aDepartment of Chemistry, R N Shetty Institute of Technology, Channasandra, Bangalore-560061, Karnataka, India. Tel: 080-28603880,.
bDepartment of Chemistry, HKBK College of Engineering, Bangalore -560045, Karnataka, India. Tel: 080 23150018,.
cDepartment of Chemistry, Dr. Ambedkar Institute of Technology, Mallathahalli, Bangalore – 560056, Karnataka, India,.
dAffiliation: Visvesvaraya Technological University, Karnataka, India.
The corrosion behaviour of Al 6063-TiO2 particulate composites in sodium sulphate medium has been studied in the present investigation. The unreinforced matrix, and the composites containing 2, 4 & 6% by weight of TiO2 particulates were prepared by liquid metallurgy route using vortex technique. Their corrosion behaviour was evaluated by potentiodynamic polarization method in decinormal and normal solutions of sodium sulphate. The open circuit potential (OCP) measurements and the potentiodynamic polarisation experiments revealed that the composites are susceptible to corrosion compared with their matrix alloy. The observed Small shift of OCP values to the negative side in composites is indicative of defect oxide layer formation in the presence of reinforcement in the matrix alloy. Polarisation curves in decinormal and normal solutions of sodium sulphate showed that the Corrosion rates and corrosion current density (Icorr) values for both matrix and composites increase with increase in concentration of sodium sulphate solution. Moreover, the corrosion rates of the composites markedly increases with increase in the TiO2 content The presence of reinforcement in matrix acting as cathodic region increases with increasing TiO2 content and increases the corresponding cathode to anode ratio in composites, resulting in the formation of pits during localised corrosion.The observed lower corrosion resistance in composites could be attributed to the microgalvanic coupling between the interfacial products formed during composite fabrication such as, Mg2Si, AlTi3 and Matrix alloy. Insulator TiO2 particulates are perceived to act as inert material and degrade the integrity of the protective oxide layer on the Al matrix alloy.
Al6063 composites, TiO2 particulates, microgalvanic coupling, interfacial products
