Effect of Chloride Ion on the Corrosion Behavior of 316L Stainless Steels in Hydrofluoric Acid Solution

In this study, the corrosion behavior of 316L stainless steel (SS) in hydrofluoric acid and chloride-containing hydrofluoric acid solutions were investigated. The immersion results show that the addition of chloride ions yields a tremendous improvement in corrosion resistance. The corrosion rate of 316L SS remarkably reduces from 68.80 to 0.48 mm/a while adding 1 M chloride ions into 23 M hydrofluoric acid solution. Through morphology and corrosion composition analysis, the high corrosion resistance in chloride-containing hydrofluoric acid solution is mainly attributed to the interaction between competitive adsorption and selective corrosion. Due to competitive adsorption, chloride ion preferentially adsorbs and dominates corrosion. It shifts the preferentially corroded phase and increases the compactness of the product layer, resulting in a remarkable reduction of the corrosion rate. Additionally, a model has been developed to further elucidate the inhibition effect of chloride ions on the corrosion of 316L SS in hydrofluoric acid solution.