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Abstract. Corrosion resistance of aluminum based alloy and its composites reinforced by tungsten carbide have been investigated. Al-Si-Cu alloy and Al-Si-Cu/WC composites reinforced with 1, 2 or 3wt.% WC were subjected to corrosive medium (0.1N NaOH) using electrochemical method to evaluate their corrosion resistance.
The results show that introducing 1% WC has a negative effect on the corrosion resistance of aluminum. While 2 and 3 % WC gave better corrosion resistance due to decreasing in electrical conductivity of Al-alloy and then reducing charge transfer. WC phase covered the passive film of Al^sub 2^O^sub 3^ which maintain passive state for long period.
The studies were performed at three temperatures 40, 50 and 60°C, and the results show shifting corrosion potentials toward noble direction with increasing temperature and obtained a variation in corrosion current densities. Polarization resistance calculated according to Stern-Geary equation confirms that the composites with 2 and 3wt% WC have more resistance compared to base alloy and composite with 1wt% WC.
Keywords: Corrosion Testing; Metal Matrix Composites; Surface Engineering; WC reinforcement.
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1. Introduction
Composite material is a product that is lighter and stronger than either of the components individually. Because of this, they can be used in more severe environments. Aluminum is probably the most common metal used for the production of metal matrix composites MMC. This is due mostly to its low density, excellent mechanical properties, and low melting point that aids in fabrication [1].
Galvanic corrosion between the matrix metal and the reinforcement fibers can occur, especially when in contact with aqueous solutions. The corrosion of SiC/Al by seawater was found by Aylor and Kain [2] to be more resistant than graphite/Al this was attributed to a lack of a galvanic driving force between the SiC and the aluminum matrix, although both composites exhibited similar mechanisms of corrosion, essentially pitting of the metal matrix around the reinforcement material.
Aluminum based composites tend to corrode in a localized manner; several studies on the corrosion of aluminum and its composites in chloride-containing solutions showed that the origin of localized attack depends highly on the alloy composition and microstructure (which is affected by the processing method). Possible mechanisms include: microgalvanic coupling between the matrix and reinforcement or...