Hot Corrosion of Nickel Chromium Alloys in Molten Sodium Sulfate Salt at 900C
Authors:Karim Ali, Matt Corey, Zack Gentry, Charles Gepford, Armen Kvryan, Kishan Patel, Andrew Sakamoto, Stephen Schoninger, Norton Thongchua
- Vilupanur Ravi, Department Chair of Chemical and Materials Engineering, California Polytechnic University - Pomona
- Juan Nava, Research Scientist, California Polytechnic University - Pomona
Zack Gentry, Andrew Sakamoto, Matt Corey, Norton Thongchua, Karim Ali, Kishan Patel Aremn Kvryan, Stephen Schoniger and Charles Gepford Faculty Advisors: Drs. Juan Carlos Nava and Vilupanur Ravi The role of chromium in the corrosion resistance of binary nickel-chromium alloys was studied by varying the chromium content in the alloys and exposing the specimens to molten sodium sulfate (Type I hot corrosion). This will be used to characterize the corrosion reaction front and face identification for each composition. Chromium is an excellent choice as an alloying element for combating corrosion because it enables the formation of a protective and adherent oxide on the surface of the alloy. Nickel-chromium samples were studied via two methods: immersion and salt drip testing. In these experiments, nickel-chromium alloys containing 2.5, 5, 7.5 and 10 wt% chromium were isothermally tested at 900°C for 25, 36, 49 and 100 hours. For salt coat testing, an aqueous salt solution was used to coat the sample at approximately 3-8 mg/cm2. For the immersion tests, the samples were exposed to molten sodium sulfate at 900C. Corroded samples were photographed subjected to X-Ray diffraction and subsequently cross-sectioned. The sectioned samples were metallographically prepared and then characterized using scanning electron microscopy (SEM) coupled with energy dispersive spectroscopy (EDS). Optical microscopy was used to evaluate the extent the attack by measuring the deepest penetrating corrosion front. The salt drip tests more closely simulated the Type I hot corrosion phenomenon given the higher oxygen content in the melt as compared to immersion tests. This resulted in an identifiable corrosion front depicted as a hot corrosion attack. In this presentation, we will be presenting the results of both tests along with the relevant characterization data. The results will be discussed with relevance to published literature.