Enhanced corrosion resistance of A3xx.x/SiCp composites in chloride media by La surface treatments

The influence of silicon carbide particles (SiCp) proportion and matrix composition of aluminium metal matrix composites (A3xx.x/SiCp) modified by lanthanum-based conversion or electrolysis coating was evaluated in 3.5 wt% NaCl aerated solution. The intermetallic compounds were preferentially covere...

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Bibliographic Details
Published in:Electrochimica acta 2006-06, Vol.51 (21), p.4367-4378
Main Authors: Pardo, A., Merino, M.C., Arrabal, R., Feliú, S., Viejo, F., Carboneras, M.
Format: Article
Language:English
Subjects:
Al/SiCp composites
Applied sciences
Conversion coating
Corrosion
Corrosion prevention
Electrolysis coating
Exact sciences and technology
Lanthanum
Metals. Metallurgy
Pitting corrosion
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Summary:The influence of silicon carbide particles (SiCp) proportion and matrix composition of aluminium metal matrix composites (A3xx.x/SiCp) modified by lanthanum-based conversion or electrolysis coating was evaluated in 3.5 wt% NaCl aerated solution. The intermetallic compounds were preferentially covered by lanthanum-based conversion coatings obtained by immersion in 50 °C solution of La(III) salt, and the intermetallic compounds, SiCp and aluminium matrix were covered by lanthanum electrolysis treatment. The corrosion process was studied on the basis of gravimetric tests and electrochemical impedance spectroscopy (EIS) during immersion in 3.5 wt% NaCl aerated solution. The composition of both La coating and corrosion products was analyzed before and after accelerated testing, by scanning electron microscopy (SEM), atomic force microscopy (AFM), low-angle X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) to determine the influence of surface microstructural changes on corrosion behaviour during exposure to the corrosive environment. The corrosion process was more influenced by the concentration of alloy elements in the matrix than by the proportion of SiCp reinforcement. Both lanthanum treated surfaces presented better behaviour to chloride solution corrosion than original composite surfaces without treatment; however, electrolysis afforded a higher degree of protection than the conversion treatment because the coating was more extensive.
ISSN:0013-4686
1873-3859
DOI:10.1016/j.electacta.2005.12.016