Studies of ZA-27 / Red Mud Metal Matrix Composites with respect to Corrosion Properties

Abstract

Conventional monolithic materials have boundaries in achieving good properties like strength, stiffness, toughness and density. To overcome these weaknesses and to meet the ever increasing demand of modern day technology, composites are most auspicious materials of recent interest. Metal matrix composites are most successful materials used for recent works in the industry. Metal matrix composites own significantly improved properties including high tensile strength, toughness, hardness, low density and good wear resistance compared to alloys or any other metal. They also exhibit increased corrosion resistance. There has been an increasing demand in composites containing low density and low cost reinforcements. In this studies popular alloy of nineties ZA-27 is chosen as matrix and red mud particulates which is obtained as a waste in the aluminium manufacturing industries is selected as reinforcement. Liquid melt metallurgy technique using vortex method is chosen for the manufacture of metal matrix composites. Reinforcement content added to matrix was 2 percent 4 percent and 6 percent. Matrix alloy was also casted in the same way for comparison. Microstructures of the composites and matrix alloy are taken by scanning electron microscope technique after machining. Static weight loss corrosion test and potentiodynamic polarization techniques test using potentiostat were conducted in different concentrations of sodium chloride solutions. Specimens for the tests mentioned already are machined from the castings according to ASTM standards. Corrosion rates were calculated after knowing the weight loss in static weight loss corrosion test. Elico company make Potentiostat / Galvanostat model CL95 was used for the determination of corrosion current and corrosion rate. In all the tests the corrosion current was found to decrease from matrix alloy to 6 percent composite. Corrosion rate was also to be decreased from matrix alloy to 6 percent composite. Hence metal matrix composites made up of ZA-27 as matrix and red mud as reinforcement are more suitable for marine applications and automobile applications in place of matrix alloy.