Hydrogen, as one of the best alternative energy carrier candidates, is easier to sustain than fossil fuel. Hydrogen demand has significantly increased as a clean energy carrier. The CuCl cycle is one of the capable thermochemical cycles which is supposed to develop hydrogen production. Since this cycle has some high temperature stages, a study on these parts is essential to realize the entirety of the cycle.

This research is about designing a system to evaluate candidate coatings following an immersion test in molten CuCl at 500°C for a prolonged time. Medium carbon steel was selected as the base metal. There were six types of combination coatings applied to evaluate the corrosion resistance of the generated coatings during the molten CuCl exposure. A ceramic of Yttria stabilized zirconia with two metallic coatings of Diamalloy 4006, and super hard steel coatings were applied in diverse combinations to the base metal using thermal spray methods.

Previous immersion apparatus was modified and improved to perform an immersion test that has a similar condition at high temperatures with a commercial hydrogen plant. All safety procedures and safety mechanisms were developed and a new geometry was designed for samples. After the immersion test, the materials were evaluated using electrochemical methods in combination with ex-situ surface analysis. The surface condition, including film structure, elemental composition, and resistivity of the materials, was examined and then compared. This examination was performed before and after the mechanism development and then compared. The majority of coatings were intact and did not fall off. New sample geometry may have affected the integrity of the sprayed coating, as there were no deep cracks or corrosions on the coated specimens. If the coating cracked, it could provide a pathway for the corrosive environment to go under the coating layer and react with the base metal. The results suggest that both Diamalloy 4006 and SHS 9172 HVOF coatings seemed to provide better protection to the underlying base metal than YSZ (ZrO₂ 18TiO₂ 10Y₂O₃).