The adsorption and inhibition effect of calcium lignosulfonate on Q235 carbon steel in simulated concrete pore solution

Abstract The corrosion inhibition of calcium lignosulfonate (CLS) for Q235 carbon steel in saturated Ca(OH) 2  + 0.1 mol/L NaCl solution was studied by means of weight loss, polarization, fluorescence microscopy (FM), scanning electron microscopy/energy dispersive spectrometry (SEM/EDS), microscopic infrared spectral imaging (M-IR) and X-ray photoelectron spectroscopy (XPS). For the steel in simulated concrete pore solution (pH 12.6), an increase of E b value and a decrease of i corr value occurred with different concentrations of CLS. The optimal content of CLS was 0.001 mol/L at which the inhibition rate was 98.86% and the E b value increased to 719 mV after 10 h of immersion. In mortar solution and in reinforced concrete environment, CLS also showed good inhibition for steel. The preferential adsorption of CLS around pits was detected by M-IR. The result illustrates that at the early stage the adsorption of CLS was heterogeneous and CLS may have a competitive adsorption with chloride ions at the active sites, which would be beneficial for decreasing the susceptibility of pitting corrosion. After the pre-filming time, an intact adsorption CLS film formed on carbon steel surface. The adsorption between CLS and calcium presented as Ca O S bonds. The adsorption of CLS on carbon steel surface occurred probably by both physisorption and chemisorption.