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On the mixed nature of cerium conversion coatings
Author(s) -
Aballe A.,
Bethencourt M.,
Botana F. J.,
Cano M. J.,
Marcos M.
Publication year - 2002
Publication title -
materials and corrosion
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.487
H-Index - 55
eISSN - 1521-4176
pISSN - 0947-5117
DOI - 10.1002/1521-4176(200203)53:3<176::aid-maco176>3.0.co;2-k
Subject(s) - cerium , dielectric spectroscopy , chemistry , aqueous solution , coating , electrochemistry , nuclear chemistry , chemical engineering , inorganic chemistry , electrode , organic chemistry , engineering
Alternative pretreatments are currently under development in order to avoid the environmental impact produced by using surface finishing processes based on chromates. Some of the environmentally friendly alternatives proposed involve the use of lanthanide based compounds. In this study, conversion coatings on AA5083 (Al‐Mg) samples developed using full immersion pretreatments in 500 ppm CeCl 3 aqueous solutions have been investigated. Their microscopic and compositional features have been analyzed using SEM images and EDS spectra. From this analysis it has been determined that this layer over the surface of the samples is of a heterogeneous composition. This coating is formed by an alumina coating covering the aluminum matrix and dispersed cerium‐rich islands deposited over the cathodic sites of the alloy. A characterization methodology is proposed based on the utilization of different electrochemical techniques, such as Open Circuit Potential monitoring (OCP), Linear Polarization (LP) and Electrochemical Impedance Spectroscopy (EIS).