Corrosion Mitigation of Nickel Alloy Metals in Molten Chloride Salts
AuthorGray, Alexis Morgan
Molten Chloride Salts
AdvisorGervasio, Dominic F.
MetadataShow full item record
PublisherThe University of Arizona.
RightsCopyright © is held by the author. Digital access to this material is made possible by the University Libraries, University of Arizona. Further transmission, reproduction, presentation (such as public display or performance) of protected items is prohibited except with permission of the author.
AbstractCorrosion mitigation of nickel alloy metals in molten chloride salts at 800C is desired for next-generation concentrating solar power plants, which use high temperature heat transfer fluids to increase operating efficiency and enable CO2 instead of the steam turbine. The ternary eutectic mix NaCl-KCl-MgCl2 is the leading candidate for the heat transfer fluids because it has high temperature stability and good heat transfer properties. However, impurities, especially water, drives corrosion of the metal containers in contact with the molten chloride salt. Although higher operating temperatures increase efficiency, the corrosion rates also increase with increasing temperatures. Purification processes have been developed to remove corrosive impurities; however leaks can reintroduce oxidant impurities. Here, new methods are discussed to detect leaks and arrest corrosion of metal in contact with molten chloride salts. There were three primary tasks in this work, described below. (1) Determine the reduction potential of nickel and chromium ions, the two major alloyed elements in Haynes 230, in molten NaCl-KCl at 800C using cyclic voltammetry and differential pulse voltammetry of the metal surface. (2) The open circuit potentials and corrosion rates have been measured for pure alloyed elements Ni, Cr, W, and Mo and alloys Haynes 230 and nichrome in binary NaCl-KCl and ternary NaCl-KCl-MgCl2 at 800C. (3) The corrosion of Haynes 230 in NaCl-KCl-MgCl2 at 800C was arrested by applying a cathodic potential. The cathodic protection of H230 was done two ways i) by forming a galvanic couple between H230 and Cr by shorting the H230 cathode to Cr, a less-noble sacrificial anode, and ii) by inserting a voltage source between the H230 and Cr anode so the cathodic potential on H230 could be increased leading to a cathodic current from the Cr anode to the H230 cathode.
Degree ProgramGraduate College