Dynamic corrosion testing of metals in solar salt for concentrated solar power

Behavior of Ni20Cr Alloy in Molten Nitrate Salts

“…In general, in Solar Salt, at immersion times greater than 500 h, the effect of temperature on the corrosion process of the alloy was observed, namely, increasing the temperature increased the mass gain, which indicates an increase in the metallic dissolution process and, therefore, a greater presence of corrosion products. This is justifiable given that corrosion in molten nitrates occurs because of their corrosive ions (O 2− , NO −2 ) formed by the thermal decomposition of nitrate ions (NO −3 ) whose presence is accelerated at temperatures above 500 °C [ 6 , 12 ]. This shows the direct relationship between the metal dissolution process and the ability of the alloy to self-heal with both temperature and immersion time.…”

“…This weight was the one used to determine the variation in mass of the alloy as a function of time. Based on the initial reaction area of the specimens, as well as their initial and final weight, their mass change was evaluated according to the following expression [ 6 ]: where the term on the left side of the expression represents the mass per unit area (lost or gained), m i is the initial mass, m f is the final mass at time t , A o is the initial reaction area of the sample, and Δ m is the mass change experienced by the sample. The mass changes thus determined represent the overlapping effects of mass gain due to corrosion, and the mass loss due to dissolution and detachment of corrosion products.…”

“…This weight was the one used to determine the variation in mass of the alloy as a function of time. Based on the initial reaction area of the specimens, as well as their initial and final weight, their mass change was evaluated according to the following expression [6]:…”

“…However, in recent years, there has been a growing interest in the corrosion problems that occur in CSP plants due to the corrosive effect of HTFs on the materials with which it is in contact. Various studies have been reported in the literature to understand the behavior of materials that are in contact with an HTF [ 2 , 3 , 4 , 5 , 6 , 7 , 8 ]. In general, HFTs have a low melting temperature, low viscosity, and low vapor pressure.…”

“…Many of the materials used are Fe-based or Ni-based, and their corrosion resistance depends on the development of a protective oxides layer (Cr 2 O 3 , Al 2 O 3 ) and the presence of other alloying elements that mainly improve their mechanical properties [ 2 , 3 , 7 , 9 ]. It has been observed that the content of both Ni and Cr improves the corrosion resistance; with a higher content of these elements, the corrosion resistance is increased [ 2 , 6 , 10 , 11 , 12 ]. Therefore, the various studies carried out to date have indicated that nickel-based alloys show excellent performance in various HFT fluids [ 4 , 5 , 7 ].…”