S. Muralidharan

Influence of substituted benzothiazoles on corrosion in acid solution

Compounds such as 2-aminobenzothiazole (ABT), 2-amino-6-chlorobenzothiazole (ACLBT), 2-amino-6-methyl benzothiazole (AMEBT) and 2-amino-6-methoxy benzothiazole (AMEOBT) have been synthesized and their inhibitive action on the corrosion of mild steel in 1 m HCl has been evaluated using weight loss, potentiodynamic polarization studies and hydrogen permeation measurements. Determination of inhibition efficiency in the presence of these compounds at different temperatures clearly indicates that ACLBT shows the best performance, even at a temperature as high as 60°C. Potentiodynamic polarization studies reveal the fact that ABT and its derivatives act as cathodic inhibitors. All these compounds are found to reduce the permeation of hydrogen through mild steel in HCl solution. The adsorption of these compounds on mild steel from HCl solutions obeys Temkins adsorption isotherm. The adsorption of 2-amino benzothiazole on the mild steel has been substantiated by Auger electron spectroscopy.

The influence of N-heterocyclics on corrosion inhibition and hydrogen permeation through mild steel in acidic solutions

The influence of N‐heterocyclics, viz. imidazole (IA), benzimidazole (BIA) and 2‐methyl imidazole (MIA) on the corrosion and hydrogen permeation through mild steel in 1 N H2SO4 and in 1N HC1 has been studied using weight loss and various corrosion monitoring techniques. Imidazole and benzimidazole inhibit the corrosion of mild steel in both the acidic solutions, but methyl imidazole accelerates the corrosion. They behave as cathodic inhibitors by influencing the cathodic polarization reaction. Except methyl imidazole, the other two compounds reduce the hydrogen permeation current in both the acids. The adsorption of these compounds on the mild steel surface from both the acids obeys Temkin’s adsorption isotherm. Trends in the increase of charge transfer resistance and decrease of capacitance values also show the adsorption of inhibitors on the metal surface.

Thiophenol as an inhibitor for the corrosion and hydrogen permeation through mild steel in acidic solutions

The influence of thiophenol on the corrosion and hydrogen permeation 1M HCl and 0.SM H2SO4 has weightloss measurements, gasometric studies and other electrochemical techniques. Thiophenol inhibits the corrosion of mild steel in both the acids, but it is found to be more effective in H2SO4. It behaves predominantly as a cathodic inhibitor. It brings down the permeation current in both the acids, but is more effective in H2SO4. The adsorption of thiophenol on the mild steel surface from both the acids obeys Temkin’s adsorption isotherm.

Technical note Influence of molecular structure of substituted benzothiazoles on corrosion inhibition and hydrogen permeation through mild steel in sulphuric acid

Abstract Aminobenzothiazole and three of its 6-substituted derivatives, namely 2-amino-6-chlorobenzothiazole (ACLBT), 2-amino-6-methoxybenzothiazole, and 2-amino-6-methylbenzothiazole, were synthesised and their inhibition of the corrosion of mild steel in 0·5M H2S04 was investigated by weight loss and some electrochemical techniques. Inhibition efficiencies of various concentrations of these compounds were determined at temperatures in the range 35–60°C. Of the four compounds, ACLBT showed the best performance, giving an inhibition efficiency as high as 97%, even at a very low concentration and at a temperature of 60°C. Potentiodynamic polarisation studies indicated that all four compounds acted predominantly as cathodic inhibitors, with adsorption from H2S04 solutions on mild steel surfaces obeying Temkins adsorption isotherm. All of the inhibitors were able to reduce hydrogen permeation through the steel surface and performance was enhanced by the addition of iodide ions. Auger electron spectroscopy a...

Influence of anions on the performance of isomers of aminobenzoic acid on the corrosion inhibition and hydrogen permeation through mild steel in acidic solutions

The influence of aminobenzoic acids on the corrosion and hydrogen permeation through mild steel in 1 m HC1 and 0.5 M H2SO4 has been studied using weight loss and gasometric measurements and various electrochemical techniques. All the three isomers of aminobenzoic acid inhibit the corrosion of mild steel both in HC1 and H2SO4 in the order ortho > meta > para. It is observed that the inhibition is greater in HCI than in H2SO4. The predominant behaviour is in the cathodic inhibitor mode. These compounds reduce the permeation current in 111 HCl and enhance it in 0.51 v1 H2SO4. The adsorption of these compounds on mild steel in 1 m HC1 and 0.5 m H2SO4 obeys Langmuirs adsorption isotherm.

INHIBITION OF CORROSION OF MILD STEEL IN ACIDIC SOLUTIONS BY QUARTERNARY SALTS OF PYRIDINIUM BASES

The influence of pyridinium chloride (PC) and n‐hexa decyl pyridinium chloride (HDPC) on the corrosion of mild steel in 5N HCl and 5N H2SO4 has been studied using techniques such as weight loss and gasometric measurements, potentiodynamic polarisation studies, linear polarisation studies and small amplitude cyclic voltametric studies. It is found that HDPC is more inhibitive than PC and both the compounds perform better in H2SO4. Polarisation studies reveal that PC behaves as an anodic inhibitor in H2SO4 and as a mixed inhibitor in HCl. Measurements of values of polarisation resistance (Rp) and double layer capacitance (Cdl) in the presence of these compounds also reveal the better performance of HDPC in both the acids. The adsorption of PC and HDPC on a mild steel surface from both the acids is found to obey Temkin’s adsorption isotherm.

Synergistic influence of iodide ions on inhibition of corrosion of mild steel in H2SO4 by N-phenyl thiourea

Abstract The synergistic action of iodide ions on the inhibition of corrosion of mild steel in 0·5M H2SO4 by N-phenyl thiourea (N-PTU) has been investigated using weight loss measurements, potentiodynamic polarisation studies, linear polarisation studies, and impedance measurements. Inhibition efficiency is found to increase with increase in the concentration of N-PTU. The inhibiting action of N-PTU is considerably enhanced by the addition of potassium iodide. The adsorption of this compound either alone or in combination with iodide ions on the metal surface is found to obey Langmuirs adsorption isotherm. The increase in surface coverage 0 in the presence of iodide ions indicates joint adsorption of N-PTU and iodide ions. The synergism parameter is defined and evaluated from the values of inhibition efficiency and surface coverage. This parameter is found to be greater than unity, which indicates that the enhanced inhibition efficiency caused by the addition of iodide ions is only due to synergism and t...

Bioequivalence Study of Simvastatin

A simple, rapid and selective method was developed for esti- mation of simvastatin from human plasma. The method involves simple protein precipitation techniques using etofy lline as inter- nal standard. Chromatographic separation was carrie d out on a reversed phase C 18 column using mixture of methanol: 2mM ammonium acetate and 500 μl of 0.5% formic acid (80 :20, v/v) at a flow rate of 1.0 ml/min with UV-VIS detection at 418.35 nm. The retention time of simvastatin and internal standard were 5.41 and 1.086 min, respectively. The method was va lidated and found to be linear in the range of 1.0-10.0 ng/mL. An open, ran- domized, two-treatment, two period, single dose cro ssover, bioequivalence study in 12 fasting, healthy, male, volunteers was conducted. After dosing, serial blood samples were collected for the period of 24 . 0 h . Various pharmacokinetic parameters including AUC 0– t , AUC 0– ∞ , C max , T max , T ½ , and elimination rate constant ( K el ) were determined from plasma concentration of both formulations. Log transformed values were comp ared by nalysis of variance (ANOVA) followed by classical 90% con- fidence interval for C , AUC 0– t and AUC 0– ∞ and was found to be within the range. These results indicated that t he analytical method was linear, precise nd accurate. Test and r eference for- mulation were found to be bioequivalent.

Stress corrosion cracking and hydrogen embrittlement susceptibility studies on modified 9Cr-1Mo steel weldments in acidic and neutral media

There is much scope for the development of new engineering materials for high temperature applications such as for tubing used in steam generation in fossil fuel and nuclear power plants and in petrochemical cracking units. The materials for such applications are often manufactured from mild steel and low alloy ferritic steels containing up to 9%Cr. Modified 9Cr-1Mo ferritic steel, prepared by incorporating vanadium and niobium, is one of the newer materials extensively used for high temperature applications. A study of weldments of this alloy and its susceptibility to stress corrosion cracking (SCC) and hydrogen embrittlement was carried out in acidic and neutral media. The anodic behaviour of modified 9Cr-1Mo under 90% proof stress was also examined. Mechanical properties of the material were assessed before and after SCC and hydrogen embrittlement tests. The SCC tests were made at various anodic potentials in 1M H 2 SO 4 and showed that the welded alloy is not susceptible to SCC in all three critical zones. The alloy was, however, susceptible to SCC in chloride environments, namely a solution containing equal volumes of 1M NaCl and 1M MgCl 2 . Fractographic analysis was carried out to determine the reasons for the failure of this alloy. The hydrogen embrittlement studies in 1M H 2 SO 4 showed that the alloy is prone to delayed hydrogen cracking at more negative potentials. The fractographic examination using scanning electron microscopy revealed the presence of adsorbed hydrogen in microvoids which were responsible for the failure of the alloy. Other possible reasons for the failure of the alloy are also discussed.

Pharmacokinetic Evaluation of Metolazone Tablets using healthy Human Volunteers

A sensitive and reproducible high performance liqui d chromatography (HPLC) method has been developed and validated for the quantification of metolazone in h uman plasma, after solid phase extraction (SPE). A Good reso- lution was achieved on a reverse-phase LichroCART Purospher ® C 18 column using the mobile phase acetoni- trile–0.5% triethylamine (35:65) in isocratic eluti on with a total run time of 15 min. The analyte, metolazone , was detected by using high performance liquid chromatog ra- phy with the support of photo diode array detector. Limit of detection and Lower limit of quantification was found to be 1 and 2.5 ng/mL. The present method was succe ss- fully applied in the pharmacokinetic study of metol azone in human plasma.