Exploring the synthesis, characterization, and corrosion inhibition of new tris-thiosemicarbazone derivatives for acidic steel settings using computational and experimental studies

A novel two tri-thiosemicarbazones derivatives, namely 2,2’,2’’-((2-Hydroxybenzene-
1,3,5-triyl)tris(methanylylidene))tris(N-benzylhydrazine-1-carbothioamide) (HBC) and
2,2’,2’’-((2-hydroxybenzene-1,3,5-triyl) tris (methanylylidene)) tris (N-allylhydrazine-1-
carbothioamide) (HAC), have been synthesized and their chemical structures were determined
using different spectroscopic and analytical approaches. Then, utilizing methods including open
circuit potential, potentiodynamic polarization, and electrochemical impedance spectroscopy, the
inhibitory effect of the synthesized thiosemicarbazones on mild steel (MS) in an acidic environment
(0.5 M H2SO4)
was thoroughly investigated. Remarkably, raising the concentration of our recently
synthesized tri-thiosemicarbazones HBC and HAC increased the inhibitory efficiency values.
The η values of the two investigated tri-thiosemicarbazones derivatives (HAC and HBC), at each
concentration are extremely high, and the maximum values of the efficiencies are 98.5% with HAC
and 98.8% with HBC at the 800 ppm. The inhibitors adsorbed on the mild steel surface and generated
a charge and mass movement barrier that protected the metal from hostile ions. According to
polarization curves, HBC and HAC act as mixed-type inhibitors. Electrochemical impedance testing
revealed a notable rise in charge transfer resistance (
Rct) readings to 4930-Ω cm2,
alongside a
reduction in the Constant Phase Element (CPE) value to 5.81 μF, suggesting increased effectiveness in
preventing corrosion. Also, density functional theory (DFT) was applied to investigate the assembled
tri-thiosemicarbazones HBC and HAC. Moreover, the adsorption mechanism of HBC and HAC on the
mild steel surface was explored using Monte Carlo simulation. Finally, the theoretical outputs were
discovered to support the practical outcomes.