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

Soumen Mandal; Jitendra Kumar Singh; Dong-Eun Lee; Taejoon Park

doi:10.3390/ma13163642

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

Materials (Basel). 2020 Aug 17;13(16):3642. doi: 10.3390/ma13163642.

Authors

Soumen Mandal¹, Jitendra Kumar Singh², Dong-Eun Lee³, Taejoon Park⁴

Affiliations

¹ Intelligent Construction Automation Center, Kyungpook National University, 80, Daehak-ro, Buk-gu, Daegu 41566, Korea.
² Innovative Durable Building and Infrastructure Research Center, Department of Architectural Engineering, Hanyang University, 1271 Sa3-dong, Sangrok-gu, Ansan 15588, Korea.
³ School of Architecture, Civil, Environment, and Energy, Kyungpook National University, 1370, Sangyegk-Dong, Buk-Gu, Daegu 702-701, Korea.
⁴ Department of Robotics Engineering, Hanyang University, 55 Hanyangdaehak-ro, Ansan, Gyeonggi-do 15588, Korea.

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 (R_p) and passive/oxide film resistance (R_o) 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.

Keywords: Raman spectroscopy; concrete pore solution; corrosion; electrochemical impedance spectroscopy; inhibitor; steel.