Investigation of new materials and methods to reduce corrosion of stainless steel in contact with molten chloride salts.

University essay from Luleå tekniska universitet/Materialvetenskap

Abstract: In this study, the corrosion resistance of three different stainless steels (304, 316 and 309) towards eutectic chloride salts is investigated. The performances of two materials to reduce the corrosion of the steels are examined: zirconium as sacrificial anode and an Al2O3 coating deposited by flame spraying. Samples are submitted to a 24 hours corrosion test at 700°C in air. The samples are characterised by weight analysis, SEM observations and EDX analysis of their surface and cross-section. The corrosion resistance of the stainless steels is not improved by adding Zr rods in direct contact with the steel, rather decreased in the areas where the rod laid. However, in these conditions, stainless steel 316 has the best resistance to highly corrosive chloride salts. The Al2O3 coating is too porous and penetrated by the salt, the steel underneath is corroded. Nevertheless, some alumina remains intact after the corrosion test, because of the high inertness of the ceramic. The presence of O2 most certainly accelerated the corrosion mechanism studied here.

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