Adsorption and corrosion inhibition effect of 2-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)phenol Schiff base on mild steel

In this study, the inhibition effect of 2-((5-mercapto-1,3,4-thiadiazol-2-ylimino)methyl)phenol Schiff base (MTMP) on mild steel corrosion in 0.5 M HCl solution was studied. For this aim, electrochemical techniques such as potentiodynamic polarization curves, weight loss (WL), electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) were used. It was shown that, the MTMP Schiff base has remarkable inhibition efficiency on the corrosion of mild steel in 0.5 M HCl solution. Polarization measurements indicated that, the studied inhibitor acts as mixed type corrosion inhibitor with predominantly control of cathodic reaction. The inhibition efficiency depends on the concentration of inhibitor and reaches 97% at 1.0 mM MTMP. The remarkable inhibition efficiency of MTMP was discussed in terms of blocking of electrode surface by adsorption of inhibitor molecules through active centers. The adsorption of MTMP molecules on the mild steel surface obeys Langmuir adsorption isotherm.     

Inhibitive effect of synthesized 2-(3-pyridyl)-3,4-dihydro-4-quinazolinone as a corrosion inhibitor for mild steel in hydrochloric acid

In this study, the inhibitive effect of synthesized 2-(3-pyridyl)-3,4-dihydro-4-quinazolinone (PDQ) as a new corrosion inhibitor for mild steel in 0.1 M hydrochloric acid media is investigated employing potentiodynamic polarization, electrochemical impedance spectroscopy (EIS) and linear polarization resistance (LPR) techniques. The results show PDQ reduces anodic dissolution, retards the hydrogen evolution reaction and its adsorption obeys the Langmuir's adsorption isotherm. By increase in temperature, corrosion current density increases, however, its increase is lower in the presence of PDQ. By increase in temperature from 25 °C to 45 °C the inhibition efficiency decreases from 93% to 83% in solution containing 200 ppm inhibitor. Thermodynamic adsorption parameters show that PDQ is absorbed by a spontaneous exothermic process and its adsorption mechanism is combination of physical and chemical style.     

Electrochemical and thermodynamic studies to evaluate inhibition effect of 2-[(4-phenoxy-phenylimino)methyl]-phenol in 1 M HCl on mild steel

Inhibition of the corrosion of mild steel in 1.0 M HCl solution by a Schiff base compound named 2-[(4-phenoxy-phenylimino)methyl]-phenol (APS) was investigated at different temperatures (25–55 °C) using electrochemical measurements. The inhibition efficiency increased as APS concentration and temperature increased. It was found that adsorption for APS on mild steel complies with the Langmuir adsorption isotherm in all studied temperature. Thermodynamic parameters (ΔG_ads, ΔH_ads and ΔS_ads) for APS adsorption on mild steel were found out and discussed at each temperature. Time dependency of mild steel in 1.0 M HCl solution in the absence and presence of APS was also studied. The surface morphology of mild steel was examined via SEM analysis.     

The corrosion inhibition and adsorption behavior of Uncaria gambir extract on mild steel in 1 M HCl

The inhibitive effect of the ethyl acetate extract of Uncaria gambir on the corrosion of mild steel in 1 M HCl solution has been investigated by weight loss measurement as well as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. The presence of this catechin-containing extract reduces remarkably the corrosion rate of mild steel in acidic solution. The effect of temperature on the corrosion behavior of mild steel was studied in the range of 303–333 K. The results from this corrosion test clearly reveal that the extract behaves as a mixed type corrosion inhibitor with the highest inhibition at 1000 ppm. Surface analyses via scanning electron microscope (SEM) shows a significant improvement on the surface morphology of the mild steel plate. Linearity of Langmuir isotherm adsorptions indicated the monolayer formation of inhibitor on mild steel surface.     

Non-equilibrium grain-boundary segregation of phosphorus in an Ni-Cr steel

In order to confirm the segregation characteristic of phosphorus in Ni-Cr steel at grain boundary, a grain boundary segregation kinetic curve of phosphorus is obtained using Auger electron spectroscopy. The results show that a peak concentration of phosphorus appears at about 60 min during isothermal ageing at 600 °C after quenching from 1000 °C. The boundary concentration of phosphorus decreases with decreasing (increasing) ageing time, when the ageing time is shorter (longer) than 60 min. These results are analyzed by the model of non-equilibrium grain boundary segregation, indicating that this peak is corresponding to the critical time for phosphorus non-equilibrium grain boundary segregation.     

Green approach to corrosion inhibition of mild steel in hydrochloric acid and sulphuric acid solutions by the extract of Murraya koenigii leaves

The inhibition of the corrosion of mild steel in hydrochloric acid and sulphuric acid solutions by the extract of Murraya koenigii leaves has been studied using weight loss, electrochemical impedance spectroscopy (EIS), linear polarization and potentiodynamic polarization techniques. Inhibition was found to increase with increasing concentration of the leaves extract. The effect of temperature, immersion time and acid concentration on the corrosion behavior of mild steel in 1 M HCl and 0.5 M H₂SO₄ with addition of extract was also studied. The inhibition was assumed to occur via adsorption of the inhibitor molecules on the metal surface. The adsorption of the extract on the mild steel surface obeys the Langmuir adsorption isotherm. The activation energy as well as other thermodynamic parameters (Q, ΔH^*, and ΔS^*) for the inhibition process was calculated. These thermodynamic parameters show strong interaction between inhibitor and mild steel surface. The results obtained show that the extract of the leaves of M. koenigii could serve as an effective inhibitor of the corrosion of mild steel in hydrochloric and sulphuric acid media.     

Cefalexin drug: A new and efficient corrosion inhibitor for mild steel in hydrochloric acid solution

Corrosion inhibition of mild steel in 1N HCl by cefalexin has been studied by electrochemical and weight loss measurements. The inhibitor showed increase in inhibition efficiency with increase in inhibitor concentration up to optimum concentration 400 ppm. Potentiodynamic polarization suggests that it is a mixed type of inhibitor. Electrochemical impedance spectroscopy was used to investigate the mechanism of corrosion inhibition. Thermodynamic parameters were calculated to investigate mechanism of inhibition. AFM is used to investigate the surface morphology of the uninhibited and inhibited mild steel.     

The inhibition effect of some pyrimidine derivatives on austenitic stainless steel in acidic media

5-Benzoyl-4-(substitutedphenyl)-6-phenyl-3,4-dihydropyrimidine-2(1H)-(thio)ones (DHPMs) (I and II) were synthesized using the Biginelli three component cyclocondensation reaction of an appropriate β-diketone, arylaldehyde, and (thio) urea. The effect of these corrosion inhibitors on the corrosion of austenitic stainless steel in 0.5 M H₂SO₄ has been studied by electrochemical methods using Tafel plot, linear polarization and electrochemical impedance spectroscopy at 298 K. The inhibition efficiencies obtained from all the methods employed are in good agreement. The adsorption of the DHPMs onto the stainless steel surface was found to follow Langmuir and Dubinin–Radushkevich adsorption isotherm models. Negative values of ΔG_ads in the acidic media ensured the spontaneity of the adsorption process. Results show DHPM I to be the best inhibitor with a mean efficiency of 91% at 2 × 10⁻³ M additive concentration.     

Green approach to corrosion inhibition of mild steel in two acidic solutions by the extract of Punica granatum peel and main constituents

The effect of the extract of Punica granatum (PG) and their main constituents involve ellagic acid (EA) and tannic acid (TA), as mild steel corrosion inhibitor in 2 M HCl and 1 M H₂SO₄ solutions was investigated by weight loss measurements. The results obtained from the weight loss measurements show that the inhibition efficiency of TA even in high concentration is very low. Thus, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) investigations were used for different concentrations of PG and EA and best concentration of TA. Potentiodynamic polarization curves indicated that PG and EA behave as mixed-type inhibitors. EIS measurements show an increase of the transfer resistance with increasing inhibitor concentration. The temperature effect on the corrosion behavior of steel without and with the PG extract was studied. The inhibition action of the extract was discussed in view of Langmuir adsorption isotherm.     

Clean hydrometallurgical route to recover zinc, silver, lead, copper, cadmium and iron from hazardous jarosite residues produced during zinc hydrometallurgy

A hydrometallurgical process for treating the hazardous jarosite residue from zinc hydrometallurgy was proposed, for not only detoxifying the residue, but also recovering the contained valuable metal components. The jarosite was initially activated and decomposed by sintering at 650 °C for 1 h. The sintered residue was leached in 6 mol L⁻¹ aqueous NH₄Cl solution at 105 °C, followed by filtration. The leaching extraction of Zn, Pb, Cu, Cd and Ag are more than 95%. During reduction with Zn powder, more than 93% of Pb, Cu, Ag and Cd can be simultaneously recovered. Then the NH₄Cl leaching residue were leached again in 30 wt% aqueous NaOH solution for 1 h at 160 °C, and about 94% of As and 73% of Si were removed from the residue. The final residue was almost completely detoxified, and contains about 55 wt% Fe, which can be used as an iron concentration.     

Comparative study of the corrosion behaviour of plasma nitrocarburised AISI 4140 steel before and after post-oxidation

In this study, the corrosion behaviour of plasma nitrocarburised AISI 4140 steel before and after post-oxidation was investigated. Plasma nitrocarburising was carried out at 530 °C, 570 °C and 630 °C for 5 h in an atmosphere consisting of 80 vol.% N₂, 17 vol.% H₂ and 3 vol.% CO₂. After nitrocarburising, plasma post-oxidation was performed at 450 °C for 1 h in a gas mixture of 50 vol.% O₂ and 50 vol.% H₂. The microstructure of the treated samples was characterized using X-ray diffraction, scanning electron microscopy and surface roughness techniques. Dynamic polarization test was also used to evaluate the corrosion resistance of the samples. The results indicated that the compound layer was composed of ε-Fe_2–3(N, C) and γ′-Fe₄(N, C) phases. The amount of ε-Fe_2–3(N, C) phase increased as the treatment temperature rose from 530 °C to 570 °C and decreased at 630 °C. The X-ray diffraction patterns of post-oxidized samples confirmed the formation of the highest amount of magnetite after post-oxidation of samples that had been nitrocarburised at 570 °C as compared with the samples that had been treated at 530 °C and 630 °C. Nitrocarburising at 570 °C followed by post-oxidation also provided the highest corrosion resistance among all treatment conditions.     

Investigation of inhibition effect of rhodanine-N-acetic acid on mild steel corrosion in HCl solution

Corrosion inhibition effect of rhodanine-N-acetic acid (R-NA) on mild steel (MS) corrosion in 0.1 M HCl solution was investigated. For this purpose, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), linear polarization resistance (LPR) as well as hydrogen gas evolution (VH₂−t) and the change of open circuit potential as a function of immersion time (E_ocp − t) were used. The MS surfaces exposed to 0.1 M HCl solution in the absence and presence of inhibitor were examined by scanning electron microscopy (SEM). The thermodynamic parameters of adsorption were calculated and discussed. In order to gain more information about the adsorption mechanism, the EIS technique was used to evaluate the potential of zero charge (PZC) and a mechanism of adsorption process was proposed. It was found that, R-NA is a good corrosion inhibitor for the MS corrosion in 0.1 M HCl solution. The inhibition efficiency increased with increasing inhibitor concentration and reached 98% at 1.0 × 10⁻² M R-NA. The high inhibition efficiency was related to adsorption of R-NA on steel surface. Surface SEM images showed a good surface coverage of inhibitor on the metal surface.     

Formation of nano-grained structure in a 301 stainless steel using a repetitive thermo-mechanical treatment

In this work effects of the thermo-mechanical parameters were investigated in order to achieve nanocrystalline structure in the as-cast AISI 301 stainless steel. In order to get nanocrystalline structure the repetitive cold rolling and subsequent annealing were used. The cold rolling was carried out at temperatures of 0, - 10 and - 196 °C with strain rate of 0.5 s^− 1 and reduction of 95%, while the annealing treatment was conducted at temperature 600 to 850 °C for 0.5 to 50 min. The results showed that the nanocrystalline austenitic structure with grain size of about 30-40 nm was obtained by annealing at 850 °C for 0.5 min after totally 95% cold rolling reduction at - 10 °C.     

Adopting a multipurpose inhibitor to control corrosion of ferrous alloys in cooling water systems

The heterocyclic compounds; 2,5-diphenylpyrazolo[1,5-c]pyrimidine-7(6H)thione (Phenyl), 5-methoxyphenyl-2-phenylpyrazolo[1,5-c]pyrimidine-7(6H)thione (Methoxy), 5-tolyl-2-phenylpyrazolo[1,5-c]pyrimidine-7(6H)thione (Tolyl), 5-tolyl-2-phenylpyrazolo[1,5-c]pyrimidine-7(6H)one (Inon), 2,5-diphenyl-3-iodopyrazolo[1,5-c]pyrimidine-7(6H)thione (Iodo) and 2,5-diphenyl-3-bromopyrazolo[1,5-c]pyrimidine-7(6H)thione (Bromo) were screened by Tafel Extrapolation and Linear Polarization Resistance techniques to detect the possibility of inhibition the uniform corrosion of carbon steel in stagnant cooling water containing 200 ppm chloride at 25 °C. The inhibition efficiencies of the studied compounds were found to decrease in the following order: Tolyl > Methoxy > Phenyl > Iodo > Bromo > Inon.     

Corrosion behavior of nitride layer obtained on AISI 316L stainless steel via simple direct nitridation route at low temperature

Newly developed low-temperature nitride synthesis route was used to introduce interstitial nitrogen into the passive layer of as-received and as-polished 316L stainless steel. The new thermochemical route is based on treating the stainless steel samples in potassium nitrate melt in an ultra pure nitrogen atmosphere at 450 °C. Electrochemical impedance spectroscopy (EIS) and dc polarization measurements have been used to evaluate the nitride layer performance in 3.5% NaCl solution. Results showed a marked increase in the corrosion resistance of nitrided stainless steel even after maintaining two weeks in NaCl solution. The effect of the treatment temperature was also studied. Data showed that the as-polished samples nitrided at 450 °C have the highest corrosion resistance. The polarization resistance (R_p) for the as-polished and as-received blank stainless steel samples was estimated by EIS were approximately 4.0 × 10⁴ Ω cm² and 2.0 × 10⁴ Ω cm², respectively. The R_p increased by a factor of 2.5–5 for the nitrided samples. Increasing the nitriding temperature from 450 to 600 °C affects negatively the corrosion resistance of stainless steel in NaCl solution. The R_p of the samples nitrided at 600 °C decreased sharply being almost 1/30 of the R_p of the samples nitrided at 450 °C. Linear polarization measurements showed that the lowest corrosion rates and highest polarization resistances obtained from the as-polished nitrided samples at 450 °C. It has been found from the potentiodynamic measurements that the E_corr of the as-polished nitrided samples at 450 °C is nobler than that measured from the other groups. The surface morphology was analysed by optical microscope and SEM-EDS under different nitriding conditions.     

Time-dependent behaviour of steel/CFRP double strap joints subjected to combined thermal and mechanical loading

Degradation of structural adhesives at elevated temperatures makes the time-dependent behaviour of adhesively-bonded steel/CFRP joints a critical issue for safety considerations of CFRP strengthened steel structures. This paper reports the examination of specimens at different load levels (i.e. 80%, 50%, and 20% of their ultimate load measured at room temperature) and constant temperatures from 35 °C to 50 °C (i.e. temperatures below and above the glass transition temperature T_g, 42 °C of the adhesive). Furthermore, a scenario of cyclic thermal loading between 20 °C and 50 °C was included to represent more realistic exposure. Joint time-dependent behaviour was demonstrated by the stiffness and strength degradation as a function of not only temperature but also time. At the same temperature level close to or above T_g, a higher load level corresponded to a shorter time-to-failure. In addition, up to 47% of strength recovery was found for the specimens subjected to cyclic temperatures compared with those under constant 50 °C which failed at the same load level. Based on the proposed temperature and time-dependent material property models, the time-dependent failure time of steel/CFRP double strap joints was well described and validated by the experimental results.     

Studies of the corrosion inhibition of copper in sodium chloride solutions using chemical and electrochemical measurements

The inhibiting effects of 2-mercapto-4-amino-5-nitroso-6-hydroxy pyrimidine (MAP) at various concentrations on the copper corrosion in 3.5% NaCl solutions at 25 °C are examined. The inhibiting efficiency of MAP is evaluated from weight loss, potentiodynamic polarization, electrochemical impedance spectroscopy (EIS), and electrochemical frequency modulation (EFM) measurements. Experimental investigations showed that MAP reduces markedly the copper corrosion in 3.5% NaCl solutions, and this reduction in corrosion rates enhances with increasing concentration of this compound. The results obtained from the different corrosion evaluation techniques are in good agreement. Polarization curves indicate that MAP is a mixed-type inhibitor. The results of EIS indicate that the value of CPEs tends to decrease and both charge transfer resistance and inhibition efficiency tend to increase by increasing the inhibitor concentration. EFM can be used as a rapid and non-destructive technique for corrosion rate measurements without prior knowledge of Tafel constants.     

Effect of carbon steel microstructure and molecular structure of two new Schiff base compounds on inhibition performance in 1 M HCl solution by DC,SEM and XRD studies

In this investigation, attempts have been made to study the inhibitive effect of N,N′-ortho-phenylen acetyle acetone imine (S1) and 4-[(3-{[1-(2-hydroxy phenyl) methylidene] amino} propyl) ethanemidol]-1,3-benzenediol (S2) in the concentration range of 50–400 ppm for mild steel with two different microstructures resulted from two different heat treatments (annealed (A) and quenched and tempered (Q&T)) in 1 M hydrochloric acid solution. Both Schiff bases acted as a mixed type inhibitors. The S1 inhibitor for both microstructures showed better inhibition efficiency than S2. The A samples indicated slightly less corrosion than Q&T samples in 1 M HCl solution in absence of inhibitor due to the formation of duplex γ-Fe₂O₃/Fe₃O₄.     

Microstructure and wear behavior of a porous nanocrystalline nickel-free austenitic stainless steel developed by powder metallurgy

This paper investigates the microstructure and dry sliding wear characteristics of a porous Cr–Mn–N austenitic stainless steel prepared by powder metallurgy. The densification of the mechanically alloyed 18Cr–8Mn–0.9N stainless steel powder is performed by sintering at 1100 °C for 20 h and subsequently water-quenching. This procedure gives rise to the development of a nanostructured austenitic stainless steel with a relative density of 85%. The porous biocompatible stainless steel exhibits an outstanding wear resistance compared with AISI 316L stainless steel samples. This is attributed to its considerable intrinsic hardness and its specific configuration of pores.     

Evaluation of interface microstructure and mechanical properties of the diffusion bonded joints of Ti-6Al-4V alloy to micro-duplex stainless steel

In the present investigation, Ti-6Al-4V and micro-duplex stainless steel was diffusion bonded in vacuum. The layer wise σ phase and λ + FeTi phase mixture were observed at the bond interface when bonded joints was processed at and above 850 °C for 90 min and at 800 °C for 120 min and longer bonding time. Effect of bonding temperature and time on the strength properties at room temperature were evaluated. The maximum tensile strength of ∼510.1 MPa and shear strength of ∼397.5 MPa along with 6.5% elongation were obtained for the diffusion couple processed at 850 °C for 90 min. Fracture surface observation in SEM using EDS demonstrates that, failure takes place through λ + FeTi phase when bonding was processed at 850 °C for 90 min and at 800 °C for 120 min, however, failure takes place through σ phase for the diffusion couples processed at and above 900 °C for 90 min and at 800 °C for 120 min and longer bonding time.