Electrochemical studies of Al 7075/zircon metal ... - Ultrascientist.org

Electrochemical studies of --- composites in natural sea water. 327weakest part of particle or fiber reinforcedcomposites. Hence the nature of the bond, whetherweak or strong, is critical in the corrosionprocess. Since the composites developed showimproved mechanical properties, it can be claimedthat the interface between the aluminium andthe reinforced zircon particle is quite strong 22 .this could have influenced the improvement inthe corrosion resistance of these composites.To support this it was observed that when thezircon particle content is increased, there is areduction in corrosion 23 .One more reason for decrease in thecorrosion rate is the inter metallic region, whichis the site of corrosion forming crevice aroundeach particle. Which may be due formation ofmagnesium inter metallic layer adjacent to theparticle during manufacture as discussed byTrzaskoma 19 . Which is evident from the EDXAresults. McIntyre et al. 24 further showed thatthe magnesium inter metallic compounds aremore active than the alloy matrix. Pitting inthe composites is associated with the particlematrix interface, because of the higher magnesiumconcentration in this region. With increase intime pitting would continue to occur at randomsites on the particle matrix interface. The activenature of the crevices would cathodicallyprotect the remainder of the matrix and restrictpit formation and propagation.ConclusionThe average corrosion rate increasesas a function of solution temperature. Zirconis a ceramic material and hence is not involvedin galvanic effect with matrix alloy. However,crevice corrosion can be observed at the zircon /Al interface, probably because of magnesiumarising at interface. Normality of solution playsa significant role in the corrosion of given MMCs.The increase in hydrogen reduction results ina higher corrosion rate. Time dependent andtemperature dependent constant does not dependon the reinforcement. However the activationenergy constant is decreased with increasingreinforcement of the composites. The extentof corrosion damage was reduced with increasingreinforcement which may be due to increasein the tensile strength as well as bonding strengthof the MMCs. Material loss from corrosionwas significantly higher in the case of matrixalloy than in the MMCs.References1. R.warren, Ceramic Matrix Composites,Chapman and Hall, New York (1992).2. S.C. Sharma, B.M. Girish, R. Kamat andB.M. Satish, J. Mater. Engg. and Perf.,8(3), 309-314 (1999).3. S.C. Sharma, K.H.W. Seah, B.M. Satishand B.M. Gerish, Mater. Design., 17(5/6),245-250 (1996).4. S.C. Tjong and Z.Y. Ma, Composites Sci.Technol., 57, 697-702 (1997).5. P. Reynaud, Composites Sci. Technol.,56, 809-814 (1996).6. E. Koya, Y. Hagiwara, S. Miura, T. Hayashi,T. Fujiwara and M. Onada, Soc. AutomativeEngrs. Inc., 55-64 (1994).7. M.K. Aghajanian, G.C. Atland, P. Barron-Antolin and A.S. Nagelberg, Metal MatrixComposites, Soc. Automotive Engrs. Inc.,73-81 (1994).8. R.D. Pruthviraj and P.V. Krupakara, Res.J. Chem. Environ., 10(3), 71-75 (2006).