Chromeno-carbonitriles as corrosion inhibitors for mild steel in acidic solution: electrochemical, surface and computational studies

Taiwo W Quadri; Lukman O Olasunkanmi; Ekemini D Akpan; Akram Alfantazi; I B Obot; Chandrabhan Verma; Amal M Al-Mohaimeed; Eno E Ebenso; M A Quraishi

doi:10.1039/d0ra07595g

Chromeno-carbonitriles as corrosion inhibitors for mild steel in acidic solution: electrochemical, surface and computational studies

RSC Adv. 2021 Jan 11;11(4):2462-2475. doi: 10.1039/d0ra07595g. eCollection 2021 Jan 6.

Authors

Taiwo W Quadri¹, Lukman O Olasunkanmi^{1

2}, Ekemini D Akpan¹, Akram Alfantazi³, I B Obot⁴, Chandrabhan Verma⁴, Amal M Al-Mohaimeed⁵, Eno E Ebenso^{1

6}, M A Quraishi⁴

Affiliations

¹ Department of Chemistry, School of Physical and Chemical Sciences, Material Science Innovation and Modelling (MaSIM) Research Focus Area, Faculty of Natural and Agricultural Sciences, North-West University (Mafikeng Campus) Private Bag X2046 Mmabatho 2735 South Africa.
² Department of Chemistry, Faculty of Science, Obafemi Awolowo University Ile-Ife 220005 Nigeria.
³ Department of Chemical Engineering, Khalifa University of Science and Technology P.O. Box 2533 Abu Dhabi United Arab Emirates.
⁴ Center of Research Excellence in Corrosion, Research Institute, King Fahd University of Petroleum and Minerals Dhahran 31261 Saudi Arabia cbverma38@gmail.com chandraverma.rs.apc@itbhu.ac.in.
⁵ Department of Chemistry, College of Science, King Saud University P.O. Box 22452 Riyadh 11495 Saudi Arabia.
⁶ Institute for Nanotechnology and Water Sustainability, College of Science, Engineering and Technology, University of South Africa Johannesburg South Africa.

Abstract

Three novel N-hydrospiro-chromeno-carbonitriles namely, 2-amino-7,7-dimethyl-1',3',5-trioxo-1',3',5,6,7,8-hexahydrospiro[chromene-4,2'-indene]-3-carbonitrile (INH-1), 3-amino-7,7-dimethyl-2',5-dioxo-5,6,7,8-tetrahydrospiro[chromene-4,3'-indoline]-2-carbonitrile (INH-2) and 3'-amino-7',7'-dimethyl-2,5'-dioxo-5',6',7',8'-tetrahydro-2H-spiro[acenaphthylene-1,4'-chromene]-2'-carbonitrile (INH-3) were synthesized using the principles of green chemistry and applied as corrosion inhibitors for mild steel in acidic medium using computational simulations and experimental methods. Experimental and computational studies revealed that inhibition effectiveness of the INHs followed the sequence: INH-3 (95.32%) > INH-2 (93.02%) > INH-1 (89.16%). The investigated compounds exhibit mixed-type corrosion inhibition characteristics by blocking the active sites on the surface of mild steel. EIS study revealed that the INHs behave as interface-type corrosion inhibitors. EDX analyses supported the adsorption mechanism of corrosion inhibition. A DFT study carried out for gaseous and aqueous forms of inhibitor molecules indicated that interactions of INHs with the mild steel surface involve charge transfer phenomenon or donor-acceptor interactions. A Monte Carlo (MC) simulation study revealed that only a fractional segment of the molecule lies parallel to the steel surface, since the INH molecules are not completely planar. The results of computational studies and experimental analyses were in good agreement.