VOL. 10, NO 22, DECEMBER, 2015 ISSN 1819-6608 ARPN Journal of Engineering and Applied Sciences © 2006-2015 Asian Research Publishing Network (ARPN). All rights reserved. www.arpnjournals.com 10392 CORROSION BEHAVIOUR OF BORON CARBIDE REINFORCED ALUMINIUM METAL MATRIX COMPOSITE Sridhar Raja K. S. 1 and Bupesh Raja V. K. 2 1 Department of Mechanical and Production Engineering, Sathyabama University, Chennai, India 2 Department of Automobile Engineering, Sathyabama University, Chennai, India E-Mail: sridhar2raja@gmail.com ABSTRACT Cast aluminium A356 is most widely used in automobiles, marine and aircraft structures. The metal matrix composite was prepared by varying the weight percentage of reinforced boron carbide particle with A356 alloy by stir casting technique. The corrosion behavior of the composite was studied by salt spray test and the corrosion rate was evaluated by calculating the weight loss in the material. It is observed that A356-B4C composite exhibited excellent corrosion when immersed in 5% NaCl solution. The SEM image of the composite also shows that the particle gets corroded surrounding the reinforced particle. Keywords: corrosion, A356, stir casting, salt spray test, weight loss. INTRODUCTION Cast aluminium alloys are widely used to produce many complex parts, due to their good liquidity. Aluminium alloys exposed to the air are naturally protected by a layer of oxide film. However, this layer is heterogeneous and does not provide adequate corrosion protection in many environments. The anodizing technology is an effective method to improve the corrosion resistance of the aluminium and it has been universally applied. Pitting attack was reported to be the major form of corrosion in Al alloy/SiCp metal matrix composites. Cast Aluminium alloy MMCs reinforced with ceramic particulates like Sic, Al2O3, SiO2,B4C,TiO2etc, By the addition of second phase into matrix material enhances not only physical and mechanical properties, but also changes the corrosion behaviour significantly. Sun Huanhuan et al. studied the corrosion behaviour of A356 composite films in NaCl solution by electrochemical impedance spectroscopy He identified that the outer layer of the composite films had good protection effect at the initial stage of the immersion corrosion. When the corrosion time was increased, the aluminium matrix was not corroded. Thus, the higher protection degree of the composite films for A356 aluminium alloy was attributed to the synergism effects of anodic film and rare earth Ce film [1]. The corrosion behaviour of 6061 Al alloy with SiC particles composite at four different temperatures (30°, 40°, 50° and 60°C) in hydrochloric acid medium (0.5 and 1 M) using Tafel extrapolation technique and weight loss method. The adsorption of the inhibitor on the composite surface is found to obey Temkins and Langmuir adsorption isotherms. The inhibition is governed by physisorption mechanism [2]. Mamatha. G. P investigated the corrosion behaviour of aluminium 7075 with SiC particle in HCL medium. Corrosion tests were conducted by weight loss method for different exposure time where 1N HCl was used as corrodent. The corrosion rate of MMCs was lower than that of matrix Al 7075 alloy under the corrosive atmosphere [3]. By means of gravimetric and electrochemical measurement A356 gives more resistance to pitting corrosion [4]. In aluminium reinforced bamboo leaf ash composite corrosion behaviour was studied by weight loss method. The specimen was immersed in H2SO4 and 5% NaCl solution and the corrosion rate was evaluated [5]. Al 7075 reinforced with zircon was immersed in natural seawater and autoclave method is employed to find the corrosion behaviour. The presence of hydrogen in the composites increases the corrosion rate. By increasing the reinforcement percentage in the composite the corrosion was decreased [6]. The corrosion behaviour of aluminium 6061 with silica particle was studied and it shows that there are some micros cracks are developed in the composites and some pits are observed due to particle dislocation [7]. From the above investigation it is intended to evaluate the corrosion resistance of boron carbide reinforced aluminium matrix composite in 5% NaCl solution which has a typical application in automobile brakes. 2. MATERIALS AND METHOD 2.1 Material The material used in this study is Aluminium 356 alloy, having the chemical composition as shown in Table- 1. Boron Carbide (B4C) particle of size 104 micron was used as the reinforcing material.