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To study the effect of inhibition of new bipyrazole derivatives on the corrosion of steel in HCl media at various temperatures.

In this study, novel corrosion inhibitors, namely bipyrazoles were synthesised and tested as corrosion inhibitors for steel in 1 M HCl. The degree of corrosion was measured using various techniques including weight loss measurements, potentiodynamic polarisation, linear polarisation resistance (Rp) and impedance spectroscopy (EIS).

It was found that 1,5,5′‐trimethyl‐1H,2′H‐3,3′‐bipyrazole (P₁) gave the best inhibition effect. The inhibition efficiency increased with the concentration of P₁ to attain 79 per cent at 10⁻³ M. Good agreement between the various methods explored was observed. Polarisation measurements also showed that P₁ acted essentially as a cathodic inhibitor. The cathodic curves indicated that the reduction of proton at the steel surface was an activating mechanism. P₁ adsorbed on the steel surface according to Frumkin adsorption model.

The synthesis route offers the possibility of other pyrazolic compounds to be tested in the future.

The inhibitory efficiency of P₁ increased with the increase of both the concentration and the temperature (in the 298‐353 K range). As such, P₁ can be used in chemical cleaning and pickling processes.

The originality of this work is the synthesis of new inhibitors based on pyrazolic organic compounds.

To evaluate the effect of natural rosemary oil as non toxic inhibitor on the corrosion of steel in H₃PO₄ media at various temperatures.

The oil was hydro‐distilled. The oil was used as inhibitor in various corrosion tests. Gravimetric and electrochemical techniques were used to characterise the corrosion mechanism.

Chromatographic analysis by GC showed that the oil was rich in 1,8‐cineole. The oil was a good inhibitor. But, its efficiency decreased with temperature.

The inhibition efficiency increased with the concentration of the natural oil to attain 73 per cent at 10 g/l. Good agreement between the various methods explored was observed. Polarisation measurements showed that rosemary oil acted essentially as a cathodic inhibitor.

The efficiency of the oil increased with the concentration but decreased with the rise of temperature in the 298‐348 K range. The natural oil could thus be used in chemical cleaning and pickling processes.

The originality of this work is the finding of a safe and cheap inhibitor from natural plants.

This paper seeks to evaluate the effect of natural menthols and their synthesised epoxy‐allylmenthols as a non‐toxic inhibitor on the corrosion of steel in HCl media at various temperatures.

Epoxy‐allylmenthols were synthesised and characterised. Gravimetric technique was used to measure the efficiency of corrosion inhibition.

Modified allylmenthol (to epoxy‐allylmenthol) exhibited a good inhibition. But its efficiency decreases with temperature.

The inhibition efficiency increases with the concentration of inhibitor to attain 74 percent at 0.8 g/l.

The efficiency of menthol derivatives increases with the concentration but decreases with rise of temperature in the 303‐328 K range. Natural inhibitor can be used in chemical cleaning and pickling processes.

The originality of this work is to find a safe and cheap eco‐friendly inhibitor from natural plants.

The influence of addition of the natural material, jojoba oil, on the corrosion of iron in molar hydrochloric acid had been studied using weight loss measurement and electrochemical polarisation methods. It was found that the corrosion rate was significantly reduced in the presence of jojoba. It was also found that the corrosion inhibition efficiency increased with the concentration of the jojoba oil to attain a 100 per cent inhibition at 0.515 g/l of jojoba oil, indicating that jojoba oil was an excellent corrosion inhibitor. The effect of temperature on the corrosion behaviour of iron indicated that the inhibition efficiency of jojoba oil decreased very slightly with the rise of temperature. It was found that the adsorption of jojoba oil on the iron, which followed the Frumkin isotherm, was the main cause to the corrosion inhibition.

Corrosion inhibitors most commonly are used in the acid pickling, cleaning and etching solutions. Plant extracts as rich and cheap resources are among the eco-friendly inhibitors. This study aims to investigate the inhibition effect of plantain extract on mild steel corrosion.

The inhibition influence of plantain extract on mild steel corrosion was investigated through Tafel polarization, electrochemical impedance spectroscopy and weight loss techniques in 1 M HCl solution. Furthermore, the sample surface morphology was verified by scanning electron microscopy.

The inhibition effect of the plantain extract was increased with the increase in the inhibitor concentration due to its adsorption on the surface of samples. The adsorption mechanism of the plantain extract on mild steel is physical adsorption and follows Langmuir isotherm.

The results obtained from different methods showed that the plantain extract has good inhibition performance on corrosion mild steel in 1 M HCl solution as a green inhibitor.

The aim of this work was to investigate how Andrographis paniculata (Burm.f.) Wall.ex Nees extract affected the corrosion of low-carbon (C) steel in 0.1M HCl.

The Andrographis paniculata (Burm.f.) Wall.ex Nees was extracted into distilled water at 70°C for 1 h. The corrosion inhibition efficiency of the extract was determined in 0.1M HCl using weight loss measurements, potentiodynamic polarization and electrochemical impedance spectroscopy. The effects of extract concentrations and of temperature were investigated.

The Andrographis paniculata (Burm.f.) Wall.ex Nees extract could inhibit the corrosion process of low-C steel in 0.1M HCl. With the extract concentration of 1 g/l, an inhibition efficiency of 96.3 per cent was obtained. The extract acted as an anodic inhibitor. The adsorption process of the extract was physisorption and it followed the Langmuir adsorption isotherm.

This paper revealed that Andrographis paniculata (Burm.f.) Wall.ex Nees cultivated in Thailand, which was extracted using a simple and environmentally friendly method, could act as a very good green corrosion inhibitor for low-C steel in 0.1M HCl solution.

To evaluate the effect of some tetrazole compounds as corrosion inhibitors of copper in HNO₃ at various temperatures.

1‐phenyl‐5‐mercapto‐1,2,3,4‐tetrazole (PMT) was selected as the best inhibitor among the tetrazole compounds tested. Gravimetric and electrochemical techniques were conducted.

PMT was an excellent inhibitor for copper in acid. Its efficiency attained 97.5 per cent and decreased slightly with temperature.

The inhibition efficiency increased with the concentration of PMT to reach 97.5 per cent at 10⁻³ M. Good agreement between the various methods explored was observed. Polarisation measurements also showed that PMT acted as a mixed inhibitor.

The efficiency of PMT increased with the concentration but decreased with rise of temperature in the 298‐333 K range. As such, PMT could be used in chemical cleaning and pickling processes.

The originality of this work was the finding of an efficient inhibitor (PMT) having a nearly 100 per cent efficiency.

The purpose of this paper is to make people aware of organic corrosion inhibitors.

As it is a literature review paper, no specific method is used.

It has been found that plant extracts and oils show inhibition efficiency up to 98 percent, so it is certain that plant extracts and oils are effective corrosion inhibitors and can be successfully used at the industrial level.

Plant extracts and oils are also found to be non‐toxic, highly efficient, renewable and cheap. But less effort has been given towards the identification of which compound is active in the extract.

The paper shows detailed account of the inhibitors obtained from plants, which are used as natural corrosion inhibitors.

The effects of natural Artemisia oil on the corrosion of steel in molar hydrochloric acid were studied by the measurements of weight loss, electrochemical and EIS polarisation. The results obtained revealed that Artemisia oil reduced the rate of corrosion. The corrosion inhibition efficiency increased with the increase of inhibitor concentration. Potentiodynamic polarisation studies clearly revealed that the presence of the natural Artemisia oil did not alter the mechanism of the hydrogen evolution reaction and acted essentially as a cathodic inhibitor. Good agreement between gravimetric and electrochemical polarisation results was noted. The effect of temperature on the corrosion behaviour of steel in 1M HCl, with and without the oil in the temperature range of 308‐353 K, indicated that inhibition efficiency increased with temperature. The adsorption of Artemisia oil on the steel is followed by Frumkin adsorption isotherm.

The purpose of this paper is to study methyl green dye (MG) as a corrosion inhibitor for low carbon steel (LCS) in hydrochloric acid (1 M) and sulphuric acid (0.5 M) and to assess the effect of temperature variation and halide additives on the inhibition efficiency.

Corrosion rates are monitored using the gravimetric technique. Inhibition efficiency is determined by comparing the corrosion rates in the absence and presence of additives. Attempts are also made to elucidate the inhibition mechanism from the trend of inhibition efficiency with change in temperature and type of acid anion.

MG reduces the corrosion rate of the LCS specimens in both acid media within the investigated temperature range by adsorption at the metal/solution interface. Inhibition efficiency increases with MG concentration but decreases with rise in temperature. Maximum values of 67 and 73 per cent are obtained in 1 M HCl and 0.5 M H₂SO₄, respectively, at [MG]=0.001 mol dm⁻³. Halide additives increase the inhibition efficiency mainly in the sulphuric acid medium.

The inhibiting effect of MG is studied within a fixed concentration range, which can be expanded for further studies. The same applies to the effect of halide additives. Also, the dye structure can be modified by introducing different functional groups, and the effect on inhibition efficiency is investigated.

The research findings can find practical application for corrosion control in aqueous acidic environments.

This paper provides new information on the application of MG for corrosion inhibiting purposes. The experimental results form part of an extensive database on the corrosion inhibiting characteristics of organic dyes.