STP1239

    An Approach to the Modelling of Atmospheric Corrosion

    Published: Jan 1995


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    Abstract

    Atmospheric corrosion is relatively complex involving interactions between a metallic substrate and a dynamic atmosphere. Modelling of other corrosion processes has been carried out with some success however, little advance has been made on the modelling of atmospheric corrosion. Successful models must incorporate a detailed understanding of the corrosion under the various deposition, evaporation and condensation regimes implicit in the diurnal cycle. A good model for atmospheric corrosion should also consider the electrochemical nature of corrosion and be able to predict the observed changes in corrosion rate during drying and re-wetting. This work develops a model based on a condensed droplet model with a central anode and a peripheral cathode and considers the effects of evaporation on the concentration of electrolyte, its conductivity and the effects of reducing droplet size on the variation in limiting oxygen reduction current. As the conductivity variation permits estimation of the anode to cathode resistance, the limiting oxygen reduction current can be used to estimate the maximum voltage drop due to resistive effects in the droplet. The model predicts that there is no significant resistive control in an evaporating droplet assuming the corrosion rate is that given by the limiting oxygen reduction current. However, in a condensate or adsorbate of uniform thickness resistive effects may become significant in layers less than 10 μm thick. In atmospheric corrosion, this has relevance with respect to repeated evaporation and condensation during wetting and drying, to the effects of rainwater washing and surface cleaning and also to micron or sub-micron thick adsorbates.

    Keywords:

    modelling, atmospheric corrosion, droplet evaporation, resistive control


    Author Information:

    Lyon, SB
    Lecturer and graduate students, Corrosion and Protection Centre, UMIST, Manchester,

    Wong, CW
    Lecturer and graduate students, Corrosion and Protection Centre, UMIST, Manchester,

    Ajiboye, P
    Lecturer and graduate students, Corrosion and Protection Centre, UMIST, Manchester,


    Paper ID: STP14911S

    Committee/Subcommittee: G01.04

    DOI: 10.1520/STP14911S


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