A simple method for the inhibition of the corrosion of carbon steel by molten nitrate salt for thermal storage in concentrating solar power applications. (December 2018)

• Record Type: Journal Article
• Authors: Grosu, Yaroslav; Nithiyanantham, Udayashankar; Zaki, Abdelali; Faik, Abdessamad
• Is Part Of: Npj Materials degradation. Volume 2(2018)
• Page Start: 1
• Page End: 8
• Publication Date: 2018-12
• Subjects: Materials -- Deterioration -- Periodicals; Materials -- Testing -- Periodicals; 620.110287
• DOI: 10.1038/s41529-018-0055-0
• Languages: English
• ISSNs: 2397-2106

Abstract

Abstract Corrosion is an important issue in high-temperature applications such as Concentrated Solar Power (CSP) technology, playing a crucial role in the long-term use of storage tanks, heat exchanger and piping materials which account for a considerable component of the investment costs. While there are many studies regarding the corrosion rates of container materials under the conditions of CSP, there is little progress in the field of their degradation prevention by anticorrosion methods. This work presents an analysis of the corrosion mechanisms between the most economical construction material—carbon steel—and molten nitrate salt. A method to protect the carbon steel against corrosion by molten salt at high temperature was proposed, involving the formation of a calcium carbonate layer on the carbon steel surface. The stability of the layer was tested under isothermal and temperature cycling conditions up to 500 °C, in both inert and air atmospheres in the presence or absence of humidity. The protection method proposed has potential to reduce investment costs for CSP technology. Carbon steels: graphite spraying improves high-temperature corrosion in molten nitrate salts Spraying a thin coat of graphite on carbon steel can significantly improve their resistance to nitrate salts at high temperatures. A team led by Yaroslav Grosu and Abdessemad Faik from CIC Energigune in Spain used spray graphitization to coat the surface of a carbon steel before burying it in a nitrate salt mixture and heating it above 300 °C. Whether in air or in an inert atmosphere, and whether held above 300 °C in humidity or thermally cycled for 500 h up to 500 °C, the sprayed graphite consistently promoted the formation of stable calcium carbonate crystals at the steel surface. This protective calcium carbonate layer stopped the steel from oxidising. Inhibiting steel corrosion when in contact with molten salts can help optimise materials for concentrated solar power technology and other high-temperature applications.