Comparative studies on the corrosion inhibition characteristics of three different triazine based Schiff’s bases, HMMT, DHMMT and MHMMT, for mild steel exposed in sulfuric acid

The inhibition behavior of three different triazine based Schiff’s bases, HMMT, DHMMT and MHMMT for mild steel corrosion in sulphuric acid has been investigated using weight loss, electrochemical studies, SEM, spectroscopic studies and basic computational studies. The inhibition efficiency increased with increase in inhibitor concentration but decreased with rise in temperature and acid concentration in the case of these three inhibitors. The order of inhibition efficiency expected from the values of band energy is in good agreement with the results obtained from weight loss and electrochemical studies. Polarization studies indicated the mixed type behavior of these inhibitors. Field emission scanning electron microscopic studies revealed that inhibitors protect the metal surface by the forming a protective film through adsorption of inhibitor molecules. Keywords: Mild steel, Corrosion inhibition, Schiff’s base

Physicochemical studies on the inhibitive properties of a 1,2,4-triazole Schiff’s base, HMATD, on the corrosion of mild steel in hydrochloric acid

The efficiency of 4-(4-hydroxy-3-methoxy benzyledene amino)-4-H-1,2,4-triazole-3, 5-dimethanol, HMATD, as corrosion inhibitor for mild steel in 0.5 M HCl has been determined by weight loss measurements and electro analytical methods. The influence of various parameters such as temperature, inhibitor concentration on the efficiency has been studied. The electrochemical impedance spectroscopic measurements revealed the inhibition action of HMATD by reducing the charge transfer through metal solution interface. Polarization curves indicate the mixed type behaviour of HMATD. The inhibitor molecule functions by blocking the active sites on metal surface by adsorption and which obeys the Langmuir adsorption isotherm. Various kinetic and thermodynamic parameters have also been calculated. Keywords: Mild steel, EIS, Activation energy, Adsorption isotherm, SE

Spectrophotometric determination of osmium(VIII) in trace amounts using ethylene thiourea (ETU) as chromogenic reagent

113-117A simple and highly sensitive spectrophotometric method has been described for the determination of trace amount of osmium(VIII) using ethylene thiourea (ETU) as a chromogenic reagent. The method is based on the formation of an instantaneous purple coloured complex at room temperature by the reaction of osmium(VIII) with ETU in strongly acidic (pH=1) solution having absorption maximum at 490 nm and is confirmed using derivative spectrophotometry. Linear calibration graphs are obtained for 0.03-3 µg/mL of the analyte. Sandell's sensitivity (1.13×10-3 µgcm-2), molar absorptivity (16.87×104 Lmol-1 cm-1), detection limit (0.0291 µg/mL) and quantitation limit (0.0833 µg/mL) are also calculated. The method is optimized and different analytical parameters were evaluated. The stoichiometry of the complex is found to be 1:3 by Job's method and mole ratio method. The stoichiometry of the complex is further confirmed by synthesizing the solid compound and characterizing it by various physicochemical methods

Inhibition of Aluminium Corrosion Using Benzothiazole and Its Phthalocyanine Derivative

Cyclic voltammetry and potentiodynamic polarization techniques were used to study the effects of 4-[4-(1,3-benzothiazol2yl)phenoxy] phthalonitrile (BT) and tetrakis[(benzo[d]thiazol-2ylphenoxy) phthalocyaninato] gallium(III)chloride (ClGaBTPc) as aluminium corrosion inhibitors in 1.0 M hydrochloric acid. The presence of the inhibitors in the concentration range of 2 to 10 μM was found to retard the aluminium corrosion process such that the inhibition efficiency was found to range from 28.2 to 76.1% for BT and from 71.5 to 82.7% for ClGaBTPc. The latter was a better inhibitor. Scanning electron microscopy and energy-dispersive X-ray measurements reveal effective metal surface protection by the inhibitors, most probably by shielding it from the corrosion attacks of Cl− from the acid. The calculated quantum chemical parameters agreed with experimental results