Title
Inhibition of pH fronts in corrosion cells due to the formation of cerium hydroxide
Author
van Soestbergen, M.
Erich, S.J.F.
Huinink, H.P.
Adan, O.C.G.
Publication year
2013
Abstract
The effect of cerium-based corrosion inhibitors on the pH front between the alkaline cathode and acidic anode in corrosion cells has been studied. The cerium component of these inhibitors can affect the pH front since it precipitates in an alkaline environment as cerium hydroxide, which is important since the corrosion inhibition mechanism of the cerium component is a result of its deposition as a highly electrical resistive (passivation) layer on the cathode. It is studied whether the cerium can reach the cathode when fed into the corrosion cell from an external source after the onset of corrosion. To this end a simulation model was set up that includes the Poisson-Nernst-Planck theory to describe ion transport and the Frumkin-Butler-Volmer equation to describe charge transfer at the electrodes. In this model both the self-dissociation of water and the formation of cerium hydroxide are taken into account. To support our findings experimentally a corrosion cell consisting of an aluminum and copper electrode was used, in which the pH fronts were visualized using a pH-indicator. Two types of inhibitors were used; namely, highly soluble CeCl3 and sparsely soluble cerium dibutylphosphate, Ce(dbp)3. The results show that CeCl3 can reduce the size of the alkaline region and reach the cathode to form a passivation layer, whereas the solubility in case of Ce(dbp)3 is too low to supply sufficient amounts of trivalent cerium cations to penetrate the alkaline region. This behavior can be explained by the simulation results, which reveal a threshold for the corrosion inhibitor solubility below which no passivation of the cathode occurs. © 2013 Elsevier Ltd. All rights reserved.
Subject
Fluid Mechanics Chemistry & Energetics
RMC - Responsive Materials & Coating
TS - Technical Sciences
Buildings and Infrastructure
Architecture Materials
Built Environment
Cerium dibutylphosphate
Corrosion inhibitor
pH front
Rare earth metal
Simulation model
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DOI
https://doi.org/10.1016/j.electacta.2013.03.148
TNO identifier
484269
ISSN
0013-4686
Source
Electrochimica Acta, 110, 491-500
Document type
article