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The iron oxide-based goethite (FeOOH) is proven to be an alternative replacement for carcinogenic chrome-based pigments. Because of its low heat stability, it tends to lose water of hydration and turns red as temperature ascends beyond 240ºC. Thus, the purpose of this paper is to increase the heat stability temperature of industrial grade (IG) goethite pigment. For this, the IG goethite pigment was surface treated with sequestrant. The properties of untreated and treated IG goethite were compared.

Three different compounds (sodium hexametaphosphate, calcium disodium ethylene diamine tetra-acetate salt, sodium gluconate) were used into the IG goethite at different concentration level. The experiments were conducted by varying the temperature and exposure time of treated and untreated samples. The total colour difference value (DE) was compared for the treated and untreated samples.

The surface treatment of IG goethite showed significant enhancement in heat stability property. From X-ray diffraction results it was confirmed that with surface treatment, there was no phase change of IG goethite even at 300ºC. Fourier transform infrared analysis states that with surface treatment when there is gradual increase in temperature from 260ºC the % transmittance of the OH (hydroxyl) deformation region band is delayed due to sequestering effect. Also, based on the total colour DE, the colour tone of surface treated IG goethite was not perceptible by human eyes even at 280ºC.

By increasing the heat stability of IG goethite, it will have increased spectrum of end usage in the high temperature coating segment. Coil coating is one of the biggest potential markets for this pigment. The increased heat stability will provide manufacturers with the option of an economical and non-toxic pigment in coil coatings and also in other sectors such as plastics, powder coatings and high temperature coatings.

The outcome of this study has been commercially implemented to produce heat stable goethite pigments in an industrial plant. The surface treated IG goethite pigments can be used in high-performance coil, powder and high temperature coatings.

The method for enhanced heat stability property of IG goethite by surface treatment with sequestrants is novel and could find numerous applications in high-performance coatings.

This paper aims to investigate the potential of sol-gel coating as replacement for hazardous hexavalent chrome passivation treatment for galvanised iron (GI) sheet. Generally, corrosion resistance properties of the GI sheet are increased by hexavalent chrome passivation treatment. But hexavalent chrome is hazardous and not environment friendly.

The aim of this study was to understand the effect of nano zinc oxide (ZnO) on corrosion behaviour of sol-gel coating prepared by hydrolysis of the 3-(Glycidoxy propyl) methyl diethoxy silane (GPTMS) and tetra-ethyl-orthosilicate (TEOS). The morphology of the film was characterised by a scanning electron microscope (SEM). The corrosion resistance of the coated samples was evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarisation curve and salt spray test.

From a different corrosion resistance study, it has been observed that sol-gel coating doped with 1 per cent nano ZnO rendered maximum corrosion protection. Beyond 1 per cent of nano ZnO, corrosion resistance property of coated galvanised steel sheet decreased drastically which may be due to agglomeration of nano ZnO and high water permeability of coated galvanised steel sheet.

The anti-corrosive property of the coating can be tested by means of atmospheric exposure which produces a real-time evaluation of the anti-corrosive nature of the coating under natural conditions rather than using an accelerated laboratory test.

It may be useful for other metal industry like aluminium. The work can be used as a guiding chemistry for development of chrome-free passivation for aluminium.

It has the potential to replace hexavalent chrome passivation.

The use of nano ZnO in sol-gel polymer matrix for the development of corrosion resistant chrome-free polymer coating for galvanised steel sheet and its corrosion resistance study (EIS curve fitting, capacitance value and water permeability) is a novel approach in this research.

The aim of this work was to study the effect of La(NO

)

on the corrosion behavior of sol-gel coating prepared by hydrolysis of 3-glycidoxypropyl)methyldiethoxysilane and 3-aminopropyltriethoxysilane. Generally, galvanized steel is subjected to a hexavalent chromium passivation treatment. Hexavalent chromium passivation is not an environment friendly product and researchers are looking for a suitable alternative for chromium passivation treatment. Some of the potential alternatives are silicate conversion coating or the use of silane-based coatings. In this context, sol-gel coating was investigated as a potential replacement for hazardous hexavalent chromium passivation treatment.

The sol-gel film was deposited on galvanized steel sheet by the dip coating method. The molecular vibration and chemical properties of sol-gel solution and coated films were obtained by infrared spectroscopy. Images from a scanning electron microscope were obtained to characterize the morphology of the film. The corrosion resistance of the coated samples was evaluated by electrochemical impedance spectroscopy (EIS), potentiodynamic polarization curves and salt spray tests.

The results indicated that La(NO

)

-doped coatings were more resistance to corrosion than undoped coating. The coating doped with 0.5 per cent La(NO

)

offered improved corrosion protection due to the inhibitive action of the La3+ ion.

This result can provide a reference for the development of chromium-free passivation for galvanized sheeting.

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.

The purpose of this paper is to report on the use of phosphorylated polyphenol (PP)-coated galvanised iron (GI) surface to study the degradation of coating with different time intervals and long-term exposure in different salty media.

The as-obtained PP complex on GI was evident by X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FT-IR), energy dispersive spectroscopy (EDS) and scanning electron microscopy (SEM). The coated coupons were exposed to different salty media such as 3.5 per cent NaCl, 1.5 per cent Na₂SO₄ and tap water at set time intervals. Electrochemical polarisation was performed to study the anodic and cathodic polarisation behaviour at each time interval.

The adherent foliolate nanopattern of iron zinc phosphate and zinc dihydrogen phosphate on GI surface was evident by SEM, FT-IR, EDS and XRD. The coated coupons exhibited good corrosion resistance. This coating performs as an alternative to time-consuming multistep operations of phosphating treatment.

The mode of the experiment treatment using modified PP coating especially on GI in different corrosive exposures at set time intervals is a novel approach in this research.

The purpose of this paper is to study the adsorption properties of a proven traditional medicine of West Africa origin, Alstonia boonei with an attempt to evaluate its application in the corrosion protection of mild steel in 5 M H₂SO₄ and 5 M HCl.

Phytochemical screening and Fourier transform infrared spectroscopy analysis were used to characterize the methanolic extract of the plant. Gravimetry, gasometry and electrochemical techniques were used in the corrosion inhibition studies of the extract and computational studies were used to describe the electronic and adsorption properties of eugenol, the most abundant phytochemical in Alstonia boonei.

The extract acted as a mixed-type inhibitor in both acidic solutions, with improved inhibition efficiency achieved with increasing concentration. While the efficiency increased with temperature for the HCl system, it decreased for the H₂SO₄ system. The mechanism of adsorption proposed for Alstonia boonei was chemisorption in the HCl system and physisorption in the H₂SO₄ system, and the adsorptions obeyed Langmuir isotherm at low temperatures. Computational parameters showed that eugenol, being a representative of Alstonia boonei, possesses excellent adsorption properties and has the potential to compete with other established plant-based corrosion inhibitors.

As opposed to pure compounds with distinctive corrosion effects, plant extracts are generally composed of a myriad of phytoconstituents that competitively promote or inhibit the corrosion process and their net effect is evident as inhibition efficiencies. This is, therefore, the main research limitation associated with the corrosion inhibition study of Alstonia boonei.

Being very rich in antioxidant properties by its proven curative and preventive effects for diseases, the interest was stimulated towards the attractive results that abound from its corrosion protection of metals via its anti-oxidation route.

Owing to the toxicity, biodegradability, and cost of most corrosion inhibitors, research attention is now focused on the development of environmentally benign, biodegradable, cheap, and efficient options. In consideration of these facts, chrysin, a phytocompound of Populus tomentosa (Chinese white poplar) has been isolated and investigated for its anticorrosion abilities on carbon steel in a mixed acid and chloride system. This highlights the main purpose of the study.

Chrysin was isolated from Populus tomentosa using column chromatography and characterized using Fourier Transform Infrared Spectroscopy and Nuclear Magnetic Resonance Spectroscopy. The investigations are outlined based on theory (Fukui indices, condensed density functional theory and molecular dynamic simulation) and experiments (electrochemical, gravimetry and surface morphology examinations).

Theoretical evaluations permitted the description of the adsorption characteristics, and molecular interactions and orientations of chrysin on Fe substrate. The interaction energy for protonated and neutral chrysin on Fe (110) were −149.10 kcal/mol and −143.28 kcal/mol, respectively. Moreover, experimental investigations showed that chrysin is a potent mixed-type corrosion inhibitor for steel, whose effectiveness depends on its surrounding temperature and concentration. The optimum inhibition efficiency of 78.7% after 24 h for 1 g/L chrysin at 298 K indicates that the performance of chrysin, as a pure compound, compares favorably with other phytocompounds and plant extracts investigated under similar conditions. However, the inhibition efficiency decreased to 62.5% and 51.8% at 318 K after 48 h and 72 h, respectively.

The novelty of this study relies on the usage of a pure compound in corrosion suppression investigation, thus eliminating the unknown influences obtainable by the presence of multi-phytocompounds in plant extracts, thereby advancing the commercialization of bio-based corrosion inhibitors.

This study aims to prevent mild steel (MS) against corrosion in 0.5 M HCl solution, 2-amino-4-methoxy-6-methyl-1,3,5-triazine was used. The effectiveness of the compound as a corrosion inhibitor was studied via electrochemical, surface and theoretical calculation techniques.

For concentrations ranging from 0.5 to 10.0 mM, almost similar polarization resistances were obtained from electrochemical impedance spectroscopy (EIS) and linear polarization resistance tests. It also investigated inhibitive activity of 2-amino-4-methoxy-6-methyl-1,3,5-triazine on the steel surface using scanning electron and atomic force microscope instruments. Langmuir adsorption is the best matched isotherm for the adsorption of the inhibitor to the steel surface.

EIS method was used to determine inhibition efficiency, which was determined to be 95.7% for 10.0 mM inhibitor containing acid solution. Density functional theory’s predictions for quantum chemistry agreed well with the other experimental results.

The methods used in this study are effective and applicable; the used organic inhibitor is 2-amino-4-methoxy-6-methyl-1,3,5-triazine; and protective effectiveness is important, which is crucial for the task of MS corrosion prevention.

The aim of this study was to investigate the activity of 4-((4-((2-hydroxyethyl)(methyl)amino)benzylidene) amino)-1,5-dimethyl-2-phenyl-1,2-dihydro-3H-pyrazol-3-one (HEMAP), a Schiff base synthesized and characterized for the first time, to the authors’ knowledge, as a novel inhibitor against corrosion of mild steel (MS) in hydrochloric acid solution.

HEMAP was characterized by some spectroscopic methods including High-Resolution Mass Spectrometry (HRMS), Proton Nuclear Magnetic Resonance (1H NMR), Carbon-13 (C13) nuclear magnetic resonance (13C NMR) and Fourier Transform Infrared Spectroscopy (FT-IR). Then, the inhibition efficiency of HEMAP on MS in a hydrochloric acid solution was investigated by potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). To explain the inhibition mechanism, the surface charge, adsorption isotherms and thermodynamic parameters of MS in the inhibitor solution were studied.

EIS tests displayed that the highest inhibition efficiency was calculated approximately as 99.5% for 5 × 10⁻² M HEMAP in 1 M HCl solution. The adsorption of HEMAP on the MS surface was found to be compatible with the Langmuir model isotherm. The thermodynamic parameter results showed that the standard free energy of adsorption of HEMAP on the MS surface was found to be more chemical than physical.

This study is important in terms of demonstrating the performance of the first synthesized HEMAP molecule as an inhibitor against the corrosion of MS in acidic media. EIS tests displayed that the highest inhibition efficiency was calculated approximately as 99.5% for 5 × 10⁻² M HEMAP in 1 M HCl solution.

The purpose of this paper is to evaluate the protective ability of mixtures of aniline and phenol as corrosion inhibitors for N80 steel in 15 per cent hydrochloric acid, which may find application as corrosion inhibitors in acidization jobs in the petroleum industry. Owing to scale plugging at well bore there will be a decline in the crude production and acidization operation has to be carried out in the oil wells, normally by using 15 per cent hydrochloric acid to remove the scale plugging and enhance crude production. If the acid alone is poured in the oil wells through tubular and casing, corrosion of the metal (N80 steel) structures takes place for which an inhibitor is also is used along with the acid.

Different concentration ratios of the inhibitor mixtures of aniline and phenol were added to the test solution (15 per cent HCl) and corrosion inhibition of N80 steel in hydrochloric acid medium containing the inhibitor additives was tested by weight loss and potentiodynamic polarization measurements. Influence of temperature (ambient temperature to 333 K) and exposure period (6‐24 h) on the inhibition behaviour was also studied. Corrosion products on the metal surface were analyzed by fourier transform infrared (FTIR) and a possible mechanism of inhibition by the compounds is suggested.

Provides information about the protective ability of inhibitor mixtures containing aniline and phenol against corrosion of N80 casing steel in 15 per cent HCl medium. The results in the present study have shown synergistic effect of all the formulations tested. The formulation of the mixture containing 0.1 per cent AL with 0.7 per cent PH has shown a maximum efficiency (75 per cent at ambient temperature) among other tested combinations in the acid medium. The inhibition efficiency exhibited by the inhibitor mixture (0.1 per cent AL with 0.7 per cent PH) in 15 per cent HCl medium at 333 K and after 24 h – test was found to be 43 and 31 per cent, respectively. The inhibitors, in appropriate combinations may find some usefulness at still higher temperatures. Electrochemical measurements indicate that the additives are active towards both sides, i.e. cathodic and anodic. FTIR results of the inhibition product film (formed on the metal surface after the corrosion test) reveal the presence of the inhibitor molecules in the surface film on the metal. Aniline and phenol molecules of the inhibitor mixture undergo condensation after their addition to the acid solution and may result in formation of protective surface film on the metal consisting of diphenylamine (as also revealed by FTIR spectroscopy) which may also contribute to the corrosion inhibition apart from the inhibition offered by aniline and phenol separately.

Normal temperatures of oil wells will be about 363 K. The results presented in this paper refer to temperatures up to 333 K, which perhaps limits its usefulness in actual field conditions. However, further research work to test the inhibition potentiality of the compounds at higher temperatures (363 K and above) is in progress, and will be communicated at a later stage.

The tested inhibitor mixtures containing aniline and phenol exhibited synergistic effect and a significant inhibition (75 per cent) at ambient temperature that also shows good inhibitive properties after longer exposure period (24 h) and higher temperature (333 K). Appropriate formulations of the compounds may also be effective at still higher temperatures and that may be worked out for possible application in oil wells as corrosion inhibitors for acidization job.

This paper offers preliminary laboratory results of some inhibitor formulations on corrosion prevention of N80 steel casing and tubular in hydrochloric acid that may be of practical help to petroleum engineers for carrying out acidization jobs in oil wells after further investigations of the compounds at higher temperatures and actual field conditions.