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Silane Coating for the Corrosion Protection of a Magnesium Alloy,
ZE41
P. Chakraborty Banerjee 1,2 , R.K. Singh Raman 1,3 , Y. Durandet 2,4 , G. McAdam 5
1 Department of Chemical Engineering, Monash University, Clayton, VIC-3800
2 CAST Cooperative Research Centre, Hawthorn VIC-3122
3 Departments of Mechanical and Aerospace Engineering, Monash University,
Clayton, VIC-3800
4 Industrial Research Institute Swinburne (IRIS), Swinburne University of
Technology, Hawthorn, VIC-3122
5 Defence Science and Technology Organisation, Fishermans Bend, VIC-3207
Presenter email address: parama.banerjee@monash.edu
Magnesium alloys are the lightest structural metallic materials with excellent
mechanical properties. Their high strength to weight ratio makes them very attractive
to the automotive and aerospace industries. However the use of magnesium alloys is
restricted due to their poor corrosion resistance. Hence, for industrial applications,
chemical surface treatments are often required. Surface treatments based on chromate
conversion coatings have been successfully used for corrosion protection and paint
adhesion, but concerns about the carcinogenic nature of Cr(VI) ions that are
subsequently released into environment have recently led to the development of
alternative coatings. Chemical surface treatments based on silanes are emerging as an
attractive environmentally friendly alternative for improving the corrosion resistance
of the metallic substrates, as well as for enhancing the compatibility of the metal
surface with paint systems.
In the present study, n-octadecyl-trimethoxy silane was applied to a magnesium alloy
ZE41. The specimens were subjected to a pre-treatment in 3 M sodium hydroxide
solution to produce a uniform layer of magnesium hydroxide which facilitates the
formation of a compact silane film. The chemical nature of the silane film was
analysed using ATR-FTIR and XPS. The corrosion resistances of the coated and
uncoated specimens in 0.1 M sodium chloride solution were characterized by
potentiodynamic polarization and electrochemical impedance spectroscopy (EIS).
Three orders of magnitude improvement in corrosion resistance was achieved on
application of the silane to the alloy’s surface.