Corrosion inhibition of carbon steel in hydrochloric acid by cationic arylthiophenes as new eco-friendly inhibitors: Experimental and quantum chemical study

doi:10.1016/j.cjche.2020.09.073

Abstract

Abstract: This study describes the adsorption behavior of three arylthiophene derivatives namely: 2-(4-amidino-3-fluorophenyl)-5-[4-methoxy phenyl] thiophene dihydrochloride salt (MA-1217), 2-(4-amidinophenyl)-5-[4-chlorophenyl] thiophene dihydrochloride salt (MA-1316) and 2-(4-amidino-3-fluorophenyl)-5-[4-chlorophenyl]thiophene dihydrochloride salt (MA-1312) at C-steel in 1.0 mol·L^-1 HCl interface using experimental and theoretical studies. Electrochemical and mass loss measurements showed that the inhibition efficiency (IE) of the arylthiophene derivatives increases with increasing concentrations and exhibited maximum efficiency 89% at 21×10^-6 mol·L^-1 (MA-1217) by mass loss method. The investigated arylthiophene derivatives obey the Langmuir adsorption isotherm. From polarization studies the arylthiophene derivatives act as mixed-type inhibitors. Surface analysis were carried out and discussed. The mode of orientation and adsorption of inhibitor molecules on C-steel surface was studied using molecular dynamics (MD) simulations. Quantum chemical parameters as well as the radial distribution function indices and binding energies confirm the experimental results.

Key words: Carbon steel, Corrosion inhibition, Adsorption, Arylthiophene derivatives, Polarization, Electrochemical frequency modulation

摘要： This study describes the adsorption behavior of three arylthiophene derivatives namely: 2-(4-amidino-3-fluorophenyl)-5-[4-methoxy phenyl] thiophene dihydrochloride salt (MA-1217), 2-(4-amidinophenyl)-5-[4-chlorophenyl] thiophene dihydrochloride salt (MA-1316) and 2-(4-amidino-3-fluorophenyl)-5-[4-chlorophenyl]thiophene dihydrochloride salt (MA-1312) at C-steel in 1.0 mol·L^-1 HCl interface using experimental and theoretical studies. Electrochemical and mass loss measurements showed that the inhibition efficiency (IE) of the arylthiophene derivatives increases with increasing concentrations and exhibited maximum efficiency 89% at 21×10^-6 mol·L^-1 (MA-1217) by mass loss method. The investigated arylthiophene derivatives obey the Langmuir adsorption isotherm. From polarization studies the arylthiophene derivatives act as mixed-type inhibitors. Surface analysis were carried out and discussed. The mode of orientation and adsorption of inhibitor molecules on C-steel surface was studied using molecular dynamics (MD) simulations. Quantum chemical parameters as well as the radial distribution function indices and binding energies confirm the experimental results.

关键词: Carbon steel, Corrosion inhibition, Adsorption, Arylthiophene derivatives, Polarization, Electrochemical frequency modulation

Abd El-Aziz S. Fouda, Mohamed A. Ismail, Abdulraqeb A. Al-Khamri, Ashraf S. Abousalem. Corrosion inhibition of carbon steel in hydrochloric acid by cationic arylthiophenes as new eco-friendly inhibitors: Experimental and quantum chemical study[J]. Chinese Journal of Chemical Engineering, 2021, 40(12): 197-217.

References

[1] C. Verma, M.A. Quraishi, E.E. Ebenso, I. Bahadur, A green and sustainable approach for mild steel acidic corrosion inhibition using leaves extract: experimental and DFT studies, J. Bio - Tribo - Corros. 4 (3) (2018) 33
[2] I.B. Obot, S.A. Umoren, N.K. Ankah, Pyrazine derivatives as green oil field corrosion inhibitors for steel, J. Mol. Liq. 277 (2019) 749–761
[3] F. El Hajjaji, R. Salim, M. Messali, B. Hammouti, D.S. Chauhan, S.M. Almutairi, M.A. Quraishi, Electrochemical studies on new pyridazinium derivatives as corrosion inhibitors of carbon steel in acidic medium, J. Bio - Tribo - Corros. 5 (1) (2018) 4
[4] R. Solmaz, Investigation of adsorption and corrosion inhibition of mild steel in hydrochloric acid solution by 5-(4-Dimethylaminobenzylidene)rhodanine, Corros. Sci. 79 (2014) 169–176
[5] A.M. Eldesoky, S.G. Nozha, The adsorption and corrosion inhibition of 8-hydroxy-7-quinolinecarboxaldehyde derivatives on C-steel surface in hydrochloric acid, Chin. J. Chem. Eng. 25 (9) (2017) 1256–1265
[6] A.S. Fouda, Department of Chemistry Faculty of Science El Mansoura University El Mansoura Egypt, Evaluation of some organic compounds containing O, N and S atoms as corrosion inhibitors for stainless steel 304 in acid solutions, Int. J. Electrochem. Sci. (2017) 5072–5091
[7] M. Bouanis, M. Tourabi, A. Nyassi, A. Zarrouk, C. Jama, F. Bentiss, Corrosion inhibition performance of 2, 5-bis(4-dimethylaminophenyl)-1, 3, 4-oxadiazole for carbon steel in HCl solution: Gravimetric, electrochemical and XPS studies, Appl. Surf. Sci. 389 (2016) 952–966
[8] R. Kumar, O.S. Yadav, G. Singh, Electrochemical and surface characterization of a new eco-friendly corrosion inhibitor for mild steel in acidic media: A cumulative study, J. Mol. Liq. 237 (2017) 413–427
[9] S.Y. Cao, D. Liu, H. Ding, J.H. Wang, H. Lu, J.Z. Gui, Corrosion inhibition effects of a novel ionic liquid with and without potassium iodide for carbon steel in 0.5?M HCl solution: an experimental study and theoretical calculation, J. Mol. Liq. 275 (2019) 729–740
[10] A.E. Elkholy, F. El-Taib Heakal, Electrochemical measurements and semi-empirical calculations for understanding adsorption of novel cationic Gemini surfactant on carbon steel in H₂SO₄ solution, J. Mol. Struct. 1156 (2018) 473–482
[11] L. Guo, I.B. Obot, X.W. Zheng, X. Shen, Y.J. Qiang, S. Kaya, C. Kaya, Theoretical insight into an empirical rule about organic corrosion inhibitors containing nitrogen, oxygen, and sulfur atoms, Appl. Surf. Sci. 406 (2017) 301–306
[12] D. Daoud, T. Douadi, S. Issaadi, S. Chafaa, Adsorption and corrosion inhibition of new synthesized thiophene Schiff base on mild steel X52 in HCl and H₂SO₄ solutions, Corros. Sci. 79 (2014) 50–58
[13] A. Ongun Yüce, B. Doğru Mert, G. Kardaş, B. Yazıcı, Electrochemical and quantum chemical studies of 2-amino-4-methyl-thiazole as corrosion inhibitor for mild steel in HCl solution, Corros. Sci. 83 (2014) 310–316
[14] A. Dutta, S.K. Saha, U. Adhikari, P. Banerjee, D. Sukul, Effect of substitution on corrosion inhibition properties of 2-(substituted phenyl) benzimidazole derivatives on mild steel in 1 M HCl solution: a combined experimental and theoretical approach, Corros. Sci. 123 (2017) 256–266
[15] N. Yilmaz, A. Fitoz, ?. Ergun, K.C. Emregül, A combined electrochemical and theoretical study into the effect of 2-((thiazole-2-ylimino)methyl)phenol as a corrosion inhibitor for mild steel in a highly acidic environment, Corros. Sci. 111 (2016) 110–120
[16] S. Kaya, C. Kaya, L. Guo, F. Kandemirli, B. Tüzün, İ. Uğurlu, L.H. Madkour, M. Saraçoğlu, Quantum chemical and molecular dynamics simulation studies on inhibition performances of some thiazole and thiadiazole derivatives against corrosion of iron, J. Mol. Liq. 219 (2016) 497–504
[17] J. Aljourani, M.A. Golozar, K. Raeissi, The inhibition of carbon steel corrosion in hydrochloric and sulfuric acid media using some benzimidazole derivatives, Mater. Chem. Phys. 121 (1–2) (2010) 320–325
[18] A. Bousskri, A. Anejjar, M. Messali, R. Salghi, O. Benali, Y. Karzazi, S. Jodeh, M. Zougagh, E.E. Ebenso, B. Hammouti, Corrosion inhibition of carbon steel in aggressive acidic media with 1-(2-(4-chlorophenyl)-2-oxoethyl)pyridazinium bromide, J. Mol. Liq. 211 (2015) 1000–1008
[19] A. Zarrouk, H. Zarrok, Y. Ramli, M. Bouachrine, B. Hammouti, A. Sahibed-Dine, F. Bentiss, Inhibitive properties, adsorption and theoretical study of 3, 7-dimethyl-1-(prop-2-yn-1-yl)quinoxalin-2(1H)-one as efficient corrosion inhibitor for carbon steel in hydrochloric acid solution, J. Mol. Liq. 222 (2016) 239–252
[20] A. Kosari, M.H. Moayed, A. Davoodi, R. Parvizi, M. Momeni, H. Eshghi, H. Moradi, Electrochemical and quantum chemical assessment of two organic compounds from pyridine derivatives as corrosion inhibitors for mild steel in HCl solution under stagnant condition and hydrodynamic flow, Corros. Sci. 78 (2014) 138–150
[21] H. Jafari, K. Akbarzade, Effect of concentration and temperature on carbon steel corrosion inhibition, J. Bio - Tribo - Corros. 3 (1) (2016) 8
[22] M.E. Ikpi, F.E. Abeng, Theoretical study on the structural effect of benzoxazin derivative as corrosion inhibitor for carbon steel in acid media, Chem. Sci. Trans. 6 (2017) 569–576
[23] M.A. Ismail, M.M. Youssef, R.K. Arafa, S.S. Al-Shihry, W.M. El-Sayed, Synthesis and antiproliferative activity of monocationic arylthiophene derivatives, Eur J Med Chem 126 (2017) 789–798
[24] C. Verma, L.O. Olasunkanmi, I. Bahadur, H. Lgaz, M.A. Quraishi, J. Haque, E.S.M. Sherif, E.E. Ebenso, Experimental, density functional theory and molecular dynamics supported adsorption behavior of environmental benign imidazolium based ionic liquids on mild steel surface in acidic medium, J. Mol. Liq. 273 (2019) 1–15
[25] A.S. Fouda, M.A. Ismail, G.Y. El-Ewady, A.S. Abousalem, Evaluation of 4-amidinophenyl-2, 2'-bithiophene and its aza-analogue as novel corrosion inhibitors for CS in acidic media: Experimental and theoretical study, J. Mol. Liq. 240 (2017) 372–388
[26] A.S. Fouda, M.A. Ismail, A.M. Temraz, A.S. Abousalem, Comprehensive investigations on the action of cationic terthiophene and bithiophene as corrosion inhibitors: experimental and theoretical studies, New J. Chem. 43 (2) (2019) 768–789
[27] A.S. Abousalem, M.A. Ismail, A.S. Fouda, A complementary experimental and in silico studies on the action of fluorophenyl-2, 2'-bichalcophenes as ecofriendly corrosion inhibitors and biocide agents, J. Mol. Liq. 276 (2019) 255–274
[28] G. Karthik, M. Sundaravadivelu, Studies on the inhibition of mild steel corrosion in hydrochloric acid solution by atenolol drug, Egypt. J. Petroleum 25 (2) (2016) 183–191
[29] JMES
[30] A.S. Fouda, A.S. Abousalem, G.Y. El-Ewady, Mitigation of corrosion of carbon steel in acidic solutions using an aqueous extract of Tilia cordata as green corrosion inhibitor, Int. J. Ind. Chem. 8 (1) (2017) 61–73
[31] A.S. Fouda, G. El-Ewady, A.H. Ali, Modazar as promising corrosion inhibitor of carbon steel in hydrochloric acid solution, Green Chem. Lett. Rev. 10 (2) (2017) 88–100
[32] M. Mobin, S. Zehra, M. Parveen, L-Cysteine as corrosion inhibitor for mild steel in 1 M HCl and synergistic effect of anionic, cationic and non-ionic surfactants, J. Mol. Liq. 216 (2016) 598–607
[33] R.S. Nathiya, S. Perumal, V. Murugesan, P.M. Anbarasan, V. Raj, Agarose as an efficient inhibitor for aluminium corrosion in acidic medium: An experimental and theoretical study, J. Bio - Tribo - Corros. 3 (4) (2017) 1–17
[34] Z.P. Sun, A. Singh, X.H. Xu, S.S. Chen, W.Y. Liu, Y.H. Lin, Inhibition effect of pomelo peel extract for N80 steel in 3.5% NaCl saturated with CO₂ solution, Res. Chem. Intermed. 43 (11) (2017) 6719–6736
[35] A. Salhi, S. Tighadouini, M. El-Massaoudi, M. Elbelghiti, A. Bouyanzer, S. Radi, S. El Barkany, F. Bentiss, A. Zarrouk, Keto-enol heterocycles as new compounds of corrosion inhibitors for carbon steel in 1 M HCl: Weight loss, electrochemical and quantum chemical investigation, J. Mol. Liq. 248 (2017) 340–349
[36] M. Yadav, T.K. Sarkar, I.B. Obot, WITHDRAWN: Indolines as novel corrosion inhibitors: Electrochemical, XPS, DFT and molecular dynamics simulation studies, Corros. Sci. (2017)?
[37] M. Yadav, R.R. Sinha, T.K. Sarkar, I. Bahadur, E.E. Ebenso, Application of new isonicotinamides as a corrosion inhibitor on mild steel in acidic medium: Electrochemical, SEM, EDX, AFM and DFT investigations, J. Mol. Liq. 212 (2015) 686–698
[38] P. Singh, A.K. Singh, V.P. Singh, Synthesis, structural and corrosion inhibition properties of some transition metal(II) complexes with o-hydroxyacetophenone-2-thiophenoyl hydrazone, Polyhedron 65 (2013) 73–81
[39] S.A. Umoren, E.I. Inam, A.A. Udoidiong, I.B. Obot, U.M. Eduok, K.W. Kim, Humic acid from livestock dung: Ecofriendly corrosion inhibitor for 3SR aluminum alloy in alkaline medium, Chem. Eng. Commun. 202 (2) (2015) 206–216
[40] A. Ostovari, S.M. Hoseinieh, M. Peikari, S.R. Shadizadeh, S.J. Hashemi, Corrosion inhibition of mild steel in 1 M HCl solution by henna extract: a comparative study of the inhibition by henna and its constituents (Lawsone, Gallic acid, α-d-Glucose and Tannic acid), Corros. Sci. 51 (9) (2009) 1935–1949
[41] A.S. Fouda, H. Megahed, D.M. Ead, Lanthanides as environmentally friendly corrosion inhibitors of iron in 3.5% NaCl solution, Desalination Water Treat. 51 (16–18) (2013) 3164–3178
[42] F. El-Taib Heakal, M.A. Deyab, M.M. Osman, A.E. Elkholy, Performance of Centaurea cyanus aqueous extract towards corrosion mitigation of carbon steel in saline formation water, Desalination 425 (2018) 111–122
[43] D.Q. Zhang, Y.M. Tang, S.J. Qi, D.W. Dong, H. Cang, G. Lu, The inhibition performance of long-chain alkyl-substituted benzimidazole derivatives for corrosion of mild steel in HCl, Corros. Sci. 102 (2016) 517–522
[44] A. Titi, N. Mechbal, A. El Guerraf, M. El Azzouzi, R. Touzani, B. Hammouti, I.M. Chung, H. Lgaz, Experimental and theoretical studies on inhibition of carbon steel corrosion by 1, 5-diaminonaphthalene, J. Bio - Tribo - Corros. 4 (2) (2018) 1–10
[45] D. Daoud, T. Douadi, H. Hamani, S. Chafaa, M. Al-Noaimi, Corrosion inhibition of mild steel by two new S-heterocyclic compounds in 1 M HCl: Experimental and computational study, Corros. Sci. 94 (2015) 21–37
[46] P. Kumar, V. Kalia, H. Kumar, H. Dahiya, Corrosion inhibition for mild steel in acidic medium by using hexadecylamine as corrosion inhibitor, Chem. Sci. Trans. 6 (2017) 497–512
[47] M.N. El-Haddad, A.S. Fouda, H.A. Mostafa, Corrosion inhibition of carbon steel by new thiophene azo dye derivatives in acidic solution, J. Mater. Eng. Perform. 22 (8) (2013) 2277–2287
[48] A.K. Singh, M.A. Quraishi, The effect of some bis-thiadiazole derivatives on the corrosion of mild steel in hydrochloric acid, Corros. Sci. 52 (4) (2010) 1373–1385
[49] M.J. Bahrami, S.M.A. Hosseini, P. Pilvar, Experimental and theoretical investigation of organic compounds as inhibitors for mild steel corrosion in sulfuric acid medium, Corros. Sci. 52 (9) (2010) 2793–2803
[50] M. Jokar, T.S. Farahani, B. Ramezanzadeh, Electrochemical and surface characterizations of morus alba pendula leaves extract (MAPLE) as a green corrosion inhibitor for steel in 1 M HCl, J. Taiwan Inst. Chem. Eng. 63 (2016) 436–452
[51] E.A. Flores, O. Olivares, N.V. Likhanova, M.A. Domínguez-Aguilar, N. Nava, D. Guzman-Lucero, M. Corrales, Sodium phthalamates as corrosion inhibitors for carbon steel in aqueous hydrochloric acid solution, Corros. Sci. 53 (12) (2011) 3899–3913
[52] A. Zarrouk, B. Hammouti, H. Zarrok, S.S. Al-Deyab, I. Warad, Thermodynamic study of metal corrosion and inhibitor adsorption processes in copper/N-1-naphthylethylenediamine dihydrochloride monomethanolate/nitric acid system: part 2, Res. Chem. Intermed. 38 (7) (2012) 1655–1668
[53] H.B. Ouici, O. Benali, Y. Harek, L. Larabi, B. Hammouti, A. Guendouzi, Inhibition of mild steel corrosion in 5 HCl solution by 5-(2-hydroxyphenyl)-1, 2, 4-triazole-3-thione, Res. Chem. Intermed. 39 (6) (2013) 2777–2793
[54] Sudheer, M.A. Quraishi, Thermodynamic and electrochemical investigation of pantoprazole: (rs)-6-(difluoromethoxy)-2- [(3, 4-dimethoxypyridin-2-yl)methylsulfinyl]-1H-benzo[d]-imidazole} as corrosion inhibitor for mild steel in hydrochloric acid solution, Arab. J. Sci. Eng. 38 (1) (2013) 99–109
[55] M. Yadav, D. Behera, S. Kumar, P. Yadav, Experimental and quantum chemical studies on corrosion inhibition performance of thiazolidinedione derivatives for mild steel in hydrochloric acid solution, Chem. Eng. Commun. 202 (3) (2015) 303–315
[56] M. ElBelghiti, Y. Karzazi, A. Dafali, B. Hammouti, F. Bentiss, I.B. Obot, I. Bahadur, E.E. Ebenso, Experimental, quantum chemical and Monte Carlo simulation studies of 3, 5-disubstituted-4-amino-1, 2, 4-triazoles as corrosion inhibitors on mild steel in acidic medium, J. Mol. Liq. 218 (2016) 281–293
[57] N. El Hamdani, R. Fdil, M. Tourabi, C. Jama, F. Bentiss, Alkaloids extract of Retama monosperma (L.) Boiss. seeds used as novel eco-friendly inhibitor for carbon steel corrosion in 1 M HCl solution: Electrochemical and surface studies, Appl. Surf. Sci. 357 (2015) 1294–1305
[58] A.K. Singh, M.A. Quraishi, Investigation of the effect of disulfiram on corrosion of mild steel in hydrochloric acid solution, Corros. Sci. 53 (4) (2011) 1288–1297
[59] V.V. Torres, V.A. Rayol, M. Magalhães, G.M. Viana, L.C.S. Aguiar, S.P. Machado, H. Orofino, E. D’Elia, Study of thioureas derivatives synthesized from a green route as corrosion inhibitors for mild steel in HCl solution, Corros. Sci. 79 (2014) 108–118
[60] G. Sığırcık, D. Yildirim, T. Tüken, Synthesis and inhibitory effect of N, N'-bis(1-phenylethanol)ethylenediamine against steel corrosion in HCl Media, Corros. Sci. 120 (2017) 184–193
[61] P. Muthukrishnan, B. Jeyaprabha, P. Prakash, Mild steel corrosion inhibition by aqueous extract of Hyptis Suaveolens leaves, Int. J. Ind. Chem. 5 (1) (2014) 5
[62] M.A. Amin, S.S.A. Ei-Rehim, E.E.F. El-Sherbini, O.A. Hazzazi, M.N. Abbas, Polyacrylic acid as a corrosion inhibitor for aluminium in weakly alkaline solutions. Part I: Weight loss, polarization, impedance EFM and EDX studies, Corros. Sci. 51 (3) (2009) 658–667
[63] E. Ituen, O. Akaranta, A. de James, S.Q. Sun, Green and sustainable local biomaterials for oilfield chemicals: Griffonia simplicifolia extract as steel corrosion inhibitor in hydrochloric acid, Sustain. Mater. Technol. 11 (2017) 12–18
[64] K. Shalabi, Y.M. Abdallah, A.S. Fouda, Corrosion inhibition of aluminum in 0.5 M HCl solutions containing phenyl sulfonylacetophenoneazo derivatives, Res. Chem. Intermed. 41 (7) (2015) 4687–4711
[65] Q. Ma, S.J. Qi, X.H. He, Y.M. Tang, G. Lu, 1, 2, 3-Triazole derivatives as corrosion inhibitors for mild steel in acidic medium: Experimental and computational chemistry studies, Corros. Sci. 129 (2017) 91–101
[66] A.O. Yüce, G. Kardaş, Adsorption and inhibition effect of 2-thiohydantoin on mild steel corrosion in 0.1 M HCl, Corros. Sci. 58 (2012) 86–94
[67] R. Solmaz, Investigation of corrosion inhibition mechanism and stability of Vitamin B1 on mild steel in 0.5 M HCl solution, Corros. Sci. 81 (2014) 75–84
[68] M.P. Chakravarthy, K.N. Mohana, C.B. Pradeep Kumar, Corrosion inhibition effect and adsorption behaviour of nicotinamide derivatives on mild steel in hydrochloric acid solution, Int. J. Ind. Chem. 5 (2) (2014) 19
[69] M. Mobin, M. Rizvi, Polysaccharide from Plantago as a green corrosion inhibitor for carbon steel in 1 M HCl solution, Carbohydr. Polym. 160 (2017) 172–183
[70] P. Bhaganna, R.J. Volkers, A.N. Bell, K. Kluge, D.J. Timson, J.W. McGrath, H.J. Ruijssenaars, J.E. Hallsworth, Hydrophobic substances induce water stress in microbial cells, Microb Biotechnol 3 (6) (2010) 701–716
[71] J.A. Cray, A. Stevenson, P. Ball, S.B. Bankar, E.C. Eleutherio, T.C. Ezeji, R.S. Singhal, J.M. Thevelein, D.J. Timson, J.E. Hallsworth, Chaotropicity: A key factor in product tolerance of biofuel-producing microorganisms, Curr Opin Biotechnol 33 (2015) 228–259
[72] I.G. Dougall, J. Unitt, Evaluation of the biological activity of compounds. The Practice of Medicinal Chemistry. Amsterdam: Elsevier, 2015: 15–43
[73] Z.Y. Hu, Y.B. Meng, X.M. Ma, H.L. Zhu, J. Li, C. Li, D.L. Cao, Experimental and theoretical studies of benzothiazole derivatives as corrosion inhibitors for carbon steel in 1 M HCl, Corros. Sci. 112 (2016) 563–575
[74] A.S. Fouda, M.A. Ismail, A.A. Al-Khamri, A.S. Abousalem, Experimental, quantum chemical and molecular simulation studies on the action of arylthiophene derivatives as acid corrosion inhibitors, J. Mol. Liq. 290 (2019) 111178
[75] L.O. Olasunkanmi, I.B. Obot, E.E. Ebenso, Adsorption and corrosion inhibition properties of N-{n-[1-R-5-(quinoxalin-6-yl)-4, 5-dihydropyrazol-3-yl]phenyl}methanesulfonamides on mild steel in 1 M HCl: experimental and theoretical studies, RSC Adv. 6 (90) (2016) 86782–86797
[76] M. El Faydy, R. Touir, M. Ebn Touhami, A. Zarrouk, C. Jama, B. Lakhrissi, L.O. Olasunkanmi, E.E. Ebenso, F. Bentiss, Corrosion inhibition performance of newly synthesized 5-alkoxymethyl-8-hydroxyquinoline derivatives for carbon steel in 1 M HCl solution: Experimental, DFT and Monte Carlo simulation studies, Phys Chem Chem Phys 20 (30) (2018) 20167–20187