Document Details
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Document Type |
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Article In Journal |
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Document Title |
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Thermodynamic and kinetic factors in chloride ion pitting and nitrogen donor ligand inhibition of aluminium metal corrosion in aggressive acid media Thermodynamic and kinetic factors in chloride ion pitting and nitrogen donor ligand inhibition of aluminium metal corrosion in aggressive acid media |
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Subject |
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Chemistry |
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Document Language |
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English |
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Abstract |
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The corrosion behaviour of aluminium in 1.0 mol l-1 solutions of HCl, H2SO4, HNO3 and HClO4 has been investigated in the presence and absence of added Cl- ions. The rate of corrosion of the metal in HCl and in acid solutions containing Cl-, was significantly higher than in the other solutions studied and is attributed to Cl- pitting. The rate of corrosion was found to be zero order overall with an observed rate constant dependence on Cl- of the form (kobs - k0) = kK2[Cl-]2/(K1[O2] + K2[Cl-]) where K1 and K2 are, respectively, the equilibrium constants for O2 and Cl- adsorption on the metal surface. The addition of the sodium salts of N-n-butyl, N-ethyl and N-phenyl dithiocarbamates was found to have an accelerating effect on the corrosion rate, whereas the addition of the quadridentate macrocyclic amine cyclam (1,4,8,11-tetraazacyclotetradecane) and its open-chain analogue DND (3,7-diazanonane-1,9-diazine) was found to offer inhibition characteristics. These latter rates were investigated at 30, 35, 40, 45 and 50°C in various amine concentrations. A mechanism involving three competitive equilibria, viz. molecular oxygen adsorption, Cl- adsorption and inhibitor adsorption, followed by a rate-determining chloride ion catalysed dissociation step is proposed for the reaction. Finally, the pitting potentials of Al in aggressive acid solutions containing various Cl- concentrations were determined from anodic polarization curves. These data were discussed and correlated to the overall mechanism of pitting corrosion. |
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ISSN |
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0956-5000 |
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Journal Name |
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Journal of the Chemical Society - Faraday Transactions |
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Volume |
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89 |
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Issue Number |
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5 |
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Publishing Year |
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1414 AH
1993 AD |
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Article Type |
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Article |
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Added Date |
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Monday, December 26, 2011 |
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Researchers
| عباس عباس العوضي | El-Awady, Abbas A | Researcher | Doctorate | abbaselawady@hotmail.com |
| Beshier A Abd-El-Nabey | Abd-El-Nabey, Beshier A | Researcher | Doctorate | |
| سعدالله قاري عزيز | Aziz, Saadullah G | Researcher | Doctorate | |
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