Corrosive behavior of 440C and M50 steels for marine applications

Abstract

The corrosion behavior of 440C and M50 steels in various corrosive mediums like artificial sea water and Hank’s balanced salt(HBS) solutions has been investigated. Initially the materials are prepared into required dimensions by using wafer cutting techniques and The surface roughness of these materials are investigated with the help of Talysurf profilometer. The solution preparation is done by using the required amount of chemicals with the help of electronic weighing balance. The materials are exposed to the prepared solutions. Finally, the materials are removed at different time periods. The corrosion rates are evaluated using a potentiostat.The characterization of corroded surfaces been carried out using with electron microscopy (SEM) equipped with energy dispersive spectrometer, Raman spectroscopy and X-Ray diffraction (XRD) at glancing angle. The following are the salient results of the study. The results shows that the corrosion rates of 440C steel is an order of magnitude less than M50 steel. The 440C and M50 steels are more reactive in sea water than HBSS solution since sea water contains large no. of Cl ions compare to HBSS. The corrosion rate of 440C is high in sea water whereas for M50 it is high in HBSS. From SEM it was revealed that the materials are severely attacked at grain boundaries in seawater than HBSS. The composition in test surfaces shown relative enrichment of Fe. Artificial seawater shows significant amount of Na, Cl, V, Mo, Cr, Ca and O2.