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Study of corrosion inhibition of C38 steel in 1M HCl solution by polyethyleneiminemethylene phosphonic acid

Study of corrosion inhibition of C38 steel in 1M HCl solution by polyethyleneiminemethylene... Int J Ind Chem (2017) 8:263–272 DOI 10.1007/s40090-017-0123-2 RESEARCH Study of corrosion inhibition of C38 steel in 1 M HCl solution by polyethyleneiminemethylene phosphonic acid 1,2 1 3 1 • • • Merah Salah Larabi Lahce`ne Abderrahim Omar Harek Yahia Received: 2 April 2016 / Accepted: 24 May 2017 / Published online: 29 May 2017 The Author(s) 2017. This article is an open access publication Abstract A new class of corrosion inhibitors, namely, Introduction polyethyleneiminemethylene phosphonic acid (PEIMPA), was synthesized and its inhibiting action on the corrosion Study of organic corrosion inhibitor is an attractive field of C38 steel in 1 M HCl at 30 C was investigated by of research due to its usefulness in various industries. various corrosion monitoring techniques such as weight Acid is widely used in various industries for the pickling loss measurements, potentiodynamic polarization, linear of ferrous alloys and steels. Because of the aggressive polarization resistance (Rp), and surface analysis (SEM and nature of the acid medium, theinhibitors arecommonly EDX) which are used to characterize the steel surface. used to reduce acid attack on the substrate metal. Most Weight loss measurements revealed that the presence of of the reported corrosion inhibitors are organic com- PEIMPA increases the inhibition efficiency by decreasing pounds containing O, N, S, and P [1–14]intheir the corrosion rate. Tafel polarization study showed that the structures. The phosphoric functions are considered to be inhibitor acts as a mixed-type inhibitor. Adsorption of the most effective chemical group against corrosion PEIMPA on the carbon steel surface was found to obey the process [15]. The use of organic phosphonic acids to Langmuir isotherm. Some thermodynamic functions of protect carbon steel against corrosion has been the sub- dissolution and adsorption processes were also determined ject of various works [16–26]. Aminomethyl-phosphonic and discussed. The SEM results showed the formation of acids are excellent sequestering agents for electroplating, protective film on the mild steel surface in the presence of chemical plating, degreasing, and cleaning. It was shown PEIMPA. The results obtained from different tested tech- that piperidin-1-yl-phosphonic acids (PPA) and (4- niques were in good agreement. phosphono-piperazin-1-yl) phosphonic acid (PPPA) are used to reduce the corrosion of iron in a NaCl medium, Keywords Corrosion  Inhibition  C38 steel  Phosphonic even if PPPA is more efficient than PPA [27]. In the present investigation, the influence of poly- acid ethyleneiminemethylene phosphonic acid (PEIMPA) as a corrosion inhibitor of carbon steel in 1 M HCl has been systematically studied by weight loss measurements, potentiodynamic polarization studies, and surface anal- & Merah Salah merrah2005@yahoo.fr ysis (SEM,EDX).Results are reported and discussed. Laboratory of Analytical Chemistry and Electrochemistry, Department of Chemistry, Faculty of Science, Tlemcen Experimental University, Tlemcen, Algeria Department of Process Engineering, Faculty of Technology, Polyethyleneiminemethylene phosphonic acid polymer Sai‹ da University, Sai‹ da, Algeria was synthesized (see Scheme 1) from commercially Laboratory of Separation and Purification Technology, available Lupasol P (polyethylenimine) according to the Department of Chemistry, Faculty of Science, Tlemcen Moedrizer–Irani reaction [28]. The synthesis was University, Tlemcen, Algeria 123 264 Int J Ind Chem (2017) 8:263–272 Scheme 1 Synthesis of polyethyleneiminemethylene phosphonic acid from Lupasol P performed in distilled water under microwave irradiation. Sheets with dimensions 20 mm 9 10 mm 9 2 mm were In a quartz reactor, a mixture of polyethylenimine (Lu- used. They were polished successively with different pasol P, 80 mmol, 3.44 g), phosphorous acid (80 mmol, grades of emery paper up 1200 grade. Each run was carried 6.68 g), and hydrochloric acid–water (1:1) solution out in a glass vessel containing 100 ml test solution. A (12 mL) was vigorously stirred and then irradiated clean weight mild steel sample was completely immersed (150 W) in a glass cylinder reactor for 1 min. A at an inclined position in the vessel. After 4 h of immersion formaldehyde aqueous solution (160 mmol) was added in 1 M HCl with and without the addition of inhibitor at and irradiated for 8 min. different concentrations, the specimen was withdrawn, Then, the precipitation was washed with distilled water rinsed with double-distilled water, washed with acetone, to remove unreacted reagents. Finally, phosphonic-modi- dried, and weighed. The weight loss was used to calculate fied Lupasol P was washed three times with distilled water the corrosion rate in milligrams per square centimeter per and ethanol. After drying, the solid was further pulverized hour. to give a brown powder. Electrochemical experiments were carried out in a The structure and purity were identified and character- glass cell (CEC/TH Radiometer) with a capacity of 1 13 ized by elemental microanalysis (Table 1) and H, C, and 500 ml. A platinum electrode and a saturated calomel P NMR spectroscopy. The spectra showed the expected electrode (SCE) were used as a counter electrode and a signals due to the polyethylenimine skeleton and methy- reference electrode. The working electrode was in the lene phosphonic units as matched to the proposed structure form of a disc cut from mild steel under investigation (Scheme 1). and was embedded in a Teflon rod with an exposed area 1 2 NMR spectral data: H NMR d (ppm): 4.92 (N–CH ); of 0.5 cm . Potentiodynamic polarizations were con- 2.33 (CH –P); 1.6 NH. C NMR d (ppm): 82.16 (N–CH ), ducted in an electrochemical measurement system 2 2 52.1 (CH –P). P NMR d (ppm): 3.91. The presence of (VoltaLab 21) which comprises a PGP201 potentiostat, a phosphonic acid was confirmed by FTIR measurement: the personal computer, and VoltaMaster4 software. The polymer displays characteristic bonds for P–O–C at polarization resistance measurements were performed by -1 -1 1050 cm , P–OH at 2372, and 2338 cm 189 and P = O applying a controlled potential scan over a small range -1 at 1172 cm . typically ±15 mV with respect to Ecorr with a scanning -1 Elemental microanalysis suggests the structure made of rate of 0.5 mV s . The resulting current is linearly fragment of the phosphonic acid polymer, corresponding plotted vs. potential, the slope of this plot at Ecorr being after calculation to x = 5 and y = 9 (Scheme 1). the polarization resistance (Rp). Corrosion current den- A 1 M HCl solution was prepared from an analytical sities were determined by extrapolating the cathodic reagent grade of HCl 37% and double-distilled water and Tafel regions from the potentiodynamic polarization was used as corrosion media in the studies. Note that the curves to the corrosion potential. The potentiodynamic solubility of polyethyleneiminemethylene phosphonic acid current–potential curves were recorded by changing the is very high in this medium. electrode potential automatically from -700 to -1 For the weight loss measurements, the experiments were -300 mV with the same scanning rate (0.5 mV s ) carried out in the solution of 1 M HCl (uninhibited and under static on the same electrode without any surface inhibited) on carbon steel containing 0.30–0.35% C, treatment. All experiments were carried out in freshly 0.15–0.35% Si, 0.035% S, 0.5–1.0% Mn, and 0.035% P. prepared solution at constant temperatures. Table 1 Elemental Microanalysis %C %H %N %O %P microanalysis of polyethyleneiminemethylene Found 30.8112 7.6250 13.2519 29.3535 18.9574 phosphonic acid Calculated (x = 5, y = 9) 30.6631 6.6989 13.5359 29.8342 19.2679 123 Int J Ind Chem (2017) 8:263–272 265 Inhibition efficiencies P % were calculated as follows: Inspection of this table shows that the inhibition effi- Weight loss measurement: ciency increases with increasing inhibitor concentration. 0 The optimum concentration required to achieve this effi- w  w P% ¼  100 ð1Þ ciency is found to be 500 ppm. The inhibition of corrosion of carbon steel by the investigated inhibitor can be where w and w are the corrosion rate of steel due to the explained in terms of adsorption on the metal surface. It is dissolution in 1 M HCl in the absence and the presence of generally assumed that the adsorption of the inhibitor at the definite concentrations of inhibitor, respectively. metal/solution interface is the first step in the mechanism of Linear polarization measurement: inhibition in aggressive media. This compound can be adsorbed on the metal surface by R R P% ¼  100 ð2Þ 0 the interaction between lone pair of electrons of hetero atoms and the metal surface. This process is facilitated by where R and R are the values of linear polarization in the the presence of vacant orbitals d of low energy in iron absence and presence of the inhibitor, respectively. atom, as observed in the transition group metals. Moreover, Polarization measurement: the formation of positively charged protonated species in 0 acidic solutions facilitates the adsorption of the compound I  I corr corr P% ¼  100 ð3Þ on the metal surface through electrostatic interactions corr between the organic molecules and the metal surface [29]. where i and i are the corrosion current densities in the corr corr absence and the presence of the inhibitor, respectively. Polarization measurements For all methods, the tests were performed in non-de- aerated solutions under unstirred conditions. Figure 1 shows the polarization curves of mild steel in 1 M The surface morphology of the samples before and after HCl, blank solution, and in the presence of different con- adding PEIMPA inhibitor in the medium 1 M HCl after centrations (100–500 ppm) of PEIMPA. With the increase 1 day of immersion was observed by scanning electron of PEIMPA concentrations, both anodic and cathodic cur- microscope (SEM) Quanta 200 FEG coupled with EDX rents were inhibited. This result shows that the addition of analysis. PEIMPA inhibitor reduces anodic dissolution and also retards the hydrogen evolution reaction. We note that the corrosion potential varies slightly after the addition of the Results and discussion inhibitor at different concentrations. Table 3 shows that an increase in inhibitor concentration Weight loss measurements is resulted in increased inhibition efficiency. It is evident from the results that the I values decrease considerably corr The gravimetric measurements of mild steel in 1 M HCl in in the presence of inhibitor and that the maximum decrease the absence and presence of various concentrations of in I coincides with the optimum concentration of corr PEIMPA investigated were determined after 4 h of immersion at 30 C. Table 2 gives values of the corrosion rates and per- -2 centage inhibition efficiency calculated from the weight -3 loss measurements for different concentrations of PEIMPA. -4 1M HCL 100 ppm PEIMPA -5 Table 2 Corrosion rates and inhibition efficiencies of PEIMPA at 200 ppm PEIMPA 300 ppm PEIMPA different concentrations in 1 M HCl 400 ppm PEIMPA -6 -2 -1 500 ppm PEIMPA Conc. (ppm) V (mg cm h ) P (%) corr -7 1 M HCl 0.703 – 100 0.195 72.15 -8 200 0.120 82.93 -700 -600 -500 -400 -300 300 0.104 85.07 E vs SCE (mV) 400 0.093 86.69 Fig. 1 Polarization curves of carbon steel in 1 M HCl in the presence 500 0.069 90.11 of different concentrations of PEIMPA at 30 C -2 Logi (mA.cm ) 266 Int J Ind Chem (2017) 8:263–272 Table 3 Potentiodynamic polarization parameters for corrosion of carbon steel in 1 M HCl with various concentrations of PEIMPA at 30 C -2 2 -1 Conc. (ppm) E vs. SCE (mV) i (mA.cm ) R (X.cm ) b (mV dec ) P (i ) (%) P (R ) (%) corr corr p c corr p 1 M HCl -501 1.94 12.98 156 – – 100 -486 0.567 68.13 143 70.77 80.94 200 -512 0.359 73.54 146 81.49 82.34 300 -497 0.343 81.77 186 82.31 84.12 400 -511 0.336 99.04 134 82.68 86.89 500 -515 0.302 104.50 153 84.43 87.57 inhibitor. Linear polarization technique was performed in 1 M HCl with various concentrations of PEIMPA. The 0,00045 corresponding polarization resistance (R ) values of carbon 0,00040 steel in the absence and in the presence of different inhi- bitor concentrations are also given in Table 3. It is apparent 0,00035 that R increases with increasing inhibitor concentration. 0,00030 The inhibition percentage (P %) calculated from R values is also presented in Table 3. We remark that P % increases 0,00025 with increasing concentration of inhibitor and attains 87% 0,00020 at 500 ppm. The inhibition efficiencies of PEIMPA 0,00015 obtained by potentiodynamic polarization and by polar- ization resistance methods are in good agreement, partic- 0,00010 ularly, at high concentrations. 0,00005 For anodic polarization, it can be seen from Fig. 1 that, 0,00005 0,00010 0,00015 0,00020 0,00025 0,00030 0,00035 in the presence of PEIMPA at all concentrations, two linear C (mol/L) inh. portions were observed. When the anodic potentials increases, the anodic current increases at a slope of b in Fig. 2 Langmuir adsorption isotherm of PEIMPA on the carbon steel a1 surface in 1 M HCl from potentiodynamic measurements the low polarization potential region. After passing a cer- tain potential E , the anodic current increases rapidly and dissolves at a slope of b in the high polarization region. a2 The adsorption isotherm can give information on the This behavior was already documented for iron in acid metal–inhibitor interaction. The adsorption isotherm can be solutions [30–33]. The rapid increase of anodic current derived from the curve surface coverage against inhibitor after E may be due to the desorption of PEIMPA mole- concentration. Surface coverage h was estimated as in cules adsorbed on the electrode. This means that the inhi- Eq. 5. The h values for different inhibitor concentrations bition mode of PEIMPA depends on electrode potential. In are tested by fitting to various isotherms. So far, the best fit this case, the observed inhibition phenomenon is generally was obtained with the Langmuir isotherm. According to described as corrosion inhibition of the interface associated this isotherm, h is related to concentration inhibitor C via with the formation of a bidimensional layer of adsorbed C 1 inhibitor species at the electrode surface [34]. Note that the ¼ þ C ð4Þ h K potential E is also denoted E in Bartos and Hackerman’s u 1 where C is the concentration of inhibitor, K is the paper [30]. Figure 1 shows also that, at potentials higher than E , PEIMPA affects the anodic reaction. This result adsorptive equilibrium constant, and h is the surface cov- corr erage and calculated by the following equation [6, 35, 36]: indicates that PEIMPA exhibits both anodic and cathodic inhibition effects. corr h ¼ 1  ð5Þ corr Adsorption isotherm where I is the corrosion current density in uninhibited corr acid and I is the corrosion current density in inhibited The adsorption of the organic compounds can be described corr acid. by two main types of interaction: physical adsorption and Plotting C/h vs. C yields a straight line, as shown in chemisorption that are influenced by the charge nature of Fig. 2. The linear correlation coefficient (r) is almost equal the metal, the type of the electrolyte, and the chemical to 1 (r = 0.9999) and the slight deviation of the slope structure of the inhibitor. C/Θ (mol/L) Int J Ind Chem (2017) 8:263–272 267 -1 a transfer from the inhibitor molecules to the metal surface (a) to form a coordinate type of bond (chemisorption). In the -2 present study, the value of DG is about between -20 ads -1 and -40 kJ mol , probably mean that the adsorption -3 mechanism of the PEIMPA on steel in 1 M HCl solution is both physisorption and chemisorption. HCl 20°C -4 HCl 30°C Noticeably, it is generally accepted that physical HCl 40°C adsorption is the preceding stage of chemisorption of HCl 50°C inhibitors on metal surface [38]. It was reported that in this -5 domaine, the surface charge of steel at E in HCl solution corr is expected to be positive. Thus, the anions are first -6 adsorbed on the steel surface creating an excess negative charge, which, in turn, facilitates physical adsorption of the -7 -750 -700 -650 -600 -550 -500 -450 -400 -350 -300 inhibitor cations [39]. Accordingly, the Cl and phospho- E v SCE (mV) nate ions adsorb and the surface becomes negatively charged. Due to the electrostatic attraction, the protonated (b) -2 PEIMPA molecules are adsorbed on carbon steel surface (physisorption). -3 Along with electrostatic force of attraction, inhibitor also adsorbs on the carbon steel surface through chemical -4 adsorption. The adsorption of free molecules could take PEIMPA 20°C PEIMPA 30°C place via interaction of the unshared pairs of electrons of -5 PEIMPA 40°C nitrogen and oxygen atoms of the –PO(OH) group and the PEIMPA 50°C -6 vacant d-orbitals of iron atoms. Therefore, inhibition takes place through both -7 physisorption and chemisorption. However, chemisorption has no substantial contribution [12]. Indeed, the PEIMPA -8 molecules are easily protonated to form ionic forms in acid -700 -600 -500 -400 -300 -200 solution. It is logical to assume that in this case, the elec- E v SCE (mV) trostatic cation adsorption is mainly responsible for the protective properties of this compound. Fig. 3 Polarization curves for C38 steel electrode in 1 M HCl (a) and in HCl? 500 ppm of PEIMPA (b) at different temperatures Effect of temperature (1.14) from the unity is attributable to molecular interac- To investigate the mechanism of inhibition and to deter- tions in the adsorbed layer which corresponds to the mine the activation energy of the corrosion process, observed physical adsorption mechanism [37]. The polarization curves of steel in 1 M HCl were determined at adsorptive equilibrium constant (K) value is 6.22 9 10 - -1 various temperatures (303–333 K) in the absence and L mol . The free energy of adsorption DG of the ads presence of 500 ppm of PEIMPA. Representative Tafel inhibitor on mild steel surface can be determined using the polarization curves for C38 steel electrode in 1 M HCl following relation: without and with 500 ppm at different temperatures are 1 DG ads shown in Fig. 3a, b. Similar polarization curves were K ¼ exp ð6Þ 55:5 RT obtained in the case of the other concentrations of PEIMPA -1 -1 (not given). The analysis of these figures reveals that where R is the gas constant (8.314 J K mol ), T is the raising the temperature increases both anodic and cathodic absolute temperature (K), and the value 55.5 is the con- current densities, and consequently, the corrosion rate of centration of water in solution expressed in M.The DG ads -1 C38 steel increases. The corresponding data are given in value calculated is -37.90 kJ mol . The negative values Table 4. In the studied temperature range (303–333 K), the of DG indicate that the adsorption of inhibitor molecule ads corrosion current density increases with increasing tem- onto steel surface is a spontaneous process. In general, it is perature both in uninhibited and inhibited solutions and the well known that the values of -DG of the order of ads -1 values of the inhibition efficiency of PEIMPA decrease -20 kJ mol or lower indicate a physisorption; those of -1 with the increase of temperature. order of -40 kJ mol or higher involve charge sharing or -2 -2 Log I (mA cm ) Log i (mA.cm ) corr corr 268 Int J Ind Chem (2017) 8:263–272 Table 4 Electrochemical Milieu T/(C) E /(mVvSCE) i /(mA/cm ) b /(mV/dec) P/(%) corr corr c parameters and the corresponding inhibition 1 M HCl 20 -466 1.46 198 – efficiencies for the corrosion of 30 -501 1.94 156 – C38 in 1 M HCl and 500 ppm PEIMPA at various 40 -459 2.83 193 – temperatures 50 -457 4.01 196 – 500 ppm PEIMPA 20 -462 0.160 180 89.04 30 -515 0.302 134 84.34 40 -486 0.562 175 80.15 50 -485 1.052 188 73.81 Figure 4 and 5 present the Arrhenius plots of the natural -4,4 logarithm of the current density vs. 1/T, for 1 M solution of -4,8 hydrochloride acid, without and with the addition of -5,2 PEIMPA and ln(i /T) with reciprocal of the absolute corr temperature, respectively. Straight lines with coefficients -5,6 1M HCl of correlation (c.c.) high to 0.99 are obtained for the sup- 500 ppm PEIMPA -6,0 porting electrolyte and PEIMPA. -6,4 The values of the slopes of these straight lines permit the calculation of the Arrhenius activation energy, E , -6,8 according to -7,2 lnI ¼ þ lnA ð7Þ -7,6 corr RT 0,00305 0,00310 0,00315 0,00320 0,00325 0,00330 0,00335 0,00340 0,00345 -1 where R is the universal gas constant and A is the Arrhe- 1/T (K ) nius factor. Fig. 5 ln(i /T) vs. 1/T for C38 steel dissolution in 1 M HCl in the corr In addition, from transition-state plot according to the presence of PEIMPA at 500 ppm following equation: I DH corr ln ¼ þ B ð8Þ in the absence and the presence of PEIMPA at 500 ppm are T RT given in Table 5. Inspection of these data reveals that the where DH is the enthalpy of activation and B is a increase in E in the presence of the inhibitor may be constant. interpreted as physical adsorption. Indeed, a higher energy The E and DHa values were determined from the barrier for the corrosion process in the inhibited solution is slopes of these plots. The calculated values of E and DH a a associated with physical adsorption or weak chemical bonding between the inhibitor species and the steel surface 0,6 [22, 40]. Szauer and Brand explained that the increase in 1M HCl 500 ppm PEIMPA activation energy can be attributed to an appreciable 0,4 decrease in the adsorption of the inhibitor on the carbon 0,2 steel surface with the increase in temperature. A corre- sponding increase in the corrosion rate occurs because of 0,0 the greater area of metal that is consequently exposed to -0,2 the acid environment [41]. The enthalpy of activation values is found to be positive -0,4 in the absence and presence of inhibitor and reflects the endothermic mild steel dissolution process. It is evident -0,6 from Table 5 that the value of DH increased in the -0,8 presence of PEIMPA than the uninhibited solution indi- 3,05 3,10 3,15 3,20 3,25 3,30 3,35 3,40 3,45 cating protection efficiency. This suggested the slow dis- 3 -1 1/Tx 10 (K ) solution and hence lower corrosion rate of mild steel [2, 7]. This result permits verifying the known thermodynamic Fig. 4 Arrhenius plots of log icorr vs. 1/T without and with 500 ppm equation between E and DH [42]: a a of PEIMPA -2 logi (mA.cm ) corr -2 -1 ln(I /T) (mA cm K ) corr Int J Ind Chem (2017) 8:263–272 269 Table 5 Apparent activation energy E and activation enthalpy DH of dissolution of C38 steel in 1 M HCl in the absence and presence of a a 500 ppm PEIMPA -1 -1 -1 Milieu E (kJ mol ) DHa (kJ mol ) E - DHa (kJ mol ) a a 1 M HCl 26.82 24.21 2.61 500 ppm PEIMPA 49.32 46.71 2.61 Fig. 6 SEM and EDX data of C38 steel immersed in 1 M HCl solution for 24 h 123 270 Int J Ind Chem (2017) 8:263–272 Fig. 7 SEM and EDX data of C38 steel immersed in 1 M HCl? 500 ppm PEIMPA for 24 h 123 Int J Ind Chem (2017) 8:263–272 271 • SEM and EDX techniques reveal that the inhibitor E  DH  a ¼ RT : ð9Þ molecules form a good protective film on the steel surface and confirm the result obtained by gravimetric Surface examination by SEM/EDX and polarization methods. Figure 6 shows the scanning electron micrographs of C38 Open Access This article is distributed under the terms of the after immersion for 24 h in 1 M HCl solution. The speci- Creative Commons Attribution 4.0 International License (http://crea men surface in Fig. 6 appears to be roughened extensively tivecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give by the corrosive environment and the porous layer of appropriate credit to the original author(s) and the source, provide a corrosion product is present. The EDX spectra show the link to the Creative Commons license, and indicate if changes were characteristics peaks of some of the elements constituting made. of the steel sample after 24 h immersion in 1 M HCl without inhibitor, which reveals the presence of oxygen and iron, suggesting, therefore, the presence of iron oxide/ References hydroxide. 1. 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Dkhireche N, Abdelhadi R, Ebn Touhami M, Oudda H, Touir R, 40. Bentiss F, Lebrini M, Lagrenee M (2005) Thermodynamic Elbakri M, Sfaira M, Hammouti B, Senhaji O, Taouil R (2012) characterization of metal dissolution and inhibitor adsorption Elucidation of dimethyldodecylphosphonate and CTAB syner- processes in mild steel/2,5-bis(n-thienyl)-1,3,4-thiadiazoles/hy- gism on corrosion and scale inhibition of mild steel in simulated drochloric acid system. Corros Sci 47:2915–2931 cooling water system. Int J Electrochem Sci 7:5314–5330 41. Szauer T, Brandt A (1981) On the role of fatty acid in adsorption 26. Kharbach Y, Haoudi A, Skalli MK, Kandri Rodi Y, Aouniti A, and corrosion inhibition of iron by amine-fatty acid salts in acidic Hammouti B, Senhaji O, Zarrouk A (2015) The role of new solution. Electrochim Acta 26:1219–1224 phosphonate derivatives on the corrosion inhibition of mild steel 42. Laidler KJ (1963) Reaction kinetics, vol 1, 1st edn. Pergamon in 1 M H2SO4 media. 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Study of corrosion inhibition of C38 steel in 1M HCl solution by polyethyleneiminemethylene phosphonic acid

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Int J Ind Chem (2017) 8:263–272 DOI 10.1007/s40090-017-0123-2 RESEARCH Study of corrosion inhibition of C38 steel in 1 M HCl solution by polyethyleneiminemethylene phosphonic acid 1,2 1 3 1 • • • Merah Salah Larabi Lahce`ne Abderrahim Omar Harek Yahia Received: 2 April 2016 / Accepted: 24 May 2017 / Published online: 29 May 2017 The Author(s) 2017. This article is an open access publication Abstract A new class of corrosion inhibitors, namely, Introduction polyethyleneiminemethylene phosphonic acid (PEIMPA), was synthesized and its inhibiting action on the corrosion Study of organic corrosion inhibitor is an attractive field of C38 steel in 1 M HCl at 30 C was investigated by of research due to its usefulness in various industries. various corrosion monitoring techniques such as weight Acid is widely used in various industries for the pickling loss measurements, potentiodynamic polarization, linear of ferrous alloys and steels. Because of the aggressive polarization resistance (Rp), and surface analysis (SEM and nature of the acid medium, theinhibitors arecommonly EDX) which are used to characterize the steel surface. used to reduce acid attack on the substrate metal. Most Weight loss measurements revealed that the presence of of the reported corrosion inhibitors are organic com- PEIMPA increases the inhibition efficiency by decreasing pounds containing O, N, S, and P [1–14]intheir the corrosion rate. Tafel polarization study showed that the structures. The phosphoric functions are considered to be inhibitor acts as a mixed-type inhibitor. Adsorption of the most effective chemical group against corrosion PEIMPA on the carbon steel surface was found to obey the process [15]. The use of organic phosphonic acids to Langmuir isotherm. Some thermodynamic functions of protect carbon steel against corrosion has been the sub- dissolution and adsorption processes were also determined ject of various works [16–26]. Aminomethyl-phosphonic and discussed. The SEM results showed the formation of acids are excellent sequestering agents for electroplating, protective film on the mild steel surface in the presence of chemical plating, degreasing, and cleaning. It was shown PEIMPA. The results obtained from different tested tech- that piperidin-1-yl-phosphonic acids (PPA) and (4- niques were in good agreement. phosphono-piperazin-1-yl) phosphonic acid (PPPA) are used to reduce the corrosion of iron in a NaCl medium, Keywords Corrosion  Inhibition  C38 steel  Phosphonic even if PPPA is more efficient than PPA [27]. In the present investigation, the influence of poly- acid ethyleneiminemethylene phosphonic acid (PEIMPA) as a corrosion inhibitor of carbon steel in 1 M HCl has been systematically studied by weight loss measurements, potentiodynamic polarization studies, and surface anal- & Merah Salah merrah2005@yahoo.fr ysis (SEM,EDX).Results are reported and discussed. Laboratory of Analytical Chemistry and Electrochemistry, Department of Chemistry, Faculty of Science, Tlemcen Experimental University, Tlemcen, Algeria Department of Process Engineering, Faculty of Technology, Polyethyleneiminemethylene phosphonic acid polymer Sai‹ da University, Sai‹ da, Algeria was synthesized (see Scheme 1) from commercially Laboratory of Separation and Purification Technology, available Lupasol P (polyethylenimine) according to the Department of Chemistry, Faculty of Science, Tlemcen Moedrizer–Irani reaction [28]. The synthesis was University, Tlemcen, Algeria 123 264 Int J Ind Chem (2017) 8:263–272 Scheme 1 Synthesis of polyethyleneiminemethylene phosphonic acid from Lupasol P performed in distilled water under microwave irradiation. Sheets with dimensions 20 mm 9 10 mm 9 2 mm were In a quartz reactor, a mixture of polyethylenimine (Lu- used. They were polished successively with different pasol P, 80 mmol, 3.44 g), phosphorous acid (80 mmol, grades of emery paper up 1200 grade. Each run was carried 6.68 g), and hydrochloric acid–water (1:1) solution out in a glass vessel containing 100 ml test solution. A (12 mL) was vigorously stirred and then irradiated clean weight mild steel sample was completely immersed (150 W) in a glass cylinder reactor for 1 min. A at an inclined position in the vessel. After 4 h of immersion formaldehyde aqueous solution (160 mmol) was added in 1 M HCl with and without the addition of inhibitor at and irradiated for 8 min. different concentrations, the specimen was withdrawn, Then, the precipitation was washed with distilled water rinsed with double-distilled water, washed with acetone, to remove unreacted reagents. Finally, phosphonic-modi- dried, and weighed. The weight loss was used to calculate fied Lupasol P was washed three times with distilled water the corrosion rate in milligrams per square centimeter per and ethanol. After drying, the solid was further pulverized hour. to give a brown powder. Electrochemical experiments were carried out in a The structure and purity were identified and character- glass cell (CEC/TH Radiometer) with a capacity of 1 13 ized by elemental microanalysis (Table 1) and H, C, and 500 ml. A platinum electrode and a saturated calomel P NMR spectroscopy. The spectra showed the expected electrode (SCE) were used as a counter electrode and a signals due to the polyethylenimine skeleton and methy- reference electrode. The working electrode was in the lene phosphonic units as matched to the proposed structure form of a disc cut from mild steel under investigation (Scheme 1). and was embedded in a Teflon rod with an exposed area 1 2 NMR spectral data: H NMR d (ppm): 4.92 (N–CH ); of 0.5 cm . Potentiodynamic polarizations were con- 2.33 (CH –P); 1.6 NH. C NMR d (ppm): 82.16 (N–CH ), ducted in an electrochemical measurement system 2 2 52.1 (CH –P). P NMR d (ppm): 3.91. The presence of (VoltaLab 21) which comprises a PGP201 potentiostat, a phosphonic acid was confirmed by FTIR measurement: the personal computer, and VoltaMaster4 software. The polymer displays characteristic bonds for P–O–C at polarization resistance measurements were performed by -1 -1 1050 cm , P–OH at 2372, and 2338 cm 189 and P = O applying a controlled potential scan over a small range -1 at 1172 cm . typically ±15 mV with respect to Ecorr with a scanning -1 Elemental microanalysis suggests the structure made of rate of 0.5 mV s . The resulting current is linearly fragment of the phosphonic acid polymer, corresponding plotted vs. potential, the slope of this plot at Ecorr being after calculation to x = 5 and y = 9 (Scheme 1). the polarization resistance (Rp). Corrosion current den- A 1 M HCl solution was prepared from an analytical sities were determined by extrapolating the cathodic reagent grade of HCl 37% and double-distilled water and Tafel regions from the potentiodynamic polarization was used as corrosion media in the studies. Note that the curves to the corrosion potential. The potentiodynamic solubility of polyethyleneiminemethylene phosphonic acid current–potential curves were recorded by changing the is very high in this medium. electrode potential automatically from -700 to -1 For the weight loss measurements, the experiments were -300 mV with the same scanning rate (0.5 mV s ) carried out in the solution of 1 M HCl (uninhibited and under static on the same electrode without any surface inhibited) on carbon steel containing 0.30–0.35% C, treatment. All experiments were carried out in freshly 0.15–0.35% Si, 0.035% S, 0.5–1.0% Mn, and 0.035% P. prepared solution at constant temperatures. Table 1 Elemental Microanalysis %C %H %N %O %P microanalysis of polyethyleneiminemethylene Found 30.8112 7.6250 13.2519 29.3535 18.9574 phosphonic acid Calculated (x = 5, y = 9) 30.6631 6.6989 13.5359 29.8342 19.2679 123 Int J Ind Chem (2017) 8:263–272 265 Inhibition efficiencies P % were calculated as follows: Inspection of this table shows that the inhibition effi- Weight loss measurement: ciency increases with increasing inhibitor concentration. 0 The optimum concentration required to achieve this effi- w  w P% ¼  100 ð1Þ ciency is found to be 500 ppm. The inhibition of corrosion of carbon steel by the investigated inhibitor can be where w and w are the corrosion rate of steel due to the explained in terms of adsorption on the metal surface. It is dissolution in 1 M HCl in the absence and the presence of generally assumed that the adsorption of the inhibitor at the definite concentrations of inhibitor, respectively. metal/solution interface is the first step in the mechanism of Linear polarization measurement: inhibition in aggressive media. This compound can be adsorbed on the metal surface by R R P% ¼  100 ð2Þ 0 the interaction between lone pair of electrons of hetero atoms and the metal surface. This process is facilitated by where R and R are the values of linear polarization in the the presence of vacant orbitals d of low energy in iron absence and presence of the inhibitor, respectively. atom, as observed in the transition group metals. Moreover, Polarization measurement: the formation of positively charged protonated species in 0 acidic solutions facilitates the adsorption of the compound I  I corr corr P% ¼  100 ð3Þ on the metal surface through electrostatic interactions corr between the organic molecules and the metal surface [29]. where i and i are the corrosion current densities in the corr corr absence and the presence of the inhibitor, respectively. Polarization measurements For all methods, the tests were performed in non-de- aerated solutions under unstirred conditions. Figure 1 shows the polarization curves of mild steel in 1 M The surface morphology of the samples before and after HCl, blank solution, and in the presence of different con- adding PEIMPA inhibitor in the medium 1 M HCl after centrations (100–500 ppm) of PEIMPA. With the increase 1 day of immersion was observed by scanning electron of PEIMPA concentrations, both anodic and cathodic cur- microscope (SEM) Quanta 200 FEG coupled with EDX rents were inhibited. This result shows that the addition of analysis. PEIMPA inhibitor reduces anodic dissolution and also retards the hydrogen evolution reaction. We note that the corrosion potential varies slightly after the addition of the Results and discussion inhibitor at different concentrations. Table 3 shows that an increase in inhibitor concentration Weight loss measurements is resulted in increased inhibition efficiency. It is evident from the results that the I values decrease considerably corr The gravimetric measurements of mild steel in 1 M HCl in in the presence of inhibitor and that the maximum decrease the absence and presence of various concentrations of in I coincides with the optimum concentration of corr PEIMPA investigated were determined after 4 h of immersion at 30 C. Table 2 gives values of the corrosion rates and per- -2 centage inhibition efficiency calculated from the weight -3 loss measurements for different concentrations of PEIMPA. -4 1M HCL 100 ppm PEIMPA -5 Table 2 Corrosion rates and inhibition efficiencies of PEIMPA at 200 ppm PEIMPA 300 ppm PEIMPA different concentrations in 1 M HCl 400 ppm PEIMPA -6 -2 -1 500 ppm PEIMPA Conc. (ppm) V (mg cm h ) P (%) corr -7 1 M HCl 0.703 – 100 0.195 72.15 -8 200 0.120 82.93 -700 -600 -500 -400 -300 300 0.104 85.07 E vs SCE (mV) 400 0.093 86.69 Fig. 1 Polarization curves of carbon steel in 1 M HCl in the presence 500 0.069 90.11 of different concentrations of PEIMPA at 30 C -2 Logi (mA.cm ) 266 Int J Ind Chem (2017) 8:263–272 Table 3 Potentiodynamic polarization parameters for corrosion of carbon steel in 1 M HCl with various concentrations of PEIMPA at 30 C -2 2 -1 Conc. (ppm) E vs. SCE (mV) i (mA.cm ) R (X.cm ) b (mV dec ) P (i ) (%) P (R ) (%) corr corr p c corr p 1 M HCl -501 1.94 12.98 156 – – 100 -486 0.567 68.13 143 70.77 80.94 200 -512 0.359 73.54 146 81.49 82.34 300 -497 0.343 81.77 186 82.31 84.12 400 -511 0.336 99.04 134 82.68 86.89 500 -515 0.302 104.50 153 84.43 87.57 inhibitor. Linear polarization technique was performed in 1 M HCl with various concentrations of PEIMPA. The 0,00045 corresponding polarization resistance (R ) values of carbon 0,00040 steel in the absence and in the presence of different inhi- bitor concentrations are also given in Table 3. It is apparent 0,00035 that R increases with increasing inhibitor concentration. 0,00030 The inhibition percentage (P %) calculated from R values is also presented in Table 3. We remark that P % increases 0,00025 with increasing concentration of inhibitor and attains 87% 0,00020 at 500 ppm. The inhibition efficiencies of PEIMPA 0,00015 obtained by potentiodynamic polarization and by polar- ization resistance methods are in good agreement, partic- 0,00010 ularly, at high concentrations. 0,00005 For anodic polarization, it can be seen from Fig. 1 that, 0,00005 0,00010 0,00015 0,00020 0,00025 0,00030 0,00035 in the presence of PEIMPA at all concentrations, two linear C (mol/L) inh. portions were observed. When the anodic potentials increases, the anodic current increases at a slope of b in Fig. 2 Langmuir adsorption isotherm of PEIMPA on the carbon steel a1 surface in 1 M HCl from potentiodynamic measurements the low polarization potential region. After passing a cer- tain potential E , the anodic current increases rapidly and dissolves at a slope of b in the high polarization region. a2 The adsorption isotherm can give information on the This behavior was already documented for iron in acid metal–inhibitor interaction. The adsorption isotherm can be solutions [30–33]. The rapid increase of anodic current derived from the curve surface coverage against inhibitor after E may be due to the desorption of PEIMPA mole- concentration. Surface coverage h was estimated as in cules adsorbed on the electrode. This means that the inhi- Eq. 5. The h values for different inhibitor concentrations bition mode of PEIMPA depends on electrode potential. In are tested by fitting to various isotherms. So far, the best fit this case, the observed inhibition phenomenon is generally was obtained with the Langmuir isotherm. According to described as corrosion inhibition of the interface associated this isotherm, h is related to concentration inhibitor C via with the formation of a bidimensional layer of adsorbed C 1 inhibitor species at the electrode surface [34]. Note that the ¼ þ C ð4Þ h K potential E is also denoted E in Bartos and Hackerman’s u 1 where C is the concentration of inhibitor, K is the paper [30]. Figure 1 shows also that, at potentials higher than E , PEIMPA affects the anodic reaction. This result adsorptive equilibrium constant, and h is the surface cov- corr erage and calculated by the following equation [6, 35, 36]: indicates that PEIMPA exhibits both anodic and cathodic inhibition effects. corr h ¼ 1  ð5Þ corr Adsorption isotherm where I is the corrosion current density in uninhibited corr acid and I is the corrosion current density in inhibited The adsorption of the organic compounds can be described corr acid. by two main types of interaction: physical adsorption and Plotting C/h vs. C yields a straight line, as shown in chemisorption that are influenced by the charge nature of Fig. 2. The linear correlation coefficient (r) is almost equal the metal, the type of the electrolyte, and the chemical to 1 (r = 0.9999) and the slight deviation of the slope structure of the inhibitor. C/Θ (mol/L) Int J Ind Chem (2017) 8:263–272 267 -1 a transfer from the inhibitor molecules to the metal surface (a) to form a coordinate type of bond (chemisorption). In the -2 present study, the value of DG is about between -20 ads -1 and -40 kJ mol , probably mean that the adsorption -3 mechanism of the PEIMPA on steel in 1 M HCl solution is both physisorption and chemisorption. HCl 20°C -4 HCl 30°C Noticeably, it is generally accepted that physical HCl 40°C adsorption is the preceding stage of chemisorption of HCl 50°C inhibitors on metal surface [38]. It was reported that in this -5 domaine, the surface charge of steel at E in HCl solution corr is expected to be positive. Thus, the anions are first -6 adsorbed on the steel surface creating an excess negative charge, which, in turn, facilitates physical adsorption of the -7 -750 -700 -650 -600 -550 -500 -450 -400 -350 -300 inhibitor cations [39]. Accordingly, the Cl and phospho- E v SCE (mV) nate ions adsorb and the surface becomes negatively charged. Due to the electrostatic attraction, the protonated (b) -2 PEIMPA molecules are adsorbed on carbon steel surface (physisorption). -3 Along with electrostatic force of attraction, inhibitor also adsorbs on the carbon steel surface through chemical -4 adsorption. The adsorption of free molecules could take PEIMPA 20°C PEIMPA 30°C place via interaction of the unshared pairs of electrons of -5 PEIMPA 40°C nitrogen and oxygen atoms of the –PO(OH) group and the PEIMPA 50°C -6 vacant d-orbitals of iron atoms. Therefore, inhibition takes place through both -7 physisorption and chemisorption. However, chemisorption has no substantial contribution [12]. Indeed, the PEIMPA -8 molecules are easily protonated to form ionic forms in acid -700 -600 -500 -400 -300 -200 solution. It is logical to assume that in this case, the elec- E v SCE (mV) trostatic cation adsorption is mainly responsible for the protective properties of this compound. Fig. 3 Polarization curves for C38 steel electrode in 1 M HCl (a) and in HCl? 500 ppm of PEIMPA (b) at different temperatures Effect of temperature (1.14) from the unity is attributable to molecular interac- To investigate the mechanism of inhibition and to deter- tions in the adsorbed layer which corresponds to the mine the activation energy of the corrosion process, observed physical adsorption mechanism [37]. The polarization curves of steel in 1 M HCl were determined at adsorptive equilibrium constant (K) value is 6.22 9 10 - -1 various temperatures (303–333 K) in the absence and L mol . The free energy of adsorption DG of the ads presence of 500 ppm of PEIMPA. Representative Tafel inhibitor on mild steel surface can be determined using the polarization curves for C38 steel electrode in 1 M HCl following relation: without and with 500 ppm at different temperatures are 1 DG ads shown in Fig. 3a, b. Similar polarization curves were K ¼ exp ð6Þ 55:5 RT obtained in the case of the other concentrations of PEIMPA -1 -1 (not given). The analysis of these figures reveals that where R is the gas constant (8.314 J K mol ), T is the raising the temperature increases both anodic and cathodic absolute temperature (K), and the value 55.5 is the con- current densities, and consequently, the corrosion rate of centration of water in solution expressed in M.The DG ads -1 C38 steel increases. The corresponding data are given in value calculated is -37.90 kJ mol . The negative values Table 4. In the studied temperature range (303–333 K), the of DG indicate that the adsorption of inhibitor molecule ads corrosion current density increases with increasing tem- onto steel surface is a spontaneous process. In general, it is perature both in uninhibited and inhibited solutions and the well known that the values of -DG of the order of ads -1 values of the inhibition efficiency of PEIMPA decrease -20 kJ mol or lower indicate a physisorption; those of -1 with the increase of temperature. order of -40 kJ mol or higher involve charge sharing or -2 -2 Log I (mA cm ) Log i (mA.cm ) corr corr 268 Int J Ind Chem (2017) 8:263–272 Table 4 Electrochemical Milieu T/(C) E /(mVvSCE) i /(mA/cm ) b /(mV/dec) P/(%) corr corr c parameters and the corresponding inhibition 1 M HCl 20 -466 1.46 198 – efficiencies for the corrosion of 30 -501 1.94 156 – C38 in 1 M HCl and 500 ppm PEIMPA at various 40 -459 2.83 193 – temperatures 50 -457 4.01 196 – 500 ppm PEIMPA 20 -462 0.160 180 89.04 30 -515 0.302 134 84.34 40 -486 0.562 175 80.15 50 -485 1.052 188 73.81 Figure 4 and 5 present the Arrhenius plots of the natural -4,4 logarithm of the current density vs. 1/T, for 1 M solution of -4,8 hydrochloride acid, without and with the addition of -5,2 PEIMPA and ln(i /T) with reciprocal of the absolute corr temperature, respectively. Straight lines with coefficients -5,6 1M HCl of correlation (c.c.) high to 0.99 are obtained for the sup- 500 ppm PEIMPA -6,0 porting electrolyte and PEIMPA. -6,4 The values of the slopes of these straight lines permit the calculation of the Arrhenius activation energy, E , -6,8 according to -7,2 lnI ¼ þ lnA ð7Þ -7,6 corr RT 0,00305 0,00310 0,00315 0,00320 0,00325 0,00330 0,00335 0,00340 0,00345 -1 where R is the universal gas constant and A is the Arrhe- 1/T (K ) nius factor. Fig. 5 ln(i /T) vs. 1/T for C38 steel dissolution in 1 M HCl in the corr In addition, from transition-state plot according to the presence of PEIMPA at 500 ppm following equation: I DH corr ln ¼ þ B ð8Þ in the absence and the presence of PEIMPA at 500 ppm are T RT given in Table 5. Inspection of these data reveals that the where DH is the enthalpy of activation and B is a increase in E in the presence of the inhibitor may be constant. interpreted as physical adsorption. Indeed, a higher energy The E and DHa values were determined from the barrier for the corrosion process in the inhibited solution is slopes of these plots. The calculated values of E and DH a a associated with physical adsorption or weak chemical bonding between the inhibitor species and the steel surface 0,6 [22, 40]. Szauer and Brand explained that the increase in 1M HCl 500 ppm PEIMPA activation energy can be attributed to an appreciable 0,4 decrease in the adsorption of the inhibitor on the carbon 0,2 steel surface with the increase in temperature. A corre- sponding increase in the corrosion rate occurs because of 0,0 the greater area of metal that is consequently exposed to -0,2 the acid environment [41]. The enthalpy of activation values is found to be positive -0,4 in the absence and presence of inhibitor and reflects the endothermic mild steel dissolution process. It is evident -0,6 from Table 5 that the value of DH increased in the -0,8 presence of PEIMPA than the uninhibited solution indi- 3,05 3,10 3,15 3,20 3,25 3,30 3,35 3,40 3,45 cating protection efficiency. This suggested the slow dis- 3 -1 1/Tx 10 (K ) solution and hence lower corrosion rate of mild steel [2, 7]. This result permits verifying the known thermodynamic Fig. 4 Arrhenius plots of log icorr vs. 1/T without and with 500 ppm equation between E and DH [42]: a a of PEIMPA -2 logi (mA.cm ) corr -2 -1 ln(I /T) (mA cm K ) corr Int J Ind Chem (2017) 8:263–272 269 Table 5 Apparent activation energy E and activation enthalpy DH of dissolution of C38 steel in 1 M HCl in the absence and presence of a a 500 ppm PEIMPA -1 -1 -1 Milieu E (kJ mol ) DHa (kJ mol ) E - DHa (kJ mol ) a a 1 M HCl 26.82 24.21 2.61 500 ppm PEIMPA 49.32 46.71 2.61 Fig. 6 SEM and EDX data of C38 steel immersed in 1 M HCl solution for 24 h 123 270 Int J Ind Chem (2017) 8:263–272 Fig. 7 SEM and EDX data of C38 steel immersed in 1 M HCl? 500 ppm PEIMPA for 24 h 123 Int J Ind Chem (2017) 8:263–272 271 • SEM and EDX techniques reveal that the inhibitor E  DH  a ¼ RT : ð9Þ molecules form a good protective film on the steel surface and confirm the result obtained by gravimetric Surface examination by SEM/EDX and polarization methods. Figure 6 shows the scanning electron micrographs of C38 Open Access This article is distributed under the terms of the after immersion for 24 h in 1 M HCl solution. The speci- Creative Commons Attribution 4.0 International License (http://crea men surface in Fig. 6 appears to be roughened extensively tivecommons.org/licenses/by/4.0/), which permits unrestricted use, distribution, and reproduction in any medium, provided you give by the corrosive environment and the porous layer of appropriate credit to the original author(s) and the source, provide a corrosion product is present. The EDX spectra show the link to the Creative Commons license, and indicate if changes were characteristics peaks of some of the elements constituting made. of the steel sample after 24 h immersion in 1 M HCl without inhibitor, which reveals the presence of oxygen and iron, suggesting, therefore, the presence of iron oxide/ References hydroxide. 1. Larabi L, Harek Y, Benali O, Ghalem S (2005) Hydrazide When PEIMPA was added into the corrosion test solu- derivatives as corrosion inhibitors for mild steel in 1 M HCl. tion (Fig. 7), a smooth surface was noticed traducing a Prog Org Coat 54:256–262 good protection effect of the corrosion inhibitor by a for- 2. Benali O, Larabi L, Tabti B, Harek Y (2005) Influence of mation of a thick and compact film. This may be inter- 1-methyl 2-mercapto imidazole on corrosion inhibition of carbon steel in 0.5 M H SO . Anti Corros Method Mater 52:280–285 cepted by the adsorption of these inhibitors on the electrode 2 4 3. Benali O, Larabi L, Mekelleche SMB, Harek Y (2006) Influence surface. of substitution of phenyl group by naphthyl in a diphenylthiourea In the presence of PEIMPA inhibitor, the EDX spectra molecule on corrosion inhibition of cold-rolled steel in 0.5 M show additional lines of nitrogen and phosphorus, due to H SO . J Mat Sci 41:7064–7073 2 4 4. 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Journal

International Journal of Industrial ChemistrySpringer Journals

Published: May 29, 2017

References