CORROSION BEHAVIOR OF UNCOATED AND COATED 316LSTAINLESS STEELS IN AQUEOUS SOLUTIONOF 99 FORMIC ACID

摘要

In petrochemical industry, 316L stainless steel is extensively used for engineeringrncomponents,I.e. distillation tower, due to better corrosion resistant properties than 304L stainless steel.rnHowever, aqueous formic acid produced from distillation of methanol can cause corrosion of the 316Lrnstainless steel at an unacceptable rate so that more noble materials were considered to be coated onrnsuch stainless steel. In the present study, corrosion behavior of 316L stainless steel coated withrn80Ni20Cr, 92Zirconia8Yttria, and Hastelloy C276 by thermal spray in comparison to the uncoatedrn316L stainless steel in aqueous 99% formic acid was studied using potentiodynamic technique.rnIt turned out that the uncoated 316L stainless steel has the best corrosion resistance. The coatings withrnthe highest to the lowest corrosion resistance can be ranked as follows: 92Zirconia8Yttria, HastelloyrnC276 and 80Ni20Cr coatings. By examination of cross sections under an optical microscope and SEM,rnit can be said that remarkably porous coatings, by which formic acid was allowed reach to the substraternand serious corrosion takes place consequently, cause reduction of corrosion resistance of the coatedrnstainless steels. In addition, corrosion of the substrate stainless steels may be accelerated byrndelaminated coatings.