Corrosion of metals in calcium nitrate based phase change material

Abstract

Phase change materials are assumed to be a promising way of a storage of the low-potential heat. In the paper, the corrosion behaviour of carbon steel, CuZn37 brass and aluminium was studied in the assumed phase change medium at 50 °C and 60 °C. The medium was a eutectic mixture of 26.09 wt% water, 63.34 wt% calcium nitrate, 10.57 wt% potassium nitrate with fusion temperature of 37.85 °C. Corrosion rate was studied via mass loss and the steel specimens were analysed after the study. It was found that even though the corrosion rate of carbon steel and aluminium is small (4.26 mg cm⁻² year⁻¹ and 1.19 mg cm⁻² year⁻¹, respectively, at 50 °C), the metals are susceptible to pitting corrosion. Brass has the lowest corrosion rate from the studied metals (0.88 mg cm⁻² year⁻¹ at 50 °C); however, it is a subject of selective corrosion with zinc preferentially dissolved. None of the metals studied is suitable for the use in the phase change materials.