FellowPhD. Niketan Sarabhai Patel
Project NameHigh-temperature properties of materials corrosion in molten salts
Host organisationInstitute of Inorganic Chemistry
Duration of the project12.11.2015 - 11.11.2018

Abstract
Study of the corrosion characteristics of the structural materials for handling high temperature molten salts is still of serious concern and importance. Even today the literature lack corrosion characterizations for molten salt systems studied above 850°C. Furthermore, the amount of materials tested and the variety of molten salts used, is also very limited. Our desire in this study is to test a spectrum of various alloys at around 800°C and more, in variety of molten salts environment. Looking at these needs, we believe that corrosion testing should include as many materials as possible that have been qualified by ASTM codes for use at the high temperatures envisioned. And therefore, we plan to investigate several high temperature alloys: nickel-based alloys HA230 and In625, Hastelloy-N, Hastelloy-X, Hastelloy-C276, Haynes-230, Haynes-242, Inconel-617, Inconel-713C, Incoloy-800H, Udiment-720 and SiC-SiC composite in fluoride salts (FLiNaK), magnesium chloride salts (MgCl2-KCl), and nitrate salts (NaNO3-KNO3 [40–60 wt%], LiNO3-NaNO3-KNO3 [30–52–18 wt%]) at a high temperature range depending on the molten salt mixture. Our main objective is to understand corrosion rates of these alloys and materials exposed to the given salts for long durations (i.e., 100–1,000 hours) in a static system and semi-empirical predictions of the thermal-physical properties of the salts.

Project Summary with Interim Results

Study of the corrosion characteristics of the structural materials for handling high temperature molten salts is still of serious concern and importance. Even today the literature lack corrosion characterizations for molten salt systems studied above 650°C. Furthermore, the amount of materials tested and the variety of molten salts used, is also very limited. Our desire in this study is to test a spectrum of various alloys at around 700°C and more, in variety of molten salts environment. Looking at these needs, we believe that corrosion testing should include as many materials as possible that have been qualified by ASTM codes for use at the high temperatures envisioned. And therefore, we plan to investigate several high temperature alloys: Haynes 230, Inconel 718, Inconel C276, Inconel 600, Nimonic 80A, Ni 201, Hastelloy C4, Haynes G35, C2000 etc. in molten fluorides, molten chlorides and molten nitrate salts at a high temperature range depending on the molten salt mixture. Our main objective is to understand corrosion rates of these alloys and materials exposed to the given salts for long durations in a static system and semi-empirical predictions of the thermal-physical properties of the salts.

Since the beginning of the project, the efforts have been made to fulfil the project objectives and deliverables. The work began by understanding the research around the globe and that also helped us in writing a thorough review article of the subject. The graphical abstract of our review paper is presented below.  

Fig. 1: Graphical abstract

Fig. 1: Graphical abstract


The set-up of the experiments was little difficult for the beginning but with time we’ve learned and made some important modifications. Most of the above mentioned alloys have been tested in molten FLiNaK salt mixture for the period of 8h, 24h, 30h and 48h period successfully. We have also found a way to extend the immersion period of up to 100h by using the vitreous carbon crucibles. Electrochemical measurements of alloys performance in FLiNaK is under progress and more clarity is expected in the near future.