Journal of Materials Research and Technology Journal of Materials Research and Technology
J Mater Res Technol 2017;6:158-70 DOI: 10.1016/j.jmrt.2016.09.002
Original Article
Inhibition effect of bamboo leaves extract on cold rolled steel in Cl3CCOOH solution
Xianghong Lia,b,, , Shuduan Denga, Nan Lib, Xiaoguang Xiec
a Yunnan Key Laboratory of Wood Adhesives and Glue Products, Southwest Forestry University, Kunming, China
b Faculty of Science, Southwest Forestry University, Kunming, China
c School of Chemical Science and Technology, Yunnan University, Kunming, China
Received 30 January 2016, Accepted 14 September 2016
Abstract

The corrosion inhibition by Dendrocalamus brandisii leaves extract (DBLE)/major flavonoid of cold rolled steel (CRS) in trichloroacetic acid (Cl3CCOOH) solution was investigated by weight loss, electrochemical techniques and atomic force microscope (AFM). The adsorption mode of four major compounds (rutin, vientin, isovientin and orientin) on Fe (001) surface was theoretically investigated by molecular dynamics (MD). The results show that DBLE is a good inhibitor, and the maximum inhibition efficiency is higher than 95%. The adsorption of DBLE on CRS surface obeys Langmuir isotherm with exothermic process. DBLE behaves as a mixed inhibitor. AFM results confirm that DBLE could retard the corrosion of CRS in Cl3CCOOH. The inhibitive action of each flavonoid is lower than DBLE, and follows the order: rutin>vientin>isovientin>orientin. The major flavonoids in DBLE are adsorbed onto Fe (001) surface through FBS (flavones backbone structure) with a nearby flat orientation.

Keywords
Corrosion inhibitor, Trichloroacetic acid, Steel, Bamboo leaves extract, Flavonoids adsorption
1Introduction

Using inhibitors is one of the most practical methods for metals protection against corrosion, especially in acid media [1]. With more and more restrictive environmental regulations, the research in the field of corrosion inhibitors has been addressed toward the goal of using cheap and effective compounds at low or “zero” environmental impact. Biodegradable plant extract could be obtained by simple extraction process from rich natural resources. Thus, the main advantage of using plant extracts as corrosion inhibitors are both economic and environmental.

Up to now, many plant extracts have been reported as effective corrosion inhibitors of steel in inorganic acids (HCl, H2SO4, H3PO4), such as henna [2,3], Nypa fruticans Wurmb [4], Zenthoxylum alatum[5], Mentha pulegium[6], olive [7], Phyllanthus amarus[8], Damsissa [9], Occimum viridis[10,11], Murraya koenigii[12], lupine [13], Ananas comosus[14], Lasianthera africana[15], Strychnos nux-vomica[16], Justicia gendarussa[17], Oxandra asbeckii[18], Ferula assa-foetida[19], coffee [20], fruit peel [21], Halfabar [22], Kopsia Singapurenis[23], Jasminum nudiflorum[24], ginkgo[25], Artemisia pallens[26], Salvia officinalis[27], Osmanthus fragran[28], Uncaria gambir[29], garlic peel[30], Neolamarckia cadamba[31], Z. alatum[32], Acalypha indica L. [33], Acer truncatum[34], Acer buergerianum[35], Tagetes erecta[36], Musa paradisica[37] and Geissospermum leave[38]. It is found that the inhibition performance of plant extract is normally ascribed to the presence in their composition of complex organic species like tannins, alkaloids and nitrogen bases, carbohydrates, amino acids, proteins and hydrolysis products. These organic compounds always contain the adsorption centers of polar functional groups with N, S, O atoms as well as conjugated double bonds or aromatic rings in their molecular structures.

However, there have been lower attentions for plant extracts as corrosion inhibitors in organic acid medium. In 2012, Piper nigrum L. leaves extract [39] was reported as an effective corrosion inhibitor for steel in citric acid (H3C6H5O7). As another frequently used organic acid, trichloroacetic acid (Cl3CCOOH) is widely used in cellulose industry [40], and in the production of TCA Na-salt used as an herbicide. Cl3CCOOH shows strong corrosiveness on metal, so there is a great need to add inhibitor to protect metals in Cl3CCOOH solution [40]. In 1974, Sampat and Vora [41] investigated the corrosion inhibition of aluminum in Cl3CCOOH by some methyl pyridine derivatives. Since the 21st Century, xylenol orange [40], amino acetanilides [42], sulphathiazole [43] and 2-acetylphenothiazine [44] have been reported as effective inhibitors for aluminum in Cl3CCOOH solution. However, after carefully checking out the published references, there is almost no report about the corrosion inhibition of steel in Cl3CCOOH solution, specially for plant extract inhibitors.

In our laboratory, much work has been conducted to study the inhibition by bamboo leaves extract on the corrosion of metals in various media. The main reason is that bamboo leaves are abundant resources (about 1200 species and 70 genera of bamboo in the world) with fast and continuous renewal. Most important of all, bamboo leaves extract is virtually nonpoisonous [45,46]. Recently, the bamboo leaves extracts have been reported as good inhibitors for steel in HCl [47,48] and in H3C6H5O7[49] media. In continuation of our previous study, the present work firstly reports the inhibition effect of Dendrocalamus brandisii leaves extract (DBLE) on the corrosion of cold rolled steel (CRS) in Cl3CCOOH solution by weight loss, polarization curves and electrochemical impedance spectroscopy (EIS) methods. The steel surface was characterized by AFM technique. Meanwhile, molecular dynamics (MD) was applied to theoretically elucidate the adsorption mode of major flavonoid molecule (rutin, vientin, isovientin, orientin) on Fe (001) surface. The electrochemical corrosion mechanism of steel in Cl3CCOOH solution is proposed. Lastly, the inhibitive mechanism of DBLE is presented according to the difference in inhibition performance between DBLE and major flavonoid.

2Experimental2.1Materials

Tests were conducted on CRS having composition (wt.%): 0.07% C, 0.3% Mn, 0.022% P, 0.010% S, 0.01% Si, 0.030% Al and the remainder Fe. Trichloroacetic acid (Cl3CCOOH) is of analytical reagent (AR) grade, and four major compounds (rutin, vientin, isovientin and orientin) are of pure standards. All of these chemical reagents are obtained from Shanghai Chemical Reagent Company of China. The aggressive solutions of 0.05–0.5M Cl3CCOOH were prepared by dilution of AR grade Cl3CCOOH with distilled water. The ionization equilibrium constant (Kaθ) of Cl3CCOOH is 2.2×10−1 (pKaθ=0.66, 20°C). The experimentally measured and calculated pH values are listed in Table 1; clearly in good agreement with the theoretically calculated pH values.

Table 1.

The experimentally measured and calculated pH values of Cl3CCOOH solutions.

c (Cl3COOH)  Measured pH  Calculated pH 
0.051.34  1.38 
0.11.10  1.13 
0.20.85  0.95 
0.30.74  0.77 
0.40.66  0.69 
0.50.57  0.62 

DBLE was extracted from D. brandisii leaves using 80% (percent by volume) C2H5OH water solution at 75°C for 2h in our laboratory, as described in our earlier work [48,50]. The production rate is about 9.7%. Fourier transform infrared spectroscopy (FTIR) of DBLE and the average content of total flavonoids in DBLE (about 28%) were fully studied in our recent paper [48]. The concentration range of DBLE was 10–200mgl−1.

2.2Weight loss and electrochemical measurements

CRS sheets of 2.5cm×2.0cm×0.06cm were abraded by a series of emery paper (grade 320–500–800) and then washed with distilled water and degreased with acetone. The weight loss and electrochemical measurements have been described in detail in our earlier reports [47–50]. The immersion time of weight loss is 3–34h, and the experimental temperature is 20–50°C. Electrochemical experiments were carried out using a PARSTAT 2273 advanced electrochemical system (Princeton Applied Research) with a conventional three-electrode system: counter electrode (platinum), reference electrode (saturated calomel electrode (SCE)) coupled to a fine Luggin capillary and working electrode (surface area is 1.0cm×1.0cm).

For the weight loss method, the corrosion rate (v) was calculated from the following equation:

where W is the average weight loss of two parallel CRS sheets (g), S the total area of one CRS specimen (m2), and t is the immersion time (h). With the calculated corrosion rate, the inhibition efficiency (ηw) was calculated as follows:
where, v0 and v are the values of corrosion rate without and with inhibitor, respectively.

Before electrochemical measurements, the electrode was immersed in test solution at open circuit potential (OCP) for 2h at 20°C to reach a stable state. The potentiodynamic polarization curves were carried out by polarizing to ±250mV vs. OCP at a sweep rate of 0.5mVs−1. Inhibition efficiency (ηp) is calculated through the corrosion current density (icorr) values [47]:

where icorr and icorr(inh) represent corrosion current density values without and with inhibitor, respectively.

Electrochemical impedance spectroscopy (EIS) was carried out at stable OCP (no extra bias voltage, 2h of immersion) over a frequency range from 100kHz to 10mHz using a 10mV root mean square (r.m.s) voltage excitation. The total number of points is 30. Inhibition efficiency (ηR) is estimated by the relation below [47]:

where Rt(0) and Rt(inh) are charge transfer resistance values in the absence and presence of the inhibitor, respectively.

2.3Atomic force microscope (AFM)

The CRS specimens of 1.5cm×1.0cm×0.06cm were prepared as described above (Section 2.2). After immersion in 0.1M Cl3CCOOH solutions without and with 200mgl−1 DBLE at 20°C for 6h, the specimens were cleaned with distilled water, dried with a cold air blaster, and then used for a Japan instrument model SPA-400 SPM Unit atomic force microscope (AFM) examinations. The AFM images were measured in tapping mode using Si3N4 tips.

2.4MD simulations

MD simulations were performed with Discover program in Materials Studio 4.1 software from Accelrys Inc. [51]. According to many MD studies about the adsorption of inhibitor on steel surface [52,53], there could be strong interaction between organic inhibitor and Fe (001) surface, so Fe (001) surface is chosen to study. Fe (001) plane was firstly cleaved from pure Fe crystal, the surface was then optimized to the energy minimum, and then was enlarged to fabricate an appropriate supercell. After that, a vacuum slab with 1Å thickness was built above the Fe (001) supercell with 31.53×31.53×15.30Å of total 1331 Fe atoms. Meanwhile, the optimized inhibitor molecules of rutin, vientin, isovientin and orientin were done with DMol3 numerical based density function theory (DFT) in Materials Studio 4.1 at PW91/DNP/COSMO level [54,55], and then the inhibitor layers were built using the Amorphous cell program. Finally, the adsorption system was built by layer builder to place the inhibitor layer to Fe (001) supercell. All these slabs are separated by a 10Å vacuum thickness to ensure that the interaction between the periodically repeated slabs along the normal of the surface is small enough. The adsorption system was optimized using COMPASS force field. The MD simulation was performed under 298K, NVT ensemble, with a time step of 1.0fs and simulation time of 1000ps.

Both adsorption energy (Eads) and binding energy (Ebin) could determine the stability of inhibitor on metal surface. They have different view angles. Eads is mainly used to study the adsorption of inhibitor on the metal surface, and it is calculated as follows [56]:

where Einh and Esurf are the energies of the free inhibitor molecule and Fe (001) plane, respectively. Etotal is the total energy of Fe (001) plane together with inhibitor molecule adsorbed on the iron surface.

On the other hand, Ebin is mainly focused on the interaction between inhibitor and metal surface, and it could be calculated by means of the following relationship:

Comparing Eq. (5) with (6), it is evident that Ebin is the negative value of the Eads[57]:

3Results and discussion3.1Weight loss measurements

The weight loss method is widely used to quantitatively determine corrosion rate (v) and inhibition efficiency (ηw) owing to its good reliability. For the present study, the relative phase difference (RPD) v and ηw for two parallel specimens are less than 5%, which confirms that the reproducibility for the present system is very precise.

3.1.1Effect of DBLE concentration on inhibition efficiency

The corrosion rates in 0.1M Cl3CCOOH solution without inhibitor are 20.37 (RPD=1.6%)gm−2h−1 at 20°C; 40.90 (RPD=1.9%)gm−2h−1 at 30°C; 58.48 (RPD=2.0%)gm−2h−1 at 40°C; and 72.60 (RPD=2.2%)gm−2h−1 at 50°C, which indicates that CRS is severely corroded by Cl3CCOOH acid. When DBLE is added to the Cl3CCOOH media, the corrosion of CRS is retarded prominently. Fig. 1 presents ηw for different DBLE concentrations (10–200mgl−1) in 0.1M Cl3CCOOH solutions at 20–50°C. Clearly, ηw increases with the inhibitor concentration at all temperatures studied. ηw increases remarkably with DBLE concentration from 10 to 100mgl−1, but a further raise in inhibitor concentration causes no appreciable change in inhibitive performance. The maximum ηw at 200mgl−1 is 96.1% (RPD=2.3%) at 20°C; 94.2% (RPD=2.3%) at 30°C; 90.4% (RPD=2.4%) at 40°C; and 85.8% (RPD=2.5%) at 50°C. Thus, DBLE acts as a good inhibitor for CRS in Cl3CCOOH media. According to our recent work, bamboo leaves extract acts as the good corrosion inhibitor for CRS in HCl [47,48], H2SO4[47] and H3C6H5O7[49], which implies that the bamboo leaves extract could be seemed as the good potential corrosion inhibitor for steel in either inorganic acid or organic acid solution.

Fig. 1.
(0.09MB).

Relationship between inhibition efficiency (ηw) and concentration of DBLE (c) in 0.1M Cl3CCOOH (weight loss method, immersion time is 6h).

Also, Fig. 1 illustrates that ηw decreases to some extent with the elevated temperature within whole inhibitor concentrations from 10 to 200mgl−1, which would be attributed to the DBLE desorption from the CRS surface due to the higher temperatures.

3.1.2Adsorption isotherm

Acid inhibitor generally exhibits inhibitive performance through adsorption on metal surface, and some adsorption isotherms have been widely used to study the adsorption behavior. In previous studies of bamboo leaves extract as corrosion inhibitors for steel in acids [47–49], the adsorption of bamboo leaves extract on steel surface follows Langmuir adsorption isotherm. For the present study, Langmuir adsorption isotherm is also applied to study the adsorption of DBLE on steel surface in CCl3COOH solution [58]:

where c is the concentration of inhibitor (mgl−1), K the adsorptive equilibrium constant (lmg−1), and θ is the surface coverage with the value of inhibition efficiency (ηw) [58].

The straight lines of c/θ vs. c at four temperatures are shown in Fig. 2, and the corresponding linear regression parameters are given in Table 2. All linear correlation coefficients (r) are almost equal to 1, and the slope values are also close to 1, so the adsorption of DBLE on CRS surface obeys the Langmuir adsorption isotherm. Larger value of K generally means stronger adsorptive ability and hence better inhibitive ability of a given inhibitor. As shown in Table 2, K decreases with an increase of the temperature, which implies that it is easy for DBLE to be adsorbed onto the steel surface in Cl3CCOOH solution at relatively low temperature. On the other hand, the adsorbed inhibitor molecules tend to desorb from the metal surface, giving rise to severe corrosive attack at high temperature.

Fig. 2.
(0.1MB).

Langmuir isotherm adsorption mode of DBLE on CRS surface in 0.1M Cl3CCOOH solution.

Table 2.

Parameters of the linear regression between c/θ and c in 0.1M Cl3CCOOH solution.

Temperature (°C)  r  Slope  K (lmg−1
20  0.9999  1.01  0.15643 
30  0.9994  0.98  0.06886 
40  0.9948  0.91  0.02936 
50  0.9902  0.87  0.01883 
3.1.3Effect of immersion time on corrosion inhibition

Fig. 3 shows the inhibition efficiency (ηw) values of 200mgl−1 DBLE for different immersion time (t) at 20°C in 0.1M Cl3CCOOH using weight loss method. ηw increases with immersion time from 3 to 6h, thereafter remains almost stable from 6 to 24h, and ηw is as high as 97.3% even when the immersion is as long as 24h. Similar results were also previously reported for bamboo leaves extract as the corrosion inhibitor for HCl and H2SO4 solutions [47]. This behavior could be attributed to the adsorptive film of inhibitor that rests upon the immersion time [47]. The inhibitive film on steel surface firstly reaches a more compact and uniform condition during prolonging immersion time (3–6h), while the adsorptive film is in a saturated state within 6–24h.

Fig. 3.
(0.05MB).

Effect of immersion time (t) on inhibition efficiency (ηw) in 0.1M Cl3CCOOH at 20°C (weight loss method).

3.1.4Effect of acid concentration on corrosion inhibition

Fig. 4 shows the relationship between corrosion rate (v) and Cl3CCOOH concentration (C) at 20°C (immersion time is 6h). It is of interest to note that the corrosion rate increases linearly with the increase of Cl3CCOOH concentration from 0.05 to 0.5M either in the absence or presence of 200mgl−1 DBLE. This unique result of steel in Cl3CCOOH is quite different from that of steel in inorganic acids (HCl, H2SO4 and H3PO4) [59]. When 200mgl−1 DBLE is added to Cl3CCOOH solution, the corrosion rate decreases sharply. This confirms that DBLE exhibits good inhibitive performance in the whole acid concentration studied. In 0.5M Cl3CCOOH solution without inhibitor, the corrosion rate reaches as high as 118.56gm−2h−1, while it is decreased to 1.68gm−2h−1 in the presence of 200mgl−1 DBLE.

Fig. 4.
(0.1MB).

Effect of acid concentration (C) on corrosion rate (v) of CRS in Cl3CCOOH at 20°C (weight loss method).

Fig. 5 illustrates the dependence of inhibition efficiency (ηw) on the concentration of Cl3CCOOH (0.05–0.5M) at 20°C. Clearly, ηw increases slightly with the concentration of Cl3CCOOH from 91.3% to 98.6% with respect to 0.05M and 0.5M. The reason might be due to the more protective film by the interaction of the inhibitor molecules with Fe2+[60] or protonated inhibitor molecules with acid anion (Cl3CCOO) at higher acid concentration.

Fig. 5.
(0.04MB).

Effect of Cl3CCOOH concentration (C) on inhibition efficiency (ηw) at 20°C (weight loss method, immersion time is 6h).

3.2Open circuit potential (OCP) – time curves

Fig. 6 shows OCP as a function of time (0–180min) in 0.1M Cl3COOH solution without and with 200mgl−1 DBLE at 20°C. For both cases, OCP initially moves positive value along with time and reaches the peak at about 20min, and then shifts to negative and gradually reaches steady state from 60 to 180min. The potentiodynamic polarization curves and electrochemical impedance spectroscopy (see later) were carried out with OCP in a steady state with immersion time of 2h, and OCP values are −409mV and −398mV vs. SCE in the absence and presence of 200mgl−1 DBLE, respectively.

Fig. 6.
(0.09MB).

OCP – time (t) curves for CRS in 0.1M Cl3CCOOH solutions at 20°C.

3.3Potentiodynamic polarization curves of DBLE

Potentiodynamic polarization curves of CRS in 0.1M Cl3CCOOH containing 0, 10, 50, 100 and 200mgl−1 DBLE at 20°C (immersion time is 2h) are shown in Fig. 7. As compared to that of the blank solution, the presence of DBLE causes the decrease in the corrosion rate of CRS in 0.1M Cl3CCOOH, i.e., shifts both cathodic curves and the anodic curves toward lower current densities. The shift of polarization curves toward the lower current density region is much more pronounced when the concentration of DBLE is increased. The results indicate that both cathodic and anodic reactions of CRS electrode corrosion in Cl3CCOOH solution are retarded by DBLE. Namely, DBLE could be arranged as a mixed-type inhibitor. The nature of polarization curves remains the same irrespective of different concentration of DBLE addition to acid solution, which suggests that the mechanism for the corrosion of steel in CCl3COOH solution does not change by adding DBLE to the acid solution.

Fig. 7.
(0.12MB).

Potentiodynamic polarization curves for CRS in 0.1M Cl3CCOOH without and with different concentrations of DBLE at 20°C (immersion time is 2h).

Inspection of Fig. 7 reveals that the cathodic polarization curves display three portions (I, II, and III), which indicates that there are both activation controlled and diffusion controlled regions for the cathodic polarization curves. Portion I might be related to the reduction of trichloroacetic acid in strong cathodic polarization region (about −0.70 to −0.65V vs. SCE). Portion II would be related to the reduction of O2 in diffusion region (about −0.65 to −0.55V vs. SCE). Portion III represents the evolution of hydrogen in activation controlled region (about −0.55V vs. SCE to OCP). In a word, there are a series of complex cathodic reduction reactions in Cl3CCOOH solution. Cl3CCOOH would be dissociated to H+ and Cl3CCOO in water solution. According to the proposed mechanism of steel in acid solution [61], the cathodic hydrogen evolution reaction follows the steps (9)(12):

Fe+H+(FeH+)ads
(FeH+)ads+e(FeH)ads
(FeH)ads+H++eFe+H2

Two (FeH)ads may combine together to liberate hydrogen as following [62]:

(FeH)ads+(FeH)ads2Fe+H2

The anion of Cl3CCOOH (Cl3CCOO) might also react with H+ to produce HCl2CCOO and H2ClCCOO[63]:

Cl3CCOO+H++2eHCl2CCOO+Cl
HCl2CCOO+H++2eH2ClCCOO+Cl

For anodic polarization curves as shown in Fig. 7, it is worth noting that two portions (IV and V) are observed, which represent the weak polarization region (OCP to −0.35V vs. SCE) and strong polarization region (−0.35 to −0.15V vs. SCE), respectively. According to the mechanism for the corrosion of mild steel in aqueous solutions of formic acid (HCOOH) [62], acetic acid (CH3COOH) [64] and peracetic acid (CH3COOOH) [65], the anodic dissolution of CRS in Cl3CCOOH solutions may be assumed as follows:

Fe+Cl3CCOO(Fe Cl3CCOO)ads
(Fe Cl3CCOO)ads(Fe Cl3CCOO)ads+e
(Fe Cl3CCOO)ads(Fe Cl3CCOO+)+e
Fe Cl3CCOO+Fe2++Cl3CCOO

Thus, the adsorption of Cl3CCOO ions on the CRS surface would be the prerequisite for the anodic dissolution to occur.

The electrochemical parameters of corrosion current densities (icorr), corrosion potential (Ecorr), cathodic Tafel slope (bc) and anodic Tafel slope (ba) are obtained by using electrochemistry powersuite software to fit weak polarization curves of Tafel polarization in the optimum linear regions of III and IV. Inhibition efficiency (ηp) values are calculated through icorr and summarized in Table 3. The presence of DBLE shifts Ecorr to positive to some extent, but the maximum change of Ecorr is lower than 85mV. Therefore, DBLE could be classified as a mixed-type inhibitor [66,67]. Clearly, icorr decreases prominently in the presence of DBLE, while ηp increases with the inhibitor concentration, and the maximum ηp reaches as high as 97.2%, which indicates that DBLE acts as a good inhibitor in Cl3CCOOH. Tafel slopes of bc and ba change upon addition of DBLE, which means that the inhibitor molecules are adsorbed on both the anodic and cathodic sites resulting in the changing rules of the potential with current densities.

Table 3.

Potentiodynamic polarization parameters for the corrosion of CRS in 0.1M Cl3CCOOH solution containing different concentrations of DBLE at 20°C (immersion time is 6h).

c (mgl−1Ecorr (mV vs. SCE)  icorr (μAcm−2bc (mV dec−1ba (mV dec−1ηp (%) 
−418.1±2.9  1386.8±19  181±51±– 
10  −385.3±2.5  628.2±12  178±31±54.7 
50  −398.5±2.1  222.7±13  152±30±83.9 
100  −388.7±3.4  108.6±138±27±92.2 
200  −389.5±2.6  38.3±10  119±24±97.2 
3.4Electrochemical impedance spectroscopy (EIS)

Fig. 8 shows the Nyquist diagrams of CRS obtained at OCP (immersion time: 2h) in 0.1M Cl3CCOOH without and with different concentrations of DBLE at 20°C. It appears as a large capacitive loop at high frequency (HF) followed also by an inductive one at low frequency (LF) values. Comparing with 0.1M Cl3CCOOH solution in the absence of inhibitor, the general shape is maintained for all tested concentrations, indicating that almost no change in the corrosion mechanism occurs as a result of the inhibitor addition [68]. In addition, the diameter of the capacitive loop in the presence of DBLE is bigger than that in blank solution and increases with the inhibitor concentration. This indicates that the impedance of inhibited substrate increases with the concentration of inhibitor.

Fig. 8.
(0.11MB).

Nyquist plots of the corrosion of CRS in 0.1M Cl3CCOOH without and with different concentrations of DBLE at 20°C (immersion time is 2h).

The Bode modulus and phase angle plots for CRS in 0.1M Cl3CCOOH containing different concentrations of DBLE are given in Fig. 9. As can be seen from Fig. 9(a), the increase of absolute impedance at low frequencies in Bode modulus confirms the higher protection with increasing the concentration of DBLE, which is related to the adsorption of the inhibitor molecules on the CRS surface. Also from Fig. 9(b), there are one phase peak at high frequency and one valley at low frequency, which again confirms that there are two time constants related to respective capacitive loop and inductive loop.

Fig. 9.
(0.23MB).

Bode plots of the corrosion of CRS in 0.1M Cl3CCOOH without and with different concentrations of DBLE at 20°C (immersion time is 2h): (a) Bode modulus; and (b) Bode phase angle plots.

The capacitive loop at HF is usually related to the charge transfer of the corrosion process and double layer behavior. These capacitive loops at HF are depressed semicircles shown in Nyquist plots and the phase angle is lower than 90° in Bode phase plots, which could be attributed to the frequency dispersion as a result of the roughness and inhomogeneous of electrode surface [68]. On the other hand, the cause of the inductive loop is still uncertain. The relaxation of adsorbed charged intermediates may result in the inductive loop [69]. This is more pronounced when the intermediates are strongly adsorbed. The relaxations of adsorbed species include Hads+[70], acid anions [71] or inhibitor species [30] on the electrode surface.

The EIS results in Cl3CCOOH solutions are simulated by the equivalent circuits shown in Fig. 10. Rs, Rt and RL are the solution resistance, charge transfer resistance and inductive resistance, respectively. CPE is a constant phase element. L is the inductance, which is intimately associated with the inductive loop. The solid lines in Figs. 8 and 9 correspond to the fitted plots for EIS experiment data using the electric circuit of Fig. 10, which indicates that the experimental data could be simulated using this equivalent circuit. The impedance parameters of CRS in Cl3CCOOH solution are listed in Table 4. The chi-squared (χ2) is used to evaluate the precision of the fitted data [72,73]. Table 4 reveals that χ2 values are low, which indicates that the fitted data have good agreement with the experimental data. It is observed that Rs is about 6–10Ωcm2 in 0.1M Cl3CCOOH, while the Rs is less than 0.5Ωcm2 for steel in 1.0M HCl and 0.5M H2SO4 solutions [47,48]. This implies that 0.1M Cl3CCOOH water solution is not very conductive. Rt is increased to more extent when DBLE is added to the 0.1M Cl3CCOOH solution, which indicates the electrode exhibits slower corrosion in the presence of the plant inhibitor of DBLE. In contrast, the decrease of CPE in the presence of DBLE comparing with that in blank Cl3CCOOH solution (without inhibitor) results from a decrease in local dielectric constant and/or an increase in the thickness of the electrical double layer. In other words, the inhibitor molecules function by adsorption at the metal/solution interface [67]. The exponent n of CPE is usually used to study the change in interfacial surface condition of steel/solution. Inspection of Table 4 reveals that n is around 0.8, which might be resulted from irregular surface of electrode or arbitrary distribution of current on electrode surface causing frequency dispersion.

Fig. 10.
(0.02MB).

Equivalent circuit used to fit the EIS.

Table 4.

EIS parameters for the corrosion of CRS in 0.1M Cl3CCOOH containing DBLE at 20°C.

c (mgl−1Rscm2Rtcm2RLcm2CPE (μFcm−2n  L (Hcm2χ2  ηR (%) 
6.18±0.06  15.14±0.50  29.82±0.80  433.2±3.0  0.8401±0.02  84±5.09×10−3  – 
10  6.15±0.09  30.91± 0.80  67.96±0.90  233.3±5.0  0.8251± 0.02  121±6.41×10−3  51.0 
50  7.63±0.12  83.01±1.20  148.01± 0.95  179.5±6.7  0.8021±0.02  1203±9.32×10−3  81.8 
100  8.14±0.16  180.50±1.30  290.40±1.20  96.6±8.2  0.8187±0.03  4666±12  2.25×10−2  91.6 
200  9.97±0.23  253.02±1.80  272.20±2.30  73.6±8.4  0.7977±0.03  4607±13  5.79×10−2  94.0 

L is as low as 84Hcm2 in blank solution (without inhibitor), which is increased with increase of concentration of DBLE. L values are especially as high as 4666 and 4607Hcm2 with the addition of 100 and 200mgl−1 DBLE, respectively. Accordingly, it is presumed that the adsorption/desorption process might mainly be the adsorbed intermediates of Hads+ and CCl3COO at low L (Cl3CCOOH, Cl3CCOOH+10mgl−1 DBLE), while the composition of Hads+, CCl3COO and DBLE inhibitor at moderate L (Cl3CCOOH+50mgl−1 DBLE), and mainly the DBLE inhibitor at high L (Cl3CCOOH+100mgl−1 DBLE, Cl3CCOOH+200mgl−1 DBLE).

From Table 4, ηR increases with the concentration of DBLE, and the maximum ηR value could also reach the high value of 94.0%. These results again confirm that DBLE exhibits good inhibitive performance for CRS in 0.1M Cl3CCOOH solution.

3.5Atomic force microscope (AFM) surface examination

AFM provides a powerful means of characterizing the microstructure [74], and is generally used in the field of metal corrosion. The three-dimensional AFM images of CRS surface are shown Fig. 11. The CRS surface before immersion seems smooth as shown in Fig. 11(a). However, it is not absolute smooth and uniform, and small precipitates appear on the steel surface, which could be attributed to some contaminates formed on AFM tip during the examination process. As for Fig. 11(b), the CRS surface after immersion in uninhibited 0.1M Cl3CCOOH for 6h exhibits a very rough surface owing to corrosive attack by CCl3COOH acid, and covered with the uneven and potholed corrosion products layer upon layer. On contrast, in the presence of 200mgl−1 DBLE, Fig. 11(c) shows that the steel surface appears the more flat, homogeneous and uniform, and even some original abrading scratches are seen on the steel surface, which indicates that DBLE retards efficiently the corrosion the steel in 0.1M Cl3CCOOH solution.

Fig. 11.
(0.28MB).

AFM three-dimensional images of CRS surface: (a) before immersion; (b) after 6h of immersion at 20°C in 0.1M Cl3CCOOH; and (c) after 6h of immersion at 20°C in 200mgl−1 DBLE+0.1M Cl3CCOOH.

3.6Corrosion inhibition of the major flavonoids

Bamboo leaves extract is composed of numerous chemical compounds, and then the inhibitive action of bamboo leaves extract would be due to the adsorption of its components on the steel surface. However, it is rather difficult to assign the inhibitive effective to a particular constituent owing to the complex chemical composition of the bamboo leaves extract. The ethanol/water extract of bamboo leaf is mainly composed of the bamboo leaf flavonoids (BLF) [75]. According to our recent work [55], there is a relation between the content of total flavonoids and inhibition efficiency, and it might be deduced that the flavonoids would be one of the contributors to the inhibitive activity. On the other hand, the major flavonoids in bamboo leaves extract are rutin, orientin, isovientin and vientin [76,77], and their molecular structures are shown in Fig. 12. In our recent work [49,54], rutin, orientin, vientin and isovientin are confirmed in the presence of bamboo leaves extract through analyzing high performance liquid chromatography (HPLC). According to the quantum chemical calculations of rutin, orientin, vientin and isovientin in our recent work [54,55], the adsorption of flavonoids is mainly through the flavones backbone structure (FBS) whose molecular structure is shown in Figs. 12(e) and (f). Noticeably, a number of flavonoids have similar chemical molecular skeleton structure of FBS, which implies that the series of flavonoids could be seemed as the potential contributors for the inhibition performance [49].

Fig. 12.
(0.23MB).

Chemical molecular structures of major components in BLE: (a) rutin; (b) orientin; (c) isovientin; (d) vientin; (e) flavones backbone structure (FBS); and (f) flavones backbone structure (FBS) of isovientin and vientin.

In the present study, the inhibition action of four major components of rutin, isovientin, vientin and orientin with 200mgl−1 in 0.1M Cl3CCOOH solution at 20°C are studied, and the results are given in Fig. 13. The inhibition efficiency of these flavonoids follows the sequence: rutin>orientin>isovientin>vientin. At all temperatures, the inhibition efficiency values range from 70% to 85%, which indicates that these flavonoids could also retard to more extent the corrosion of steel in Cl3CCOOH solution. Also, the inhibition efficiency decreases with the temperature.

Fig. 13.
(0.08MB).

Relationship between inhibition efficiency (ηw) of major flavonoids with 200mgl−1 and temperature in 0.1M CCl3COOH.

MD simulations have been done to further study the adsorption behavior of the four flavonoids molecules of rutin, orientin, isovientin and vientin on the Fe (001) surface. Through the analysis of the temperature and energy, it takes about 250ps for the adsorption system containing both Fe (001) surface and the studied inhibitor molecule to reach equilibrium. The adsorption system is at steady state and fluctuates slightly from 500ps to 1000ps. Fig. 14 shows the adsorption configurations on Fe (001) surface for inhibitor molecules, and the corresponding Eads and Ebin values are listed in Table 5.

Fig. 14.
(0.57MB).

Equilibrium adsorption configuration of inhibitors on Fe (001) planes obtained by MD simulations: (a) rutin; (b) orientin; (c) isovientin; and (d) vientin.

Table 5.

Values of adsorption energy (Eads) and binding energy (Ebin) between the molecules and Fe (001) plane.

Molecule  Eads (kJmol−1Ebin (kJmol−1
Rutin  1104.35  −1104.35 
Orientin  890.01  −890.01 
Isovientin  831.83  −831.83 
Vientin  830.95  −830.95 

As can be seen from Fig. 14, these flavonoids are adsorbed on Fe (001) surface through FBS with a nearby flat orientation. In other words, the adsorption center is FBS, which is in accordance with the previous result of quantum chemical calculations [54,55]. Moreover, the values of Eads in Table 5 reveal the sequence of rutin>orientin>isovientin>vientin, meaning that the adsorptive ability on steel surface follows the expected trend: rutin>orientin>isovientin>vientin. On the other hand, magnitude of Ebin is indicative of stability of adsorptive system, and Ebin follows the order: rutin<vientin<isovientin<orientin. More negative value of Ebin suggests a more stable adsorption system and leads to the higher inhibitive action. Accordingly, inhibition efficiency for four studied inhibitors is ranked as rutin>orientin>isovientin>vientin based on the parameters of Eads and Ebin. Thus, the theoretical inference is in good agreement with experimental data.

The difference in their inhibitive action can be explained on the basis of their molecular structure. The FBS of rutin and orientin as shown in Fig. 12(e) has one additional hydroxyl group (–OH) than the FBS of isovientin and vientin as shown in Fig. 12(f). The substitution –OH is the additional center of adsorption, which causes more adsorption centers and corresponding better inhibition performance. Consequently, rutin and orientin give better inhibitive performance than isovientin and vientin. Besides the FBS, this classification of inhibition efficiency could be attributed to the difference in sugar substitute to the FBS. Rutin has the disaccharide substituents to FBS, while orientin has the monosaccharide substituent. The disaccharide substituents have more oxygen atoms, thus rutin has higher inhibitive performance than orientin. It should be noted that the substitutional group of both isovientin and vientin are the same. However, Fig. 13 shows that isovientin gives slightly better inhibitive performance than vientin. This difference in inhibition efficiency could be explained on the basis of substitution group position.

Noticeably, the inhibitory value of each flavonoid is lower than the crude extract of DBLE, which may suggest that other composition compounds have additional contribution to the inhibitive performance. The same conclusion was also reported for bamboo leaves extract as the corrosion inhibitor for steel in H3PO4 solution [54]. Similar comparative results between plant extract and its major component have also been reported for the coffee extract [20] and A. pallens[26]. Besides the flavonoids, the ethanol/water extract of bamboo leaf contains amino acid, chlorophyll and amylose [78], and these compounds contain many O, N atoms in functional groups (O–H, CO, C–O, N–H) and O-heterocyclic rings. Thus, it is reasonable to deduce that these compounds get to be protonated in the acid solution. In Cl3CCOOH solution, Cl3CCOO could be adsorbed onto the steel surface, then the protonated compounds approach the steel surface due to the electrostatic attraction. In addition, O, N atoms with plentiful lone electrons could be considered responsible for the adsorption centers on steel surface. Coordinate bond could be formed by partial transference of electrons from the N atoms to the metal surface.

4Conclusions

  • (1)

    DBLE acts as a good inhibitor for the corrosion of CRS in 0.1M Cl3CCOOH solution, and ηw value of 120mgl−1 DBLE is higher than 94% at 20°C. Inhibition efficiency (ηw) increases with the inhibitor concentration, immersion time and acid concentration, but decreases with the temperature. The adsorption of DBLE on steel surface obeys Langmuir adsorption isotherm.

  • (2)

    The cathodic reductions of CRS in CH3COOH involve hydrogen evolution, H+ reaction with dissolved O2, and the dechlorination of Cl3CCOO. For the anodic dissolution, the adsorption of Cl3CCOO ions on the CRS surface would be the prerequisite to occur, and both Fe2+ and Fe3+ ions are the dominant products.

  • (3)

    DBLE acts as a mixed-type inhibitor for CRS in 0.1M Cl3CCOOH solution. EIS spectra exhibit a large capacitive loop at high frequencies followed by an inductive one at low frequency values. Comparing with blank solution, the presence of DBLE enhances Rt while reduces CPE.

  • (4)

    AFM clearly shows that CRS suffers severe corrosive attack by Cl3CCOOH, and the presence of DBLE could drastically retard the corrosion of steel in CCl3COOH media.

  • (5)

    MD simulations reveal that the major flavonoids in DBLE are adsorbed on Fe (001) surface through FBS with a nearby flat orientation. The sequence of either Eads or Ebin is in accordance with that of inhibition efficiency: rutin>orientin>isovientin>vientin.

  • (6)

    The crude extract of DBLE exhibits better inhibition performance than the major flavonoids. Other composition compounds could have additional contribution to inhibitive performance.

Conflicts of interest

The authors declare no conflicts of interest.

Acknowledgements

This work was carried out in the frame of research projects funded by the National Natural Science Foundation of China (51161023) and Training Program of Young and Middle Aged Academic and Technological Leaders in Yunnan Province (2015HB049).

References
[1]
G. Trabanelli
Inhibitors an old remedy for a new challenge
Corrosion, 47 (1991), pp. 410-419
[2]
A. Ostovari,S.M. Hoseinieh,M. Peikari,S.R. Shadizadeh,S.J. Hashemi
Corrosion inhibition of mild steel in 1M HCl solution by henna extract: a comparative study of the inhibition by henna and its constituents (lawsone, Gallic acid, a-d-Glucose and Tannic acid)
Corros Sci, 51 (2009), pp. 1935-1949
[3]
A.Y. El-Etre,M. Abdallah,Z.E. El-Tantawy
Corrosion inhibition of some metals using lawsonia extract
Corros Sci, 47 (2005), pp. 385-395
[4]
K.O. Orubite,N.C. Oforka
Inhibition of the corrosion of mild steel in hydrochloric acid solutions by the extracts of leaves of Nypa fruticans Wurmb
Mater Lett, 58 (2004), pp. 1768-1772
[5]
L.R. Chuanhan,G. Gunasekaran
Corrosion inhibition of mild steel by plant extract in dilute HCl medium
Corros Sci, 49 (2007), pp. 1143-1161
[6]
A. Bouyanzer,B. Hammouti,L. Majidi
Pennyroyal oil from Mentha pulegium as corrosion inhibitor for steel in 1M HCl
Mater Lett, 60 (2006), pp. 2840-2843
[7]
A.Y. El-Etre
Inhibition of acid corrosion of carbon steel using aqueous extract of olive leaves
J Colloid Interface Sci, 314 (2007), pp. 578-583 http://dx.doi.org/10.1016/j.jcis.2007.05.077
[8]
P.C. Okafor,M.E. Ikpi,I.E. Uwah,E.E. Ebenso,U.J. Ekpe,S.A. Umoren
Inhibitory action of Phyllanthus amarus extracts on the corrosion of mild steel in acidic media
Corros Sci, 50 (2008), pp. 2310-2317
[9]
A.M. Abdel-Gaber,B.A. Abd-El Nabey,I.M. Sidahmed,A.M. El-Zayady,M. Saadawy
Effect of temperature on inhibitive action of Damsissa extract on the corrosion on steel in acidic media
Corrosion, 62 (2006), pp. 293-299
[10]
E.E. Oguzie
Evaluation of the inhibitive effect of some plant extracts on the acid corrosion of mild steel
Corros Sci, 50 (2008), pp. 2993-2998
[11]
E.E. Oguzie
Studies on the inhibitive effect of Occimum viridis extract on the acid corrosion of mild steel
Mater Chem Phys, 99 (2006), pp. 441-446
[12]
M.A. Quraishi,A. Singh,V.K. Singh,D.K. Yadav,A.S. Singh
Green approach to corrosion inhibition of mild steel in hydrochloric acid and sulphuric acid solutions by the extract of Murraya koenigii leaves
Mater Chem Phys, 122 (2010), pp. 114-122
[13]
A.M. Abdel-Gaber,B.A. Abd-El-Nabey,M. Saadawy
The role of acid anion on the inhibition of the acidic corrosion of steel by lupine extract
Corros Sci, 51 (2009), pp. 1038-1042
[14]
U.F. Ekanem,S.A. Umoren,I.I. Udousoro,A.P. Udoh
Inhibition of mild steel corrosion in HCl using pineapple leaves (Ananas comosus L.) extract
J Mater Sci, 45 (2010), pp. 5558-5566
[15]
N.O. Eddy,S.A. Odoemelam,A.O. Odiongenyi
Joint effect of halides and ethanol extract of Lasianthera africana on corrosion of mild steel in H2SO4
J Appl Electrochem, 39 (2009), pp. 849-857
[16]
P.B. Raja,M.G. Sethuraman
Strychnos nux-vomica an eco-friendly corrosion inhibitor for mild steel in 1M sulfuric acid medium
Mater Corros, 60 (2009), pp. 22-28
[17]
A.K. Satapathy,G. Gunasekaran,S.C. Sahoo,K. Amit,R.V. Rodrigues
Corrosion inhibition by Justicia gendarussa plant extract in hydrochloric acid solution
Corros Sci, 51 (2009), pp. 2848-2856
[18]
M. Lebrini,F. Robert,A. Lecante,C. Roos
Corrosion inhibition of C38 steel in 1M hydrochloric acid medium by alkaloids extract from Oxandra asbeckii plant
Corros Sci, 53 (2011), pp. 687-695
[19]
M. Behpour,S.M. Ghoreishi,M. Khayatkashani,N. Soltani
The effect of two oleo-gum resin exudates from Ferula assa-foetida and Dorema ammoniacum on mild steel corrosion in acidic media
Corros Sci, 53 (2011), pp. 2489-2501
[20]
V.V. Torres,R.S. Amado,C. Faia de Sá,T.L. Fernandez,C.A.S. Riehl,A.G. Torres
Inhibitory action of aqueous coffee ground extracts on the corrosion of carbon steel in HCl solution
Corros Sci, 53 (2011), pp. 2385-2392
[21]
J.C. Rocha,J.A.C.P. Gomes,E. D’Elia
Corrosion inhibition of carbon steel in hydrochloric acid solution by fruit peel aqueous extracts
Corros Sci, 52 (2010), pp. 2341-2348
[22]
A.M. Abdel-Gaber,B.A. Abd-El-Nabey,I.M. Sidahmed,A.M. El-Zayady,M. Saadawy
Inhibitive action of some plant extracts on the corrosion of steel in acidic media
Corros Sci, 48 (2006), pp. 2765-2779
[23]
R.P. Bothi,R.A. Abdul,O. Hasnah,A. Khalijah
Inhibition effect of Kopsia Singapurenis extract on the corrosion behavior of mild steel in acid media
Acta Phys – Chim Sin, 26 (2010), pp. 2171-2176
[24]
X.H. Li,S.D. Deng,H. Fu
Inhibition by Jasminum nudiflorum Lindl. leaves extract of the corrosion of cold rolled steel in hydrochloric acid solution
J Appl Electrochem, 40 (2010), pp. 1641-1649
[25]
S.D. Deng,X.H. Li
Inhibition by Ginkgo leaves extract of the corrosion of steel in HCl and H2SO4 solution
Corros Sci, 55 (2012), pp. 407-415
[26]
S. Garai,S. Garai,P. Jaisankar,J.K. Singh,A. Elango
A comprehensive study on crude methanolic extract of Artemisia pallens (Asteraceae) and its active component as effective corrosion inhibitors of mild steel in acid solution
Corros Sci, 60 (2012), pp. 193-204
[27]
N. Soltani,N. Tavakkoli,M. Khayatkashani,M.R. Jalali,A. Mosavizade
Green approach to corrosion inhibition of 304 stainless steel in hydrochloric acid solution by the extract of Salvia officinalis leaves
Corros Sci, 62 (2012), pp. 122-135
[28]
L.G. Li,X.P. Zhang,J.L. Lei,J.X. He,S.T. Zhang,F.S. Pan
Adsorption and corrosion inhibition of Osmanthus fragran leaves extract on carbon steel
Corros Sci, 63 (2012), pp. 82-90
[29]
K.W. Tan,M.J. Kassim,C.W. Oo
Possible improvement of catechin as corrosion inhibitor in acidic medium
Corros Sci, 65 (2012), pp. 152-162
[30]
S.S. de Assunção Araujo Pereira,M.M. Pêgas,T.L. Fernández,M. Magalhaes,T.G. Schöntag,D.C. Lago
Inhibitory action of aqueous garlic peel extract on the corrosion of carbon steel in HCl solution
Corros Sci, 65 (2012), pp. 360-366
[31]
P.B. Raja,A.K. Qureshi,A.A. Rahim,H. Osman,K. Awang
Neolamarckia cadamba alkaloids as eco-friendly corrosion inhibitors for mild steel in 1M HCl media
Corros Sci, 69 (2013), pp. 292-301
[32]
G. Gunasekaran,L.R. Chauhan
Eco friendly inhibitor for corrosion inhibition of mild steel in phosphoric acid medium
Electrochim Acta, 49 (2004), pp. 4387-4395
[33]
M. Sivaraju,K. Kannan
Inhibitive properties of plant extract (Acalypha indica L.) on mild steel corrosion in 1N phosphoric acid
Inter J Chem Tech Res, 2 (2010), pp. 1243-1253
[34]
X.H. Li,H. Fu,J. Zhang,X.Y. Liu
Corrosion inhibition of Acer truncatum leaves extractive for steel in sulfuric acid solution
Corros Sci Prot Tech, 23 (2011), pp. 61-64
[in Chinese]
[35]
X.H. Li,S.D. Deng,H. Fu,X.Y. Liu
Corrosion inhibition of Acer buergerianum leave extractive for steel in HCl solution
Corros Prot, 21 (2010), pp. 287-290
[in Chinese]
[36]
P. Mourya,S. Banerjee,M.M. Singh
Corrosion inhibition of mild steel in acidic solution by Tagetes erecta (Marigold flower) extract as a green inhibitor
Corros Sci, 85 (2014), pp. 352-363
[37]
G. Ji,S. Anjum,S. Sundaram,R. Prakash
Musa paradisica peel extract as green corrosion inhibitor for mild steel in HCl solution
Corros Sci, 90 (2015), pp. 107-117
[38]
M. Faustin,A. Maciuk,P. Salvin,C. Roos,M. Lebrini
Corrosion inhibition of C38 steel by alkaloids extract of Geissospermum laeve in 1M hydrochloric acid: electrochemical and phytochemical studies
Corros Sci, 92 (2015), pp. 287-300
[39]
P. Matheswaran,A.K. Ramasamy
Corrosion inhibition of mild steel in citric acid by aqueous extract of Piper nigrum L.
E-J Chem, 9 (2012), pp. 75-78
[40]
P.S. Desai,R.T. Vashi
Inhibitive efficiency of xylenol orange as corrosion inhibitors for aluminum in trichloroacetic acid
Indian J Chem Tech, 17 (2010), pp. 50-55
[41]
S.S. Sampat,J.C. Vora
Corrosion inhibition of 3s aluminium in trichloroacetic acid by methyl pyridines
Corros Sci, 14 (1974), pp. 581-595
[42]
R.T. Vashi,P.S. Desai
Amino acetanilides as corrosion inhibitors for aluminum in trichloroacetic acid
Bull Electrochem, 23 (2007), pp. 87-93
[43]
P.S. Desai,R.T. Vashi
Inhibitive efficiency of sulphathiazole for aluminum corrosion in trichloroacetic acid
Anti-Corros Methods Mater, 58 (2011), pp. 70-75
[44]
E.E. Ebenso,P.C. Okafor,U.J. Ekpe
Studies on the inhibition of aluminium corrosion by 2-acetylphenothiazine in chloroacetic acids
Anti-Corros Methods Mater, 50 (2003), pp. 414-421
[45]
B.Y. Lu,X.Q. Wu,X.W. Tie,Y. Zhang,Y. Zhang
Toxicology and safety of anti-oxidant of bamboo leaves. Part 1: Acute and subchronic toxicity studies on anti-oxidant of bamboo leaves
Food Chem Toxicol, 43 (2005), pp. 783-792 http://dx.doi.org/10.1016/j.fct.2005.01.019
[46]
B.Y. Lu,X.Q. Wu,J.Y. Shi,Y.J. Dong,Y. Zhang
Toxicology and safety of anti-oxidant of bamboo leaves. Part 2: Developmental toxicity test in rats with antioxidant of bamboo leaves
Food Chem Toxicol, 44 (2006), pp. 1739-1743 http://dx.doi.org/10.1016/j.fct.2006.05.012
[47]
X.H. Li,S.D. Deng,H. Fu
Inhibition of the corrosion of steel in HCl, H2SO4 solutions by bamboo leaf extract
Corros Sci, 62 (2012), pp. 163-175
[48]
X.H. Li,H. Fu,S.D. Deng
Inhibition effect of Dendrocalamus brandisii leaves extract on steel in hydrochloric acid solution
J Chin Soc Corros Prot, 21 (2011), pp. 149-154
[in Chinese]
[49]
X.H. Li,S.D. Deng,X.G. Xie,H. Fu
Inhibition effect of bamboo leaves extract on steel and zinc in citric acid solution
Corros Sci, 87 (2014), pp. 15-26
[50]
X.H. Li,S.D. Deng
Inhibition effect of Dendrocalamus brandisii leaves extract on aluminum in HCl, H3PO4 solutions
Corros Sci, 65 (2012), pp. 299-308
[51]
Materials Studio 4.1
Accelrys Inc., (2006)
[52]
X. Liu,S. Chen,H. Ma,G. Lin,L. Shen
Protection of iron protection by stearic acid and steric imidazoline self-assembled monolayers
Appl Surf Sci, 253 (2006), pp. 814-820
[53]
J. Zhang,S.Q. Hu,Y. Wang,W.Y. Guo,J.X. Liu,L. You
Theoretical investigation on inhibition mechanism of 1-(2-hydroxyethyl)-2-alkyl-imidazoline corrosion inhibitors
Acta Chim Sin, 66 (2008), pp. 2469-2475
[54]
X.H. Li,S.D. Deng,H. Fu,X.G. Xie
Synergistic inhibition effects of bamboo leaf extract/major components and iodide ion on the corrosion of steel in H3PO4 solution
Corros Sci, 78 (2014), pp. 29-42
[55]
X.H. Li,S.D. Deng,X.G. Xie,G.B. Du
Inhibition effect of bamboo leaf extract on the corrosion of aluminum in HCl solution
Acta Phys – Chim Sin, 30 (2014), pp. 1883-1894
[56]
J. Zhang,W.M. Zhao,W.Y. Guo,Y. Wang,Z.P. Li
Theoretical evaluation of corrosion inhibition performance of benzimidazole corrosion inhibitors
Acta Phys – Chim Sin, 24 (2008), pp. 1239-1244
[57]
B. Xu,Y. Liu,X.S. Yin,W.Z. Yang,Y.Z. Chen
Experimental and theoretical study of corrosion inhibition of 3-pyridinecarbozalde thiosemicarbazone for mild steel in hydrochloric acid
Corros Sci, 74 (2013), pp. 206-213
[58]
X.H. Li,X.G. Xie,S.D. Deng,G.B. Du
Inhibition effect of two mercaptopyrimidine derivatives on cold rolled steel in HCl solution
Corros Sci, 92 (2015), pp. 136-147
[59]
P.B. Mathur,T. Vasudevan
Reaction rate studies for the corrosion of metals in acids – I, iron in mineral acids
Corrosion, 38 (1982), pp. 171-178
[60]
X.H. Li,S.D. Deng,H. Fu
Corrosion inhibition of red tetrazolium for cold rolled steel in hydrochloric acid
Chin J Appl Chem, 26 (2009), pp. 1075-1079
[61]
G. Bereket,A. Yurt,H. Türk
Inhibition of the corrosion of low carbon steel in acidic solution by selected polyelectrolytes and polymers
Anti-Corros Methods Mater, 50 (2003), pp. 422-435
[62]
M.M. Singh,A. Gupta
Corrosion behavior of mild steel in formic acid solutions
Mater Chem Phys, 46 (1996), pp. 15-22
[63]
M.D. Esclapez,M.I. Díez-García,V. Sáez,I. Tudela,J.M. Pérez,J.G. García
Spectroelectrochemical study of trichloroacetic acid reduction at copper electrodes in an aqueous sodium sulfate medium
Electrochim Acta, 56 (2011), pp. 8138-8146
[64]
Y.M. Gao,S.M. Wang,Y.X. Xu,W.T. Wu
Corrosion behavior and mechanism of A3 steel in acetic acid
Corros Prot, 27 (2006), pp. 11-13
[65]
Q. Qu,S. Jiang,L. Li,W. Bai,J. Zhou
Corrosion behavior of cold rolled steel in peracetic acid solutions
Corros Sci, 50 (2008), pp. 35-40
[66]
P. Mourya,P. Singh,A.K. Tewari,R.B. Rastogi,M.M. Singh
Relationship between structure and inhibition behavior of quinolinium salts for mild steel corrosion: experimental and theoretical approach
Corros Sci, 95 (2015), pp. 71-87
[67]
M.A. Hegazy,M. Ali,M.M. Emara,M.F. Bakr,A.H. Youssef
Evaluating four synthesized Schiff bases as corrosion inhibitors on the carbon steel in 1M hydrochloric acid
Corros Sci, 65 (2012), pp. 67-76
[68]
S.D. Deng,X.H. Li,H. Fu
Nitrotetrazolium blue chloride as a novel corrosion inhibition of steel in sulfuric acid solution
Corros Sci, 52 (2010), pp. 3840-3846
[69]
M.A. Amin,Q. Mohsen,O.A. Hazzai
Synergistic effect of I ions on the corrosion inhibition of Al in 1.0M phosphoric acid solutions by purine
Mater Chem Phys, 114 (2009), pp. 908-914
[70]
M.A. Amin,S.S. Abd El-Rehim,E.E.F. El-Sherbini,R.S. Bayyomi
The inhibition of low carbon steel corrosion in hydrochloric acid solutions by succinic acid: Part I. Weight loss, polarization, EIS, PZC, EDX and SEM studies
Electrochim Acta, 52 (2007), pp. 3588-3600
[71]
M. Lagrenée,B. Mernari,M. Bouanis,M. Traisnel,F. Bentiss
Study of the mechanism and inhibiting efficiency of 3,5-bis(4-methylethiophenyl)-4H-1,2,4-triazole on mild steel corrosion in acidic media
Corros Sci, 44 (2002), pp. 573-588
[72]
M.A. Jingling,J. Wen,L.I. Gengxin,X.V. Chunhua
The corrosion behaviour of Al–Zn–In–Mg–Ti alloy in NaCl solution
Corros Sci, 52 (2010), pp. 534-539
[73]
W.R. Osório,L.C. Peixoto,P.R. Goulart,A. Garcia
Electrochemical corrosion parameters of as-cast Al–Fe alloys in a NaCl solution
Corros Sci, 52 (2010), pp. 2979-2993
[74]
A.A. Gewirth,B.K. Niece
Electrochemical applications of in-situ scanning probe microscopy
Chem Rev, 97 (1997), pp. 1129-1162
[75]
W.J. Jing
Research progress of flavonoids in bamboo leaf (FBL)
Sci-Tech Inf Dev Econ, 19 (2009), pp. 139-141
[76]
H.G. Tang,W.D. Zheng,Z.D. Chen
Component study on flavonoids from leaves of Dendrocalamus latiflorus
Chin Agric Sci Bull, 21 (2005), pp. 114-118
[77]
H.Y. Li,J.Y. Sun,J.M. Zhang,D. Shou
Determination of orientin, isoorientin, isovitexin in Bamboo leaf from different sources by HPLC
Chin Tradit Pat Med, 26 (2004), pp. 208-210
[78]
Y.D. Yue,H.Q. Cao,F. Tang
Advance in bamboo chemical ingredients and its utilizations
J Anhui Agric Univ, 34 (2007), pp. 328-333
Copyright © 2016. Brazilian Metallurgical, Materials and Mining Association
J Mater Res Technol 2017;6:158-70 DOI: 10.1016/j.jmrt.2016.09.002