A novel tera-dentate salen ligand and its Fe(III) complex was synthesized and characterized via several spectroscopic and physicochemical techniques. The corrosion rate inhibition of nickel and its alloys inspired the utilization of the L ligand and its FeL complex as vital and eco-friendly inhibitors. To assess their effectiveness, both Tafel plot analysis and electrochemical impedance spectroscopy were employed to examine the electrochemical properties of L and the FeL complex. The results show that corrosion current density (I_corr) steadily drops when the additive concentration is increased, but the inhibition efficiency increases. It has been observed that the efficiency of inhibition rises with temperature, particularly at high temperatures (55 °C) when 1 × 10⁻³ M of L and FeL are present as additives, with η = 90.5% and 92.7%, respectively. Additionally, the findings propose that the adsorption mechanism of both L and FeL additive reptiles follows the Langmuir design isotherm. Electrochemical impedance spectroscopy has also verified these findings. DFT calculations were employed to prove the structure of the investigated FeL complex and its activity as a corrosion inhibitor.

Ni‐based alloys have excellent corrosion resistance and are widely used in the petrochemical industry. In this study, the effect of sulfuric acid on the corrosion resistance of Ni was analyzed by electrochemical tests and theoretical studies in the absence and presence of 2‐([(1E)‐(2‐hydroxyphenyl)methylene]amino)benzoic acid (H2 L). Sulfuric acid's corrosive effect, notably in fertilizer production, poses challenges for materials like nickel used in storage and transport. Discussion of nickel corrosion which is frequently used to handle sulfuric acid is given in this paper. The corrosion behavior of nickel (Ni) metal and the inhibitory effect of 2‐([(1E)‐(2‐hydroxyphenyl)methylene]amino)benzoic acid (H₂L) were investigated using a combination of electrochemical and computational approaches. In this study, 0.5 M sulfuric acid served as the corrosive medium. The inhibitory effect of H₂L was evaluated using Tafel plots and electrochemical impedance spectroscopy. Results show a gradual decrease in the corrosion current density (I_corr.) over time, accompanied by an increase in inhibition efficiency, attributed to rising additive concentrations. The maximum inhibition efficiency (η=97.8 %) was achieved at 1×10⁻⁵ M additive concentration and 25 °C. The additive predominantly affects the anodic reaction compared to the cathodic reaction and reduces NiO formation on electrode surfaces. Increasing solution temperature enhances inhibition efficiency, indicating chemisorption following the Langmuir model, supported by electrochemical impedance spectroscopy. Scanning electron microscopy (SEM) analysis confirms that H2 L inclusion significantly enhances nickel corrosion resistance. Charge‐discharge processes of Ni were studied in 0.5 M H₂SO₄ containing various dosages of the additive at applied distinct current densities. It is interesting to note that both discharging time and specific capacitance rises with raising the applied current density at each dosage of additive in 0.5 M H₂SO₄. The most enhancements were obtained at presence of 1×10⁻⁵ M of the additive, as corrosion resistance and specific capacitance (0.391 mAh at 90 mA cm⁻²). Also, improved power and energy features are obtained in the presence of this concentration of the additive. Theoretical Density Functional Theory (DFT) studies reveal that H₂L possesses a low ΔE_gap, facilitating chemical adsorption during the inhibition process, underlining the innovative nature of this corrosion inhibition strategy. Furthermore, the H₂L−Ni interaction was effectively simulated using the DFT/B3LYP/6‐311+G**, providing valuable insights into the compound's corrosion inhibition capabilities.