Corrosion resistance of MA5 magnesium alloy with electric-arc coatings
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CORROSION RESISTANCE OF MA5 MAGNESIUM ALLOY WITH ELECTRIC-ARC COATINGS N. R. Chervins’ka We study the possibilities of increasing the corrosion resistance of MA5 magnesium alloy by applying aluminum electric-arc coatings from D16 and AMg6 solid wires, a mixture of wires of different kinds (D16 + AMg6), and a powder wire in an aluminum sheath with B4 C + Ni Cr B Si mixture. The electrochemical characteristics of these coatings are studied in a 3% NaCl aqueous solution. It is shown that aluminum electric-arc coatings strongly increase the corrosion resistance of the alloy. The best characteristics are exhibited by the AMg6 coatings. Keywords: corrosion resistance, magnesium alloy, electric-arc coatings.
Magnesium alloys are promising structural materials due to their small specific density and the abilities to absorb the impact energy and vibrations. They are used, in particular, in various branches of the machine-building industry [1, 2]. However, as their disadvantages, we can mention the insufficient corrosion resistance and low wear resistance in the process of friction. This is why it is reasonable to cover their surfaces with electricarc coatings. The aim of the present work is to study the electric-arc aluminum coatings on MA5 magnesium alloy. Materials and Procedure For our investigations, we chose MA5 magnesium alloy (0.15 – 0.5% Mn, 7.8 – 9.2% Al, 0.2 – 0.8% Zn, balance Mg). Note that this alloy is used especially extensively. We studied flat specimens 20 × 30 mm in size with electric-arc coatings sprayed from D16 and AMg6 wires, a mixture of different wires (D16 + AMg6), and a powder wire in the aluminum sheath with B4 C + Ni Cr B Si mixture. The coatings were applied in the following mode: an arc voltage U = 32 V, a current strength I = 150 A, a pressure of an air flow P = 0.6 MPa, and a distance of spraying l = 150 mm. The thickness of the coatings was ∼ 300 μm. Prior to spraying, the surfaces of the specimens were shot blasted to a surface roughness R z = 40 – 50 to guarantee the required cohesive forces between the coating and the matrix. The microstructure of layers was studied with a scanning electron microscope (LEO-1455VP). The electrochemical characteristics of the alloys were found by using an IPC-Pro potentiostat with saturated silver–silver-chloride reference electrode. The tests were carried out in a 3% NaCl aqueous solution at room temperature. The polarization curves were recorded in the potentiodynamic mode. The sweep rate of the potential was equal to 2 mV / sec. Karpenko Physicomechanical Institute, Ukrainian National Academy of Sciences, Lviv, Ukraine; e-mail: [email protected]. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 45, No. 4, pp. 117–119, July – August, 2009. Original article submitted June 24, 2009. 1068–820X/09/4504–0605
© 2009
Springer Science+Business Media, Inc.
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Fig. 1. Microstructures of electric-arc coatings on MA5 alloy: (a) AMg6 coating, (b) D16 coating, (c) coating sprayed from the powder wire in
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