Cyclic polarization analysis of corrosion behavior of ceramic coating on 6061 Al/SiCp composite for marine applications
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The study on the corrosion behavior of the composite and evaluation of surface modification technique are of importance since the addition of reinforcement particles affects the continuity of inherent oxide layer on the matrix and hence its corrosion resistance. The present study deals with the investigations of effect of ceramic coating on the corrosion behavior of 6061 Al/SiCP (20 volume % reinforcement) composite in 3.5 M NaCl solution at high temperatures namely 30 and 40°C using potentiodynamic polarization technique and cyclic polarization plots. Aluminum coating by magnetron sputtering technique is employed on the composite and it is subjected to heat treatment at 200°C for duration of 2 h for the alumina formation. The alumina coating formed on the composite surface acts as corrosion protective coating. The potentiodynamic polarization technique is used to determine the corrosion rate of the composite specimen with and without ceramic coating in the corrosion media. The cyclic polarization technique is used to study the pitting behavior of the composite with and without ceramic coating. The microstructural analysis is carried out using scanning electron microscopy (SEM). X-RD analysis shows the amorphous nature of Alumina coating obtained on the composite. The results show that the peak aged composite is more prone to corrosion among the aged group of composites but when coated with alumina shows a vast improvement in pitting nucleation resistance even at high temperatures.
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