Modifying the corrosion environment inside FGD plant using inhibitors

摘要

THE CORROSION problems of wet lime/limestone systems used for flue-gas desulphurization (FGD) in thermal-power plants is of great concern. The frequent variations in the acidity, and the chloride- and fluoride-ion concentrations experienced by the system, often cause major corrosion failure and pose a serious threat to the materials of construction. The currently-used materials (mostly type 316L stainless steel) seem to be effective but are not satisfactory, as they often fail to meet their life expectancy. The present study intends to evaluate the influence of 2-mercaptobenzothiazolydisulphide (MBTDS) and 2-mercaptobenzimidazolyldisuphide (MBIDS) on the localized corrosion of 316L stainless steel in a simulated FGD environment by performing cyclic anodic-polarization measurements. Both MBTDS and MBIDS were found to be effective in the breakdown and pit-protection potential, thereby improving the material's performance. The possible mode of adsorption and the way in which the inhibitors prevent the attack of the passive film by chloride ions present in the environment are discussed in detail. The present study concludes that both MBTDS and MBIDS are effective inhibitors for FGD systems.