Dense carbon film coated 316L via in-situ synthesized CaC2 in FLiNaK molten salts and its high performance of anti-corrosion property

Abstract Dense carbon film coated on 316L stainless steel was achieved by electrochemical deposition in molten fluoride salt (LiF-NaF-KF 46.5–11.5-42.0 mol%, FLiNaK, m.p. 727K) using C 2 2- as the C source. The C 2 2- source was in-situ synthesized in the high temperature eutectic salt by adding mixed Ca/C powders. Results of cyclic voltammetry confirmed the formation of CaC 2 and the obtained C coated 316L samples demonstrate satisfactory electrochemical deposition via synthesized C 2 2- . SEM images show that a dense and tunable thickness of C film can be fabricated in this FLiNaK–Ca/C–CaC 2 system in the range of 2.0–6.0 μm by optimizing the deposition conditions such as concentrations of Ca/C, deposition potentials, temperatures and times. Characterizations of the as-prepared C film by Raman spectroscopy imply that deposited films are predominantly composed of low degree crystallization structures. The anti-corrosion behavior of this coated material was verified by potentiodynamic polarization. Compared to bare 316L material, corrosion rate suppression by a factor of more than 16 was determined for a 4.0  μm C coated 316L sample in 0.1M HCl+0.5M NaCl solution, indicating the coating provides extremely high anti-corrosion performance.