Corrosion Performance of Ni-Based Alloys in Sodium Metavanadate

Hot corrosion or molten salt corrosion is a form of corrosion which consumes materials to high corrosion rates, because it destroys the protective oxide layer formed on the metal surface. Therefore, it has been developed more resistant materials such as superalloys which have been manufactured for high temperature applications. A study of the corrosion performance of Ni-based alloys (Inconel 600, 601, 617 and 625) in NaVO3 molten salt at 700 °C was realized. In order to determine the corrosion resistance of the alloys, electrochemical techniques and weight loss tests were used. Electrochemical techniques applied were polarization potentiodynamic curves, open circuit potential and the linear polarization resistance. Analyses were conducted by scanning electron microscopy and X-ray diffraction to analyze the products of corrosion. It was observed that Inconel 600 and 601 showed the best corrosion resistance, however the Inconel 617 and 625 showed a low performance. It is known that Cr is responsible for the corrosion resistance; this due to the formation of the protective layer of Cr2O3, however, the Ni content plays an important role in the performance of this type of materials, as well as the other alloying elements (Al, Ti, Nd, Co and Mo).