Adsorption and Inhibition Behavior of Calcium Lignosulfonate on Steel in NaCl + Ca(OH)₂ Solutions with Different pH Values

摘要

Potentiodynamic polarization measurements, microscopy infrared imaging (M-IR) and X-rayphotoelectron spectroscopy (XPS) were used to study the adsorption and inhibition behavior ofcalcium lignosulfonate (CLS) on Q235 steel in 0.1 mol/L NaCl + Ca(OH)2 solution (pH 7 ~ 12.5). Inthe solution of pH between 7 and 9.5, carbon steel was in active state. 0.001 mol/L CLS in the solutioneffectively inhibited both the cathodic and the anodic reactions. When the solution pH value increasedto 9.5~10.5, passivation occurred and the main compositions of the passive film include Fe2O3,FeOOH, FeO and CaO/Ca(OH)2. CLS promoted the passive state and raised the pitting corrosionpotential Eb. In the solution of pH 7~9.5, an inhibition film formed by adsorption of the sulfonic acidgroup and benzene ring in CLS molecular on the surface. When the pH value increased to 10.5, a Ca- O-S co-adsorption structure could form between O3 group in CLS and the outer side layer of thepassive film which is composed of CaO/Ca(OH)2. The strong adsorption characteristic between O32+ group in the adsorbed CLS on the surface and Ca ions in solution may further improve thecompactness of the adsorption film.