Cathodic Protection Using Aluminum Metal in Chloride Molten Salts as Thermal Energy Storage Material in Concentrating Solar Power Plants

Angel G Fernández,Luisa F Cabeza

doi:10.3390/app10113724

Abstract

The new generation of concentrated solar power (CSP) plants to be developed presents a great challenge related to the increase in maximum operating temperature since molten salt CSP technologies require alternative salt chemistries such as chloride. The cathodic protection strategy involves the addition of a sacrificial metal to prevent corrosion of the alloy tested as container material in a CSP plant. In this paper, aluminum (Al) metal was analyzed as a corrosion inhibitor in OCT and HR224 alloys, obtaining corrosion rates of 4.37 and 0.27 mm/y, respectively. It has been confirmed that the use of Al metal can reduce the anodic current which is directly related to the corrosion rate. The formation of protective alumina scales (Al2O3) was assessed by scanning electron microscopy (SEM) and X-ray diffraction (XRD), confirming the corrosion model results from electrochemical impedance spectroscopy monitoring tests.

Highlights

In the last years, an opportunity has been identified to obtain higher power-generation efficiencies in concentrated solar power (CSP) plants using supercritical CO2 Brayton power cycle
The selection of high-temperature molten salt chemistry is needed and due to their low cost and high decomposition temperature, molten chlorides have been proposed as a feasible option
The electrochemical impedance spectroscopy (EIS) cell was composed of a working electrode (WE, with the alloy to be tested), a quasi-reference (RE, platinum wire), and a counter (CE, platinum mesh) electrode

Summary

Introduction

An opportunity has been identified to obtain higher power-generation efficiencies in concentrated solar power (CSP) plants using supercritical CO2 (sCO2 ) Brayton power cycle. The CSP technology needs to integrate high-temperature storage materials able to work in the range of 550 ◦ C to 750 ◦ C [1] For this purpose, the selection of high-temperature molten salt chemistry is needed and due to their low cost and high decomposition temperature, molten chlorides have been proposed as a feasible option. According to Mehos et al [1], the cost for the chloride salt system is dominated by the cost of the material to contain the storage material hot salt tank (70%) due to the expense and size of this tank In this case, the cold tank would be built using austenitic stainless steel since the operating temperature for this tank would be 520 ◦ C. This cost simulation was carried out using Haynes 230 alloy in the hot tank and AISI 347 in the cold storage tank

Methods

Results

Conclusion