Relationship between inhibition performance of melamine derivatives and molecular structure for mild steel in acid solution
Introduction
With the extensive use of acid solutions in oil well acidizing, pickling, descaling, and cleaning, the protection of mild steel in these fields has attracted increasing attention in recent years [1], [2]. Among different types of acids, hydrochloric acid is often used in many applications since it is low cost and readily available. However, it normally requires inhibitors to prevent the mild steel from corrosion due to its strong acidity [3]. Usually, 0.5 and 1.0 M HCl solutions were chosen as the corrosive medium to study the corrosion inhibition efficiency of inhibitor for mild steel [4], [5], [6]. Previous studies showed that the compounds containing N atoms and aromatic rings exhibited good inhibitive performance for mild steel due to the formation of coordination bonds between the electron pair of N and steel surface [7], [8].
It is well known that melamine is a typical nitrogen-enriched compound with a triazine ring and other three N atoms, which can be used as a corrosion inhibitor. However, the poor water solubility greatly impedes its application. To solve this problem, different kinds of substituent groups have been introduced to melamine ring to improve its solubility, and corrosion inhibition performances of some melamine derivatives have been studied for the protection of mild steel [9], [10], [11]. Additionally, these derivatives have high inhibition efficiency, which may be attributed to the adsorption of protonated sites and sharing of π electrons and lone pair electrons with the iron atom. Thus, the introduction of foreign groups affects not only the solubility but also the corrosion inhibition efficiency. It is important to investigate the relationship between the molecular structure of melamine derivatives and the corresponding inhibition effect to develop effective corrosion inhibitors. However, very few studies have studied and discussed this issue.
In this work, a set of homologous amino group substituted melamine derivatives, N2,N4,N6-trimethyl-1,3,5-triazine-2,4,6-triamine (T1), N2-(2-(dimethylamino)ethyl)-1,3,5-triazine-2,4,6-triamine (T2), N2-(3-(dimethylamino)propyl)-1,3,5-triazine-2,4,6-triamine (T3), N2,N4,N6-tris(2-(dimethylamino)ethyl)-1,3,5-triazine-2,4,6-triamine (T4), and N2,N4,N6-tris(3-(dimethylamino)propyl)-1,3,5-triazine-2,4,6-triamine (T5) were investigated as corrosion inhibitors, and the influences of their molecular structures on the inhibition performances were also discussed. Fig. 1 depicts the molecular structures of the five compounds. It can be found that all of them have one or three similar substituents, which are expected to endow the derivatives with different inhibition effects. Besides, the introduction of amino group remarkably improves their water solubility. The corrosion inhibition efficiencies of these derivatives for the mild steel in 0.5 M HCl were evaluated by potentiodynamic polarization (DPR), electrochemical impedance spectroscopy (EIS), and weight loss methods. Also, the surface morphologies of steel samples after immersed in test solution were observed using scanning electron microscope (SEM). To study the adsorption configurations of these corrosion inhibitors on iron surface, Monte Carlo simulations were conducted. Finally, the inhibition mechanisms of these inhibitors and the relationship between their inhibition efficiencies and the molecular structures were discussed.
Section snippets
Materials
The analytical reagent grade HCl (37%) was diluted to 0.5 M as the corrosion medium with ultrapure water. The inhibitors (T1, T2, T3, T4, and T5) were synthesized according to our previously–reported procedure [12] and were dissolved in 0.5 M HCl to get different concentrations. The mild steel coupons with elements of C, 0.22%; Si, 0.30%; Mn, 0.65%; S, 0.050%; P, 0.045%; Cr, 0.030%; Ni, 0.030%; Cu, 0.030%; and Fe (balance) were cut into 1 × 1 × 1 cm3 and made into working electrode for electrochemical
Open circuit potential
A stable potential without external current impressed on the electrode surface is necessary for DPR and EIS measurements [22]. The variations of OCP (vs. SCE) as a function of immersion time with and without different concentrations of inhibitors were recorded and are shown in Fig. 2. From Fig. 2, the initial OCP value in the blank solution is −0.495 V (vs. SCE), and increases to nearly −0.490 V (vs. SCE) after 790 s, and remains constant in the rest of the time. For each inhibitor with various
Conclusions
In this study, the inhibition performances of five homologous melamine derivatives were investigated using electrochemical measurements, weight loss method, and Monte Carlo simulations. It is found that the five derivatives are mix-type inhibitors. The adsorption of them on the steel surface obeys Langmuir adsorption isotherm. It is concluded that the introduction of tertiary amino groups into melamine provides the compound with better inhibition performance than that containing the same number
Acknowledgement
This work was financially supported by the National Natural Science Foundation of China (No. 21675131, 21273174) and the Municipal Science Foundation of Chongqing City (No. CSTC-2015jcyjB50001, CSTC-2013jjB00002).
References (40)
- et al.
Adsorption properties and inhibition of mild steel corrosion in sulphuric acid solution by ketoconazole: experimental and theoretical investigation
Corros. Sci.
(2010) - et al.
The isoxazolidines: a new class of corrosion inhibitors of mild steel in acidic medium
Corros. Sci.
(2003) - et al.
Corrosion inhibition of carbon steel using novel N-(2-(2-mercaptoacetoxy)ethyl)-N,N-dimethyl dodecan-1-aminium bromide during acid pickling
Corros. Sci.
(2013) - et al.
Assessment of the inhibition efficiency of 3,4-diaminobenzonitrile against the corrosion of steel
Corros. Sci.
(2016) Investigation of corrosion inhibition mechanism and stability of vitamin B1 on mild steel in 0.5 M HCl solution
Corros. Sci.
(2014)- et al.
Inhibition properties and adsorption behavior of imidazole and 2-phenyl-2-imidazoline on AA5052 in 1.0 M HCl solution
Corros. Sci.
(2014) - et al.
Aminic nitrogen-bearing polydentate Schiff base compounds as corrosion inhibitors for iron in acidic media: a quantum chemical calculation
Corros. Sci.
(2008) - et al.
Corrosion inhibition of carbon steel in hydrochloric acid by furan derivatives
Electrochim. Acta
(2008) - et al.
Experimental and quantum chemical studies of synthesized triazine derivatives as an efficient corrosion inhibitor for N80 steel in acidic medium
J. Mol. Liq.
(2015) - et al.
The inhibition effect of 2,4,6-tris (2-pyridyl)-1,3,5-triazine on corrosion of tin, indium and tin-indium alloys in hydrochloric acid solution
Corros. Sci.
(2010)
Experimental and theoretical studies of benzothiazole derivatives as corrosion inhibitors for carbon steel in 1 M HCl
Corros. Sci.
Electrochemical impedance spectroscopy investigations of epoxy zinc rich coatings: role of Zn content on corrosion protection mechanism
Electrochim. Acta
Inhibition effect of two mercaptopyrimidine derivatives on cold rolled steel in HCl solution
Corros. Sci.
New 1H-pyrrole-2,5-dione derivatives as efficient organic inhibitors of carbon steel corrosion in hydrochloric acid medium: electrochemical, XPS and DFT studies
Corros. Sci.
Theoretical studies of three triazole derivatives as corrosion inhibitors for mild steel in acidic medium
Corros. Sci.
Molecular dynamic and quantum chemical calculations for phthalazine derivatives as corrosion inhibitors of mild steel in 1 M HCl
Corros. Sci.
Theoretical evaluation of corrosion inhibition performance of some pyrazine derivatives
Corros. Sci.
An electrochemical and theoretical evaluation of 4,6-diamino-2- pyrimidinethiol as a corrosion inhibitor for mild steel in HCl solutions
Corros. Sci.
The substituted 1,3,4-oxadiazoles: a new class of corrosion inhibitors of mild steel in acidic media
Corros. Sci.
Aminopyrimidine derivatives as inhibitors for corrosion of 1018 carbon steel in nitric acid solution
Corros. Sci.
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