Title : A successful process to prevent corrosion of rich Gd-based room temperature magnetocaloric material during ageing
The corrosion during the heat transport process in a magnetocaloric effect-based cooling device is mimicked by subjecting the room temperature magnetocaloric material Gd6Co1.67Si3 to controlled water flow. Detailed microprobe, surface and depth profile analyses are studied. The water flow effect is first explained based on the elemental electrochemical oxidation and on an erosion phenomenon. Then the corrosion is expected to be controlled by selecting experimental conditions allowing ageing process in the passive region of Pourbaix diagram for cobalt. New corrosion tests by exposing material in passive fluid (KOH) up to 1 year have proved the neglected degradation of the material justified by X-Ray photoelectron spectroscopy (XPS) and deep profile Auger spectroscopy, and thus the control of its corrosion. The effective control of the corrosion when material is exposed to KOH can be an universal procedure in magnetocaloric based cooling prototype.
Keywords: magnetocaloric effect, corrosion, elemental electrochemical oxidation, erosion, control of corrosion, ageing, XPS