INVESTIGATION EFFECT OF BENZOTRIAZOLE ON THE CORROSION OF

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1 INVESTIGATION EFFECT OF BENZOTRIAZOLE ON THE CORROSION OF BRASS-MM55 ALLOY IN ARTIFICIAL SEAWATER BY TAFEL EXTRAPOLATĐON AND NEW METHOD DYNAMIC EIS K.DAROWICKI 1, H.GERENGI 2, G.BEREKET 2, P.SLEPSKI 1 1 Gdansk University of Technology, Chemical Faculty, Department of Electrochemistry, Corrosion and Material Engineering, Narutowicza Str. 11/12, , Gdansk, POLAND 2 Eskisehir Osmangazi University, Department of Chemistry, Faculty of Arts and Science, Eskişehir, TURKEY ABSTRACT: The electrochemical behaviour of brass-mm55 alloy was studied in artificial seawater in the presence of benzotriazole (BTA) by using Tafel extrapolation and Dynamic Electrochemical Impedance Spectroscopy (DEIS). Both methods clearly show that benzotriazole, inhibit the corrosion of brass-mm55 alloy in artificial seawater and the value of inhibition efficiency increases with increasing concentration of BTA. But it was found that a few hours of duration were not sufficient for right calculation of corrosion inhibition in aggressive environment. Usefulness of the DEIS technique in the investigation of aggressive environment (non-stationary) phenomena has been proved in the field of inhibitor researches. Keywords: Corrosion; Artificial seawater; Benzotriazole (BTA); Dynamic EIS (DEĐS), Tafel extrapolation 1. INTRODUCTION: Copper and its alloys are widely used in industry because of their excellent electrical and thermal conductivity and are often used in heating and cooling system (1,2). Especially brass, has been widely used as tubing material for condensers and heat exchangers in various cooling water systems (3,4). Due to those various industrial applications and economic importance of brass its protection against corrosion attracted much attention. However it corrodes easily in chloride containing aqueous solutions and air, which limits its use. But the majority of marine propellers from the smallest to the largest are made from copper alloys (5). Brass-MM55, especially, has been used such as casting propellers and rudders (6). This type of brass also used in valve bodies, pump parts and non magnetic binnacle fittings (7). One of the most important methods in corrosion protection is to use inhibitors (8). Inhibitors are chemicals that act to slow down corrosion. They are the preferred method of corrosion control in closed and recirculation cooling and heater systems. The effectiveness of an organic substance as an inhibitor depends on the structure of the inhibitor (9) and the stability of the chelate formed on the metal surface (10). Most organic substances employed as copper corrosion inhibitors protect the metal by forming a chelate on the metal surfaces (11). Benzotriazole (BTA) is known as one of the best corrosion inhibitors for copper and its alloys in a wide range of environments (12 16). Also BTA has low toxicity and presents no ecological hazard although precautions should be taken (17). It is generally assumed that BTA forms a polymeric cuprous complex on the metal surface which prevents further copper dissolution (18,19). Most of above studies were concerned that BTA adsorbed on the cupper alloys surface like reaction (1). *Corresponding author. Tel: ; address: huararat@hotmail.com

2 n(bta)aq + ncu [Cu(BTA)]n + nh + + ne - (1) Brass has been widely studied in %3,5 NaCl media where it has been observed that the chloride ion has a strong influence on the copper corrosion mechanism (20). However, according to laboratory tests, these solutions not always accurately reproduce the corrosion losses in the natural seawater, because, in addition to chlorides, other impurities in the salt composition can pronouncedly affect the corrosion (21). Therefore, in this investigation it is proposed to study the electrochemical behaviour of brass-mm55 in artificial seawater. Darowicki et al. (22-24) have presented a new mode of electrochemical impedance measurement. In this method (DEIS), the impedance spectra are determined for narrow periods of time. So, this method can be appropriate for impedance measurements of corrosion. The purpose of this work is to present a novel method; Dynamic electrochemical impedance spectroscopy, which has never been employed in the investigation of inhibition of inhibitors and compare with the results obtained from Tafel extrapolation method 2. EXPERIMENTAL APPROACH 2.1 Materials Electrochemical measurements were all carried out in a three-electrode type cell with separate compartments for the reference electrode (Ag/AgCl) and the counter electrode was platinum (Pt) plate. During the all measurements, the solution was stirred with magnetic bar (500 rot/min). The working electrode was brass-mm55. The area of this electrode was 0.2 cm 2 and surface of the working electrode was prepared by grinding abrasive paper of gradation. Next they were rinsed with distilled water and degreased with acetone. In each DEIS experiment, after 10 minutes of the beginning of the experiment we added BTA. Thus, we investigated how BTA acted on our sample but in Tafel extrapolation experiments the working electrode was immersed in aerated artificial seawater and allowed to stabilize for 60 minutes [25]. Brass-MM55 had the composition; (wt. %): 55 Cu, 4 Mn, 1 Fe, 0.6 Al and the rest Zn. Chemical Composition of the artificial seawater is given in Table 1 [26]. ph of our solution was 8.10 and Resistivity was (ρ) 25 Ω-cm. We measured resistivity with Nilsson electrical resistance Conductance meter model 400. We used commercial benzotriazole that produce from Roanal firm from Budapest- Hungary with product number [Scheme 1]. Scheme 1. Structures of benzotriazole

3 Table 1. Analyze of artificial seawater that we used Component Concentrations, g/l NaCl 24,53 MgCl 2 5,20 Na 2 SO 4 4,09 CaCl 2 1,16 NaHCO 3 0,201 KBr 0,101 H 3 BO 3 0, Method Dynamic Electrochemical Impedance Spectroscopy (DEIS) All measurements were performed on a setup assembled in the Gdansk University of Technology by Department of Electrochemistry Corrosion and Materials Engineering. Generation of the current was performed with a National Instruments Ltd. PCI-6120 digitalanalog card. The same card was used for measurement of the current and voltage signals. Autolab PGSTAT 30 equipment was used to supply galvanostatic condition and also, as a current-voltage converter. The perturbation signal was a package composed of current sinusoids of the frequency range 4.5 khz to 700 mhz. The low limit of measurement frequency depended on the length of analyzing window (10s). In other words the low frequency limit depended on the time scale of the analysis performed. The sampling frequency was 12.5 khz Tafel extrapolation Parstat 2263 potansiyostat hardware and special software was used to analyze the results. This technique uses data obtained from cathodic and anodic polarization measurements. The perturbation potential was +/- 250 mv. Our scan rate was 1 mvs -1. The polarisation resistance (Rp) was calculated using the Stern Geary Equation (27): i corr β β 2,303 β 1 a c = (2) ( βa + c) Rp 3. RESULTS DISCUSSION 3.1. Dynamic Electrochemical Impedance Spectroscopy (DEIS) Results Ten minutes after starting every DEIS experiment, inhibitor added quickly to corrosion cell. For one experiment we determined 100 spectra. All those spectra were analyzed in ZSimpwin 3.10 program (28). This program gives good information about circuit. We

4 obtained that R(Q(RW)) circuit [Scheme 2] model gives best fitting to our spectra. Brass- MM55, without inhibitor (fig.1) and with M, M, M and M BTA, DEIS results were depicted in figs. 2, 3, 4 and 5. Key; Rs = Resistance of electrolyte in bulk R ct = Charge transfer resistance at the metal surface W = Warburg impedance Q = Constant phase element Scheme 2. An electrical circuit of R(Q(RW)) model Fig. 1. DEIS result of Brass-MM55, without inhibitor in artificial seawater

5 Fig. 2. DEIS result of Brass-MM55, with M BTA in artificial seawater Fig. 3. DEIS result of Brass-MM55, with M BTA in artificial seawater

6 Fig. 4. DEIS result of Brass-MM55 with, M BTA in artificial seawater Fig. 5. DEIS result of Brass-MM55, with M BTA in artificial seawater The percentage inhibition efficiency (IE%) is calculated from the charge transfer resistance values (29) by using following equation (3). 1 1 Rct Rct( inh) IE (%) = 100 (3) 1 R ct

7 Where R ct(inh) and R ct are the charge transfer resistance values with and without inhibitors respectively. Change of R ct by the time was given in figure 6. and inhibition efficiency values are given in table 2. It is clear that, the R ct values increased in the presence of inhibitor. Impedance figures 1 to 5 and from figure 6 results shows that system was non-stationary till nearly three hours. Fig. 6. R ct change of Brass-MM55 in artificial seawater by using different concentration of BTA ( M BTA, M BTA, M BTA, M BTA, no inhibitor) Table 2. Inhibition efficiency values of BTA on Brass-MM55 by DEIS in artificial seawater Concentrations R ct (Ohm cm 2 ) Inhibition efficiency (IE%) No inhibitor M BTA M BTA M BTA M BTA

8 3.2. Tafel extrapolation (TP) results Fig. 7. Brass-MM55 alloy in artificial seawater; no inhibitor ( ); 0.01 M BTA ( ); M BTA (x); M BTA (o); M BTA (----) added solution polarization curves Table 3. Polarization results of Brass-MM55 in artificial seawater, with and without benzotriazole (BTA) addition Concentrations βa βc Rp (mv/dec) (mv/dec) (mv) (µa/cm2) (Ohm cm2) No inhibitor M BTA M BTA M BTA M BTA E corr i corr Tafel extrapolation (TP) results are presented in table 3. It can be seen that corrosion potentials (E corr ) changes to anodic part but this is not in order with concentration of inhibitors. Also the values of cathodic Tafel slope (βc) and anodic Tafel slope (βa) of benzotriazole derivatives are found to change with inhibitor concentration, indicates that the inhibitors controlled both the reactions. The percentage inhibition efficiency (IE%) of corrosion of brass-mm55 is calculated by corrosion current density (i corr ) as follows (30):

9 icorr icorr( inh) IE (%) = 100 (4) i corr Where i corr(inh) and i corr are the corrosion current density values with and without inhibitors respectively. Inhibition efficiency (IE%) results are shown in table 4. Table 4. Inhibition efficiency values of BTA on Brass-MM55 by TP in artificial seawater Concentrations Inhibition efficiency (IE%) No inhibitor M BTA M BTA M BTA M BTA Tafel extrapolation (TP) results and Dynamic Electrochemical Impedance Spectrum (DEIS) results such as Rct and inhibition efficiency (IE%) are different from each other. Those differences were reported in previous researches (31-34). We thought that such differences could depend on scan rate and also frequency of methods. But two techniques had a similar trend. 4. CONCLUSIONS - Tafel extrapolation (TP) method is a good method that gives information about mechanism of corrosion system. But for right calculation we have to find when the system was stationary. - Dynamic Electrochemical Impedance Spectrum (DEIS) method, should be used before every experiment for to take knowledge about system. - Benzotriazole (BTA) has excellent inhibition properties on brass-mm55 in artificial seawater. BTA, behaves as mixed type inhibitor. - The results of this study demonstrate that Dynamic Electrochemical Impedance Spectrum (DEIS) is a relatively rapid measurement technique, which gives information about how and when inhibitor influence on our sample. - Dynamic Electrochemical Impedance Spectrum (DEIS) method results were more realistic than Tafel extrapolation method.

10 REFERENCES 1. Stupnisek-Lisac, E., Loncaric Bozic, A., Cafuk, I., Corrosion 54, 713, Zaky, A.M., British Corrosion Journal 36, 59, North, R.F., Pryar, M.J., Corrosion Science 10, 297, Quartarone, G., Moretti, G., Bellami, T., Corrosion 54, 606, Howard Rogers, T., Marine Corrosion Book, ISBN (T ), Barbara, R., Henryk, K., Maly poradnik Mechanika, ISBN(621(058)), Asan, A., Kabasakaloğlu, M., Işıklan, M., Kılıç, Z., Corrosion Science 47, 1534, Costa, J.M., Luch, J.M.L., Corrosion Science 24, 929, Dus, B., Smialowska, Z.S., Corrosion 28, 105, Duprat, M., Bui, N., Dabost, F., Corrosion 35, 392, Walker, R., Corrosion 29, 290, Fox, P.G., Lewis, G., Boden, P.J., Corrosion Science 19, 457, Costa, S.L.F.A., Agostinho, S.M.L., Corrosion 45, 472, Ashour, E.A., Sayed, S.M., Ateya, B.G., J. Appl. Electrochemistry 25, 137, Laz, M.M., Souto, R.M., Gonzalec, S., Salvarezza, R.C., Ariva, A.J., J.Appl. Electrochemistry 22, 112, Oddy, W.A., Stud. Cons. 19, 188, Babic, R., Metikos-Hukuvic, M., Loncar, M., Electrochimica Acta 44, 2413, Youda, R., Nishihara, H., Aramaki, K., Electrochimica Acta 35, 35, Kear, G., Barker, B.D., Walsh, F.C., Corrosion Science 46, 109, Sinyavskii, V. S., Kalinin, V. D., Protection of Metals, 41, 317, Darowicki, K., Orlikowski, J., Lentka, G., Jour. of Electroanalytical Chem. 486, 106, Darowicki, K., Orlikowski, J., Arutunow, A., J Solid State Eletrochem 8, 352, Darowicki, K., Slepski, P., Szocinski, M., Progress in Organic Coatings 52, 306, Tadeja, K., Ingrid, M., Boris, P., Applied Surface Science, 253, 8863, Darowicki, K., Gerengi, H., Bereket, G., Slepski, P., Zielenski, A., Jour. of Corrosion 14, 90, Stern, M., Geary, A.L., Electrochemical Society 104, 56, Quraishi, M.A., Sardar, R., J. Applied Electrochemistry 33, 1163, Asan, A., Kabasakaloğlu, M., Işıklan, M., Kılıç, Z., Corrosion Science, 47, 1534, Stratfull, R.F., Corrosion of Reinforcement in Concrete Construction, Society of Chemical Industry, London, 287, Soleymani, H.R., Ismail, M.E., Cement and Concrete Research 34, 2037, Akid, R., Mills, D.J., Corrosion Science 43, 1203, Zhu, B., Lindbergh, G., Electrochimica Acta 46, 2593, 2001

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