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The synergistic inhibition effect of rare earth cerium(IV) ion and iso-vanillin on the corrosion of cold rolled steel in 1.0 M H2SO4 solution
Materials Letters 61 (2007) 2514 – 2517 www.elsevier.com/locate/matlet
The synergistic inhibition effect of rare earth cerium(IV) ion and iso-vanillin on the corrosion of cold rolled steel in 1.0 M H2SO4 solution Xianghong Li a,⁎, Shuduan Deng b , Guannan Mu c , Qing Qu c a
b
Department of Fundamental Courses, Southwest Forestry University, Kunming 650224, P.R. China Department of Wood Science and Technology, Southwest Forestry University, Kunming 650224, P.R. China c Department of Chemistry, Yunnan University, Kunming 650091, P.R. China Received 12 June 2006; accepted 27 September 2006 Available online 13 October 2006
Abstract The synergistic inhibition effect of rare earth cerium(IV) ion and iso-vanillin (3-hydroxy-4-methoxy-benzaldehyde) on the corrosion of cold rolled steel (CRS) in 1.0 M H2SO4 solution was first investigated by weight loss and potentiodynamic polarization methods. The results revealed that iso-vanillin had a moderate inhibitive effect on the corrosion of CRS in 1.0 M H2SO4 solution, while cerium(IV) ion had a negligible effect. However, incorporation of Ce4+ with iso-vanillin significantly improved the inhibition performance. The inhibition efficiency for Ce4+ in combination with iso-vanillin was higher than the summation of inhibition efficiency for single Ce4+ and single iso-vanillin, which was synergism in nature. © 2006 Elsevier B.V. All rights reserved. Keywords: Cold rolled steel; Sulfuric acid; iso-Vanillin; Cerium(IV) ion; Corrosion inhibitor; Synergism
1. Introduction Synergism is a combined action of compounds greater in total effect than the sum of the individual effects. Synergism of corrosion inhibitors is either due to the interaction between components of the inhibitor composition or due to interaction between the inhibitor and one of the ions present in the aqueous solution [1]. Synergistic inhibition is an effective means to improve the inhibitive force of inhibitor, to decrease the amount of usage, and to diversify the application of inhibitor. It plays an important role in not only theoretical research on corrosion inhibitors but also practical work [2]. In previous investigations, synergism between organic inhibitors and halide ions on metal corrosion in acidic solution has been researched by many authors [2–8]. The synergistic inhibition effects of organic inhibitor/ metallic ion mixture [9–12], organic inhibitor/organic inhibitor mixture [13–16] and inorganic inhibitor/inorganic inhibitor
⁎ Corresponding author. E-mail address: [email protected] (X. Li). 0167-577X/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2006.09.048
mixture [17] on corrosion of metal in acidic media have also been studied. Forsyth et al. [18] have studied the synergistic corrosion inhibition of mild steel by rare earth (RE) Ce3+ and sodium salicylate in 0.1 M NaCl neutral media. Aramaki [19,20] investigated the synergism of RE Ce3+/inorganic compound Na2Si2O5 mixture and Ce3+/organic compound C8H17S(CH2)2COONa (NaOTP) mixture on the corrosion of zinc in 0.5 M NaCl. However, there is little report in the literature about the synergism between RE ions and other compounds on metal corrosion in strong acidic media. In our laboratory, much work has been conducted to study the synergism between RE ions and other compounds on the corrosion of some metals and alloys in strong acidic media. In 1996, the synergistic inhibition between anionic surfactant (sodium dodecyl sulfonate, SDS) and La3+ for mild steel corrosion in 1.0 M HCl was reported [12]. Recently, the synergistic effect of Na2MoO4 and Ce4+ on CRS corrosion inhibition in 1.0 M HCl was also investigated [21]. In the present work, the synergism between Ce4+ and organic compound iso-vanillin on CRS in sulfuric acid is first studied by weight loss and potentiodynamic
X. Li et al. / Materials Letters 61 (2007) 2514–2517
2515
Fig. 1. Chemical molecular structure of iso-vanillin.
polarization methods. It is hoped to get general information on synergism between organic inhibitor and RE ion in strong acid solution. 2. Experimental The composition and preparation of cold rolled steel (CRS) coupons have been described in detail in earlier reports [22,23]. Both iso-vanillin (3-hydroxy-4-methoxy-benzaldehyde) and cerium(IV) sulfate tetrahydrate (Ce(SO4)2·4H2O) were obtained from Shanghai Chemical Reagent Company of China, and of analytical-reagent grade. Fig. 1 shows the molecular structure of the iso-vanillin. The weight loss and potentiodynamic polarization measurements have also been described in detail in earlier reports [22,23]. The immersion time of weight loss is 6 h, and the experimental temperature is 20 °C. The inhibition efficiency (IE) of weight loss measurement was calculated as follows [22]: IE% ¼
W0 −W 100 W0
ð1Þ
where W0 and W are the values of the average weight loss without and with addition of inhibitor, respectively. IE of potentiodynamic polarization measurement was defined as: IE% ¼
Icorr −IcorrðinhÞ 100 Icorr
Fig. 2. Relationship between inhibition efficiency (IE) and concentration of inhibitor (C) in 1.0 M H2SO4 at 20 °C.
steel surface would take place through all these functional groups. The simultaneous adsorption of the three functional groups forces the isovanillin molecule to be horizontally oriented at the metal surface. It can be seen from Fig. 2 that IE increases with the Ce4+ concentration. However, the maximum inhibition efficiency was only about 20%. The poor inhibitive ability may be interpreted as follows: it is well known that the steel surface charges positive in H2SO4 because of Ecorr − Eq=0 (zero charge potential) N 0 [24], thus it is difficult for the Ce4+ to approach the positively charged steel surface due to the electrostatic repulsion. In addition, it was impossible for the cerium(IV) ion to form rare earth metal (REM) conversion coatings on CRS in strong acidic media [21]. 3.2. Synergism between cerium(IV) ion and iso-vanillin Fig. 3 shows the inhibition efficiency in 1.0 M H2SO4 with different concentration ratios of iso-vanillin and Ce4+ at a total blend
ð2Þ
where Icorr and Icorr(inh) are the uninhibited and inhibited corrosion current density values, respectively, determined by extrapolation of Tafel lines to the corrosion potential. 3. Results and discussion 3.1. Effect of single iso-vanillin and single Ce4+ on inhibition efficiency The values of inhibition efficiency obtained from the weight loss for different iso-vanillin and Ce4+ concentrations in 1.0 M H2SO4 at 20 °C are given in Fig. 2. The results show that inhibition efficiency increases with the concentration of inhibitors from 25 to 500 mg l− 1. The maximum inhibition efficiency was about 64% for iso-vanillin at a concentration of 500 mg l− 1. The moderate inhibition performance of single iso-vanillin may be explained as follows: iso-Vanillin is an aromatic aldehyde containing carbonyl, methoxy and hydroxyl groups arranged around the aromatic ring. The adsorption of iso-vanillin on
Fig. 3. The relationship between inhibition efficiency and different concentration ratios of iso-vanillin and Ce4+ at a total blend concentration of 500 mg l− 1 in 1.0 M H2SO4 at 20 °C.
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X. Li et al. / Materials Letters 61 (2007) 2514–2517
concentration of 500 mg l− 1 at 20 °C. It can be seen from Fig. 3 that the synergism between cerium(IV) ion and iso-vanillin was exhibited. Namely, the inhibition efficiency for Ce4+ in combination with isovanillin is higher than the summation of inhibition efficiency for single Ce4+ and single iso-vanillin, which is synergism in nature. For example, IEs 50 mg l− 1 iso-vanillin and 450 mg l− 1 Ce4+ are only 35% and 19%, respectively, while their complex has 92% IE. A high inhibition efficiency, 92% was obtained by a mixture of 25–200 mg l− 1 isovanillin and 300–475 mg l− 1 Ce4+. 3.3. Polarization studies The polarization behaviour of CRS in 1.0 M H2SO4 in the absence and presence of different concentrations of iso-vanillin and Ce4+ at 20 °C is shown in Fig. 4. The potentiodynamic polarization parameters are shown in Table 1. It is clear that the presence of single 100 mg l− 1 iso-vanillin causes a decrease in the corrosion rate i.e. it shifts the cathodic curve to more negative potential. The inhibitor has a significant effect on the rate of hydrogen evolution reaction. On the other hand, the inhibitor has a slight effect on the anodic curves. It may be concluded that single iso-vanillin acts as a cathodic-type inhibitor in 1.0 M H2SO4. Table 1 reveals that the corrosion current (Icorr) decreases and there is a moderate IE in the presence of 100 mg l− 1 iso-vanillin. The corrosion potential (Ecorr) does not change obviously. Both the cathodic Tafel slopes (bc) and the anodic Tafel slopes (ba) do not change obviously, which indicates that the mechanism of the corrosion reaction does not change and the corrosion reaction is inhibited by a simple adsorption mode. It can be seen from Fig. 4 that the cathodic reaction of electrode is slightly inhibited by the presence of Ce4+, while the anodic reaction is not inhibited compared with the blank. Table 1 shows that Icorr decreases slightly and there is a poor IE in the presence of 400 mg l− 1 Ce4+. In addition, Ecorr does not change obviously. Both bc and ba do not change obviously, which indicates that the mechanism of the corrosion reaction of steel does not change. Fig. 4 clearly shows that both anodic and cathodic reactions are drastically inhibited, which indicates the iso-vanillin/Ce4+ mixture acts as a mixed-type inhibitor [25]. The complex of 100 mg l− 1 iso-vanillin– 400 mg l− 1 Ce4+ causes Ecorr to shift to the anodic direction. Both bc and ba do change obviously, and Icorr decreases remarkably. The inhibition efficiency calculated from corrosion current density reaches a considerable value (95.3%).
Table 1 Potentiodynamic polarization parameters for the corrosion of cold rolled steel in 1.0 M H2SO4 containing different concentrations of iso-vanillin and Ce4+ at 20 °C C (isovanillin) (mg l− 1)
C (Ce4+) Ecorr (mg l− 1) (mV)
0 100 0 100
0 0 400 400
Icorr bc ba IE (μA cm− 2) (mV dec− 1) (mV dec− 1) (%)
− 443.6 432.0 − 450.2 250.3 − 448.3 349.5 − 412.6 20.2
125 124 122 136
46 37 48 39
– 42.1 19.1 95.3
From Table 1, it can be concluded that inhibition efficiencies (IE) obtained from weight loss, and electrochemical polarization curves are in good agreement. 3.4. Explanation for synergism When iso-vanillin was mixed with Ce4+ in 1.0 M H2SO4, the new complex of iso-vanillin–Ce4+ was formed [26]. The cathodic process of steel corrosion was suppressed by covering the surface with iso-vanillin firstly, while the new complex of iso-vanillin–Ce4+ then precipitated at the defect of the adsorption of the iso-vanillin film (double tight film) to prevent the anodic process mostly, thus inhibiting the anodic and cathodic reactions at the same time, which drastically improves the inhibition efficiency, and produces strong synergistic inhibition effect.
4. Conclusion 1. iso-Vanillin acts as a moderate inhibitor for the corrosion of cold rolled steel (CRS) in 1.0 M H2SO4. Cerium(IV) ion has a negligible effect on the corrosion rate of CRS in 1.0 M H2SO4, the maximum efficiency value is only about 20%. 2. There is a strong synergism between iso-vanillin and Ce4+ in 1.0 M H2SO4. Namely, the inhibition efficiency for Ce4+ in combination with iso-vanillin is higher than the summation of inhibition efficiency for single Ce4+ and single iso-vanillin. 3. iso-Vanillin prominently acts as a cathodic-type inhibitor in 1.0 M H2SO4. Cerium(IV) ion has a slight effect on the cathodic reaction in 1.0 M H2SO4. However, the iso-vanillin/ Ce4+ mixture behaves as a mixed-type inhibitor, which dramatically inhibits both anodic and cathodic reactions, and produces strong synergistic inhibition effect. Acknowledgement This work was carried out in the frame of a research project funded by the Chinese National Science Foundation (Grant No. 50261004). References
Fig. 4. Potentiodynamic polarization curves for cold rolled steel in 1.0 M H2SO4 containing different concentrations of iso-vanillin and Ce4+ at 20 °C.
[1] E. Kalman, I. Lukovits, G. Palinkas, ACH—Models Chem. 132 (4) (1995) 527. [2] G.N. Mu, X.M. Li, F. Li, Mater. Chem. Phys. 86 (2004) 59. [3] E.E. Ebenso, Mater. Chem. Phys. 79 (2003) 58. [4] Y. Feng, K.S. Siow, W.K. Teo, A.K. Hsieh, Corros. Sci. 41 (1999) 829. [5] T. Du, J. Chen, D. Cao, Br. Corros. J. 35 (2000) 229. [6] D.Q. Zhang, L.X. Gao, G.D. Zhou, J. Appl. Electrochem. 33 (2003) 361.
X. Li et al. / Materials Letters 61 (2007) 2514–2517 [7] G.K. Gomma, Mater. Chem. Phys. 55 (1998) 241. [8] E.E. Oguzie, C. Ugaegbu, C.N. Ogukwe, B.N. Okolue, A.I. Onuchukwa, Mater. Chem. Phys. 84 (2004) 263. [9] I. Sekine, Y. Hirakawa, Corrosion 42 (1986) 272. [10] I. Singh, M. Singh, Corrosion 43 (1987) 425. [11] D.D. Singh, T.B. Singh, B. Gaur, Corros. Sci. 37 (1995) 1005. [12] G.N. Mu, T.P. Zhao, M. Liu, T. Gu, Corrosion 52 (1996) 853. [13] M. Hosseini, S.F.L. Mertens, M.R. Arshadi, Corros. Sci. 45 (2003) 1473. [14] R.F.V. Villamil, G.G.O. Cordeiro, J. Matos, E. Delia, S.M.L. Agostinho, Mater. Chem. Phys. 78 (2002) 448. [15] R.F.V. Villamil, P. Corio, J.C. Rubim, S.M.L. Agostinho, J. Electroanal. Chem. 472 (1999) 112. [16] R.F.V. Villamill, P. Corio, J.C. Rubim, S.M.L. Agostinlto, J. Electroanal. Chem. 535 (2002) 75.
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[17] G.N. Mu, T.P. Zhao, J. Yunnan Univ. (China) 21 (4) (1999) 279. [18] M. Forsyth, C.M. Forsyth, K. Wilson, T. Behrsing, G.B. Deacon, Corros. Sci. 44 (2002) 2651. [19] K. Aramaki, Corros. Sci. 44 (2002) 1361. [20] K. Aramaki, Corros. Sci. 44 (2002) 871. [21] G.N. Mu, X.H. Li, Q. Qu, J. Zhou, Acta Chim. Sin. 62 (24) (2004) 2386 (in Chinese). [22] X.H. Li, G.N. Mu, Appl. Surf. Sci. 252 (2005) 1254. [23] G.N. Mu, X.H. Li, J. Colloid Interface Sci. 289 (2005) 184. [24] D.P. Schweinsberg, V. Ashworth, Corros. Sci. 28 (1988) 539. [25] G.N. Mu, X.H. Li, Q. Qu, J. Zhou, Corros. Sci. 48 (2006) 445. [26] G.L. Zhao, J. Zhejiang Normal Univ. 23 (2) (2000) 172 (in Chinese).
The synergistic inhibition effect of rare earth cerium(IV) ion and iso-vanillin on the corrosion of cold rolled steel in 1.0 M H2SO4 solution Xianghong Li a,⁎, Shuduan Deng b , Guannan Mu c , Qing Qu c a
b
Department of Fundamental Courses, Southwest Forestry University, Kunming 650224, P.R. China Department of Wood Science and Technology, Southwest Forestry University, Kunming 650224, P.R. China c Department of Chemistry, Yunnan University, Kunming 650091, P.R. China Received 12 June 2006; accepted 27 September 2006 Available online 13 October 2006
Abstract The synergistic inhibition effect of rare earth cerium(IV) ion and iso-vanillin (3-hydroxy-4-methoxy-benzaldehyde) on the corrosion of cold rolled steel (CRS) in 1.0 M H2SO4 solution was first investigated by weight loss and potentiodynamic polarization methods. The results revealed that iso-vanillin had a moderate inhibitive effect on the corrosion of CRS in 1.0 M H2SO4 solution, while cerium(IV) ion had a negligible effect. However, incorporation of Ce4+ with iso-vanillin significantly improved the inhibition performance. The inhibition efficiency for Ce4+ in combination with iso-vanillin was higher than the summation of inhibition efficiency for single Ce4+ and single iso-vanillin, which was synergism in nature. © 2006 Elsevier B.V. All rights reserved. Keywords: Cold rolled steel; Sulfuric acid; iso-Vanillin; Cerium(IV) ion; Corrosion inhibitor; Synergism
1. Introduction Synergism is a combined action of compounds greater in total effect than the sum of the individual effects. Synergism of corrosion inhibitors is either due to the interaction between components of the inhibitor composition or due to interaction between the inhibitor and one of the ions present in the aqueous solution [1]. Synergistic inhibition is an effective means to improve the inhibitive force of inhibitor, to decrease the amount of usage, and to diversify the application of inhibitor. It plays an important role in not only theoretical research on corrosion inhibitors but also practical work [2]. In previous investigations, synergism between organic inhibitors and halide ions on metal corrosion in acidic solution has been researched by many authors [2–8]. The synergistic inhibition effects of organic inhibitor/ metallic ion mixture [9–12], organic inhibitor/organic inhibitor mixture [13–16] and inorganic inhibitor/inorganic inhibitor
⁎ Corresponding author. E-mail address: [email protected] (X. Li). 0167-577X/$ - see front matter © 2006 Elsevier B.V. All rights reserved. doi:10.1016/j.matlet.2006.09.048
mixture [17] on corrosion of metal in acidic media have also been studied. Forsyth et al. [18] have studied the synergistic corrosion inhibition of mild steel by rare earth (RE) Ce3+ and sodium salicylate in 0.1 M NaCl neutral media. Aramaki [19,20] investigated the synergism of RE Ce3+/inorganic compound Na2Si2O5 mixture and Ce3+/organic compound C8H17S(CH2)2COONa (NaOTP) mixture on the corrosion of zinc in 0.5 M NaCl. However, there is little report in the literature about the synergism between RE ions and other compounds on metal corrosion in strong acidic media. In our laboratory, much work has been conducted to study the synergism between RE ions and other compounds on the corrosion of some metals and alloys in strong acidic media. In 1996, the synergistic inhibition between anionic surfactant (sodium dodecyl sulfonate, SDS) and La3+ for mild steel corrosion in 1.0 M HCl was reported [12]. Recently, the synergistic effect of Na2MoO4 and Ce4+ on CRS corrosion inhibition in 1.0 M HCl was also investigated [21]. In the present work, the synergism between Ce4+ and organic compound iso-vanillin on CRS in sulfuric acid is first studied by weight loss and potentiodynamic
X. Li et al. / Materials Letters 61 (2007) 2514–2517
2515
Fig. 1. Chemical molecular structure of iso-vanillin.
polarization methods. It is hoped to get general information on synergism between organic inhibitor and RE ion in strong acid solution. 2. Experimental The composition and preparation of cold rolled steel (CRS) coupons have been described in detail in earlier reports [22,23]. Both iso-vanillin (3-hydroxy-4-methoxy-benzaldehyde) and cerium(IV) sulfate tetrahydrate (Ce(SO4)2·4H2O) were obtained from Shanghai Chemical Reagent Company of China, and of analytical-reagent grade. Fig. 1 shows the molecular structure of the iso-vanillin. The weight loss and potentiodynamic polarization measurements have also been described in detail in earlier reports [22,23]. The immersion time of weight loss is 6 h, and the experimental temperature is 20 °C. The inhibition efficiency (IE) of weight loss measurement was calculated as follows [22]: IE% ¼
W0 −W 100 W0
ð1Þ
where W0 and W are the values of the average weight loss without and with addition of inhibitor, respectively. IE of potentiodynamic polarization measurement was defined as: IE% ¼
Icorr −IcorrðinhÞ 100 Icorr
Fig. 2. Relationship between inhibition efficiency (IE) and concentration of inhibitor (C) in 1.0 M H2SO4 at 20 °C.
steel surface would take place through all these functional groups. The simultaneous adsorption of the three functional groups forces the isovanillin molecule to be horizontally oriented at the metal surface. It can be seen from Fig. 2 that IE increases with the Ce4+ concentration. However, the maximum inhibition efficiency was only about 20%. The poor inhibitive ability may be interpreted as follows: it is well known that the steel surface charges positive in H2SO4 because of Ecorr − Eq=0 (zero charge potential) N 0 [24], thus it is difficult for the Ce4+ to approach the positively charged steel surface due to the electrostatic repulsion. In addition, it was impossible for the cerium(IV) ion to form rare earth metal (REM) conversion coatings on CRS in strong acidic media [21]. 3.2. Synergism between cerium(IV) ion and iso-vanillin Fig. 3 shows the inhibition efficiency in 1.0 M H2SO4 with different concentration ratios of iso-vanillin and Ce4+ at a total blend
ð2Þ
where Icorr and Icorr(inh) are the uninhibited and inhibited corrosion current density values, respectively, determined by extrapolation of Tafel lines to the corrosion potential. 3. Results and discussion 3.1. Effect of single iso-vanillin and single Ce4+ on inhibition efficiency The values of inhibition efficiency obtained from the weight loss for different iso-vanillin and Ce4+ concentrations in 1.0 M H2SO4 at 20 °C are given in Fig. 2. The results show that inhibition efficiency increases with the concentration of inhibitors from 25 to 500 mg l− 1. The maximum inhibition efficiency was about 64% for iso-vanillin at a concentration of 500 mg l− 1. The moderate inhibition performance of single iso-vanillin may be explained as follows: iso-Vanillin is an aromatic aldehyde containing carbonyl, methoxy and hydroxyl groups arranged around the aromatic ring. The adsorption of iso-vanillin on
Fig. 3. The relationship between inhibition efficiency and different concentration ratios of iso-vanillin and Ce4+ at a total blend concentration of 500 mg l− 1 in 1.0 M H2SO4 at 20 °C.
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X. Li et al. / Materials Letters 61 (2007) 2514–2517
concentration of 500 mg l− 1 at 20 °C. It can be seen from Fig. 3 that the synergism between cerium(IV) ion and iso-vanillin was exhibited. Namely, the inhibition efficiency for Ce4+ in combination with isovanillin is higher than the summation of inhibition efficiency for single Ce4+ and single iso-vanillin, which is synergism in nature. For example, IEs 50 mg l− 1 iso-vanillin and 450 mg l− 1 Ce4+ are only 35% and 19%, respectively, while their complex has 92% IE. A high inhibition efficiency, 92% was obtained by a mixture of 25–200 mg l− 1 isovanillin and 300–475 mg l− 1 Ce4+. 3.3. Polarization studies The polarization behaviour of CRS in 1.0 M H2SO4 in the absence and presence of different concentrations of iso-vanillin and Ce4+ at 20 °C is shown in Fig. 4. The potentiodynamic polarization parameters are shown in Table 1. It is clear that the presence of single 100 mg l− 1 iso-vanillin causes a decrease in the corrosion rate i.e. it shifts the cathodic curve to more negative potential. The inhibitor has a significant effect on the rate of hydrogen evolution reaction. On the other hand, the inhibitor has a slight effect on the anodic curves. It may be concluded that single iso-vanillin acts as a cathodic-type inhibitor in 1.0 M H2SO4. Table 1 reveals that the corrosion current (Icorr) decreases and there is a moderate IE in the presence of 100 mg l− 1 iso-vanillin. The corrosion potential (Ecorr) does not change obviously. Both the cathodic Tafel slopes (bc) and the anodic Tafel slopes (ba) do not change obviously, which indicates that the mechanism of the corrosion reaction does not change and the corrosion reaction is inhibited by a simple adsorption mode. It can be seen from Fig. 4 that the cathodic reaction of electrode is slightly inhibited by the presence of Ce4+, while the anodic reaction is not inhibited compared with the blank. Table 1 shows that Icorr decreases slightly and there is a poor IE in the presence of 400 mg l− 1 Ce4+. In addition, Ecorr does not change obviously. Both bc and ba do not change obviously, which indicates that the mechanism of the corrosion reaction of steel does not change. Fig. 4 clearly shows that both anodic and cathodic reactions are drastically inhibited, which indicates the iso-vanillin/Ce4+ mixture acts as a mixed-type inhibitor [25]. The complex of 100 mg l− 1 iso-vanillin– 400 mg l− 1 Ce4+ causes Ecorr to shift to the anodic direction. Both bc and ba do change obviously, and Icorr decreases remarkably. The inhibition efficiency calculated from corrosion current density reaches a considerable value (95.3%).
Table 1 Potentiodynamic polarization parameters for the corrosion of cold rolled steel in 1.0 M H2SO4 containing different concentrations of iso-vanillin and Ce4+ at 20 °C C (isovanillin) (mg l− 1)
C (Ce4+) Ecorr (mg l− 1) (mV)
0 100 0 100
0 0 400 400
Icorr bc ba IE (μA cm− 2) (mV dec− 1) (mV dec− 1) (%)
− 443.6 432.0 − 450.2 250.3 − 448.3 349.5 − 412.6 20.2
125 124 122 136
46 37 48 39
– 42.1 19.1 95.3
From Table 1, it can be concluded that inhibition efficiencies (IE) obtained from weight loss, and electrochemical polarization curves are in good agreement. 3.4. Explanation for synergism When iso-vanillin was mixed with Ce4+ in 1.0 M H2SO4, the new complex of iso-vanillin–Ce4+ was formed [26]. The cathodic process of steel corrosion was suppressed by covering the surface with iso-vanillin firstly, while the new complex of iso-vanillin–Ce4+ then precipitated at the defect of the adsorption of the iso-vanillin film (double tight film) to prevent the anodic process mostly, thus inhibiting the anodic and cathodic reactions at the same time, which drastically improves the inhibition efficiency, and produces strong synergistic inhibition effect.
4. Conclusion 1. iso-Vanillin acts as a moderate inhibitor for the corrosion of cold rolled steel (CRS) in 1.0 M H2SO4. Cerium(IV) ion has a negligible effect on the corrosion rate of CRS in 1.0 M H2SO4, the maximum efficiency value is only about 20%. 2. There is a strong synergism between iso-vanillin and Ce4+ in 1.0 M H2SO4. Namely, the inhibition efficiency for Ce4+ in combination with iso-vanillin is higher than the summation of inhibition efficiency for single Ce4+ and single iso-vanillin. 3. iso-Vanillin prominently acts as a cathodic-type inhibitor in 1.0 M H2SO4. Cerium(IV) ion has a slight effect on the cathodic reaction in 1.0 M H2SO4. However, the iso-vanillin/ Ce4+ mixture behaves as a mixed-type inhibitor, which dramatically inhibits both anodic and cathodic reactions, and produces strong synergistic inhibition effect. Acknowledgement This work was carried out in the frame of a research project funded by the Chinese National Science Foundation (Grant No. 50261004). References
Fig. 4. Potentiodynamic polarization curves for cold rolled steel in 1.0 M H2SO4 containing different concentrations of iso-vanillin and Ce4+ at 20 °C.
[1] E. Kalman, I. Lukovits, G. Palinkas, ACH—Models Chem. 132 (4) (1995) 527. [2] G.N. Mu, X.M. Li, F. Li, Mater. Chem. Phys. 86 (2004) 59. [3] E.E. Ebenso, Mater. Chem. Phys. 79 (2003) 58. [4] Y. Feng, K.S. Siow, W.K. Teo, A.K. Hsieh, Corros. Sci. 41 (1999) 829. [5] T. Du, J. Chen, D. Cao, Br. Corros. J. 35 (2000) 229. [6] D.Q. Zhang, L.X. Gao, G.D. Zhou, J. Appl. Electrochem. 33 (2003) 361.
X. Li et al. / Materials Letters 61 (2007) 2514–2517 [7] G.K. Gomma, Mater. Chem. Phys. 55 (1998) 241. [8] E.E. Oguzie, C. Ugaegbu, C.N. Ogukwe, B.N. Okolue, A.I. Onuchukwa, Mater. Chem. Phys. 84 (2004) 263. [9] I. Sekine, Y. Hirakawa, Corrosion 42 (1986) 272. [10] I. Singh, M. Singh, Corrosion 43 (1987) 425. [11] D.D. Singh, T.B. Singh, B. Gaur, Corros. Sci. 37 (1995) 1005. [12] G.N. Mu, T.P. Zhao, M. Liu, T. Gu, Corrosion 52 (1996) 853. [13] M. Hosseini, S.F.L. Mertens, M.R. Arshadi, Corros. Sci. 45 (2003) 1473. [14] R.F.V. Villamil, G.G.O. Cordeiro, J. Matos, E. Delia, S.M.L. Agostinho, Mater. Chem. Phys. 78 (2002) 448. [15] R.F.V. Villamil, P. Corio, J.C. Rubim, S.M.L. Agostinho, J. Electroanal. Chem. 472 (1999) 112. [16] R.F.V. Villamill, P. Corio, J.C. Rubim, S.M.L. Agostinlto, J. Electroanal. Chem. 535 (2002) 75.
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[17] G.N. Mu, T.P. Zhao, J. Yunnan Univ. (China) 21 (4) (1999) 279. [18] M. Forsyth, C.M. Forsyth, K. Wilson, T. Behrsing, G.B. Deacon, Corros. Sci. 44 (2002) 2651. [19] K. Aramaki, Corros. Sci. 44 (2002) 1361. [20] K. Aramaki, Corros. Sci. 44 (2002) 871. [21] G.N. Mu, X.H. Li, Q. Qu, J. Zhou, Acta Chim. Sin. 62 (24) (2004) 2386 (in Chinese). [22] X.H. Li, G.N. Mu, Appl. Surf. Sci. 252 (2005) 1254. [23] G.N. Mu, X.H. Li, J. Colloid Interface Sci. 289 (2005) 184. [24] D.P. Schweinsberg, V. Ashworth, Corros. Sci. 28 (1988) 539. [25] G.N. Mu, X.H. Li, Q. Qu, J. Zhou, Corros. Sci. 48 (2006) 445. [26] G.L. Zhao, J. Zhejiang Normal Univ. 23 (2) (2000) 172 (in Chinese).