| A corrosion inhibitor is a chemical compound that,when added to a liquid or gas,decreases the corrosion rate of a material,typically a metal or an alloy.In many corrosion control methods,the addition of corrosion inhibitors has become a kind of simple,effective,applicable and important anti-corrosion means,especially,adding organic corrosion inhibitor into the acidic corrosive medium has been widely used in petroleum and chemical industries such as boiler pickling.Organic inhibitors,having oxygen,nitrogen,sulfur,unsaturated bond,or aromatic rings can adsorb onto the outward transition metal surface by electrostatic interactions between the inhibitor and metal(physical adsorption)or by coordinate covalent bonds(chemical adsorption),creating an aggressive media for metal protection.This paper mainly synthesized two kinds of small organic molecules:triphenylamine dialdehyde(TD)and cytosine-L-alanine derivatives(CLAD),in addition,uses biological macromolecules(DNA)as inhibitors for the first time.This paper studies the above three kinds of compounds as carbon steel in the medium of hydrochloric acid corrosion inhibition and mechanism of inhibitor,makes efforts to promote the research of green organic corrosion inhibitor system.The main contents are as follows:(1)Triphenylamine dialdehyde(TD)was obtained by oxidation reaction with Three aniline,and its complex with arginine and KI was used as corrosion inhibitor for carbon steel in 1 M HCl solution.Weight loss method found that when the formula is:50 mg·L-1 Triphenylamine dialdehyde + 50 mg·L-1 Arginine + 100 mg·L-1 KI,the best efficiency of up to 92%;The compound corrosion inhibitor is a mixed type corrosion inhibitor on the metal surface,which accords with the isothermal adsorption theory and forms a good protective film;At the same time,the synergistic mechanism of potassium iodide was also discussed;The results of quantum chemistry calculation showed that the polar groups contained in Triphenylamine dialdehyde and Arginine could be well adsorbed;In addition,the model is explained by simple adsorption model.(2)A novel environmental-friend corrosion inhibitor named cytosine-L-alanine derivative was synthesized by using small biological molecules to protect the X80 steel surface in HCl solution.The weight loss measurement,polarization curves,electrochemical impedance spectroscopy(EIS)and SEM measurement were used to systematically investigate the inhibition performance of cytosine-L-alanine derivatives.The results showed that the corrosion inhibition efficiency of cytosine-L-alanine derivatives reached 91%,which was 78%higher than that of L-alanine.And it was found that the impeded electron transfer,reduced metal dissolution and inhibited corrosion progress of metal surface were derived from the compact and uniform protective film.The adsorption of cytosine-L-alanine derivatives obeyed the Langmuir adsorption isotherm,and adsorption behaviors included physical adsorption and chemical adsorption.Moreover,the quantum chemistry calculation parameters(EHOMO,ELUMO and △N)proved that the high corrosion inhibition efficiency of cytosine-L-alanine derivatives was associated with its strong adsorption as a barrier film on the steel surface.The results further demonstrated that the KI mixed cytosine-L-alanine derivatives was an alternative strategy to enhance the inhibition efficiency and reduce the cost.(3)Performence of biological macromolecule DNA as a green inhibitor on carbon steel in 1M HCl was investigated by means of electrochemical,FTIR,XPS and theoretical calculation methods.Among the studied,compound DNA exhibited maximum inhibition efficiency(η%)of 92%.The adsorption of the green inhibitor was found to obey the Langmuir’s isotherm model.FTIR data and XPS analysis clearly indicated that the adsorption mechanism of DNA on carbon steel surface is mainly controlled by a chemisorption process.Using quantum chemistry calculation to determine the relationship between the DNA molecular structure change and the corrosion inhibition efficiency. |
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