Adsorption Isotherm and Activation Energy of Inhibition of Alkaloids on Mild Steel Surface in Acidic Medium

Alkaloids as green inhibitors were extracted from three different plants Rhynchostylis retusa, Artimesia vulgaris,and Solanum tuberosum. Weight loss measurement in mild steel has been carried out in the presence and absence of green inhibitors individually in an acidic medium. Weight loss measurements at different temperatures are used to calculate thermodynamic parameters. The weight loss measurements at different concentrations are used to find adsorption isotherm and found that it obeys Langmuir adsorption isotherm with R2 values 1, 1, 0.996 for three inhibitors. Activation energy, enthalpy, and entropy of the three inhibitors have been calculated. It is found that the value of all these parameters increased in the addition of inhibitors. The free energy of the system is calculated and found (-17.46 kJ mol-1) indicating that the adsorption process is spontaneous and there is physical adsorption at the MS-Inhibitor interface.

Development and Implementation of Green Inhibitors of Gas Hydrate Formation in the Fields of Western Siberia

The effect of biodegradable polysaccharides – sodium (NaCMC) and ethanolammonium salts of carboxymethylcellulose, dextran and arabinogalactan on the process of gas hydrate formation was studied in order to search for new "green" inhibitors of low-concentration gas hydrate formation. The ability of polysaccharides to inhibit gas hydrate formation was studied in a quasi-equilibrium thermodynamic experiment. A mixture of hydrocarbon gases with a composition typical of the composition of petroleum gas and containing 78% methane was used as a gas-hydrate-forming model medium. It was found that in concentrations of 0.005, 0.0065 and 0.008%, dextran, NaCMC and arabinogalactan as thermodynamic inhibitors exceed methanol by 170-270 times in inhibitory properties. Dextran is superior to NaCMC and arabinogalactan in terms of inhibition efficiency, reduction of gas hydrate formation rate and induction time. Since with an increase in the concentration of polysaccharides, the pressure drop of gas hydrate formation increases and the rate of formation of gas hydrates decreases according to the mechanism of action, the studied polysaccharides can be attributed to both thermodynamic and kinetic inhibitors. It is established that the molecular weight of water-soluble polysaccharides has a significant effect on their inhibitory properties. A polysaccharide with a molecular weight of 250,000 demonstrated the highest inhibitory activity among the studied samples of NaCMC, which is 400 times more effective than methanol. NaCMC with a mass of 700 thousand did not have any effect on the formation of hydrates. Among the ethanolammonium salts, the monoethanolammonium salt CMC showed the greatest effectiveness in inhibiting the formation of tetrahydrofuran hydrates. An increase in its concentration from 0.02 to 0.1% leads to an increase in the induction time required for the nucleation and subsequent growth of crystals by 10 times. When switching from mono - to di - and triethanolammonium salts of carboxymethylcellulose, the inhibition efficiency decreases. It is shown that sodium and ethanolammonium salts of carboxymethylcellulose, arabinogalactan and dextran are promising for creating new "green" highly effective inhibitors of gas hydrate formation on their basis. The results of laboratory and field tests of the preparative form of the "green" gas hydrate formation inhibitor at the fields of Western Siberia are presented. It was found that at dosages of 500 g/m3 or less, there is no formation of hydrate plugs in the annulus of wells.

Case-Studies on Green Corrosion Inhibitors

Corrosion in metals and its alloys is an inevitable phenomenon but can be controlled by suitable classical methods like process control, cathode protection, surface treating methods, impurity reduction in metals and addition of metals to form alloys. Nevertheless, the employment of corrosion inhibitors is still a noteworthy and simplest of all the above processes in protecting the metals and alloys especially in acidic media. Protection of metals against corrosion not only prevents corrosion but also is beneficial in terms of money loss as far as industrial equipment, surfaces and vessels are concerned. Since the use of organic and inorganic inhibitors are highly discouraged due to their high cost and toxicity, necessity has adequately aroused the development of corrosion inhibitors which are natural and green. Trends, nowadays, focussed in controlling corrosion in various metals and alloys through green corrosion inhibitors consisting of natural elements alone. In contrast to the inorganic inhibitors, green corrosion inhibitors are characterized by biodegradability, low cost and meagre toxicity. Several researchers are now turning themselves towards the research of green inhibitors which are of no threat to humans and the ecosystem. The current discussion is focussed on the fundamentals of corrosion, corrosion inhibition, materials used for it and case studies of green inhibitors used for corrosion control in various conventional and monolithic metals.

Green Corrosion Inhibitors for Coatings

Corrosion is emerging as a potential hazard which abolishes metals and their structures and hence become an imperative menace. It is an omnipotent and omnipresent process which is present in every environment, i.e., air, soil, water. Green chemistry is one of the notable branches of chemistry that focuses on the protection of environment and human well–being in an economically viable approach allowing dodging of toxins and reducing hazards due to corrosion. Green chemistry exploited well–known strategy namely green inhibitors to prevent, control or impede the growth of corrosion. Green inhibitors are eco–friendly, cost–effective, renewable natural products which are favourable over toxic synthetic corrosion inhibitors. Extracts of natural products contain natural products containing alkaloids, carboxylic acids, nicotine, polyphenols, quinine, terpenes, and other functional groups possessing elements like C, N, O, S, etc., prompting adsorption via forming a thin layer (coating) on the metallic surface to shield the surface and encumber corrosion. In the field of economical loop, this approach develops various potential applications in manufacturing areas other than ‘Trash to treasure’. Even though a bunch of experiments have been performed and several research articles have been in print, however, the area of green inhibitors is still demanding more investigation on this open issue. More and more interest in the area extended the research, consequentially to a large variety of tried molecules. Nevertheless, the most accepted protocols are classical and, therefore, are incompetent to completely portray the probable worth of inhibitors. Hence all above stated features should be the objective of the contemporary research so that productive analysis to emphasize the weak areas of the green inhibitors field and tackle the prospect research in the field that still requires validation.

Application of green inhibitors for corrosion control in metals. review

This review article characterizes the green inhibitors applied to control corrosion in metals and maintain the safety and profitability of the production process, since the corrosive phenomenon is insoluble, but can be mitigated with time. For this article, some case studies related to corrosion problems in metals are included, such as the accident in Aloha and the explosion in Guadalajara. Subsequently, the generalities of inhibitors for corrosion control are named, and the physisorption and chemisorption processes are compared. Then, inorganic, organic, synthetic, and green inhibitors are analyzed. The latter seek to replace the synthetic ones, for example, through aloe vera and other plant materials.