Effects of molten-salt LiNO 3 on high-temperature corrosion behaviour of absorption tubes of a concentrating solar power system

Abstract

The main aim of the present research was to investigate the effects of a ternary nitrate salt (NaNO₃–KNO₃–LiNO₃) on high-temperature corrosion behaviour of stainless steel 321 (SS 321) in a parabolic trough collector in a concentrating solar power system. The corrosion behaviour of SS − 321 was examined in a ternary salt (LiNO₃ (25 wt-%)-NaNO₃ (25 wt-%)-KNO₃ (50 wt-%)) at 400°C and 550°C for 250 h, 500 h and 1000 h, and the obtained findings were then compared with the results of a solar salt ((NaNO₃ (60 wt-%)-KNO₃ (40 wt-%)). In order to determine the quantitative corrosion behaviour of SS − 321, the results of immersion tests and microstructural investigations obtained through scanning electron microscopy and energy-dispersive X-ray microanalysis were also considered. It was found that the addition of lithium nitrate (LiNO₃) to solar salt formed resistant oxide layers on the surface of SS 321 and subsequently, increased its corrosion resistance ability.