Investigation of copper deposition on steel in molten copper chloride

Abstract

Hydrogen is considered as the most prominent candidate for clean energy generation. The Copper Chloride (Cu-Cl) cycle has been chosen as an effective cycle for production of hydrogen due to its comparatively lower operating temperatures and cost. While most materials subjected to the molten Cu-Cl environment are bound to corrode, stainless steel (SS) materials are coated with a layer of copper. This thesis study is primarily aimed at understanding the phenomenon of copper deposition on steel and also investigating the possibility of using this layer as a protective barrier against corrosion. Experiments are conducted with SS material being tested in molten Cu-Cl at 5000C for different immersion durations. Sol-gel coating methods are also tested for their ability to withstand the harsh Cu-Cl environment. Results show that, both the substrate and the copper coatings obtained, disintegrate as the immersion duration in molten Cu-Cl is increased. The sol-gel coating method also fails owing to its high porosity levels. It is concluded that since the iron in steel has more affinity towards chloride ions, it most likely reacts with molten copper chloride to form iron chloride thus leading to the formation of copper layer on its surface. This layer of copper is weak and discontinuous and cannot be construed to behave as a protective barrier against corrosion.