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The purpose of this study is to compare the inhibitive effect of polyaniline (PAni) and N-cetyl-N,N,N trimethyl ammonium bromide (CTAB)-stabilized PAni in a hydrochloric acid (HCl) medium.

PAni has been deposited potentiodynamically on mild steel in the presence of CTAB as a stabilizing agent to achieve high corrosion inhibition performance by the polymer deposition. The corrosion inhibition studies of CTAB-stabilized PAni inhibitor in 0.1 M HCl acidic solution was carried out by electrochemical methods, namely, open-circuit potential, potentiodynamic polarization and electrochemical impedance spectroscopy technique.

The results of electrochemical studies have shown that the CTAB-stabilized PAni inhibitor has higher corrosion efficiency than PAni on mild steel in 0.1 M HCl solution. The maximum per cent efficiency evaluated using the potentiodynamic polarization method is approximately 91.9.

CTAB-stabilized PAni has never been studied as a corrosion inhibitor for mild steel in an acidic medium. The investigations demonstrate relatively the better corrosion inhibition efficiency and high dispersion of the polymer in the acidic medium.

This paper aims to compare the inhibitive effects of polyaniline (PAni), poly(p-toluidine) and poly(aniline-co-p-toluidine) in hydrochloric acid (HCl) solution.

The electrochemical deposition of PAni, poly(p-toluidine) and poly(aniline-co-p-toluidine) on pure copper metal was studied potentiodynamically. The copolymer deposited was characterized by Fourier transform infrared (FTIR) spectroscopy, ultraviolet (UV)-visible spectroscopy and scanning electron microscopy (SEM). The corrosion inhibition studies on copper electrode were performed using electrochemical methods, viz, open circuit potential (OCP) measurements, potentiodynamic polarization scans and electrochemical impedance spectroscopy (EIS) tests, conducted in 0.1 M HCl solution.

The results of the study reveal that the copolymer of poly(aniline-co-p-toluidine) at the optimum concentration of 1 × 10−3 M has better corrosion inhibition efficiency as compared to PAni and poly(p-toluidine).

The conducting polymers are difficult to deposit on the metal surface because of their high dissolution tendency before the electropolymerization potential of the monomer is achieved.

From an environmental viewpoint, poly(aniline-co-p-toluidine) is a toxic and hazardous conducting polymer.

The paper demonstrates that poly(aniline-co-p-toluidine) showed better dispersion in different organic solvents and had higher corrosion inhibition efficiency than PAni.

The purpose of this paper is to study the inhibitive effect of p‐toluene sulfonic acid (p‐TSA) doped polyaniline on corrosion of copper in 0.1 M hydrochloric acid (HCl) solution.

The electrochemical deposition of polyaniline doped with p‐TSA on pure copper metal was studied potentiodynamically. The electrochemical study of the working electrode was performed at open‐circuit potential, then using potentiodynamic polarization and also with electrochemical impedance spectroscopy in 0.1 M HCl solution. The p‐TSA doped polymer deposit was characterized using Fourier transform infrared spectroscopy, with the UV‐vis and thermogravimetric analysis/differential scanning calorimetry techniques. The morphology of the deposited polymer was studied by scanning electron microscopy.

The results revealed that the p‐TSA self‐doped polymer had better corrosion inhibition efficiency than did the un‐doped polyaniline. It exhibited approximately 88.9 percent inhibition efficiency at 2x10⁻³ M concentration of p‐TSA, according to charge transfer resistance (R_ct) values evaluated from Nyquist plots.

The high dissolution tendency of metal surfaces generally occurs before the electropolymerization potential of the monomer is achieved. It was difficult to electrodeposit the conducting organic polymer on the surface of metal.

Some organic conducting polymers are toxic and hazardous from the environmental viewpoint. The electrochemical deposition of p‐TSA doped polyaniline is impractical for larger structures.

The paper demonstrates that p‐TSA doped polyaniline is environmentally benign and can be used for the protection of copper metal as a cathodic inhibitor.

The paper developed a novel gallic acid-based rust conversion emulsion (RCE) that is applied in the treatment of rusted steels. The purpose of this paper is to investigate the methods for the synthesis of RCE and study the mechanism of rust conversion.

Conversion emulsion was prepared using styrene, acrylate and self-developed gallic acid (GA)-based rust converter (GRC) via seed emulsion polymerisation. The polymerisable GRC was synthesised by the ring-opening reaction of glycidyl methacrylate with natural GA. The effects of the GRC dosage and its feeding modes on the RCE synthesis were analysed. The corrosion resistance, surface morphology, composition and mechanism of rust conversion coatings were studied using electrochemical tests, scanning electron microscopy, Raman spectroscopy and X-ray photoelectron spectroscopy (XPS), respectively.

The results showed that conversion coating on rusted steels treated with RCE, with various dosages of GRC (weight per cent), synthesised using seed emulsion polymerisation, exhibited the best adhesion and corrosion resistance. Raman spectroscopy revealed that RCE converted the original multiphase rust into stable crystalline phases of α-Fe₂O₃ and Fe₃O₄. According to XPS and energy dispersive X-ray analysis, the phenolic hydroxyl groups of RCE were proposed to chelate with Fe ions to form macromolecular ferrum compounds.

The pre-rusted steels demonstrated a better corrosion resistance than rust-free steels after treatment with RCE.

The paper developed a novel GA-based RCE with high efficiency and environment-friendly method.

This work is expected to replace the conventional rust conversion paints and cause a significant impact on extending the service life of rusted steels.

The purpose of this paper is to evaluate the corrosion inhibition potential of mangrove (Rhizopora apiculata) tannin in hydrochloric acid medium on copper with the view of developing a natural corrosion inhibitor.

The mangrove tannin was extracted from the mangrove bark and its anticorrosion potential was studied by weight loss, electrochemical and scanning electron microscopy (SEM) analysis.

It has been found that the mangrove tannin effectively inhibits the corrosion on copper metal in hydrochloric acid solution. The results of the electrochemical and weight loss methods showed that the inhibition efficiency of mangrove tannin increases with increasing its concentration. Inhibition is achieved through the adsorption of tannin molecules onto the copper surface and the adsorption follows the Langmuir adsorption isotherm model. SEM study also supports the adsorption of the inhibitor molecules onto the copper surface.

In this paper, mangrove tannin has been studied for the first time as a potential copper corrosion inhibitor in hydrochloric acid medium. The anticorrosion effect of tannin has been proven by standard methods. This natural inhibitor could find use in industries where copper is used as a fabrication metal.

This paper aim to investigate the influence of PA on the corrosion behavior of carbon steel with blast cleaned or pre-rusted treatments, and interpret the inhibition mechanism of PA on the steel with different surface treatments.

The influence of PA on the corrosion behavior of blast cleaned or rusty steel was investigated by means of electrochemical impedance spectroscopy (EIS). The EIS data were analyzed using the @ZsimpWin commercial software. The morphology and component of steel after immersion were characterized by scanning electron microscopy (SEM), energy dispersive spectrometer (EDS), Fourier transformation infrared (FTIR) and X-ray diffractometer (XRD).

EIS analysis results indicated that PA had good corrosion inhibition for blast cleaned or rusty steel. SEM, EDS, FTIR and XRD further indicated that PA had two main corrosion inhibition processes for the corrosion inhibition of blast cleaned or rusty steel: corrosion dissolution and formation of protective barrier layers.

Most published works focus the attention only toward the effect of corrosion inhibitor for the clean metal surfaces. However, the surface condition of metal sometimes is unsatisfactory in the practical application of corrosion inhibitor, such as existing residual rust. Some studies also have shown that several corrosion inhibitors could be applied on partially rusted substrates. These inhibitors mainly include tannins and phosphoric acid, but not PA. Therefore, the authors investigated the influence of PA on the corrosion behavior of carbon steel with blast cleaned or pre-rusted treatments in this paper.

The purpose of this study is to develop green/natural corrosion inhibitors. Adina cordifolia leaves extract (ACLE) was screened for its corrosion inhibition potential for mild steel (MS) corrosion in 0.5 M H₂SO₄ medium.

Adina cordifolia (AC) leaves were subjected to cold ethanol extraction and concentrated after refluxed with double distilled water. The resultant concentrate was screened for corrosion inhibition studies using sequence of standard corrosion monitoring techniques, namely, gravimetric analysis, electrochemical studies and scanning electron microscopy (SEM).

Gravimetric analysis provided evidence that the prepared ACLE showed dose dependent corrosion inhibition; impedance study revealed that the ACLE increases the charge transfer resistance and decreases double layer capacitance while polarization curves indicated that ACLE acts as a mixed-type inhibitor. Further studies over MS surface/test solutions through SEM and Fourier-Transform Infrared spectroscopy evident the formation of ACLE protective film protects MS.

AC’s methanol extract developed in this work can be used as a green corrosion inhibitor over industrial applications.

For the first time, AC leaves were tested as corrosion inhibitors for MS corrosion in 0.5 M H₂SO₄ medium. The results evidenced that ACLE will be a promising corrosion inhibitor, which could be usable in industries as a green corrosion inhibitor.