EFFECT OF CARBON ADDITION ON CORROSION BEHAVIOR OF Fe-Al ALLOYS

Abstract

Corrosion behavior of two samples of Fe-Al alloys having compositions as (wt.%) Fe-11.5%A1-0.5%C and Fe-11.5%Al were examined in acidic and alkaline environments by electrochemical methods of corrosion testing. Austenitic Stainless steel (21.7%Cr-8.1 1%Ni-0.31 %C-0.28%N) and Mild Steel samples were also tested to carry out comparative evaluation. It was found that addition of carbon resulted in decreased resistance to electrochemical corrosion. High temperature oxidation test at 600°C, 700°C and 1000°C was also carried out on both alloys. Carbon addition resulted in slight reduction in oxidation resistance at 700° C. While at 600° C the samples were almost proving to be inert for oxidation. At 1000°C oxidation attack was found to be lower than that at 700°C. This was due to formation of Alumina layer at this temperature. At 700°C Aluminium content was found to be insufficient for the formation of Alumina but at 1000°C it became sufficient. For Fe-11.5%Al a uniform layer of Alumina was formed which was not the case for Fe-11.5%A-0.5%C. This was due to presence of carbide phase in Fe-11.5%A-0.5%C which resulted in the difference of parabolic rate constant between the samples. XRD analysis of oxidation samples at 700°C reveal that Fe203 is forming on the surface of the samples. When XRD analysis of oxidation samples at 1000°C is done then formation of Alumina is confirmed on both the samples. SEM pictures of the corroded samples were also studied to examine their surface morphology and mechanism of corrosion.