Fractal textured surfaces for high temperature corrosion mitigation in molten salts

Abstract

Mitigation of corrosion of structural materials in contact with molten salts is imperative in high temperature applications such as nuclear and solar thermal power plants. This paper introduces, for the first time, a novel approach to corrosion mitigation through fractal surface texturing and details a systematic corrosion study of a variety of structural materials. Multiscale fractal textured surfaces on SS316, In800H, In718, In625, and Ha230 were fabricated via chemical etching, whose parameters were optimized to obtain surface fractal dimensions above 1.90. The influence of grown oxides was examined by annealing the optimized etched surfaces with high fractal dimensions at a high temperature. The corrosion mitigation characteristics of plain, etched and etched-annealed surfaces were systematically studied in molten 60% NaNO 3 + 40% KNO 3 at 600 °C. The fractal textured surfaces are shown to reduce corrosion rate by 30% for ferrous alloys and by over 80% and up to 87% for high nickel content alloys. Elemental composition analysis reveals that the corrosion oxides are correspondingly diminished on fractal textured surfaces compared to plain surfaces. The study is significant in that any existing material may be made more corrosion resistant through this simple surface modification and treatment.