Experimental validation of Dynamic Electrolyte Film Model for atmospheric corrosion modelling

Bangalore Gangadharacharya, K. (Contributor), Van Den Steen, N. (Speaker), Daan De Wilde (Contributor), Claessens, R. (Contributor), Terryn, H. (Contributor), Darja Pecko (Contributor)

Activiteit: Talk or presentation at a conference

Description

Abstract
The evolution of electrolyte film thickness due to the variation of environmental humidity and temperature has a significant influence on the
atmospheric corrosion mechanisms. Although many studies on atmospheric corrosion of metals have been made in the recent past, little is
known about the influence of electrolyte thickness evolution on corrosion. Therefore, Dynamic Electrolyte Film Corrosion Model (DEFCM)
has been developed in our group. DEFCM is the combination of two models: The Dynamic Electrolyte Film Model (DEFM) and an
elementary Corrosion Model (CM) to link the evolution of uniform film with its effect on corrosion. DEFM describes the evolution of the
uniform electrolyte film thickness in the presence of hygroscopic salts due to condensation/evaporation of atmospheric vapor, whereas CM is
an elementary corrosion model that estimates the resulting corrosion depth. The DEFCM results were indirectly compared with accelerated
corrosion tests, but the direct comparison with film thickness as a function of time is still missing. Therefore, in this work, we focus on
experimental validation of DEFM with direct measurement of the uniform film thickness evolution on metal surface in cyclic condensation
and evaporation regimes under strict environmental control. For the first time, a cyclic variation of film thickness is continuously measured
using an interferometric optical device to have a periodic increase and decrease of film thickness. At any given relative humidity and
temperature of the environment, both condensation and evaporation of the film are promoted by cooling the metal surface below and above
dew point temperature respectively with the help of a Peltier element. The thickness measurements of a condensing water vapor film are done
both on a clean metal surface and in the presence of hygroscopic salts. By doing so, the DEFM is evaluated and improved if necessary. The
optical device used has a limited detection capability at lower film thicknesses and a loss of intensity at higher thicknesses resulting from the
bulging of growing film due to surface tension forces. This limitation restricts the measurable range of the thickness to be between 5 and 20
microns. However, this range is sufficient for making a reliable comparison with the results from the model. Along with key findings, the
scope for future work about numerical modelling of atmospheric corrosion is discussed.
Periode9 sep 201913 sep 2019
Gehouden opEuropean Federation of Corrosion
Mate van erkenningInternational