System development for evaluating performance of corrosion resistant coatings exposed to molten copper chloride salt

•Developing a system to evaluate candidate coatings.•Immersion test in the molten CuCl at 500 °C for a prolonged time.•The corrosion rate tended to zero over time.•No more oxygen exists to react with the bare exposed metal.•Sealing mechanism verified.

Hydrogen, as one of the best alternative energy carrier candidates, is an important sustainable substitute for fossil fuels. Hydrogen demand has significantly increased as a clean fuel. To improve the green content of the future hydrogen economy, hydrogen must be produced in a clean method. The Cu–Cl cycle is one of the capable thermochemical cycles which is supposed to provide clean hydrogen production. Since this cycle has some high temperature stages, a study on these parts is essential to realize the entirety of the cycle, including the high temperature anti-corrosion equipment materials and the system to evaluate the performance of the materials.In one of the high temperature steps, molten Cu–Cl is produced as an intermediate product, which brings in the challenges of equipment materials selection. This paper is about developing a system to evaluate candidate coatings following an immersion test in the molten Cu–Cl at 500 °C for a prolonged time (i.e. 4 h, 10 h, 48 h, and 100 h). This system was developed in order to run the experiments in safe manner as a fire/smoke/corrosion resistant coating.Previous immersion test design was improved to perform an immersion test that mimics 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. It was proved that this system was capable to evaluate the performance of coatings at high temperature for molten salts and the system could accommodate coating tests in a safe manner. Later, some ceramics with metallic coatings were applied and then analysed in diverse combinations to the base metal (medium carbon steel) using thermal spray methods.The design and the performance of mechanism improvements are evaluated by measuring the corrosion rate. A study of weight change of the specimen on exposure, which is indicative of corrosion rate, represents the effectiveness of the developed sealing mechanism. The corrosion rate decreased and then approached to zero, as such sealing mechanism performed well under the experimental conditions.