The corrosion of aluminum in saline environment in the presence of ferrous gluconate was studied using weight loss and linear polarization methods. The corrosion rates were studied in different concentrations of ferrous gluconate 0.5, 1.0, 1.5, and 2.0 g/mL at 28°C. Experimental results revealed that ferrous gluconate in saline environment reduced the corrosion rate of aluminum alloy at the different concentrations studied. The minimum inhibition efficiency was obtained at 1.5 g/mL concentration of inhibitor while the optimum inhibition efficiency was achieved with 1.0 g/mL inhibitor concentration. The results showed that adsorption of ferrous gluconate on the aluminium alloy surface fits Langmuir adsorption isotherm. The potentiodynamic polarization results showed that ferrous gluconate is a mixed type inhibitor. Ferrous gluconate acted as an effective inhibitor for aluminium alloy within the temperature and concentration range studied. The data obtained from weight loss and potentiodynamic polarization methods were in good agreement.

Currently, the use of synthetic inhibitors in preventing corrosion is destructive to the environment; therefore, natural inhibitors might be an alternative and innovative solution to this challenge, owing to their sustainability. Herein, wasted avocado seed extract was examined as a sustainable and green inhibitor for API 5L X65 pipeline steel at an ambient temperature using the gravimetric analysis, the potentiodynamic polarization curve, and linear polarization resistance techniques. The inhibitor’s chemical characterization was carried out with Fourier-transform infrared spectroscopy (FTIR), and the morphological characterization was carried out by detailed scanning electron microscopy and energy-dispersive X-ray spectroscopy (SEM/EDX). The result showed that the extract decreased the corrosion rate by retarding the cathodic and anodic electrochemical reactions, with a maximum efficiency of 88% at 5 g/L. The extract was adsorbed physically onto the X 65 steel following the Langmuir adsorption isotherms. The electrochemical studies showed that the agro-waste was a mixed-type inhibitor. The SEM image of the X65 steel with the extract showed thin film formation on the steel surface. The extract can be substituted for synthetic inhibitors, which are toxic, scarce, and costly.

Corrosion processes are responsible for huge losses in industry. Though organic, inorganic and mixed material inhibitors were used for a long time to combat corrosion, the environmental toxicity of organic corrosion inhibitors has prompted the search for inorganic corrosion inhibitors. The effect of gluconates as novel corrosion inhibitors on the corrosion of aluminum alloy in acidic and saline media was investigated by electrochemical and weight loss techniques. The effect of inhibitor concentration was also investigated. High resolution scanning electron microscopy equipped with energy dispersive spectroscopy (HR-SEM/EDS) was used to characterize the surface morphology of the metal before and after corrosion. Experimental results revealed that gluconates in the studied solution decreased the corrosion rate at the different concentrations studied. The experimental results obtained from potentiodynamic polarization method showed that the presence of the gluconates in 3.5% NaCl and 0.5 M H 2 SO 4 solutions decreases the corrosion current densities (icorr) and corrosion rates (CR), and increases the polarization resistance (Rp). It was observed that the inhibitor efficiency depends on the corrosive media, concentration of the inhibitor and the substrate material. The adsorption characteristics of the gluconates were also described. Good correlation exists between the results obtained from both methods.