Corrosion resistance of aluminum against acid activation: Impact of benzothiazole-substituted gallium phthalocyanine

This study describes the adsorption behavior of organic inhibitors at the aluminum-HCl solution interface and their corrosion inhibition performance. The organic inhibitors employed are: 4-(benzo [d]thiazol-2ylthio)phthalonitrile (BTThio) and tetrakis[(benzo[d]thiazol-2-yl-thio)phthalocyaninato]gallium(III) chloride (ClGaBTThioPc). The corrosion behavior of these inhibitors is investigated using electrochemical and computational techniques. Open circuit potential results reveal predominant cathodic character for the mechanism of aluminum corrosion inhibition by the inhibitors. Inhibition efficiency values from potentiodynamic polarization measurements increase from 46.9 to 70.8% for BTThio and 59.7 to 81.0% for ClGaBTThioPc within the concentration range of 2 to 10 µM. Scanning electron microscopy (SEM) measurements reveal protection of the metal surface from acid attack, in the presence of the inhibitors and energy dispersive X-ray (EDX) measurements show that the most probable way by which the inhibitors protect the metal surface would be by shielding it from the corrosion attacks of Cl− from the acid. Quantum chemical parameters corroborate well with experimental findings

Cassane diterpenoids from Lonchocarpus laxiflorus

Igoli JO, Onyiriuka SO, Letzel M, Nwaji MN, Gray AI. Cassane diterpenoids from Lonchocarpus laxiflorus. NATURAL PRODUCT COMMUNICATIONS. 2008;3(1):5-10.Phytochemical investigation of the stem bark of Lonchocarpus laxiflorus yielded three new cassane diterpenoids, lonchocassane A [cassa-13 (14), 15-dien-18, 20-dioic acid], lonchocassane B [cassa-13 (14), 15-dien-20-oxo-18-oic acid] and lonchocassane C [cassa-13 (14), 15-dien-20-carboxyl-18-methylcarboxylate]. The known compounds. betulinic acid, betulinic acid acetate, betulin, lupeol, lupenone, trilinoleate, hexacosanyl and triacontanyl caffeates, 4-hydroxy-4-methylpentan-2-one, beta-sitosterol, beta-sitosterol acetate and stigmasterol were also isolated. The structures and identities of the compounds were established by spectroscopic methods

Effects of water thickness and glazing slope on the performance of a double-effect solar still

This paper presents the effects of water thickness and glazing slope on the performance of a double-effect solar still. The effect of the air gap between the water interface and the glazing was also considered. Energy balance equations were developed for the different components of the system. The development of the equations was made considering the thermal resistances offered by the humid-air media in both chambers of the double-effect still. Numerical computation was conducted for a typical day in Owerri. The results obtained were compared with data from a previous experimental study. The water temperatures in the upper and lower basins increased with a reduction in thickness. However, the yield profile did not follow a similar trend to that of the temperature. This was attributed to the influence of the upper water on the lower-glazing temperature. The temperatures of the still components initially reduced with a deviation from the latitude angle (La) and later increased with an increase in glazing slope. The diurnal yield of the system attained a maximum value of 3.04 kg/m2 at an optimum angle of La+15∘ Increasing the glazing slope from La to La+15∘ improved the distillate yield by 47.9%

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