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Phosphonic acids are good complexing agents. However, they are not good as inhibitors except for a very few. Synergistic inhibition is offered in the presence of metal cations like Ca²⁺, Mg²⁺, Zn²⁺ and others in neutral media. The zinc ion is an ideal choice. The part of zinc ions are now replaced by polymers, azoles to prepare eco‐friendly inhibitor formulations. They are also used as corrosion inhibitors in concrete, coatings, rubber blends, acid cleaners, anti‐freeze coolants, etc. Discusses the various applications of phosphonic acids and their action mechanisms.

Gallic acid is a substance that is widely found in nature. Initially, it was only used as a corrosion inhibitor to retard the rate of corrosion of metals. In recent years, with intensive research by scholars, the modification of coatings containing gallic acid has become a hot topic in the field of metal protection. This study aims to summarize the various preparation methods of gallic acid and its research progress in corrosion inhibitors and coatings, as well as related studies using quantum chemical methods to assess the predicted corrosion inhibition effects and to systematically describe the prospects and current status of gallic acid applications in the field of metal corrosion inhibition and protection.

First, the various methods of preparation of gallic acid in industry are understood. Second, the corrosion inhibition principles and research progress of gallic acid as a metal corrosion inhibitor are presented. Then, the corrosion inhibition principles and research progress of gallic acid involved in the synthesis and modification of various rust conversion coatings, nano-coatings and organic resin coatings are described. After that, studies related to the evaluation and prediction of gallic acid corrosion inhibition on metals by quantum chemical methods are presented. Finally, new research ideas on gallic acid in the field of corrosion inhibition and protection of metals are summarized.

Gallic acid can be used as a corrosion inhibitor or coating in metal protection.

There is a lack of research on the synergistic improvement of gallic acid and other substances.

The specific application of gallic acid in the field of metal protection was summarized, and the future research focus was put forward.

To the best of the authors’ knowledge, this paper systematically expounds on the research progress of gallic acid in the field of metal protection for the first time and provides new ideas and directions for future research.

Inhibition of carboxylic acids of aluminium corrosion in hydrochloric acid and sodium hydroxide solutions has been studied using weight‐loss and hydrogen evolution methods. The order of inhibition action of aromatic acids depends on the number and position of the carboxylic groups and the other substituents in the benzene ring. Increase of the chain length increases the inhibiting power of aliphatic acids. The inhibition efficiency in NaOH is higher than that in HCI solutions. The action of inhibition was discussed in terms of the chemical structure of the inhibitors.

Introduction The corrosion of iron has been extensively studied in various media. In nitric acid solutions, the corrosion of iron is much faster than in other mineral acids at comparable concentrations. This is attributed to an autocatalytic process involving some nitrogen oxides, nitrous acid and/or some iron complexes. At high nitric acid concentrations, passivation of iron takes place. The factors affecting the dissolution and the passivation processes are not fully understood. The effect of various inhibitors on the corrosion of iron in acid media has been studied. Thus Ammar et al. have studied the passivation of iron and the effect of some anions, e.g. Br− and I− on the passive film. The effect of amides as inhibitors for iron in nitric acid has been reported by Fouda and Gouda. These authors have found that the corrosion process is controlled by the reaction of amides with HNO3 and not by the surface reaction. The effect of aniline and some aminobenzoic acids on the rate of corrosion of iron has been reported. The present work is aimed at examining the efficiencies of some aniline substitutes as corrosion inhibitors for the corrosion of iron in concentrated nitric acid solution.

Mushrooms have always been treasured and appreciated, thanks to their nutritional as well as medicinal properties. The purpose of this paper is to reveal these properties such as antioxidant activities and enzyme inhibition potentials of three mushroom species from Ordu, Turkey. Furthermore, phenolic profiles which are believed to be source of these properties are investigated.

The assays followed to determine total phenolic, flavonoid and antioxidant contents, antioxidative and enzyme inhibition activities are spectrophotometric methods. Phenolic profiles of mushroom samples were investigated by using the HPLC system.

The highest phenolic content was found for Lactarius deliciosus. Pyrogallol was the major phenolics in all three samples. Total phenolic content values supported that finding. But, total flavonoid content was the maximum for Cantharellus cibarius. The magnitude of the antioxidant activities revealed by the different tests varied between species. Furthermore, inhibition potential degrees on acetylcholinesterase, butrylcholinesterase, tyrosinase and urease activities were worth mentioning. Lactarius pyrogalus had anti-tyrosinase activity with a 26.229 percent inhibition rate. IC₅₀ values for urease inhibition effect of mushroom samples were in the range of 0.37–0.90 mg/mL.

Enzyme inhibitory potentials for L. pyrogalus was revealed first time. On the other hand, studies on anti-tyrosinase activity of mushrooms are very rare, while almost no studies have been conducted on anti-urease activity. So, the results of present study are very valuable. Thus, the obtained data not only increase the ecological importance of the region but also provide significant contributions to the literature in terms of new sources rich in antioxidants.

This paper aims to evaluate the inhibition efficiency of norfloxacin on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions.

Evaluation was carried out by electrochemical techniques such as electrochemical impedance spectroscopy and potentiodynamic polarization studies. Scanning electron microscopy was used, and it finally confirmed the existence of the adsorbed film.

The electrochemical measurements showed that norfloxacin has good inhibition efficiency on the corrosion of copper in 1.0 M nitric acid and 0.5 M sulfuric acid solutions. The inhibition action of norfloxacin in both of the corrosive media was observed to be of mixed type but with more of cathodic nature. The temperature dependence of the corrosion rate was studied in the temperature range from 35 to 55°C and the activation energy (E_a) was calculated. The adsorption of norfloxacin molecules on copper surface obeyed Langmuir adsorption isotherm. Studies on the potential of zero charge have been carried out to establish the mechanism of adsorption of the inhibitor onto the metal surface. The thermodynamic parameters such as the adsorption equilibrium constant (K_ads) and the free energy of adsorption (ΔG_ads) were calculated. The value of free energy of adsorption very close to −40 kJmol⁻¹ indicates that the adsorption is through electrostatic coulombic attraction and chemisorption. The decrease in value of E_a with the addition of inhibitor also shows the chemisorption of the inhibitor on the metal surface.

This paper indicates that norfloxacin can act as a good inhibitor for the corrosion of copper in both the acid media.

The paper reports an investigation into the use of aqueous extracts of rice bran as a green inhibitor for corrosion of carbon steel in hydrochloric acid (HCl) solution.

Extracts from the rice bran were used as the main component of an environmentally friendly corrosion inhibitor for use in HCl pickling processes. Inhibition behavior on carbon steel in HCl was investigated by means of mass‐loss tests, polarization curves, electrochemical impedance spectroscopy and atomic force microscopy.

The results show that the extract exhibited good inhibition performance in 1 M HCl. The inhibition efficiency increased with increase in the concentration of the inhibitor and was only moderately affected by temperature variations in the range 303‐363 K. The inhibitive action was due to adsorption on the A3 steel and the adsorption process was consistent with the Langmuir isotherm. The free energy of adsorption (ΔG_ads.) was −4.192 kJ/mol. The negative value of ΔG_ads. indicated spontaneous adsorption of the inhibitor occurred on the surface of A3 steel.

Rice bran extract is an effective inhibitor and can be used to protect carbon steel from corrosion in HCl solution.

The rice bran extracts are an effective green inhibitor and can be widely used in the pickling of metals.

Although much work has been done on the rate of diffusion‐controlled corrosion under forced convection (moving solution), little has been done on the rate of diffusion‐controlled corrosion under natural convection which takes place in stagnant solutions. In diffusion‐controlled corrosion, the rate of corrosion is determined by the rate of transfer of the depolarizer or by the rate of removal of the corrosion products to or from the corroding surface respectively. In the case of stagnant solutions, transfer of the depolarizer to the corroding surface and removal of the corrosion products take place by diffusion and natural convection which arises from the density difference between the bulk solution and the interfacial solution, the interfacial solution being more dense than the bulk solution owing to the dissolution of the metal at the interface. This density difference result in a downward flow which enhances the rate of diffusion controlled corrosion. According to the hydrodynamic boundary layer theory the magnitude of natural convection depends on the physical properties of the solution us well as the geometry and orientation of the solid surface. Diffusion‐controlled metallic dissolution of vertical and horizontal surfaces has been studied earlier.

The effectiveness of bisquaternary ammonium salt N,N′‐Bis(dodecyldimethyl)‐3‐oxa‐1,5‐ pentanediammonium dichloride used as corrosion inhibitor for carbon steel in 1.0 M HCl was investigated by weight loss and electrochemical techniques. Surfaces were characterised by scanning electron microscopy. The performance of the bisquaternary ammonium salt was also compared with that of urotropine, a commercial corrosion inhibitor for acid media in industry practice. The results showed good inhibiting action of the inhibitor. The inhibition efficiency increases with the inhibitor concentration but is temperature–independent. N,N′‐Bis(dodecyldimethyl)‐3‐oxa‐1,5‐pentanediammonium dichloride acts mainly as a mixed‐type inhibitor. The inhibition of this bisquaternary ammonium compound was assumed to occur via adsorption of the inhibitor molecule on the metal surface without affecting the corrosion mechanisms. The adsorption of the inhibitor on the metal surface in HCl solution was found to obey Frumkin's isotherm.

This study considers the problem of preventing the penetration of corrosion‐active components into the protective coating of various materials. It is shown that inhibitors involved into micropores and various coating defects seriously reduce the rate of penetration. The mass‐transfer aspects of the inhibition of acid diffusion into coatings were analyzed. It is shown that the effectiveness of inhibition cannot be easily related to the chemical composition of inhibitors.