniques are described, which allow the investigation of the corrosion kinetics of metal surfaces which are covered by very thin or even adsorbed electrolyte layers. In this first part the experimental arrangement is discussed in detail, which is used to measure simultaneously corrosion rates and corrosion potentials of atmospherically corroding iron surfaces during several wet/dry transitions without touching the surface under investigation. The theoretical basis for the measurement of electrode potentials using a Kelvin probe as a reference electrode is evaluated. Additional experiments have been performed to check the validity of the measured Volta potential and its correlation to the corrosion potential of the metal/electrolyte interface. The results prove that the potential drop across the oxide scale formed on top of the iron surface is small if the surface is kept in a humid environment (e.g. 95% relative humidity). Then, the Volta potential difference between surface and Kelvin probe can be directly correlated to the corrosion potential of the corroding metal surface. © 1990.