Corrosion Behavior of Eutectic Molten Salt solution on Stainless Steel 316L

Abstract

The effect of eutectic molten salt on the corrosion behavior of a stainless steel 316L was investigated. To be used as thermal energy storage fluid, low melting point is one of the utmost important thermal properties amongst other. Eutectic salt was defined as a combination of two or more salt at different composition producing lower melting point than of it purest form. Four types of salts, sodium chloride (NaCl), potassium nitrate (KNO3), lithium nitrate (LiNO3), and sodium nitrate (NaNO3) were used to form fifteen mixtures of different composition to be tested on SS316L. The composition based on weight ratio was generated using response surface methodology (RSM). Eutectic composition of molten salt used as thermal energy storage fluid can possibly affect the corrosion occurrences due to the existence of Cl− ion and thereby influence the lifespan of the 316L stainless steel. This study indicates that the compositional different of eutectic mixture significantly affected the lifespan of the 316L stainless steel against corrosion. Two types of approaches are used in describing the corrosion behavior, which are resistance potential, Rp and corrosion rate. After test of 24hours in total immersion condition, 316L stainless samples have developed a scale of corrosion products made up of multiple oxides. Highest proportion of NaCl salt inhibits higher corrosion rate in eutectic molten salt as observed in resistance potential value and corrosion rate. Morphology of the stainless steel SS316L was further investigated under scanning electron microscope (SEM).