Performance and Mechanism of a Composite Scaling鈥揷orrosion

'HVDOLQDWLRQ

Contents lists available at ScienceDirect

Desalination

journal homepage: www.elsevier.com/locate/desal

Performance and mechanism of a composite scaling–corrosion inhibitor used in seawater: 10-Methylacridinium iodide and sodium citrate ⁎ Weiwei Zhanga, Hui-Jing Lia,b, , Liwei Chena, Jiani Suna, Xingyi Mac, Yunfei Lia, Chao Liua, ⁎ Xu Hana, Boyi Panga, Yan-Chao Wua,b, a School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, PR China b Weihai Institute of Marine Biomedical Industrial Technology, Wendeng District, Weihai 264400, PR China c Department of Chemical & Biological Engineering, Korea University, Seoul 136713, Republic of Korea

ARTICLE INFO ABSTRACT

Keywords: An environment-friendly scaling–corrosion inhibitor composed of 10-methylacridinium iodide (MAI) and so- Mild steel dium citrate (SC) was developed, whose scale inhibition performance were studied through weight loss, elec- Seawater trochemical techniques, static tests and surface analysis techniques (SEM, SECM, XPS, XRD). The optimum mass Corrosion inhibition ratio of MAI and SC corrosion inhibition was found to be 1:2, and the optimum mass ratio of scale inhibition was Scale inhibition 1:3. The experimental results showed that MAI–SC mixture as mixed-type scaling–corrosion inhibitor with ex- Surface analysis cellent corrosion (ηw = 92.7%) and scale inhibition performance (ηCa = 98.3%). The electrochemical stability of the inhibitor ﬁlm was investigated by chronoamperometry (CA). SEM and XRD simulations indicated that the MAI–SC mixture inhibitor can distort and disperse the crystal lattice of calcium carbonate without forming scale, and it plays a dominant role in the inhibition of calcite (110) surface growth. The structure-activity relationship between the molecule structure of the MAI–SC mixture and its scale–corrosion inhibition performance was discussed based on the quantum chemistry calculation.

1. Introduction exploited to decrease the difference between desalination water tests and the related practical steel protection. Even so, most of the existing With the fast growth of manufacturing and heavy industries such as scale inhibitors face problems such as non-biodegradability and poor steel, power generation and chemical industry, the demand for fresh scale inhibition performance, which cannot meet the requirements of water in industrial production is increasing, which has increased the industrial application. Besides, in industrial operations, a single type of scarcity of water resources. Committed to alleviating water pressure, corrosion inhibitor is often insufficient to meet actual steel protection seawater is increasingly used in industrial applications, especially in requirements. Accordingly, the combination of corrosion inhibitors cooling systems and desalination plants. However, seawater contains should be fully utilized to improve the scale inhibition effect. Gu et al. corrosive media such as chloride ions, sulfate ions and carbonate ions, [6] studied the formulation of scale inhibitors for oilfield water, and which can easily corrode equipment and cause potential danger [1,2]. found that when the formulation was 50 mg/L MA-AMPS and 8 mg/L In addition, the continuous evaporation and concentration of water will imidazoline, the scale inhibition rate could reach up to 93.42%, and the lead to the deterioration of circulating water quality, scaling on the corrosion inhibition rate of mild steel could reach up to 90.42%, with surface of equipment and pipelines, reducing the heat transfer capacity excellent corrosion inhibition performance. Meanwhile, with the de- of equipment, and even causing accidents such as boiler explosion. An velopment of green chemistry, an environment-friendly and efficient economical and practical way to control or inhibit the corrosion and composite inhibitor, which can overcome not only the corrosion pro- scaling in seawater utilization is the usage of corrosion and scale in- blem but also the scaling problem, has become the high priority of mild hibitors owing to their high efficiency, easy operation and low-price. steel protection. Considering that sodium citrate (SC) is nontoxic and The corrosion and scale inhibitors are believed to act by adsorbing their with excellent chelating ability to metal ions such as Ca2+and Fe2+, active functionalities on the steel surface and forming a film of physical and has strong abilities in biodegradation, dispersion and resistance to or chemical properties to isolate the steel from the aggressive en- redeposition [7,8], we anticipated that sodium citrate combined with vironment [3–5]. Various corrosion and scale inhibitors have been appropriate organic inhibitors can give a practical scaling-corrosion

⁎ Corresponding authors at: School of Marine Science and Technology, Harbin Institute of Technology, Weihai 264209, PR China. E-mail addresses: [email protected] (H.-J. Li), [email protected] (Y.-C. Wu). https://doi.org/10.1016/j.desal.2020.114482 Received 1 March 2020; Received in revised form 17 April 2020; Accepted 20 April 2020

(OVHYLHU%9$OOULJKWVUHVHUYHG W. Zhang, et al. 'HVDOLQDWLRQ inhibitor platform for the application of steel in seawater. inhibitors at 30 °C for 72 h, and followed the methodological steps of As a kind of N-heterocyclic organic compounds, acridinium deri- the previous work [12]. Corrosion rate can be expressed by the fol- vatives are widely concerned because of their effective nitrogen atoms lowing relational Eq. (1): and conjugated π-bond structures, which can form coordination bonds WW− fi v = 12 with iron atoms to form a dense adsorption lm on the surface of steel st× (1) [5]. Moreover, acridinium-based materials have the characteristics of simple synthesis, low toxicity and unique anti-corrosion activity. Thus, where W1 and W2 (mg) are the weight loss of mild steel in the presence 2 the combination of acridinium derivatives with SC has a great appli- and absence of inhibitors, respectively, s (cm ) is the area of steel ffi η cation prospect in the scale and corrosion inhibition performance of samples, and t (h) is the soaking time [5]. The inhibition e ciency ( w) seawater utilization. was calculated by Eq. (2): In this study, acridine was synthesized for the first time via one-pot vvo − ηw = × 100% annulation of 2-aminobenzophenone and cyclohexanone in the pre- vo (2) sence of iodine under an atmosphere of oxygen, in which water was the only by-product. 10-Methylacridinium iodide (MAI), prepared by the where vo is the corrosion rate in the absence of inhibitor and v is the condensation of acridine and methyl iodide, was designed here as a corrosion rate in the presence of inhibitor. representative scaling-corrosion inhibitor for mild steel utilization, which combined with sodium citrate was used as a probe to estimate 2.3. Electrochemical measurements for corrosion inhibition the potential inhibition effect. The inhibition behavior of the mixture of MAI and SC was studied by weight loss method, potentiodynamic po- The electrochemical test system is identical to that described in our larization, electrochemical impedance spectroscopy (EIS). The stability previous reports [13,14]. Before each experiment, the working elec- fi of the inhibitor film was investigated by chronoamperometry (CA) at trode is rst contacted with the tested solution for 30 min to achieve its anodic and cathodic potentials. Scanning electron microscopy (SEM), stable open-circuit potential (OCP) at room temperature. Potentiody- scanning electrochemical microscopy (SECM) and X-ray photoelectron namic anodic and cathodic polarization curves were performed using a −1 − − spectroscopy (XPS) were used to measure the surface morphology of scan rate equal to 1 mV s from 900 mV up to 450 mV in relation adsorption film. The scale inhibition effect was determined by static to the stable OCP. Electrochemical impedance measurements were scale inhibition test. The scale inhibition mechanism of the inhibitor conducted over a frequency range from 100 kHz to 50 mHz at the stable was investigated by SEM and XRD. The scaling–corrosion mechanism open-circuit potential with an AC wave of 5 mV. CA measurements between the MAI–SC mixture and the mild steel surface was studied via were carried out by applying constant anodic and cathodic potentials quantum chemical calculation. for 1 h.

2. Experimental 2.4. Static tests for scale inhibition

2.1. Materials and solutions The scale inhibition performance was measured by CaCO3 deposition method based on Chinese national standard method (GB/T 16632- Working electrodes were prepared from mild steel specimens with 2008) [3,15]. The tests were maintained for 10 h in a water bath at – the following composition: C (0.056%), Mn (0.18%), P (0.035%), Si 80 °C in the presence of a certain amount of the MAI SC mixture. The fi (0.26%), S (0.06%) and remainder Fe. The size of mild steel specimens solution was cooled to room temperature and ltered, and the content 2+ fi for weight loss, electrochemical, and surface analysis experiments have of residual Ca in the ltrate was titrated with EDTA. The scale in- ffi been detailed in our previous work [5]. Before each measurement, mild hibition e ciency can be calculated from Eq. (3): steel coupons were manually abraded with 400, 800 and 1000 mesh [Ca2++ ]− [Ca2 ] η = f o × 100% water grit papers, washed with double distilled water, degreased with s 2++2 [Ca ]i − [Ca ]o (3) ethanol and then dried in warm air. The experiments involved were 2+ 2+ fi carried out in a seawater solution without or with inhibitors. The ty- where [Ca ]f is the Ca concentration in the ltrate after heating 2+ 2+ fi pical composition of Weihai seawater was listed in Table S1 [Supple- with inhibitors, [Ca ]o is the Ca concentration in the ltrate after 2+ 2+ mentary Information]. heating without inhibitors, [Ca ]i is the Ca concentration in the Acridines were usually prepared from two aromatic substrates with starting solution. hazardous by-products and limited substrate scopes. To circumvent this problem, Wang et al. [9] have developed an elegant acridine synthesis 2.5. Surface analysis from 2-aminophenyl ketones and cyclohexanones using hazardous tert- butyl hydroperoxide as the oxidant. We [10] and Deng et al. [11] in- 2.5.1. SEM and SECM analysis for corrosion inhibition dependently accomplished the above reaction in the presence of a The mild steel sample was taken out from the test solution after palladium-catalyst with unhazardous oxygen as the oxidant. Herein, being immersed for 72 h in seawater without and with the MAI–SC this reaction was achieved in our laboratory under metal-free condi- mixture. The analysis was performed using the scanning electron mi- tions without the use of hazardous tert-butyl hydroperoxide as the croscope (SUPR™ 55, Zeiss, Germany) with an accelerating voltage of oxidant. Indeed, acridine was synthesized for the first time via one-pot 20 kV to observe its surface corrosion appearance. Additionally, SECM annulation of 2-aminobenzophenone and cyclohexanone in the pre- (Uniscan Instruments Ltd., U.K.) was performed using a four-electrode sence of iodine under an atmosphere of oxygen, in which oxygen is the system containing a working electrode, a probe, a counter electrode and sole oxidant with water as the only by-product. Subsequently, MAI was a reference electrode. synthesized by refluxing the acridine and methyl iodide in acetonitrile for 8 h, and the molecular structure was confirmed by 1H NMR and 13C 2.5.2. XPS analysis NMR as illustrated in Fig. S1 [Supplementary Information]. Sodium X-ray photoelectron spectroscopy (XPS) analysis of the surface film citrate was purchased from Aladdin reagent company. of mild steel was carried out using a Thermo VG Scientific ESCALAB 250 spectrometer with a monochromatic Mg Κα X-ray source. 2.2. Weight loss tests for corrosion inhibition 2.5.3. Characterization of scale deposits The weight loss tests were carried out in seawater without or with Morphology and size changes of calcium carbonate were detected

W. Zhang, et al. 'HVDOLQDWLRQ by SEM (SUPR™ 55, Zeiss, Germany) and X-ray diﬀraction (Japan D/ θ Frumkin: exp(−= 2fθ ) Kads C max 2500). 1 − θ (6) where C is the inhibitor concentration, θ represents the surface cov- 2.6. Quantum chemical analysis erage, which was calculated according to Eq. (2), f is the factor of en-

ergetic inhomogeneity, and Kads is the adsorption equilibrium constant. MM2 and MOPAC in the Chem3D software package were used to The high linearity and low deviations revealed that the adsorption of construct the initial configuration of the scale inhibitor molecules, and MAI–SC is based on the Langmuir formulation. The high values of Kads − the semi-empirical PM3-SCF-MO method was used to pre-optimize the (51,240 M 1) got from the intercepts of Fig. S2a demonstrated that the fi fi molecular con guration. Then, the con guration of the pre-optimized adsorption of the MAI–SC mixture happened spontaneously. Eq. (7) was molecules were fully optimized at the B3LYP/6-31G(d,p) level of 0 used to calculate the standard adsorption free energy (ΔGads) values: Gaussian 09 package. The quantitative parameters of MAI and SD, such ∆=−GRTK0 as atomic charges, atomic distances, frontier orbital energy (EHOMO, ads ln(55.5ads ) (7) E ), energy gap (ΔE) and the fraction of electrons transferred (ΔN) LUMO where R is the gas constant, and T is the thermodynamic temperature. A were calculated to analyze their relationship with scale-corrosion in- well-recognized judgment that the absolute value of hibition. 0 −1 ΔGads < 20 kJ·mol is represented as physisorption process, likely due to the electrostatic attraction between charged metal surface and in- 3. Results and discussion 0 −1 hibitors. On the contrary, the |ΔGads| value > 40 kJ·mol is represented as chemisorption, which is due to the charge sharing or 3.1. Corrosion inhibitive action of MAI–SC mixture 0 transfer between iron atoms and inhibitors [5]. The ΔGads value in this − work was −37.44 kJ.mol 1, manifesting the adsorption of the MAI–SC 3.1.1. Weight loss experiments mixture on the surface of mild steel is a clarification of the mixed Table 1 showed the corrosion rate (v) and inhibition efficiency (η ) w physisorption and chemisorption interactions. Further understanding of of mild steel in seawater with a series of concentrations of inhibitors, the adsorption mechanism will be elaborated in the following sections. which were measured by weight loss method. As shown in Table 1, the single MAI and SC have certain corrosion effects, and the v increases 3.1.3. Potentiodynamic polarization (PDP) with increasing concentration. When the concentration was > 150 − Polarization curve measurements can explore the mechanism of the mg∙L 1, the inhibition rate did not change much. When 200 mg/L MAI electrode reaction process and determine the type of corrosion in- was added to the solution alone, the ηw decreased, which was attributed hibitor. The PDP curves obtained for mild steel in seawater without and to the formation of micelle adsorption on steel surface when the con- with MAI, SC, and the MAI–SC mixture were shown in Fig. 1. Listed in centration of inhibitor was high, so that the structure of the adsorption Table 2 were the related electrochemical parameters derived from the layer was loose and the η was reduced. Furthermore, the addition of w linear partial extrapolation of anodic and cathodic curves and inhibi- MAI–SC has increased ηw significantly compared to the use of MAI or SC tion efficiency (η ) calculated by Eq. (8): alone, indicating that they have synergistic effect. In seawater, SC i might interact electro-statically with MAI to form complex structure ii0 − η (%)= corr corr × 100 leading to adsorption on the steel surface, covering larger surface area i i 0 corr (8) and thus offering greater resistance towards corrosion. At a mass ratio 0 of MAI to SC is 1:2, the inhibition efficiency ηw is high, reaching 92.7%. where, icorr is the corrosion current density in the absence of inhibitor and icorr is the corrosion current density in the presence of inhibitor, 3.1.2. Adsorption isotherms obtained from the Tafel plots. As illustrated in Fig. 1, under the same The mechanism of inhibitor adsorption can be characterized by potential, the anodic and cathodic current densities of the mild steel – their adsorption isotherms. Generally, an adsorption type can be as- electrode containing the MAI SC mixture (Fig. 1c) is not only smaller sessed by the adsorption isotherms such as Temkin, Frumkin and than the non-contained, but also smaller than the MAI (Fig. 1a) or SC – Langmuir isotherms (Fig. S2 in Supplementary Information), which (Fig. 1b) alone, showing that the MAI SC mixture can sharply reduce were calculated by the following equations: the anodic dissolution of the steel and delay the cathodic evolution of hydrogen. In Table 2, the potential of each test system was transferred C 1 Langmuir: =+C relatively higher relative to the blank and > 85 mV, indicating that the θK ads (4) MAI, SC and MAI–SC mixture were mainly restrained the anode activity of mild steel [16]. This meant that the anodic dissolution of mild steel Temkin:exp(fθ ) = Kads C (5) was more favored than the cathodic evolution of hydrogen gas. Besides, after adding MAI–SC mixture, the corrosion current density decreased Table 1 obviously, and the values of the anodic and cathodic Tafel slopes (βa & Weight loss results of mild steel in seawater with different concentrations of β ) did not change much, indicating that the mixture of MAI–SC acted MAI and SC. c delay the corrosion process by blocking the reactive sites on mild steel −2 −1 η cMAI (mg/L) cSC (mg/L) v (mg cm h ) w (%) surface without modifying the metal dissolution mechanism [17,18]. Another noteworthy from Table 2 is that the single MAI and SC have a 0 0 4.25 ± 0.049 – ff η 50 0 2.48 ± 0.037 41.6 certain corrosion inhibition e ect, and the i gradually increased with 100 0 1.35 ± 0.032 68.2 the increase of the concentration. When the concentration reached − 150 0 0.86 ± 0.026 79.8 150 mg∙L 1, the corrosion inhibition rate was not changed much. 200 0 1.01 ± 0.029 76.2 While, the MAI–SC mixture increased the ηi more than either MAI or SC 0 50 2.79 ± 0.036 34.4 ff 0 100 1.90 ± 0.028 55.2 alone, indicating the synergistic e ect between MAI and SC improved 0 150 1.21 ± 0.025 71.5 the surface coverage. The greatest inhibition performance reached up to 0 200 1.14 ± 0.019 73.2 93.80% at a mass ratio of MAI to SC is 1:2, which agreed well with the 50 25 0.95 ± 0.022 77.6 results of weight loss tests. In subsequent corrosion studies, MAI 50 50 0.50 ± 0.017 88.2 (50 mg/L), SC (100 mg/L) and MAI–SC (MAI: 50 mg/L; SC: 100 mg/L) 50 100 0.31 ± 0.020 92.7 50 150 0.37 ± 0.018 91.3 were investigated. Compared with the reported inhibition efficiency of other

W. Zhang, et al. 'HVDOLQDWLRQ

acridinium derivates by the PDP method were shown in Table S2 [Supplementary Information] [12,14,19,20]. Based on these data, it indicated that MAI–SC is an excellent corrosion inhibitor for mild steel protection in corrosive media in comparatively lower concentrations. It can be reasonably explained that when SC is added into the seawater – solution, it will be hydrolyzed to generate C5H7O5COO anions. As the adsorption of MAI on the electrode surface made the metal surface – display positive charges, C5H7O5COO anions moved to the metal surface by the coulombic force and adsorbed on the metal surface. The bridge phenomenon will be formed between the citric acid anion adsorbed on mild steel surface and the positive center of MAI molecule [21], improving the coverage of the corrosion inhibitor on mild steel surface, and thus aﬀecting the anodic and cathodic corrosion process of steel.

3.1.4. Electrochemical impedance spectroscopy (EIS) Fig. 2(a) and (b) presented the Nyquist and Bode plots, respectively, in seawater without and with the MAI, SC, and MAI–SC mixture. As shown in Fig. 2a, there is an increase in diameter of the capacitive loop when compared to the system without inhibitor, and further increases with the addition of the MAI–SC mixture. Meanwhile, all Nyquist plots show similar capacitive loops, indicating that the mechanism of corrosion remains the same with or without inhibitors. It is also observed that the loops are flattened, which is attributed, in the literature, to the heterogeneity inherent to the surface of solid electrodes during corrosion, and are commonly referred to as dispersion effects [22,23]. For the blank electrode, a single-phase horn on the Bode plots (Fig. 2b) indicates that the corrosion process on steel surface is mainly controlled by the charge transfer step. While with the MAI, SC and MAI–SC mixture, the phase angles of electrode showed two peaks, showing that two phase constants associated with the double-layer impedance exist at the interface between mild steel and solution. Accordingly, the impedance spectra of Fig. 2 could be fitted by equivalent circuits R(QR) and R(Q(R (QR))) (Fig. S3 in Supplementary Information), respectively. Chi-square (χ2) was adopted to assess the accuracy of the fitting data. All the results provided low χ2 values (Table 3), reflecting that the fitting data agree well with the experimental results. The fitted parameters listed in

Table 3 include Rf (film resistance), Rct (charge transfer resistance), Cf (film capacitance) and Cdl (double layer capacitance). Considering that the behavior of double layer capacitance is not equal to pure capacitance when dispersion effect exists, the constant phase angle element CPE was used instead of a double layer capacitance. The impedance of the CPE is expressed by Eq. (9):

n −1 ZCPE= [()]Yjw 0 (9)

where Y0 is the magnitude of CPE and n represents the deviation from the ideal behavior falling between −1 and 1, ωmax =2πfmax and 2 j = −1. Besides, the Cdl was calculated for the CPE including circuit based on Eq. (10):

n−1 Yw0 () Cdl = sin(nπ ( /2)) (10)

Also, the ηz for each inhibitor concentration was calculated using the Eq. (11): RR− 0 ()p p η (%) = × 100 z R p (11)

0 where Rp is equal to Rct in the absence of inhibitor and Rp is the sum of Rf and Rct in the presence of inhibitor, obtained from the electrochemical impedance diagrams. Fig. 1. Polarization curves for mild steel in seawater containing: (a) MAI, (b) SC According to Table 3, with the addition of MAI or SC inhibitors, the and (c) MAI–SC. Rct value increased compared to that in the absence of inhibitor. When the two inhibitors were combined, the Rct value further increased to 2 7163 Ω cm , with ηz as high as 91.4%. A large Rct is associated with a slower corroding system. The observed increase in Rf with the MAI–SC

W. Zhang, et al. 'HVDOLQDWLRQ

Table 2 Polarization curve parameters for diﬀerent working electrodes in seawater.

−2 a −1 a −1 cMAI (mg/L) cSC (mg/L) Ecorr (mV vs. SCE) icorr (μAcm ) β a (mV dec ) −β c (mV dec ) ηi (%)

00−712 ± 7.59 11.24 ± 0.086 72.9 ± 2.14 436.9 ± 4.09 – 50 0 −654 ± 5.46 5.69 ± 0.073 68.3 ± 1.89 421.4 ± 5.12 49.4 100 0 −637 ± 7.21 3.11 ± 0.049 71.5 ± 2.05 439.3 ± 4.89 72.3 150 0 −651 ± 6.03 1.94 ± 0.065 64.9 ± 2.12 434.6 ± 5.54 82.7 200 0 −641 ± 5.24 2.20 ± 0.057 70.1 ± 2.08 427.1 ± 3.98 80.4 050−640 ± 4.78 6.67 ± 0.076 72.8 ± 1.97 435.7 ± 4.43 40.7 0 100 −619 ± 6.73 4.57 ± 0.053 80.2 ± 3.22 473.3 ± 6.41 59.3 0 150 −626 ± 5.78 2.85 ± 0.045 77.5 ± 2.65 458.6 ± 5.23 74.6 0 200 −616 ± 7.04 2.69 ± 0.043 82.9 ± 3.13 469.2 ± 4.76 76.1 50 25 −646 ± 7.45 2.20 ± 0.037 69.5 ± 1.54 417.6 ± 4.08 80.4 50 50 −639 ± 6.98 1.04 ± 0.024 80.3 ± 2.89 438.4 ± 5.34 90.7 50 100 −624 ± 5.73 0.66 ± 0.021 83.5 ± 3.06 460.8 ± 5.44 94.1 50 150 −621 ± 5.39 0.81 ± 0.032 78.6 ± 2.85 464.1 ± 6.13 92.8

a βa and βc were derived through nonlinear least-squares ﬁtting of data to the corresponding theoretical equation within the (Ecorr ± 20) mV potential window.

double layer capacitor [12,24,25]. The decrease of capacitance and the increase of resistance can be attributed to the displace of water molecules by the inhibitor molecules at the metal/solution interface, forming a protective film to prevent the corrosion of mild steel. It is also worth mentioning that the n values did not vary significantly, showing the charge transfer controls the dissolution mechanism of steel. Fur- thermore, the highest impedance at low frequency (50 mHz) and phase angle values at high frequency (10 kHz) of the steel also verified the effective inhibition performance of the MAI–SC mixture. These results show that the MAI–SC mixture has better corrosion resistance than the MAI and SC alone, which is corresponding to the results of polarization curve.

3.1.5. Electrochemical stability analysis In order to examine the electrochemical stability of the inhibitor film, CA measurements were carried out at anodic and cathodic potentials, which were previously determined according to the PDP curves (Fig. 1). The CA curves obtained in seawater in the absence and presence of the MAI–SC mixture were shown in Fig. S4 [Supplementary Information]. As shown in Fig. S4, the current density in the inhibitor- free solution is very high and almost remains unchanged during operation time. Under the anodic potential, a sharp drop in the current was observed in the first 150 s without inhibitor, which may be due to the accumulation of corrosion products at the metal/solution interface due to the increase of metal dissolution, and then rendered the diffusion of ions. However, both the anodic and cathodic current density decreased significantly after adding the MAI–SC mixture to seawater solution. The current densities in the presence of inhibitor remained almost constant within 1 h with the potential of cathode and anode were −0.724 V(SCE) and −0.524 V(SCE), respectively. It indicated the electrochemical stability of the MAI–SC mixture, which could be tightly adsorbed on the steel surface and thereby formed a stable protective film on the steel surface [26]. As the MAI–SC mixture has good electrochemical stability, it is expected to become a practical scaling-corrosion inhibitor for steel used in seawater, which motivated us to further study its scaling–corrosion inhibition performance.

3.1.6. SEM and SECM analysis Fig. 2. Nyquist plots (a) and Bode plots (b) for mild steel in seawater without Surface morphology analysis can clearly provide the corrosion and with MAI (50 mg/L), SC (100 mg/L), or MAI–SC (MAI: 50 mg/L; SC: morphological characteristics of the mild steel surface and verify the 100 mg/L). existence of inhibitor adsorption ﬁlm. Fig. 3 showed the surface images of mild steel after 72 h of immersion in blank seawater, seawater with MAI, seawater with SC, and seawater with the MAI–SC mixture ob- mixture indicated that more inhibitor molecules were adsorbed on the tained by SEM. The image showed that in the absence of inhibitor metal surface to form a dense protective ﬁlm. However, the values of Cf (Fig. 3a), the metal surface is too rough due to the seawater attack. On and Cdl values displayed a decline tendency with the presence of MAI, the other hand, smooth surfaces can be observed when immersing mild SC or MAI–SC mixture, which might be caused by the decrease of local steel in seawater in the presence of 50 mg/L MAI or 100 mg/L SC dielectric constant and/or an increase in the thickness of the electric (Fig. 3b, c), and the corrosion is serious in an area not covered by

W. Zhang, et al. 'HVDOLQDWLRQ

Table 3 EIS parameters for diﬀerent working electrodes in seawater.

a b c d e f 2 Inhibitors Rct Y0(1) Cdl (n1) Rf Y0(2) Cf (n2) χ ηz − − − − − − − (Ω cm2) (μΩ 1 cm 2 sn) (μFcm 2) (Ω cm2) (μΩ 1 cm 2 sn) (μFm 2) (10 3) (%)

Blank 616 595.2 290.3 (0.82) –– – 4.42 – MAI 1317 386.7 228.1 (0.67) 10.1 182.5 47.8 (1) 1.07 53.6 SC 1592 318.4 144.9 (0.71) 9.2 144.6 43.5 (1) 1.31 61.5 MAI–SC 7163 212.4 102.9 (0.68) 30.9 40.3 10.3 (1) 3.26 91.4

a The standard deviation varied between 8.1 and 27.4. b The standard deviation varied between 6.4 and 9.2. c The standard deviation varied between 5.9 and 8.1. d The standard deviation varied between 0.56 and 2.03. e The standard deviation varied between 2.2 and 7.4. f The standard deviation varied between 0.61 and 2.45. corrosion inhibitor. In contrast, a significant reduction of specimen the presence of the MAI-SC mixture. This is attributed to the reduction corrosion is observed after adding the MAI–SC mixture (Fig. 3d), with of tip current by encountering obstacles in the diffusion field around the only a little corrosive pitting. Therefore, the combination of MAI and SC tip, showing that MAI-SC mixture have a good effect of corrosion in- can not only greatly improve the corrosion inhibition effect, but also hibition and can be co-adsorbed on the mild steel surface. suppress the severe local corrosion of metals. This is due to the Fe-MAI complex film formed on the steel surface when MAI is used at a low concentration in seawater, which is relatively loose and has poor 3.1.7. XPS analysis chloride resistance. After the addition of SC, it has a fast adsorption rate The XPS spectrum of bare mild steel surface and the surface of mild on the metal surface and has a good film-reinforcing effect. At the same steel immersed in seawater containing the MAI–SC mixture was shown time, it forms a water-insoluble protective film with stronger adsorption in Fig. 5. It can be seen from Fig. 5a that there are two kinds of binding and complexation ability and better chloride resistance on the steel energy of Fe element on the surface of bare steel, namely 706.74 eV and surface together with MAI, preventing the dissolution of metallic iron. 711.46 eV, corresponding to the elemental Fe and Fe2O3, respectively. The protection performance of inhibitor can be also judged by the However, when the mild steel surface was immersed in the MAI–SC magnitude and distribution of current peaks in SECM image. As shown inhibitor (Fig. 5a, red), the binding energy of Fe is single peak with a in Fig. 4a, the image of metal surface displayed multiple current peaks peak value of 711.67 eV, and no elemental Fe exists. It indicated that Fe (maximum 992 nA) due to current fluctuations caused by the anode exists in the surface film mainly in the form of Fe2O3 and Fe (III) dissolution of the steel substrate [12,18]. The maximum current density complex [23]. Fig. 5b showed that the binding energies of C element on of the steel is greatly reduced to 588 nA and 478 nA in the presence of two kinds of mild steels surface were basically the same, and no in- MAI and SC (Fig. 4b, c), which was further reduced to 91 nA (Fig. 4d) in formation about the valence state of C element can be obtained. The increased of C content on the steel surface with the MAI–SC inhibitor is

Fig. 3. SEM images of mild steel surfaces: (a) seawater, (b) MAI, (c) SC and (d) MAI–SC.

W. Zhang, et al. 'HVDOLQDWLRQ

Fig. 4. SECM images of mild steel surfaces: (a) seawater, (b) MAI, (c) SC and (d) MAI–SC. due to the complexation of the MAI–SC mixture and Fe on the surface of MAI and SC are 50 mg/L and100 mg/L, respectively and the tem- mild steel. In addition, the binding energy of O on two kinds of mild perature is 60 °C, the ηCa is close to 98.3%. This may be due to the steels surface was slightly different, and the binding energy at the increase of carboxyl groups in the MAI–SC mixture inhibitor, which highest peak was 530.2 eV, indicating that O existed mainly in the form changed the chelation degree with Ca2+ or attached to interfere with − of O2 . Fig. 5c showed a shoulder at 531.1 eV for the MAI–SC mixture calcium scale crystal growth, destroyed the crystal structure of calcium − treated steel, indicating the presence of eOH and/or eCOO , which scale, and thus achieved a good scale inhibition effect. Besides, with the indicates that SC in the inhibitor was also involved in the formation of increase of temperature, the ηCa decreased, but it is still above 94.5%. surface film. The XPS analysis of N (Fig. 5d) showed that the peak The CaCO3 scale inhibition efficiency decreased with the increase of the appeared at 398–401 eV, indicating that N was trivalent, and it should temperature, which might be due to the lower solubility of CaCO3 at a be the peak of the binding energy of eCeN in MAI formed on the higher temperature, thus leading to a faster precipitation rate. The re- surface film of mild steel [17]. This showed that MAI was also involved sults show that the MAI-SC mixture has good scale inhibition perfor- in the formation of mild steel surface film. mance of calcium carbonate and can be used as a scale inhibitor. Through XPS analysis, the main components of the film-forming on the mild steel surface in seawater containing the MAI–SC inhibitor are − Fe (III), C (IV), O2 , N (III) and a small amount of Fe (II) complex, 3.2.2. SEM images of scale crystals which effectively inhibit the corrosion of mild steel in seawater. SEM analysis was applied to investigate the morphological variation of scale crystals (Fig. 6). As shown in Fig. 6a, the CaCO3 crystal formed without the composite inhibitor had a regular shape and compact 3.2. Scale inhibition of MAI–SC mixture structure, and the surface of the scale crystal was smooth, which in-

dicated that the growth regular of CaCO3 crystal. After MAI–SC mixture 3.2.1. Performance of MAI–SC mixture for scale inhibition was added (Fig. 6b), CaCO3 crystal was irregular and twisted com- The eﬀect of ratio and temperature of the MAI–SC inhibitor on pletely, showing a good dispersion state, which indicated that the ad-

CaCO3 scaling was investigated (Fig. S5 in Supplementary Information). dition of the MAI–SC mixture inhibitor destroyed the normal growth of Samples were exposed to 50 mg/L MAI solution with diﬀerent ratios of CaCO3 crystal. This is because the carboxyl groups (eCOOH) in the SC at 60 °C and 70 °C, respectively. The scale inhibition rate of CaCO3 composite inhibitor generate negatively charged carboxylate ions in (ηCa) increased gradually with the decrease of the MAI-to-SC ratio, seawater [27–29], which will preferentially adsorb on the active which changed little after the ratio reached 1:3. When the amounts of growth point of the speciﬁc crystal surface of CaCO3, resulting in crystal

W. Zhang, et al. 'HVDOLQDWLRQ

Fig. 5. High-resolution XPS spectra for mild steel samples in seawater without and with MAI–SC. (For interpretation of the references to color in this ﬁgure, the reader is referred to the web version of this article.) distortion, thus hindering the further growth of the crystal. is to form a strong Coulomb interaction with Ca2+ on the growth surface of calcium carbonate crystal, thereby occupying the growth point 2+ 3.2.3. XRD analysis of Ca and preventing the formation of calcium carbonate scale [31].

Fig. 7 showed the XRD spectrum of CaCO3 crystal under blank test Fig. S6 [Supplementary Information] showed an optimized molecular conditions and with the addition of the MAI–SC mixture inhibitor. In structure of MAI and SC. The atomic charges of MAI and SC molecules the blank sample (Fig. 7a), the calcium scale showed a very strong were listed in Table S3 [Supplementary Information]. It can be seen diffraction peak at 29.39° corresponding to 104 face of calcite, and a from that the negative charge numbers of the O atoms are all above strong diffraction peak appeared at 35.97° corresponding to 110 face of 0.50, which indicates that the O atoms are prone to generate strong 2+ calcite, indicating that 104 and 110 faces were the main growth sur- electrostatic effects with Ca , thereby inhibiting the formation of faces. Besides, the diffraction peaks at 23.09°, 39.38°, 43.16°, 47.48° calcium scale. In addition to O atom, the N atom in MAI also has a and 48.44° corresponded to the calcite crystal faces 102, 100, 113, 202 higher negative charge, which has a stronger Coulomb effect. It also and 018, respectively [4]. After adding the scale MAI–SC inhibitor shows that the N atom plays an important role in inhibiting the for- (Fig. 7b), the diffraction peak strength at 29.39° is the largest, but mation of calcium carbonate scale. Besides, C15 for MAI, and C2 and C4 weaker than the diffraction strength of the non-corrosion inhibitor, and for SC have a negative charge of about 0.19 to 0.22, indicating that they the diffraction peak of 110 crystal surface at 35.97° was disappeared, also have a certain contribution to scale inhibition. which indicated that the inhibition of the scale inhibitor is mainly on In the study of atomic charge, negatively charged groups play an 110 and 104 crystal faces. At the same time, strong diffraction peaks important role in inhibiting scale. If the spatial distance of these func- appear at 26.21°, 36.17°, 39.59°, 43.45°, and 48.71°, which are the tional groups is close to the related ion spacing of the calcium carbonate crystal faces of aragonite and vaterite. With the participation of the crystal plane, a strong adsorption behavior will occur [32]. As a result, 2+ 2– MAI–SC mixture, the form and structure of CaCO3 crystals were altered, the further deposition of Ca and CO3 is blocked, and the growth which suggested the crystal growth of CaCO3 was blocked by the and development of calcium carbonate crystals is inhibited. Table S4 MAI–SC mixture. As calcite is the most stable structure in calcium [Supplementary Information] displayed the distances between calcium carbonate, the scale formed without scale inhibitor will be very hard, cations on crystal faces of calcium carbonate [33]. Table S5 [Supple- while aragonite and vaterite are relatively soft and unstable compared mentary Information] showed the distance between some atoms in MAI with calcite, which are easily to be washed away by water [30]. The and SC molecules. Comparing Tables S4 and S5, it could be seen that mechanisms for scale inhibition can be explained by the interaction of both MAI and SC have an atomic distance close to 0.4048 nm of the eCOOH/eOH with Ca2+, allowing the scale inhibitor to be adsorbed (104) and (102) faces of calcite. In addition, the O15-O8 distance on the calcium carbonate surface, occupying the active growth site of (0.406 nm) and O13-O8 distance (0.421 nm) of SC are close to the 2– the free CO3 deposit in the solution, blocking the growth of the CaCO3 calcium ion spacing of 0.413 and 0.424 on vaterite (002) and (020), crystal or causing it to undergo lattice distortion. respectively. Therefore, it can be inferred that SC molecules can be adsorbed on the surface of both calcite crystals and vaterite crystals to 3.3. Quantum chemical calculations prevent their subsequent growth. This is consistent with the previous experimental results. Therefore, the synergy between MAI and SC can fi 3.3.1. Structure-activity relationship of scale inhibition performance better adsorb on the speci c crystal planes of calcium scale, which Generally, the more negative charge an atom has, the much easier it makes the crystal surface distorted, resulting in lattice distortion, the

W. Zhang, et al. 'HVDOLQDWLRQ

Fig. 6. SEM images of CaCO3 crystals in (a) seawater and (b) the seawater containing MAI–SC.

W. Zhang, et al. 'HVDOLQDWLRQ

provide better inhibition eﬃciency. The electron fraction (ΔN), transferred from the inhibitor to the metal surface, can also be analyzed and predicted the relationship between corrosion inhibition and molecular structure. Recent studies have shown that the electronegativity can be measured by the work function (Φ) of metal surface [34,35], so the ΔN could be obtained from Eq. (12): Φχ− ∆=N inh ηη+ 2(Fe inh ) (12)

where χ is electronegativity and η is global hardness, as calculated from Eqs. (13) and (14):

−−EE χ = HOMO LUMO 2 (13)

EE− η = LUMO HOMO 2 (14)

In Eq. (12), ηFe has a value of 0 eV, and Φ is 4.82 eV of the Fe (110) plane. Generally speaking [35], the value of ΔN > 0 indicates that electrons are transferred from molecule to metal surface, and vice versa in the case of ΔN < 0. As shown in Table 4, the ΔN value was positive for SC but was negative for MAI, suggesting the MAI–SC complex can provide electrons to form coordination bonds mainly in SC and accept electrons to form feedback bonds mainly in MAI, showing the better synergistic eﬀect of MAI and SC on corrosion control.

4. Conclusions

The performance of the MAI–SC mixture as a scaling-corrosion inhibitor for mild steel protection in sweater was studied by systematic methods and characterizations. The main conclusions are as follows:

(a) The MAI–SC mixture as an environment-friendly scaling–corrosion inhibitor has excellent scale and corrosion inhibition performance under the optimal ratio of MAI to SC. The corrosion inhibition ef-

ﬁciency is as high as 92.7% (mMAI:mSC = 1:2), and the scale inhibition rate of CaCO3 is 98.3% (mMAI:mSC = 1:3). (b) Electrochemical studies implied that the MAI–SC mixture act as a mixed inhibitor that mainly suppress the anodic dissolution of mild steel to control corrosion. (c) Corrosion morphology analysis by SEM, SECM and XPS indicating Fig. 7. XRD pattern of the CaCO3 crystals in (a) seawater and (b) the seawater containing MAI–SC. that inhibitors promote surface protection by decreasing the interaction of the metal surface with the corrosive solution. The pro- − tective ﬁlm is mainly composed of Fe (III), C (IV), O2 , N (III) and a scale body generated is soft and easy to be washed away by water. small amount of Fe (II) complex. (d) SEM and XRD showed that the use of MAI–SC mixture altered the

3.3.2. Structure-activity relationship of corrosion inhibition performance form and structure of CaCO3 crystals, and the MAI–SC mixture plays The electron densities of HOMO and LUMO were calculated to study a dominant role in the inhibition of calcite (110) surface growth. the corrosion protection mechanism of corrosion inhibitor on mild (e) Quantum chemical calculation indicated that the MAI–SC inhibitor steel. The HOMO and LUMO diagrams of the MAI, SC and MAI–SC has scale inhibition eﬀects mainly on the (104) and (102) faces of mixture were shown in Fig. 8, which are related to the donor-acceptor calcite, and on the (002) and (020) faces of vaterite. The frontier interactions of inhibitive chemicals with target metals [5]. Several key molecular orbitals (HOMO and LUMO) showed that the bond for- Δ Δ quantum chemical parameters such as EHOMO, ELUMO, E, and N were mation between inhibitor–metal took place by retro-donation and listed in Table 4. As reported previously [5], the higher of EHOMO, the charge transfer between the Fe (110) antibonding orbital of the more likely molecules are to provide electrons. Similarly, the lower of inhibitor (N and O-atoms). ELUMO value, the stronger electron acceptability of inhibitor molecules. It is noted from Table 4 that SC possessed a higher EHOMO and MAI possessed a lower ELUMO, which play an important role in donating- CRediT authorship contribution statement accepting electrons to form valence bonds with iron atoms. Further- more, the separation energy (ΔE) is of important use for the determi- Weiwei Zhang: Investigation, Writing-original draft. Hui-Jing Li: nation of the adsorption activity of corrosion inhibitors on metal sur- Conceptualization, Supervision. Liwei Chen: Methodology. Jiani Sun: face, and smaller ΔE indicates that the compound has higher reactivity Methodology. Xingyi Ma: Software. Yunfei Li: Data curation. Chao and inhibition eﬃciency. According to Table 4, MAI–SC showed a lower Liu: Data curation. Xu Han: Formal analysis. Boyi Pang: Validation. ΔE value than MAI and SC, indicating the MAI–SC system is expected to Yan-Chao Wu: Writing-review & editing, Funding acquisition.

W. Zhang, et al. 'HVDOLQDWLRQ

Fig. 8. The frontier orbital density distributions of MAI, SC and MAI–SC.

Table 4 Tetrahydroacridines as corrosion inhibitor for X80 steel corrosion in simulated The calculated quantum chemical parameters for MAI, SC and MAI–SC. acidic oilfield water, J. Mol. Liq. 293 (2019) 111478. [6] T. Gu, P. Su, X. Liu, J. Zou, X. Zhang, Y. Hu, A composite inhibitor used in oilfield: Inhibitor EHOMO (eV) ELUMO (eV) ΔE (eV) ΔN MA-AMPS and imidazoline, J. Pet. Sci. Eng. 102 (2013) 41–46. [7] K. Sakhaee, M. Nicar, K. Hill, C.Y.C. Pak, K. Sakhaee, Contrasting effects of po- MAI −10.11 −6.65 3.46 −1.029 tassium citrate and sodium citrate therapies on urinary chemistries and crystal- SC −5.89 −1.07 4.82 0.278 lization of stone-forming salts, Kidney Int. 24 (1983) 348–352. MAI–SC −7.49 −5.41 2.08 −0.784 [8] K.I. Sallam, Antimicrobial and antioxidant effects of sodium acetate, sodium lactate, and sodium citrate in refrigerated sliced salmon, Food Control 18 (2007) 566–575. [9] G.C. Senadi, G.K. Dhandabani, W.P. Hu, J.J. Wang, Metal-free annulation/aerobic oxidative dehydrogenation of cyclohexanones with o-acylanilines: efficient synth- Declaration of competing interest eses of acridines, Green Chem. 18 (2016) 6241–6245. [10] W.L. Mu, M. Wang, H.J. Li, D.M. Huang, Y.Y. Zhang, C.Y. Li, Y. Liu, Y.C. Wu, Palladium-catalyzed regioselective oxidative annulation of cyclohexanones and 2- The authors declare no conflict of interest. aminophenyl ketones using molecular oxygen as the sole oxidant, Adv. Synth. Catal. 359 (2017) 4250–4257. Acknowledgments [11] X. Chen, Y. Xie, C. Li, F. Xiao, G.J. Deng, Synthesis of substituted acridines through a palladium-catalyzed condensation/cyclization/tautomerization sequence, Eur. J. Org. Chem. (2017) 577–581. This work was supported by Shandong Provincial Key Research and [12] W.W. Zhang, Y.W. Wang, H.J. Li, Y.H. Liu, R. Tao, S.Y. Guan, Y.H. Li, Y.C. Wu, Development Program (2019GSF108089), Shandong Provincial Natural Synergistic inhibition effect of 9-(4-chlorophenyl)-1,2,3,4-tetrahydroacridines and Tween-80 for mild steel corrosion in acid medium, J. Phys. Chem. C 123 (2019) Science Foundation (ZR2019MB009), National Natural Science 14480–14489. Foundation of China (21672046, 21372054), and Found from the [13] W.W. Zhang, H.J. Li, Y.W. Wang, Y. Liu, Q.Z. Gu, Y.C. Wu, Gravimetric, electro- Huancui District of Weihai City. chemical and surface studies on the anticorrosive properties of 1-(2-pyridyl)-2- thiourea and 2-(imidazol-2-yl)-pyridine for mild steel in hydrochloric acid, New J. Chem. 42 (2018) 12649–12665. Appendix A. Supplementary data [14] W.W. Zhang, H.J. Li, H. Li, C. Ma, Q. Pan, L. Chen, M.R. Wang, Y.C. Wu, Anticorrosion performance of acriflavine–Zn2+ system for mild steel in seawater Supplementary data to this article can be found online at https:// utilization, J. Mol. Liq. 299 (2020) 112152. [15] H. Wang, M. Gao, Y. Guo, Y. Yang, R. Hu, A natural extract of tobacco rob as scale doi.org/10.1016/j.desal.2020.114482. and corrosion inhibitor in artificial seawater, Desalination 398 (2016) 198–207. [16] W.W. Zhang, H.J. Li, C. Wang, L.J. Wang, L. Gen, H. Ma, Q. Pan, Y.C. Wu, ff References Synergistic e ect of 1-(2,5-dioxoimidazolidin-4-yl)urea and Tween-80 towards the corrosion mitigation of mild steel in HCl, New J. Chem. 43 (2019) 13899–13910. [17] M. Tourabi, K. Nohair, M. Traisnel, C. Jama, F. Bentiss, Electrochemical and XPS [1] M. Sareni, C. Dehghanian, M.M. Sabet, The effect of molybdate concentration and studies of the corrosion inhibition of carbon steel in hydrochloric acid pickling hydrodynamic effect on mild steel corrosion inhibition in simulated cooling water, solutions by 3,5-bis(2-thienylmethyl)-4-amino-1,2,4-triazole, Corros. Sci. 75 (2013) Corros. Sci. 48 (2006) 1404–1412. 123–133. [2] J.A. Leenbeer, Comprehensive approach to preparative isolation and fraction of [18] W.W. Zhang, H.J. Li, Y.W. Wei, Y. Liu, Y.C. Wu, Adsorption and corrosion inhibition dissolved organic carbon from natural water and wastewater, Environ. Sci. Technol. properties of pyridine-2-aldehyde-2-quinolylhydrazone for Q235 steel in acid 15 (1981) 578–587. medium: electrochemical, thermodynamic, and surface studies, Mater. Corros. 69 [3] Y. Gao, L. Fan, L. Ward, Z. Liu, Synthesis of polyaspartic acid derivative and eva- (2018) 1638–1648. luation of its corrosion and scale inhibition performance in seawater utilization, [19] H. Ju, T. Peng, Y. Li, Acridine as effective corrosion inhibitor for hot dipped coat- Desalination 365 (2015) 220–226. ings on steels in diluted HCl solution, Adv. Mater. Res. 79 (2009) 1035–1038. [4] G. Liu, M. Xue, H. Yang, Polyether copolymer as an environmentally friendly scale [20] E.D. Akpan, I.O. Isaac, L.O. Olasunkanmi, E.E. Ebenso, E.M. Sherif, Acridine-based and corrosion inhibitor in seawater, Desalination 419 (2017) 133–140. thiosemicarbazones as novel inhibitors of mild steel corrosion in 1 M HCl: synthesis, [5] W.W. Zhang, H.J. Li, M. Wang, L.J. Wang, Q. Pan, X. Ji, Y. Qin, Y.C. Wu, electrochemical, DFT and Monte Carlo simulation studies, RSC Adv. 9 (2019)

W. Zhang, et al. 'HVDOLQDWLRQ

29590–29599. [28] A. Harada, K. Kataoka, On-oﬀ control of enzymatic activity synchronizing with [21] D. Li, S. Chen, S. Zhao, H. Ma, The corrosion inhibition of the self-assembled Au, reversible formation of supramolecular assembly from enzyme and charged block and Ag nanoparticles ﬁlms on the surface of copper, Colloid. Surface. A 273 (2006) copolymers, J. Am. Chem. Soc. 121 (1999) 9241–9242. 16–23. [29] Y. Xu, B. Zhang, L. Zhao, Y. Cui, Synthesis of polyaspartic acid/5-aminoorotic acid [22] M.M. Solomon, H. Gerengi, S.A. Umoren, Carboxymethyl cellulose/silver nano- graft copolymer and evaluation of its scale inhibition and corrosion inhibition particles composite: synthesis, characterization and application as a benign corro- performance, Desalination 311 (2013) 156–161.

sion inhibitor for St37 steel in 15% H2SO4 medium, ACS Appl. Mater. Interfaces 9 [30] C. Wang, S.P. Li, T.D. Li, Calcium carbonate inhibition by a phosphonate-termi- (2017) 6376–6389. nated poly(maleic-co-sulfonate) polymeric inhibitor, Desalination 249 (2009) 1–4. [23] W. Zhang, R. Ma, H.H. Liu, Y. Liu, S. Li, L. Niu, Electrochemical and surface analysis [31] J.P. Räsänen, E. Pohjala, H. Nikander, T.A. Pakkanen, Ab initio studies on orga- studies of 2-(quinolin-2-yl)quinazolin-4(3H)-one as corrosion inhibitor for Q235 nophosphorus compounds. 5. Interactions of dianionic bisphosphonate compounds steel in hydrochloric acid, J. Mol. Liq. 222 (2016) 671–679. with magnesium and calcium, J. Phys. Chem. 100 (1996) 8230–8239. [24] B.D. Mert, A.O. Yüce, G. Kardas, B. Yazici, Inhibition effect of 2-amino-4-methyl- [32] A.G. Xyla, J. Mikroyannidis, P.G. Koutsoukos, The inhibition of calcium carbonate pyridine on mild steel corrosion: experimental and theoretical investigation, Corros. recipitation in aqueous media by organophosphorus compounds, Colloid Interface Sci. 85 (2014) 287–295. Sci. 153 (1992) 537–551. [25] A. Anejjar, R. Salghi, A. Zarrouk, O. Benali, H. Zarrok, B. Hammouti, S.S. Al-Deyab, [33] B. Bendiksen, J.S. Gill, Molecular Modeling in Scale Control—An Experimental N. Benchat, A. Elaatiaoui, Adsorption and corrosion inhibition of steel in hydro- Verification and Its Limitations, NACE Intelnational, Corrosion, Houston Tex, 1996. chloric acid solution by 3-bromo-2-phenylimidazol[1,2- α] pyridine, Int. J. [34] H. Lgaz, K.S. Bhat, R. Salghi, S. Jodeh, M. Algarra, B. Hammouti, I.H. Ali, Electrochem. Sci. 8 (2013) 11512–11525. A. Essamri, Insights into corrosion inhibition behavior of three chalcone derivatives [26] R. Solmaz, Investigation of corrosion inhibition mechanism and stability of Vitamin for mild steel in hydrochloric acid solution, J. Mol. Liq. 238 (2017) 71–83. B1 on mild steel in 0.5 M HCl solution, Corros. Sci. 81 (2014) 75–84. [35] Y. Meng, W.B. Ning, B. Xu, W.Z. Yang, K.G. Zhang, Y. Chen, L.H. Li, X. Liu, [27] Y. Xu, L. Wang, L. Zhao, Y. Cui, Synthesis of polyaspartic acid–- J.H. Zheng, Y.M. Zhang, Inhibition of mild steel corrosion in hydrochloric acid aminobenzenesulfonic acid grafted copolymer and its scale inhibition performance using two novel pyridine Schiff base derivatives: a comparative study of experi- and dispersion capacity, Water Sci. Technol. 64 (2011) 423–430. mental and theoretical results, RSC Adv. 7 (2017) 43014–43029.