The ability to analyze different electrochemical corrosion phenomena, in–situ, without requiring any form of electrode perturbation has strongly attracted the attention of corrosion researchers towards the application of electrochemical noise (EN) analysis method. With the ability to analyze stochastic and chaotic electrode potential and current fluctuations at E_OCP, the EN analysis method is capable of providing information about the kinetics and mechanism of metallic corrosion with accuracy that can match conventional electrochemical techniques. Herein, we review the recent applications of EN analysis method to electrochemical corrosion research. We discuss briefly the theory behind the measurement of EN, and then highlight some of its application in the evaluation of corrosion inhibitors, pitting corrosion, coatings on metals, microbiologically–induced corrosion, as well as CO₂–corrosion. The drawbacks of the EN analysis method have also been highlighted and future considerations on the use of this important electrochemical technique have also been proposed.

An amine-functionalized glucose namely hexamethylene-1,6-bis(N-D-glucopyranosylamine) (HGA) was synthesized and characterized. The corrosion inhibition behavior of HGA on API X60 steel in 3.5 wt% NaCl saturated with CO₂ was evaluated by electrochemical impedance spectroscopy (EIS), electrochemical frequency modulation (EFM), linear polarization resistance (LPR), potentiodynamic polarization (PDP) and scanning electron microscopy (SEM). The adsorption of HGA on the API X60 mild steel surface obeyed the Langmuir isotherm. The results of potentiodynamic polarization indicated that the HGA molecule behaved as a mixed type inhibitor by reducing both the anodic and the cathodic electrochemical reactions. The maximum corrosion inhibition efficiency obtained was 91.82% at a concentration of 2.27 × 10⁻⁴ M (100 ppm). HGA reduced the extent of localized pitting corrosion on the steel surface. The inhibitor is protonated in the system and assumes a parallel orientation during adsorption on the steel. The oxygen and nitrogen atoms serve as reactive centers for adsorption, based on quantum chemical calculations and Monte Carlo simulations in the protonated form.

A newly synthesized pyrimidine–based compound, 5-(4-hydroxy-3-methoxyphenyl)-2,7-dithioxo-2,3,5,6,7,8-hexahydropyrimido[4,5-d]pyrimidin-4(1H)-one (PP), was evaluated as a promising inhibitor for the CO₂ corrosion of API X60 steel in NACE 1D196 brine solution. Under rotation speed of 1000 rpm, electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization (PDP) were complemented with scanning electron microscopy (SEM), X-ray diffraction (XRD) and Attenuated total reflectance infrared (ATR-IR) techniques to assess the corrosion inhibition performance. PP provided inhibition efficiency up to 90% at 20 ppm. It adsorbs on the Fe (110) phase on the steel using its heteroatoms and aromatic rings. Its adsorption greatly reduces the steel surface pitting corrosion.

The present work reports the application of 1,3,5-tris(4-methoxyphenyl)-1,3,5-triazinane for the inhibition of X60 steel corrosion in 3.5% NaCl saturated with CO₂. The compound was synthesized using a facile ultrasonic irradiation method, and for the first time, a comparative analysis of the static and hydrodynamic conditions was performed. The results of open circuit potential (OCP) vs. time and the potentiodynamic polarization are presented herein. The inhibitor showed a better performance (>97% efficiency) in the hydrodynamic conditions compared to the static conditions (>90% efficiency). The OCP vs. time results indicated a negative shift of the potential with inhibitor, revealing a primarily cathodic-type mechanism. Potentiodynamic polarization showed that the introduction of the triazine derivative significantly lowered the corrosion current densities suggesting that the inhibitor acted by adsorption and exhibited a mixed type of inhibition behavior with predominance of cathodic effect. The inhibitor adsorption on the steel surface followed the Langmuir isotherm.