Corrosion protection of low-cost carbon steel with SS-309Mo and Inconel-625 bimetallic weld overlay

The dissimilar weld overlay coatings of components can lead to corrosion. In the present work, two different weld overlay layers (SS-309Mo and Inconel-625) are deposited on IS2062 grade B carbon steel, in order to avoid distortions and improve corrosion resistance. The microstructural investigations revealed that the intermediate layer SS-309Mo on carbon steel prevents the dilution by aiding crack-free weld overlay of Inconel-625 on the top. The corrosion behaviour of the coatings is studied using Linear Polarization Resistance and the Electrochemical Impedance Spectroscopy. The corrosion rate of the coatings decreased by two orders of magnitude compared to that of low carbon steel substrate. The corrosion rate of the deposited Inconel-625 along with intermediate SS-309Mo is 1.16 x 10(-3) and is comparable to that of bare Inconel-625 (1.12 x 10(-3) mmpy). Further, the immersion tests for 14 days show that, the depositions are stable with the formation of the passive film.