Inhibitory Properties of Neomycin Thin Film Formed on Carbon Steel in Sulfuric Acid Solution. Electrochemical and AFM Investigation

Abstract

Our study aims to implement a strategy to reduce the carbon steel corrosion rate in sulfuric acid solution, using an expired drug with adsorption affinity on the metal surface. To investigate the corrosion protection efficiency of an environmental friendly inhibitor, namely neomycin sulfate (NMS), the electrochemical measurements were applied on carbon steel immersed in 1.0 M H2SO4 solution with and without NMS. The protective layer formed on the steel surface was studied by atomic force microscopy (AFM). The potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) showed that the presence of the neomycin sulfate in acid solution leads to the decrease in corrosion current density (icorr) and the increase of polarization resistance (Rp). The mixed mechanism between physical and chemical adsorption of NMS molecules on the steel surface was proposed according to the Langmuir adsorption isotherm. The Atomic Force Microscopy (AFM) indicated that the NMS molecules contributed to a protective layer formation by their adsorption on the steel surface. The AFM parameters such as: rootmean-square roughness (Rq); average roughness (Ra) and maximum peak to valley height (Rp-v) revealed that in the presence of NMS a smoother surface of carbon steel was obtained, compared to the steel surface corroded in sulfuric acid blank solution.

Anticorrosive coating based on poly(vinyl acetate) formed by electropolymerization on the copper surface

“…The inhibition efficiency (IE) was determined using eqs. and , this being presented in Table . …”

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“…Finally, the samples (1 inch × 1 inch) were placed in a shaking incubator for the whole experimental period (24 h). To determine the amount of drug released, a 3 mL solution was taken from the outside released medium, and absorbance was measured at the selected λ max (lidocaine = 263 nm; neomycin = 262 nm) using UV–visible light spectroscopy and a standard curve; the amount of drug released was then calculated [ 14 , 15 ].…”