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Aims to evaluate the effectiveness of 2‐amino 4‐phenyl thiazde (APT) and its three anils as inhibitors for the corrosion of mild steel in 1M HCl. Discusses the variation of inhibition efficiency with temperature. Gives account of experimental procedures on mild steel strips for weight loss measurements and potentiodynamic polarization studies.

This paper mainly aims to study the influence of some thiosemicarbazides, namely, 1‐hydroxyphenyl‐4‐phenyl thiosemicarbazide (HPT), 1,4‐diphenyl thiosemicarbazide (DPT), 1‐aminophenyl‐4‐phenyl thiosemicarbazide (APT) and 1‐cinnamyl‐4‐phenyl thiosemicarbazide (CPT) on the corrosion inhibition of carbon steel in hydrochloric and sulphuric acid.

All inhibition experiments were conducted on carbon steel in 1N HCl and 1N H₂SO₄ solution. Weight loss experiments were carried out according to the ASTM standard procedure. Polarization studies were carried out in a three‐electrode cell assembly connected to an EG&G Princeton applied research potentiostat/galvanostat (model 173).

For all the compounds a consistent trend of increase in inhibition efficiency was observed as a function of inhibitor concentration. The adsorption of all the compounds on to the carbon steel surface in the acidic solution was found to obey the Tempkin's adsorption isotherm. The values of activation energy and free energy of adsorption for all the compounds were also calculated. Polarization measurement revealed that the studied thiosemicarbazides act predominantly as mixed inhibitors in both the acid solutions, with the exception of DPT, which predominantly behaved as a cathodic inhibitor in 1N HCl.

These inhibitors could have application in industries, where hydrochloric and sulphuric acid solution are used to remove scale and salts from steel surfaces, such as acid cleaning of tankage and pipeline, and may render dismantling unnecessary.

This paper reveals that thiosemicarbazides can be successfully used for protection of carbon steel corrosion in acid solutions.

2‐undecane‐5‐mercapto‐1‐oxa‐3, 4‐diazole (UMOD), 2‐heptadecene‐5‐mercapto‐1‐oxa‐3, 4‐diazole (HMOD) and 2‐decene‐5‐mercapto‐1‐oxa‐3, 4‐diazole (DMOD) were synthesized in the laboratory and their influence on the inhibition of corrosion of mild steel in 1N HCI and 1N H₂SO₄ was investigated by weight‐loss and potentiodynamic polarization techniques. The inhibition efficiency of these compounds was found to vary with concentration, temperature and immersion time. Good inhibition efficiency (IE) was evidenced in both acid solutions, remaining high (> 90 per cent) even at the concentration of 25ppm. The adsorption of these compounds on the steel surface for both acids was found to obey Temkin’s adsorption isotherm. The values of activation energy and free energy of adsorption indicated physical adsorption on mild steel surface. The potentiodynamic polarization data have shown that compounds studied are mixed type inhibitors.

The purpose of this paper is to investigate the inhibitive effect of azathiones, namely cyclopentyl‐tetrahydro‐azathione, cyclohexyl‐tetrahydro‐azathione and isobutyl‐methyl‐tetrahydro‐azathione on the corrosion of carbon steel in formic and acetic acid solution. The effect of inhibitor concentration, immersion time, acid concentration, and solution temperature on the inhibition efficiencies of the selected azathiones were studied systematically.

The synthesis of inhibitor was confirmed by methods such as Fourier transform infrared and nuclear magnetic resonance studies. All inhibition experiments were conducted on carbon steel in 20 percent formic acid and 20 percent acetic acid solution. Weight loss experiments were carried out according to the American Society for Testing and Materials standard procedure. Polarization studies were carried out in a three electrode cell assembly connected to an EG&G Princeton Applied Research potentiostat/galvanostat (model 173). The electrochemical impedance technique was carried out using Zahner IM‐6 electrochemical workstation at a frequency range of 5‐100 Hz. The scanning electron microscopy (SEM) study was carried out using a VP LEO model no. 435 microscope for the surface characterization of inhibited and uninhibited metal surfaces.

Various thermodynamic parameters were calculated using weight loss data in order to elaborate the mechanism of corrosion inhibition. Polarization measurements revealed that the studied azathiones acted predominantly as mixed inhibitors. Electrochemical impedance measurements revealed that the compounds were adsorbed onto the carbon steel surface and the adsorption obeyed the Langmuir adsorption isotherm. The SEM study showed that the inhibited metal surfaces were smoother than were uninhibited metal surfaces.

The presence of high efficiency and low cost inhibitors is essential for protection of carbon steel. In comparison with conventional carbon steel corrosion inhibitors, these findings would be considered as a step forward in development of new corrosion inhibitor.

This paper reveals that azathiones can be used successfully for the protection of carbon steel surfaces exposed in acid solution.

Although stainless steel (SS) has good corrosion resistance in most aqueous solutions, it suffers corrosion in some solutions which contain aggressive ions such as sulfide ions. This study aims to use some cephalosporins (cefotaxime, cephapirin and cefazolin) as corrosion inhibitors of commercial SS in 0.5 M H₂SO₄ solution containing sulfide ions at 30°C.

The study was carried out using weight loss method, potential-time, linear polarization, potentiodynamic polarization, electrochemical impedance measurements, scanning electron microscopy, Fourier transform infrared and energy dispersive X-ray analysis.

The presence of the cephalosporin compound in the corrosive medium shifted the corrosion potential of SS to much positive side, which enhances self-passivation of SS, and the shifting increased with increasing inhibitor concentration. The cephalosporin compounds worked as effective inhibitors with mainly anodic and the efficiency increase as cefotaxime < cephapirin < cefazolin. The inhibitors form a protective adsorbed layer, which enriches the surface content of Ni and Cr and thus assists the SS to be passive.

The antibiotics cephalosporins could be used as effective corrosion inhibitors for SS in acidic solutions containing sulfide ions. The inhibitors enhances the the passive oxide film of SS even in presence of aggressive ions such as sulfide ions.

The influence of 4‐amino‐5‐mercapto‐3 n‐propyl‐1‐2‐4‐triazole (AMPT) on corrosion and hydrogen permeation through mild steel in 0.5M H₂SO₄ and 1M HCl has been studied using weight loss measurements and various electrochemical techniques. AMPT is found to be more inhibitive in H₂SO₄ than in HCl. Potentiodynamic polarisation studies clearly prove the fact that this compound behaves as a mixed inhibitor; but predominantly as a cathodic inhibitor. Hydrogen permeation studies and AC impedance measurements also indicate an improved performance of the compound in H₂SO₄. The adsorption of this compound on the mild steel surface obeys Temkin’s adsorption isotherm.

Attempts are made to utilize the aqueous extracts of natural compounds, namely cordia latifolia and curcumin, as corrosion inhibitors for mild steel in cooling systems, and their inhibition efficiencies are compared with that of Hydroxyethylidene 1‐1 diphosphonic acid (HEDP). HEDP is also blended with aqueous extracts of natural compounds so as to improve their inhibition efficiency. The blowdown of the cooling system is also analysed for environmental factors.

The purpose of this paper is to set out a study of a Mannich base, which was synthesized and used as an acidizing corrosion inhibitor first, and to the corrosion inhibitor mechanism.

A Mannich base, 1-phenyl-3-(1-pyrrolidinyl)-propanone (PHPP), was synthesized with acetophenone, pyrrolidine and formaldehyde at pH = approximately 2-3. The structure of PHPP was characterized by elemental analysis and Fourier transform infrared spectroscopy (FTIR). The corrosion inhibition of PHPP on N80 steel in 15 per cent hydrochloric acid (HCl) was studied by weight loss method, scanning electron microscope (SEM) and energy dispersive X-ray analysis (EDAX), and the adsorption behavior of PHPP on the surface of N80 steel was discussed.

The results showed that the inhibition efficiency reached to 99.8 per cent and corrosion rate was 2.65 g·m-2·h-1 at 0.6 per cent of PHPP concentration in 15 per cent HCl, which indicated that PHPP presented excellent corrosion inhibition performance. The results of SEM and EDAX analysis showed that PHPP could be absorbed on the surface of N80 steel. The adsorption process of PHPP on the surface of N80 steel was chemisorption. This process was spontaneous and obeyed Langmuir adsorption isotherm.

It was found that PHPP presented excellent corrosion inhibition performance, and it is practicable to enhance oil production in oilfield development as a oil-well acidizing inhibitor. The study results can provide theoretical guidelines for the development of the inhibitor.

Selected condensation products of aromatic aldehydes and thiosemicarbazide have been synthesized and evaluated as corrosion inhibitors of mild steel in 1N hydrochloric acid and 1N sulphuric acid by weight loss and potentiodynamic polarization methods. The values of activation energy and free energy of adsorption have also been determined to understand the mechanism of inhibition. The potentiodynamic polarization studies carried out at room temperature revealed that all the compounds are of mixed type inhibitors in both the acids. The adsorption of all the condensation products on the mild steel surface from both the acids has been found to obey Temkin’s adsorption isotherm. The inhibition efficiency of these compounds has been found to vary with the nature and concentration of the compounds, temperature, immersion time and nature of the acids.

Macrocyclic compounds constitute a potential class of corrosion inhibitors. In an attempt to develop effective corrosion inhibitors we have synthesized four macrocyclic compounds by condensing o‐ethylene diamine and o‐phenylene diamine with ethylacetoacetate and succinic acid; Their inhibiting action was evaluated on corrosion of mild steel in HCI and H₂SO₄ by weight loss and potentiodynamic polarization methods. A macrocyclic compound derived by condensing o‐phenylene diamine with ethylacetoacetate exhibited best performance by giving IE of 98 per cent at 500 ppm concentration. The potentiodynamic polarization studies revealed that the tested compounds are either mixed type or predominantly cathodic inhibitors. IE of all the investigated compounds increased significantly on addition of a small concentration KI in both acids due to synergism.