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Combination of cerium and polyaniline conversion layers on aluminum alloys as a corrosion-resistant coating

Grant number: 05/04641-4
Support type:Scholarships in Brazil - Post-Doctorate
Effective date (Start): April 01, 2006
Effective date (End): March 31, 2008
Field of knowledge:Physical Sciences and Mathematics - Chemistry - Physical-Chemistry
Principal Investigator:Artur de Jesus Motheo
Grantee:Sandra Regina de Moraes
Home Institution: Instituto de Química de São Carlos (IQSC). Universidade de São Paulo (USP). São Carlos , SP, Brazil


Aluminum is one of the most versatile metals, a fact that is due to the large number of alloy formation possibilities and their use in numerous applications. The corrosion resistance of aluminum and its alloys in aqueous media has been attributed to the fast formation of an oxide film (Al2O3) on the surface of the metal. However, it is also known that oxide films have distinct electrochemical properties depending on constituents of the aqueous medium. The oxide film can be destroyed in aggressive media (e.g. acidic, basic or chloride-containing solutions). In the presence of chloride the formation of aluminum chlorides occurs, decreasing the corrosion resistance. As the oxide layer is not an efficient agent for the protection against corrosion, the use of protective coverings is an alternative to minimize corrosion processes. Among the known conversion layers, the most used for industrial applications are those based on hexavalent chromium (Cr(VI)). However, chromium is dangerous to the environment as well as to human health. In order to replace the chromium layers, new protective agents have been developed. The conversion coating of cerium is an example but until now a systematic study to optimize the composition of the deposition bath has not been performed. Knowing that polyaniline presents excellent protective properties against corrosion for metals (including aluminum and its alloys), the possibility exists that combining the conversion coating of cerium with polyaniline layers the protective effect will increase. However, this combination must be evaluated and optimized taking into account the different methods of application on the metal surface. These include: i) electroless deposition of cerium in order to promote anchorage sites for the electropolymerization of aniline and ii) simultaneous deposition of cerium and polyaniline. So, the combination of the two processes seems to be a promising alternative, increasing both the protection against corrosion of the metal and also the mechanical properties of the covering layers.

Scientific publications
(References retrieved automatically from Web of Science and SciELO through information on FAPESP grants and their corresponding numbers as mentioned in the publications by the authors)
BANCZEK, E. P.; MORAES, S. R.; ASSIS, S. L.; COSTA, I.; MOTHEO, A. J. Effect of surface treatments based on self-assembling molecules and cerium coatings on the AA3003 alloy corrosion resistance. MATERIALS AND CORROSION-WERKSTOFFE UND KORROSION, v. 64, n. 3, p. 199-206, MAR 2013. Web of Science Citations: 7.
SALAZAR-BANDA, GIANCARLO R.; MORAES, SANDRA R.; MOTHEO, ARTUR J.; MACHADO, SERGIO A. S. Anticorrosive cerium-based coatings prepared by the sol-gel method. Journal of Sol-Gel Science and Technology, v. 52, n. 3, p. 415-423, DEC 2009. Web of Science Citations: 28.

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