M. Traisnel

Study of the mechanism and inhibiting efficiency of 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole on mild steel corrosion in acidic media

Abstract The efficiency of a new triazole derivative, namely, 3,5-bis(4-methylthiophenyl)-4H-1,2,4-triazole (4-MTHT) has been studied for corrosion inhibition of mild steel in 1 M hydrochloric acid (HCl) and 0.5 M sulphuric acid (H 2 SO 4 ). Corrosion inhibition was studied using electrochemical methods and weight loss measurements. These studies have shown that 4-MTHT was a very good inhibitor. 4-MTHT behaved better in 1 M HCl than in 0.5 M H 2 SO 4 and inhibition efficiencies up to 99% and 80% can be obtained in 1 M HCl and 0.5 M H 2 SO 4 , respectively. Activation energies ( E a ) in the presence and absence of 4-MTHT were obtained by measuring the temperature independence of the corrosion current. The potential of zero charge of mild steel was studied by ac impedance method, and the mechanism of adsorption has been discussed. The adsorption of 4-MTHT followed Langmuirs adsorption isotherm in both acids.

The corrosion inhibition of mild steel in acidic media by a new triazole derivative

A new corrosion inhibitor, namely, 3,5-bis (2-thienyl)-4-amino-1,2,4-triazoles (2-TAT) has been synthesised and its inhibiting action on the corrosion of mild steel in acid baths (1 M HCl and 0.5 M H2SO4) has been investigated by various corrosion monitoring techniques, such as corrosion weight loss tests and electrochemical impedance spectroscopy. The electrochemical study reveals that this compound is an anodic inhibitor. Changes in impedance parameters (Rt and Cdl) are indicative of the adsorption of 2-TAT on the metal surface, leading to the formation of a protective film which grows with increasing exposure time. 2-TAT is able to reduce the steel corrosion more effectively in 1 M HCl than in 0.5 M H2SO4. The adsorption of this inhibitor is also found to obey the Langmuir adsorption isotherm in both acids. 2-TAT is considered as a non-cytotoxic substance.

Inhibiting effects of 3,5-bis(n-pyridyl)-4-amino-1,2,4-triazoles on the corrosion for mild steel in 1 M HCl medium

Abstract A new class of corrosion inhibitors, namely, 3,5-bis(n-pyridyl)-4-amino-1,2,4-triazoles (n-PAT) has been synthesised and its inhibiting action on the corrosion of mild steel in 1 M HCl has been investigated by various corrosion monitoring techniques such as corrosion weight loss tests and electrochemical impedance spectroscopy. The electrochemical study reveals that these compounds are anodic inhibitors. The adsorption of (n-PAT) on the steel surface obeys the Langmuir adsorption isotherm.

Corrosion inhibition of mild steel by the new class of inhibitors [2,5-bis(n-pyridyl)-1,3,4-thiadiazoles] in acidic media

The inhibitor effect of 2,5-bis(n-pyridyl)-1,3,4-thiadiazoles (n-PTH) on the corrosion of mild steel in 1 M HCl and 0.5 M H2SO4 have been investigated using weight loss and electrochemical impedance spectroscopy. Results obtained reveal that these compounds are mixed-type inhibitors and behave better in 1 M HCl than in 0.5 M H2SO4. The adsorption of n-PTH on the mild steel surface in both acidic media follows a Langmuir isotherm model.

A new triazole derivative as inhibitor of the acid corrosion of mild steel: electrochemical studies, weight loss determination, SEM and XPS

Abstract The effect of addition of 2[5-(2-pyridyl)-1,2,4-triazol-3-yl] phenol (PPT) on mild steel dissolution in 1 M hydrochloric acid is studied through electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation curves and gravimetric measurements. The obtained results showed that PPT revealed a good corrosion inhibition. Potentiodynamic polarisation studies indicate that PPT is a mixed-type inhibitor. The effect of temperature on the corrosion behaviour of mild steel in 1 M HCl with addition of 80 mg/l of PPT was studied in the temperature range from 25°C to 60°C. The associated activation corrosion and free adsorption energies have been determined. Scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) of the mild steel revealed that PPT is absorbed on the steel surface. PPT appears to function through the general adsorption mode following the Langmuir adsorption isotherm model.

The inhibition action of 3,6-bis(2-methoxyphenyl)-1,2-dihydro-1,2,4,5-tetrazine on the corrosion of mild steel in acidic media

Abstract The inhibition effect of 3,6-bis(2-methoxyphenyl)-1,2-dihydro-1,2,4,5-tetrazine (2-MDHT) on the corrosion of mild steel in acidic media has been investigated by weight loss and various electrochemical techniques. Results obtained reveal that this organic compound is a very good inhibitor. 2-MDHT is able to reduce the corrosion of steel more effectively in 1 M HCl than in 0.5 M H 2 SO 4 . Potentiodynamic polarisation studies showed that 2-MDHT is a mixed-type inhibitor in 1 M HCl and cathodic-type in 0.5 M H 2 SO 4 . 2-MDHT acts on the cathodic reaction without changing the mechanism of the hydrogen evolution reaction. Surface analyses were also carried out to establish the mechanism of corrosion inhibition of mild steel in acidic media. The adsorption of this inhibitor on the mild steel surface in both acids obeys the Langmuir absorption isotherm. The effect of temperature on the corrosion behaviour of mild steel in 1 M HCl with addition of 100 mg l −1 of 2-MDHT was studied in the temperature range 25–60°C. The associated activation corrosion and free adsorption energies have been determined.

Influence of 2,5-bis(4-dimethylaminophenyl)-1,3,4-thiadiazole on corrosion inhibition of mild steel in acidic media

An example of a new class of corrosion inhibitors, namely, 2,5-bis(4-dimethylaminophenyl)-1,3,4-thiadiazole (DAPT) was synthesized and its inhibiting action on the corrosion of mild steel in 1 M HCl and 0.5 M H2SO4 at 30 °C was investigated by various corrosion monitoring techniques. A preliminary screening of the inhibition efficiency was carried out using weight loss measurements. At constant acid concentration, inhibitor efficiency increases with concentration of DAPT and is found to be more efficient in 0.5 M H2SO4 than in 1 M HCl. Potentiostatic polarization studies showed that DAPT is a mixed-type inhibitor. The effect of temperature on the corrosion behaviour of mild steel in 1 M HCl with addition of DAPT was studied in the temperature range from 25 to 60 °C. Its was shown that adsorption is consistent with the Langmuir isotherm for 30 °C. The negative free energy of adsorption in the presence of DAPT suggests chemisorption of thiadiazole molecules on the steel surface.

2,5-Bis(n-methoxyphenyl)-1,3,4-oxadiazoles used as corrosion inhibitors in acidic media: correlation between inhibition efficiency and chemical structure

Abstract The efficiency of 2,5-bis( n -methoxyphenyl)-1,3,4-oxadiazoles ( n -MOX), as corrosion inhibitors for mild steel in 1 M HCl and 0.5 M H 2 SO 4 have been determined by weight loss measurements and electrochemical studies. The results showed that these inhibitors revealed a good corrosion inhibition even at very low concentrations. Comparison of results among those obtained by the studied oxadiazoles showed that 2-MOX was the best inhibitor. It is found to behave better in 1 M HCl than in 0.5 M H 2 SO 4 . Polarisation curves indicate that 2-MOX is a mixed inhibitor in 1 M HCl, but in 0.5 M H 2 SO 4 , the inhibition mode of 2-MOX depends on the electrode potential and acts essentially as a cathodic inhibitor. The inhibition efficiency slightly increases with temperature in the range from 25 to 60 °C, the associated activation energy have been determined. The addition of 2-MOX leads to decrease this activation energy. The adsorption of 2-MOX on the mild steel surface in both acidic media follows a Langmuir isotherm model. Significant correlations are obtained between inhibition efficiency with the calculated chemical indexes, indicating that variation of inhibition with structure of the inhibitors may be explained in terms of electronic properties.

Inhibition of acidic corrosion of mild steel by 3,5-diphenyl-4H-1,2,4-triazole

The inhibitor effect of 3,5-diphenyl-4H-1,2,4-triazole (DHT) on the corrosion of mild steel in hydrochloric acid solution was investigated at 30°C using electrochemical and weight loss measurements. Polarisation curves revealed that this organic compound act as mixed-type inhibitor and inhibition efficiencies up to 98% can be obtained. The inhibition efficiency calculated from these techniques are in reasonably good agreement. X-ray photoelectron spectroscopy (XPS) spectra of the steel surface treated with the 1 M HCl solution containing the DHT molecules revealed their adsorption on the surface. The DHT appears to function through the general adsorption mode following the Langmuir adsorption isotherm model.

Investigation of the inhibitive effect of substituted oxadiazoles on the corrosion of mild steel in HCl medium

Abstract The influence of 2,5-bis(4-nitrophenyl)-1,3,4-oxadiazole (PNOX) and 2,5-bis(4-aminophenyl)-1,3,4-oxadiazole (PAOX) on the corrosion of mild steel in hydrochloric acid was studied in relation to the concentration of oxadiazoles using various electrochemical techniques and weight loss measurements. The results showed that PAOX inhibited the corrosion of mild steel in 1 M HCl whereas PNOX accelerated it. PAOX suppressed both cathodic and anodic processes of steel corrosion in 1 M HCl by its chemisorption on the surface via sharing electrons between nitrogen or oxygen and iron atoms. PAOX was adsorbed on the mild steel surface according to a Langmuir isotherm adsorption model. The electronic properties of PNOX and PAOX obtained by using the AM1 semi-empirical quantum chemical approach, were correlated with their experimental efficiencies.