Effect of Phosphate-Based Inhibitor on Corrosion Kinetics and Mechanism for Formation of Passive Film onto the Steel Rebar in Chloride-Containing Pore Solution

Abstract

In the present study, different contents, i.e., 1–3% of 0.5 M ammonium phosphate mono basic (APMB), were used as corrosion inhibitor to reduce the corrosion of steel rebar. Electrochemical impedance spectroscopy (EIS) results showed that up to 24 h of exposure, polarization resistance (Rp) and passive/oxide film resistance (Ro) gradually decreased in simulated concrete pore (SCP) + 3.5 wt.% NaCl solution owing to the reduction in pH of the solution. The steel rebar exposed in 2% inhibitor containing SCP + 3.5 wt.% NaCl solution exhibited 90% inhibition efficiency after 1 h of exposure. X-ray photoelectron spectroscopy (XPS) and Raman spectroscopy confirmed the formation of thermodynamically very stable and sparingly soluble goethite (α-FeOOH), maghemite (γ-Fe2O3), and iron phosphate (FePO4) as passive/oxide film onto the steel rebar surface exposed to 2% inhibitor containing SCP + 3.5 wt.% NaCl solution.

Corrosion Inhibition Mechanism of Steel Reinforcements in Mortar Using Soluble Phosphates: A Critical Review

“…3− ] = [F − ], the following expression can be obtained: Phosphate compounds are known to precipitate at a wide range of pH levels [44]. According to Mandal et al [117], in the presence of phosphates a passive layer is generated on steel containing oxides/hydroxides such as goethite (α-FeOOH) and akaganeite (β-FeOOH); both are thermodynamically very stable and sparingly soluble phases, lepidocrocite (γ-FeOOH) and maghemite (γ-Fe 2 O 3 ) as well as the thermodynamic stable iron phosphate (FePO 4 ). These oxides and oxyhydroxides are also generated on bare steel exposed to continental and marine environments [118].…”

Corrosion Protection of Q235 Steel Using Epoxy Coatings Loaded with Calcium Carbonate Microparticles Modified by Sodium Lignosulfonate in Simulated Concrete Pore Solutions

“…The presence of one-time constant corresponding to the coatings at the initial stage of the soaking were fitted by equivalent electrical circuit ( Figure 9 a) to model the EIS spectra. The impedance spectra of the coating at the later period of immersion revealed two-time constants: the inhibition properties of the coating are reflected at lower frequency, while the other at higher frequency indicates the corrosion phenomena appearing on the metal-coating interface [ 47 ].…”

Effect of Chloride Ions Concentrations to Breakdown the Passive Film on Rebar Surface Exposed to L-Arginine Containing Pore Solution

“…The electrochemical studies were carried out in simulated concrete pore (SP) solutions. The chemical composition for the synthesis of this solution was described in our earlier published work [ 28 , 29 , 30 ] and others [ 31 , 32 ] where NaOH, KOH, and CaO were used. In this solution, SP was filtered with Whatman paper where insoluble CaO was removed.…”

“…The steel surface was rinsed with distilled water prior to taking the SEM images to ascertain the removal of deposit salts. The other details about characterization techniques are described in our earlier published papers [ 29 , 30 ].…”

“…The steel surface was rinsed with distilled water prior to taking the SEM images to ascertain the removal of deposit salts. The other details about characterization techniques are described in our earlier published papers [29,30] The OCP measurement results are shown in Figure 1. The OCP of the passivated steel rebar stabilized by adsorbing the LA at the surface, which formed the Fe-Zwitterion complex that protects rebar from corrosion [34].…”