Quebracho tannin as corrosion inhibitor in neutral media and novel rust conversion agent for enhanced corrosion protection

Abstract

In the present work, the anticorrosive properties of quebracho tannins extract (QE) were tested in neutral solution to protect mild steel and a new rust conversion agent based on QE was developed. QE remarkably rich of total phenolic compounds (TPC) (2630.1 ± 11.43 mg gallic acid equivalent (GAE)/g) and flavonoids (81.36±1.20 mg quercetin equivalent (QUE)/g) was revealed. QE have shown good antioxidant activity (75% and 68% DPPH and ABTS radical scavenging activities at 500 mg/L of QE, respectively). The inhibition corrosion process of steel in 3.5% NaCl solution by QE have been studied using potentiodynamic polarization and polarization resistance measurements. The steel surface is acquired by scanning electron microscopy (SEM). Density functional theory (DFT) was used to give further insight into the adsorption and inhibition mechanism of QE on the steel surface. A tannin primer was prepared and coated panels were tested in salt spray chamber.