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Inhibiting acids Hydrochloric acid solution POLYRAD 0515A and 1110A manufactured by Hercules Powder Co. Ltd. have received wide acceptance as corrosion inhibitors for use in hydrochloric acid solution. This acid, in common with other industrial acids, will corrode iron and steel vessels during processing unless they are protected by the presence of a suitable inhibitor. In the case of hydrochloric acid, a number of processes such as metal cleaning, metal pickling and oil well acidifying operations necessitate the use of a soluble, heat‐stable inhibitor in the acid solution.

The industrial expansion of the post‐war period has resulted in the development of new products and processes, specialised equipment and new materials of construction. Materials science, technology and engineering, has emerged as an independent discipline during the last decade. These changes have brought up the importance of corrosion problems and the urgency to apply preventive methods. It is probably true to say at the present time that the losses due to metallic corrosion give a fair index of the industrial prosperity of a nation. A developing country like India had to face the challenge posed by corrosion, and there is now an increasing awareness of the imperative need for corrosion research and the application of the findings to meet specific situations.

The purpose of this paper is to evaluate the inhibitive effect of a polyaniline copolymer, namely, poly(aniline‐co‐o‐anthranilic acid) solution, on the corrosion of carbon steel in hydrochloric acid. The effect of the different concentrations of the corrosion inhibitor also was investigated.

Fourier transform infrared spectroscopy was used to characterise the polyaniline copolymer. Weight loss measurements, potentiodynamic polarization and electrochemical impedance spectroscopy were carried out to determine the corrosion inhibition efficiency. Scanning electron microscopy was used to observe the morphology of the corroded surface.

The results indicated that polyaniline copolymer solution acts as an effective corrosion inhibitor for carbon steel in hydrochloric acid solution and that the adsorption of the compound on the metal surface obeys the Langmuir adsorption isotherm.

The corrosion inhibitor could have wide applications in the acid washing industry to reduce the corrosion rate of carbon steel in hydrochloric acid.

This paper reveals a new type of corrosion inhibitor prepared from a polyaniline copolymer.

Much progress has been made in the field of corrosion technology in the last few years and many new corrosion‐resisting materials have been developed, including improved types of plastics and metals such as zirconium, titanium and tantalum. Plastics are finding extensive use as lining materials for chemical plant operating at moderate temperatures, but the poor thermal conductivity of most plastics makes them unsuitable for the transfer of heat. The recently developed metals and their alloys are extremely expensive to produce and fabricate and, so far, their use has been confined to certain specialised applications, although full‐scale production of zirconium is being carried out in America, mainly because of the low capacity of the metal for absorbing thermal neutrons. At the moment, however, these metals, because of their high cost, cannot compete commercially on a large scale with the older well‐established corrosion‐resisting alloys such as the high‐silicon iron alloys. The excellent corrosion resistance of the high‐silicon iron alloys, even at high temperatures, and their high thermal conductivity have established them as almost standard alloys for acid concentration and cooling plant construction. The following article outlines their composition and properties.

Organic compounds containing sulphur, nitrogen and oxygen atoms are capable of retarding metallic corrosion. As the thiourea molecule contains one sulphur and two nitrogen atoms, thiourea and its derivatives are potential corrosion inhibitors. While extensive investigations have been carried out on inhibitor properties of thiourea, due attention has not yet been paid to a systematic study of inhibitor action of thiourea derivatives. However, several substituted thioureas have been investigated as corrosion inhibitors. The applications of thiourea and its derivatives as corrosion inhibitors reported in literature up to 1967 are narrated in this article.

This concluding part reviews the actions of inhibitors to acidic, ammonical, organic, atmospheric and miscellaneous product corrosion on aluminium. The comprehensive reference list is also concluded.

The purpose of this study is to further improve the performance of surface texture, the chemical polishing method was introduced and the effect of it on the surface morphology and tribological properties of the surface texture was investigated.

The surface texture was processed on the surface of 304 stainless steel with laser technology in air medium. Hydrochloric acid solution (pH 2.4 ± 0.05) was selected and used to soak the prepared texture samples for 12 h. The surface morphology and elemental content of the samples were measured with the white light interferometry, SEM and EDS. To obtain the effect of acid corrosion on the tribological properties of textured surfaces, the samples were tested under dry friction and oil lubrication conditions.

The detailed study shows that the melt and burr of surface texture produced with laser processing was reduced due to the corrosion effect of hydrochloric acid. Therefore, the better interfacial tribological properties was obtained due to the improvement of surface-textured morphology.

The main contribution of this work is to provide a new reference for improving surface texture quality. It also lays a foundation for improving the tribological properties of the textured interface.

The peer review history for this article is available at: https://publons.com/publon/10.1108/ILT-04-2023-0094/

To investigate the inhibitive effect of Delonix regia extracts to reduce the corrosion rate of aluminium in acidic media. The study was a trial to find a low cost and environmentally safe inhibitor to reduce the corrosion rate of aluminium.

The inhibition efficiency was evaluated using the hydrogen evolution technique at 30°C. The mechanism of adsorption inhibition and type of adsorption isotherm was characterised from trends of inhibition efficiency and kinetic data.

Delonix regia extracts inhibited the corrosion of aluminium in hydrochloric acid solutions. The inhibition efficiency increased with increasing concentration of the inhibitor but decreased with increase in exposure time. The acid extracts (hydrochloric acid seeds extract (HSE) and hydrochloric acid leaf extract (HLE)) were found to be more effective than the ethanolic extracts (ethanol seeds extract (ASE) and ethanol leaves extract (ALE)) and the inhibition followed the order: HSE (93.6 per cent) > HLE (83.5 per cent) > ASE (63.9 per cent) > ALE (60.4 per cent). The low negative values of ΔG_ad: −20.14 kJ mol⁻¹ for HSE, −18.08 kJ mol⁻¹ for HLE, −15.96 kJ mol⁻¹ for ASE and −15.12 kJ mol⁻¹ for ALE, as calculated from the Langmuir isotherm, indicated that the inhibitor molecules adsorbed onto aluminium by a physiosorption‐based mechanism. A first‐order type of reaction mechanism was obtained from the kinetic treatment of the H₂ gas evolution data.

Further investigations involving electrochemical studies such as polarization method should shed further light on the mechanistic aspects of the corrosion inhibition.

This paper provides new information on the possible application of Delonix regia as an environmentally friendly corrosion inhibitor under the specified conditions. This environmentally friendly inhibitor could find possible applications in metal surface anodizing and surface coatings.

Introduction Aldehydes, ketones, amines, anilines and organic sulphur compounds are being studied in this laboratory as corrosion inhibitors for aluminium alloys. The present paper deals with salicylaldehyde, p‐hydroxybenzaldehyde, cinnamicaldehyde and anisaldehyde as corrosion inhibitors for aluminium‐57S in hydrochloric acid solutions. It is known that the behaviour of inhibitors changes with the metal or even with the change in the composition of the alloy.

In this work, a kind of Mannich base (C₂₁H₂₅NO) was synthesized with cinnamal aldehyde, acetophenone and diethylamine in a condensing reflux device based on the conventional method. Optimization of the inhibitor concentration was explored.

Spectral properties of this compound was investigated by FTIR, and its inhibition efficiency and mechanism on N80 steel in 20% hydrochloric acid solution were studied by weight loss measurement, electrochemical measurement (potentiodynamic polarization and electrochemical impedance spectroscopy) and surface analytical measurement (scanning electron microscope with energy dispersive spectrometer).

The results showed that the new inhibitor reduced the double-layer capacitance and increased the charge transfer resistance. The inhibition efficiency is 99.7% when the concentration of C21H25NO is 3%. The adsorption of C₂₁H₂₅NO on N80 steel surface in 20% HCl solution was found to be spontaneous and steady. Observed from the steel surface, an inhibition film was confirmed to be presented after adding inhibitor and successfully hindered the corrosive ions from reaching the bulk steel.

A new Mannich base (C₂₁H₂₅NO) was synthesized by cinnamal aldehyde, acetophenone and diethylamine for the corrosion prevention of N80 steel in 20% hydrochloric acid solution.