Study on Synergistic Corrosion Inhibition Effect between Calcium Lignosulfonate (CLS) and Inorganic Inhibitors on Q235 Carbon Steel in Alkaline Environment with Cl.

Bing Lin,Yingying Wang,Hu Wang,Yu Zuo,Junlei Tang

doi:10.3390/molecules25184200

Abstract

The synergistic corrosion inhibition effect between calcium lignosulfonate (CLS) and three kinds of inorganic inhibitors (Na2MoO4, Na2SnO3, and NaWO4) with various molar ratios on Q235 carbon steel in alkaline solution (pH 11.5) with 0.02 mol/L NaCl was investigated by cyclic potentiodynamic polarization, electrochemical impedance spectroscopy, linear polarization, scanning electron microscopy, and X-ray photoelectron spectroscopy. Molybdate and stannate in hybrid inhibitor could promote the passivation of steel and form a complex film, which could suppress the corrosion effectively. Moreover, the insoluble metal oxides in the complex film formed by three kinds of inorganic inhibitor could help the adsorption of CLS onto the steel surface. The CLS molecules could adsorb onto the steel surface and metal oxides to form an adsorption film to protect the steel from corrosion. A three-layer protection film formed by a hybrid inhibitor, including passivation film, deposition film, and adsorption film, would effectively inhibit the corrosion reactions on the steel surface. The CLS compound with molybdate with the ratio of 2:3 shows the best inhibition effect on both general corrosion and localized corrosion.

Highlights

Alkaline environment is a common corrosion condition in reinforced concrete system, marine environment, and industrial desulfurization installation
The synergistic inhibition effect and mechanism of calcium lignosulfonate (CLS) compound with molybdate, stannate, and tungstate in alkaline environment with 0.02 mol/L Cl− were studied in this work, and the following conclusions can be drawn: The electrochemical measurements including Cyclic Potentiodynamic Polarization (CPP) curves and electrochemical impedance spectroscopy (EIS) results reveal that hybrid inhibitors have a better inhibition effect than using CLS or inorganic alone at the same concentration for both general corrosion and localized corrosion
The hybrid inhibitor formed by CLS and molybdate shows the best inhibition effect out of all hybrid inhibitors, and the best ratio of CLS and inorganic inhibitor is 2:3

Summary

Introduction

Alkaline environment is a common corrosion condition in reinforced concrete system, marine environment, and industrial desulfurization installation. The corrosion of carbon steel in alkaline environment has been extensively studied in recent years owing to its industrial relevance. In the reinforced concrete system, the corrosion of reinforcing steel is the main reason leading to the premature deterioration of reinforced concretes [1,2]. The corrosion of reinforcing steel in concrete is related to the presence of chloride ions and carbonation of concrete, which may result in corrosion initiation as a sequence of several events. The use of corrosion inhibitors is one such strategy, which has the advantages of simple use, as well as being economical and controllable, among others. Corrosion inhibitors used for steel rebar in concrete include inorganic compounds, organic compounds, and hybrid inhibitors [4]

Results

Discussion

Conclusion