Phenylurea-based corrosion inhibitor with ultra-high protection efficiency under acidic conditions

The pickling process often poses significant environmental challenges, particularly due to the addition of surfaceactive organic compounds to acidic solutions to inhibit corrosion on stainless steel surfaces. To minimize the generation of waste solutions and prevent excessive corrosion of stainless steel, the development of highefficiency corrosion inhibitors for pickling solutions is of substantial practical and industrial importance. In this study, organic corrosion inhibitors prepared from aniline, o-phenylenediamine, m-phenylenediamine, pphenylenediamine with 1,4-phenylene diisocyanate were investigated. The structure of the resulting inhibitor films was characterized using FTIR, EDS, Mapping, and SEM, revealing good homogeneity and density, which effectively form protective layers on metal surfaces. The inhibitors exhibited excellent corrosion inhibition performance, with the protection efficiency of aniline-based inhibitors reaching 98.6 % at a concentration of 200 ppm in a 1 M HCl solution, significantly reducing the dissolution of Q235 stainless steel (Q235SS). Additionally, the relationship between inhibitor performance and molecular structure was analyzed using DFT calculations. The results demonstrate that phenylurea-based corrosion inhibitors with large it-conjugated planar structures and amine-based polar functional groups provide superior corrosion protection in HCl corrosive media.