Investigation of inhibition efficiencies of Novel bis-oxindole and bis(spiro(triazole-oxindole)) for the corrosion of copper in sulfuric acid medium

Abstract

The condensation reaction of bis-oxindole with aniline derivatives produced three derivatives of 1,1-(propane-1,3-diyl)bis(3-(substitutedphenylimino)-indoline-2-one). In addition, one spiro-triazole-oxindole derivative was created by 1,3-dipolar cycloaddition of hydrazonoyl chloride on the C = N of the latter Schiff base. The spectral analyses of these bis-oxindole/spiro-triazole-oxindole series proved their structure. The four synthesized bis-oxindole/bis-spiro-triazole-oxindoles, denoted 3a, 3b, 3c, and 6, were tested as copper corrosion inhibitors in 1.0 M H2SO4 at 298 K. For all studied organic compounds, weight loss (WL) was used; electrochemical techniques (potentodynamic polarization (PDP) and electrochemical impedance spectroscopy (EIS)) were used for the compound with the highest inhibition efficiency (% IE). The current findings revealed that the tested compounds were determined to be effective inhibitors, and their% IEs were discovered to be dependent on their concentrations and structures. At the same concentrations, the WL results revealed that the order of the% IEs of the tested compounds was: 3a 3c 3b 6 (compound 6 was found to have the highest% IE). The examined compounds’ high IEs are attributed to the forceful adsorption of such molecules on the copper surface, which results in the formation of an adhered protecting layer. Such adsorption was discovered to follow the Langmuir adsorption isotherm. The kinetics of corrosion inhibition by the investigated compounds revealed a negative-first order process, supporting the obtained high% IEs. According to PDP results, compound 6 behaves as a mixed inhibitor with a cathodic majority. The collected results for the compound 6 regarding the values of % IEs obtained via the three employed techniques were compared and designated a good concordance between all utilized techniques.