Formamidine-Based Thiuram Disulfides as Efficient Inhibitors of Acid Corrosion of Mild Steel: Electrochemical, Surface, and Density Functional Theory/Monte Carlo Simulation Studies

Ekemini D Akpan; Segun D Oladipo; Taiwo W Quadri; Lukman O Olasunkanmi; Esther E Nwanna; Bernard Omondi; Eno E Ebenso

doi:10.1021/acsomega.2c00985

Formamidine-Based Thiuram Disulfides as Efficient Inhibitors of Acid Corrosion of Mild Steel: Electrochemical, Surface, and Density Functional Theory/Monte Carlo Simulation Studies

ACS Omega. 2022 Jul 20;7(30):26076-26091. doi: 10.1021/acsomega.2c00985. eCollection 2022 Aug 2.

Authors

Ekemini D Akpan¹, Segun D Oladipo^{2

3}, Taiwo W Quadri⁴, Lukman O Olasunkanmi^{5

6}, Esther E Nwanna⁷, Bernard Omondi⁸, Eno E Ebenso¹

Affiliations

¹ College of Science, Engineering and Technology University of South Africa, Johannesburg 1710, South Africa.
² School of Chemistry and Physics, University of Kwazulu-Natal, Westville Campus, Private Bag X54001, Durban 4000, South Africa.
³ Department of Chemical Sciences, Olabisi Onabanjo University, P.M.B. 2002, Ago-Iwoye 120107, Nigeria.
⁴ Department of Chemistry, School of Physical and Chemical Sciences, Faculty of Natural and Agricultural Sciences, North-West University (Mafikeng Campus), Private Bag X2046, Mmabatho 2735, South Africa.
⁵ Department of Chemistry, Faculty of Science, Obafemi Awolowo University, Ile-Ife 220005, Nigeria.
⁶ Department of Chemical Sciences, University of Johannesburg, P.O. Box 17011, Doornfontein Campus, Johannesburg 2028, South Africa.
⁷ Department of Biochemistry, Federal University of Technology, P.M.B 704, Akure 340110, Nigeria.
⁸ School of Chemistry and Physics, University of Kwazulu-Natal, Pietermaritzburg Campus, Private Bag X01, Scottsville 3209, South Africa.

Abstract

Electrochemical, surface, and density functional theory (DFT)/Monte Carlo (MC) simulation studies were used in investigating the characteristics of N,N'-(disulfanne-1,2-dicarbonothioyl)bis(N,N'-bis(2,6-dimethylphenyl)formimidamide) (DS1), N,N'-(disulfanne-1,2-dicarbonothioyl)bis(N,N'-bis(2,6-diisopropylphenyl)formimidamide) (DS2), N,N'-(disulfanne-1,2-dicarbonothioyl)bis(N,N'-dimesitylformimidamide) (DS3), and N,N'-(disulfanne-1,2-dicarbonothioyl)bis(N,N'-bis(2,6-dichlorophenyl)formimidamide) (DS4) as inhibitors of acid corrosion of mild steel. The inhibitors were found to effectively reduce the rates of steel dissolution at the anode as well as cathodic hydrogen evolution. The order of inhibition efficiencies of studied compounds is DS1 (PDP/LPR/EIS: 98.60/97.98/96.94%) > DS2 (PDP/LPR/EIS: 98.36/96.86/96.90%) > DS3 (PDP/LPR/EIS: 94.66/87.44/94.30%) > DS4 (PDP/LPR/EIS: 83.57/77.02/75.17%) at 1.00 mM, and the overall efficiencies appeared to depend on the molecular and electronic structures of the compounds. The compounds offered high resistance to charge transfer across the electrode/electrolyte system by forming adsorbed film whose resistance increased with an increase in concentration. Findings suggested that the adsorption process involved combined chemisorption and physisorption. DFT calculations and MC simulations provided theoretical justifications for the experimental results.