WC-CoCr coatings sprayed by high velocity oxygen-fuel (HVOF) flame on AA7050 aluminum alloy: electrochemical behavior in 3.5% NaCl solution

The electrochemical behaviour of WC-CoCr coatings with 10 (W10), 15 (W15) and 20 (W20) torch passes, sprayed by HVOF flame on AA7050 aluminium alloy substrate, evaluated in 3.5% NaCl solution, was compared using open-circuit potential measurements, electrochemical impedance spectroscopy and polarisa...

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Bibliographic Details
Published in:Materials research (São Carlos, São Paulo, Brazil) São Paulo, Brazil), 2007-12, Vol.10 (4), p.377-385
Main Authors: Magnani, Marina, Suegama, Patrícia Hatsue, Recco, Abel André Cândido, Guilemany, Josep Maria, Fugivara, Cecílio Sadao, Benedetti, Assis Vicente
Format: Article
Language:English
Subjects:
aluminum alloy
corrosion resistance
EIS
ENGINEERING, CHEMICAL
HVOF
MATERIALS SCIENCE, MULTIDISCIPLINARY
METALLURGY & METALLURGICAL ENGINEERING
WC-CoCr
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Summary:The electrochemical behaviour of WC-CoCr coatings with 10 (W10), 15 (W15) and 20 (W20) torch passes, sprayed by HVOF flame on AA7050 aluminium alloy substrate, evaluated in 3.5% NaCl solution, was compared using open-circuit potential measurements, electrochemical impedance spectroscopy and polarisation curves. The coating surfaces and their cross sections were characterised by XRD and the Rockwell-C hardness test, and also by optical microscopy and SEM before and after the corrosion tests. The electrochemical data showed that sample W10 had higher corrosion resistance than the others. In some tests, aluminium salts on the coating surface were identified by EDS, indicating the corrosion of the substrate. Using aluminon, aluminium ions were detected, and analysing the surface by stereomicroscopy showed hydrogen bubbles, both indicating that the electrolyte reached the substrate and galvanic corrosion possibly occurred. The physical characterisation showed that sample W10 had a lower number of cracks and pores, justifying its higher corrosion resistance. 21 refs.
ISSN:1516-1439
1980-5373
1516-1439
DOI:10.1590/S1516-14392007000400010