Corrosion Behaviours of Aged Haynes 282 and Inconel 718 in Acidic and Alkaline Environments

Abstract

Haynes 282 and Inconel 718 are superalloy materials originally designed and used in aero- and land-based gas turbine engines. However, they are being considered and used in challenging environments such as nuclear power plants, chemical, and petrochemical plants due largely to their high creep strength and corrosion resistance at low and high temperatures. Recently, there is quest for their uses in the oil and gas refineries. This work examines the corrosion behaviour of these two materials in acidic and alkaline environments; similar to that in the petroleum refinery. The samples were cut, aged, and electrochemically characterized using VersaSTAT 3 model potentiostat with graphite counter electrode and Ag-AgCl SCE. The Linear polarization corrosion test conducted revealed that the corrosion rate, break down potential(Ecorr) and the corrosion current(Icorr)  of the aged Haynes 218 are 0.05mmpy, 0.198V, 5.032µA in dilute HNO3 ; 0.145mmpy,16.23V,13.48 µA in dilute NaOH while those of aged Inconel 718 are 0.068mmpy,96.5V,63.56 µA in the dilute HNO3  and 0.026mmpy,0.41V,2.478 µA in the dilute NaOH respectively. These results showed that aged Haynes 282 has a higher corrosion resistance than aged Inconel 718  in the acidic medium ,but, the reverse in the alkaline medium .However better corrosion  passivation was obtained in HNO3 for the two materials than in NaOH.Keywords- Superalloys, Haynes 282, Inconel 718, Tafel  Extrapolation Method.