Studies on Pitting Corrosion of Al–Cu–Li Alloys Part III: Passivation Kinetics of AA2098–T851 Based on the Point Defect Model
In this paper, the passivation kinetics of AA2098−T851 was investigated by a fundamental theoretical interpretation of experimental results based on the mixed potential model (MPM). The steady state passive layer formed on the AA2098−T851 in NaHCO<sub>3</sub> solution...
| Main Authors: | , , , |
|---|---|
| Format: | Article |
| Language: | English |
| Published: |
MDPI AG
2019-06-01
|
| Series: | Materials |
| Subjects: | |
| Online Access: | https://www.mdpi.com/1996-1944/12/12/1912 |
| id |
doaj-cc8e54b18bb84b11bb52c7cdf88d53a3 |
|---|---|
| record_format |
Article |
| spelling |
doaj-cc8e54b18bb84b11bb52c7cdf88d53a32020-11-25T00:16:47ZengMDPI AGMaterials1996-19442019-06-011212191210.3390/ma12121912ma12121912Studies on Pitting Corrosion of Al–Cu–Li Alloys Part III: Passivation Kinetics of AA2098–T851 Based on the Point Defect ModelElmira Ghanbari0Alireza Saatchi1Xiaowei Lei2Digby D. Macdonald3Department of Materials Science and Engineering, University of California at Berkeley, Berkeley, CA 94720, USADepartment of Materials Science and Engineering, University of California at Berkeley, Berkeley, CA 94720, USADepartment of Materials Science and Engineering, University of California at Berkeley, Berkeley, CA 94720, USADepartment of Materials Science and Engineering, University of California at Berkeley, Berkeley, CA 94720, USAIn this paper, the passivation kinetics of AA2098−T851 was investigated by a fundamental theoretical interpretation of experimental results based on the mixed potential model (MPM). The steady state passive layer formed on the AA2098−T851 in NaHCO<sub>3</sub> solution in a CO<sub>2</sub> atmosphere upon potentiostatic stepping in the anodic direction followed by stepping in the opposite direction was explored. Potentials were selected in a way that both anodic passive dissolution of the metal and hydrogen evolution reaction (HER) occur, thereby requiring the MPM for interpretation. Optimization of the MPM on the experimental electrochemical impedance spectroscopy (EIS) data measured after each potentiostatic step revealed the important role of the migration of Al interstitials in determining the kinetics of passive layer formation and dissolution. More importantly, it is shown that the inequalities of the kinetics of formation and dissolution of the passive layer as observed in opposite potential stepping directions lead to the irreversibility of the passivation process. Finally, by considering the Butler−Volmer (B−V) equation for the cathodic reaction (HER) in the MPM, and assuming the quantum mechanical tunneling of the charge carriers across the barrier layer of the passive film, it was shown that the HER was primarily controlled by the slow electrochemical discharge of protons at the barrier layer/solution (outer layer) interface.https://www.mdpi.com/1996-1944/12/12/1912Al–Cu–Li alloyspoint defect modelmixed potential modelpassivation kinetics |
| collection |
DOAJ |
| language |
English |
| format |
Article |
| sources |
DOAJ |
| author |
Elmira Ghanbari Alireza Saatchi Xiaowei Lei Digby D. Macdonald |
| spellingShingle |
Elmira Ghanbari Alireza Saatchi Xiaowei Lei Digby D. Macdonald Studies on Pitting Corrosion of Al–Cu–Li Alloys Part III: Passivation Kinetics of AA2098–T851 Based on the Point Defect Model Materials Al–Cu–Li alloys point defect model mixed potential model passivation kinetics |
| author_facet |
Elmira Ghanbari Alireza Saatchi Xiaowei Lei Digby D. Macdonald |
| author_sort |
Elmira Ghanbari |
| title |
Studies on Pitting Corrosion of Al–Cu–Li Alloys Part III: Passivation Kinetics of AA2098–T851 Based on the Point Defect Model |
| title_short |
Studies on Pitting Corrosion of Al–Cu–Li Alloys Part III: Passivation Kinetics of AA2098–T851 Based on the Point Defect Model |
| title_full |
Studies on Pitting Corrosion of Al–Cu–Li Alloys Part III: Passivation Kinetics of AA2098–T851 Based on the Point Defect Model |
| title_fullStr |
Studies on Pitting Corrosion of Al–Cu–Li Alloys Part III: Passivation Kinetics of AA2098–T851 Based on the Point Defect Model |
| title_full_unstemmed |
Studies on Pitting Corrosion of Al–Cu–Li Alloys Part III: Passivation Kinetics of AA2098–T851 Based on the Point Defect Model |
| title_sort |
studies on pitting corrosion of al–cu–li alloys part iii: passivation kinetics of aa2098–t851 based on the point defect model |
| publisher |
MDPI AG |
| series |
Materials |
| issn |
1996-1944 |
| publishDate |
2019-06-01 |
| description |
In this paper, the passivation kinetics of AA2098−T851 was investigated by a fundamental theoretical interpretation of experimental results based on the mixed potential model (MPM). The steady state passive layer formed on the AA2098−T851 in NaHCO<sub>3</sub> solution in a CO<sub>2</sub> atmosphere upon potentiostatic stepping in the anodic direction followed by stepping in the opposite direction was explored. Potentials were selected in a way that both anodic passive dissolution of the metal and hydrogen evolution reaction (HER) occur, thereby requiring the MPM for interpretation. Optimization of the MPM on the experimental electrochemical impedance spectroscopy (EIS) data measured after each potentiostatic step revealed the important role of the migration of Al interstitials in determining the kinetics of passive layer formation and dissolution. More importantly, it is shown that the inequalities of the kinetics of formation and dissolution of the passive layer as observed in opposite potential stepping directions lead to the irreversibility of the passivation process. Finally, by considering the Butler−Volmer (B−V) equation for the cathodic reaction (HER) in the MPM, and assuming the quantum mechanical tunneling of the charge carriers across the barrier layer of the passive film, it was shown that the HER was primarily controlled by the slow electrochemical discharge of protons at the barrier layer/solution (outer layer) interface. |
| topic |
Al–Cu–Li alloys point defect model mixed potential model passivation kinetics |
| url |
https://www.mdpi.com/1996-1944/12/12/1912 |
| work_keys_str_mv |
AT elmiraghanbari studiesonpittingcorrosionofalculialloyspartiiipassivationkineticsofaa2098t851basedonthepointdefectmodel AT alirezasaatchi studiesonpittingcorrosionofalculialloyspartiiipassivationkineticsofaa2098t851basedonthepointdefectmodel AT xiaoweilei studiesonpittingcorrosionofalculialloyspartiiipassivationkineticsofaa2098t851basedonthepointdefectmodel AT digbydmacdonald studiesonpittingcorrosionofalculialloyspartiiipassivationkineticsofaa2098t851basedonthepointdefectmodel |
| _version_ |
1725382639147286528 |