Ce3+ is better or Ce4+ better for corrosion inhibition? if Ce3+ is better then why oxidizing agents are added with Ce?
Dear Dr. Muhammad junaid Anjum ,
as was demonstrated in several studies, the use of additive in Ce based treatment solution could improve the anticorrosive performance of the Cerium based surface film. Thus, the effect of the addition of different hydrogen peroxide concentrations (1-20 mM) in the cerium-based bath was evaluated. A more uniform and protective film was formed from the solution containing 6 mM H2=2 with pH=3,6. This additive produces the oxidation of Ce3+ to Ce 4+ favoring the incorporation of Ce (IV) in the protective film. This film generally has a yellowish colour (whereas the presence of Ce 3+ is related to a white colour).
For more details, please see the source:
Cerium Oxide: Applications and Attributes
Edited by Sher Bahadar Khan and Kalsoom Aktar
Published by IntechOpen (2019)
Best regads, Pierluigi Traverso
dear Muhammad junaid Anjum ;
the Pourbaix potential-pH diagram indicates that Ce3+ formed insoluble hydroxide and oxides at pH-values are over 8.
At pH lower than 3, the inhibition was most probably
a result of the competitive adsorption of Ce3+ with
H+ ions on the cathodic sites of the electrode surface.
Although Ce3+ ions are not directly involved in the
redox reactions, they provide indirect influence on
the electrode phenomenon by blocking the hydrogen
evolution reaction. If two substances, H+ and Ce3+
compete for the given sites, the adsorption of H+
in the solution is dependent on the relative concentration of H+/Ce3+. therefore I think that the reason for adding the oxidizing agent is to adjust the PH of the solution.
for more details please read;
https://www.tandfonline.com/doi/pdf/10.1080/17518253.2014.952684
The influence of Ce3+ ions on the corrosion rate of stainless steel in acidic solutions of different pH values Aljana Petek & Sebastijan Kovačič
Thank you very much Pierluigi Traverso Mahmood H. M.
Your answers are really helpful.
Dear Dr. Muhammad junaid Anjum ,
it was a pleasure for me to be able to help you with your research activity.
Good work and best regards, Pierluigi Traverso
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