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Numerical simulation of laser-MIG hybrid welded Q235 steel was conducted using finite element simulation software with a 3D model. The thermal analysis was performed with a combined ellipsoid-Gaussian heat source. Double ellipsoid heat source and Gaussian heat source (Gauss rotating body heat source and Gauss cylinder heat source) were utilized to represent arc and laser heat, respectively. The effects of power distribution on the temperature evolution and the geometry of molten pool were numerically investigated. The simulated temperature field shows that the increase of the power ratio of laser in laser-MIG hybrid welding (LMHW) is more conducive to improve the peak temperature, leading to remelt interlayer and promote interlayer heat accumulation. Meanwhile, the depth-to-width-ratio (DTW) of molten pool increases with the risen laser power. The change of DTW value with $R$ value is more obvious when the $R(P_{\mathrm{\text{L}}}/P_{\mathrm{\text{MIG}}})$ value is greater than 1. Comparison of the calculated and validation experiment results suggested that the LMHW process is characterized well by the combined heat source model. Fine weld joint with good shape of molten pool morphology is obtained when the DTW of first pass, second pass and third pass are 0.94, 0.34 and 0.27, respectively.

In this investigation, attempts have been made to study the inhibitive effect of hexamethylenetetramine (HMTA) on carbon steel in 10% HCl (mass%) by weight loss, potentiodynamic polarization, EIS, and AFM. Results indicate that inhibition efficiency (IE) of HMTA increases with the increase in pickling immersion time from 10 to 60 min, and IE also increases with the increase in temperature. At higher temperatures (80°C), the IE values are higher and almost independent of pickling time. HMTA can be adsorbed on the surface of metal and reduce the corrosion rate of metal. HMTA is a kind of mixed inhibitor and can retard both the anodic dissolution and cathodic hydrogen evolution reactions independently. IE increases with the concentration of HMTA. Electrochemistry measurement shows that adsorption follows the Langmuir isotherm and the value of free energies of adsorption (ΔG_ads) is < 0, so the adsorption process can occur automatically. AFM analyses show HMTA can affect the surface roughness and protect metal.

This paper describes the inhibition effect of 1-benzyl piperazine (P1) and bis(1-benzyl piperazine) thiuram disulfide (P2) towards the corrosion of C38 steel in 5.5 M H₃PO₄ solution by potentiodynamic polarization and weight loss methods. The influence of inhibitor concentration and temperature on inhibitory behavior of P2 were investigated. The inhibition efficiency (IE) was found to be dependent on the type of piperazine and its concentration. The IE for 10^-3 M P2 in 5.5 M H₃PO₄ is greater than 98%. Polarization studies clearly revealed that both P1 and P2 act as mixed-type inhibitors. Adsorption isotherms were fitted by the Langmuir isotherm. Adsorption energies ( and ) were evaluated. Kinetic parameters were determined.

The nanocomposite Al₂O₃–Y₂O₃ films were prepared on the surface of carbon steel by an electrochemical process and a sintering process. High-resolution field emission scanning electron microscopy (FE-SEM) and X-ray photoelectron spectroscopy (XPS) were used to characterize the films, indicating that the films have nanostructures and the deposited alumina layers have a composition close to the stoichiometry of Al₂O₃. SEM and mass gain measurement are adopted to study the oxidation resistance of films on carbon steel. It is proved that this kind of film is effective in protecting the substrate from oxidation. The mechanisms accounting for such effects have been discussed.

The corrosion inhibition characteristics of 2,2′-bipyridine (BIPY) and 2,2′-bipyridine-3,3′-dicarboxylic acid (BIDA), on carbon steel in sulphuric acid solutions was studied using potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques at 20°C, 30°C and 40°C. The results indicate that the organic compounds inhibit the corrosion of mild steel in H₂SO₄ solutions and the extent of inhibition increases with inhibitor concentration and decreases with temperature. A mixed-inhibition mechanism is proposed for the inhibitive effects of the compounds. The order of inhibition efficiency obtained was BIDA>BIPY. There is a good correlation between the quantum chemical parameters and experimentally determined inhibition efficiency of the inhibitors. The adsorption characteristics of the inhibitor were approximated by Temkin isotherm. Morphological study of the carbon steel electrode surface was undertaken by scanning electron microscope (SEM) and the interfacial species formed on the surface in the presence of inhibitors analyzed by Infrared spectroscopy.

The extraction of linseed oil (LO) was realized by refluxing method. The extracted oil was identified by gas chromatography method coupled with mass spectrometry (GC-MS). In order to contribute to the protection of the environment, one contemplates to try on LO as a green corrosion inhibitor. The corrosion inhibition of LO was studied by weight loss and electrochemical methods. The obtained results showed that the LO is an effective inhibitor of the carbon steel corrosion in 1M HCl solution, the inhibition efficiency increased with concentration to reach 88% at 200ppm. Furthermore, the adsorption of the inhibitor on the surface of metal in 1M HCl solution was found to obey Langmuir’s adsorption isotherm. The influences of temperature were also studied in the range from 298K to 328K. The kinetic and thermodynamic data of activation dissolution process were determined and discussed.

In this paper, for Q235 carbon steels in NaNO₂ solutions with different concentrations of NO${}_2^{-}$, a passive film composed of mainly Fe₂O₃ was formed on the Q235 surface, and the effects of NO${}_2^{-}$ concentrations on the properties of passive film were studied by electrochemical methods and microstructural analyses. The applications of electrochemical impedance spectroscopy (EIS), Mott–Schottky (MS) plot, scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS) were carried out to characterize the resistance, defect, morphology and composition of passive film, respectively. The passive film resistance and defect, respectively, increased and decreased with the increase of NO${}_2^{-}$ concentration until the NO${}_2^{-}$ concentration was up to 0.01M, which was the critical NO${}_2^{-}$ concentration of stable passivation for the Q235 surface. The relation between the electrochemical behavior and the passive film was also discussed in detail.

In this study, the effect of diamond interlayer on the tribological properties of titanium aluminum nitride (TiAlN) film sliding against medium carbon steel is investigated in dry rotary friction tests, by evaluating the coefficients of friction (COFs), wear rates, worn surfaces and element transitions of the contacted surfaces in the cemented carbide (WC-Co)-steel, TiAlN-steel, microcrystalline diamond (MCD)-steel, TiAlN/MCD-steel, micro- and nano-crystalline diamond (MNCD)-steel and TiAlN/MNCD-steel contacting pairs. It is found that compared with the TiAlN monolayer, the TiAlN/MCD bilayer film shows 57% higher COF, while the COF of TiAlN/MNCD multilayer inversely drops as much as 54%, due to the distinguished surface diamond grain morphologies of the MCD and MNCD interlayers as well as the copied effect of the TiAlN layer with relatively small thickness. Meanwhile, the diamond interlayer can provide robust load support for the top TiAlN layer, induce the wear mechanism transform from the abrasive wear to adhesive wear, and result in the mild wear of TiAlN/MCD and TiAlN/MNCD multilayers compared to the TiAlN monolayer. Moreover, the softer TiAlN top layer on MCD and MNCD interlayers can effectively improve the storage capacity of element oxygen and worn steel ball debris as well as accelerating the surface chemical reactions to form a smoother continuous ionic metal oxides tribofilm in the contacted zones due to its good self-lubricating property. Among all the hard coatings discussed when sliding against medium carbon steel, the TiAlN/MNCD coating shows the lowest COF and mild wear, due to the robust load support capacity of the beneath MNCD layer as well as the good self-lubricated and tribofilm formation capacity of the top TiAlN layer, which shows broad application potential in carbon steel machining.

In pure Na₂MoO₄ solutions with different concentrations of MoO${}_4^{2-}$ (0.01, 0.04, 0.06, 0.08 and 0.10 mmol/L), a passive film was formed on the surface of Q235 carbon steel spontaneously, and the influences of MoO${}_4^{2-}$ concentrations on the passive film characteristics were investigated. The electrochemical and microstructural techniques of electrochemical impedance spectroscopy (EIS), Mott–Schottky plot (MSP), scanning electron microscope (SEM) and X-ray photoelectron spectroscope (XPS) were applied to characterize the passive film characteristics, including resistance, defect, microstructure and composition. The resistance and defect of passive film respectively increased and decreased with increased MoO${}_4^{2-}$ concentration up to 0.08mmol/L, which was the critical MoO${}_4^{2-}$ concentration of complete passivation for the Q235 surface. The passive film formed in the 0.08mmol/L Na₂MoO₄ solution showed a dense microstructure and was composed of Fe₂(MoO${}_4{)}_3$ mainly. Further, in this work, the relation between characteristic and anti-corrosion of passive film was also discussed.

Pitting corrosion of carbon steel in sodium chloride solution induced by Ce${}^{3+}$ and the synergistic inhibition effects of Ce${}^{3+}$ and Zn${}^{2+}$/SiO${}_3^{2-}$ were investigated using in-situ observation and electrochemical methods. The results showed that the presence of Ce${}^{3+}$ could result in severe pitting corrosion and a positive shift in the corrosion potential. It was found that individual Ce${}^{3+}$, Zn${}^{2+}$, or SiO${}_3^{2-}$ had low inhibition efficiencies, whereas the combination of Ce${}^{3+}$ and Zn${}^{2+}$ or SiO${}_3^{2-}$ proved to be highly effective in inhibiting the development of pits in two different ways and in enhancing the corrosion resistance. The pitting corrosion and inhibition mechanisms were discussed based on the results.

Corrosion suppression effect of the combination of citrus paradise and cymbopogon oil distillates on mild steel (MS) in 0.5M H₂SO₄ and HCl solution was studied by potentiodynamic polarization, open circuit potential measurement, optical microscopy characterization, and ATF-FTIR spectroscopy. The distillates performed adequately in both acids at all concentrations considered with average inhibition efficiency above 90%. Corrosion rate of the non-inhibited steel at 7.690 and 2.819mm/y from both acids were substantially reduced to values between 0.465 and 0.466mm/y in H₂SO₄ while the values in HCl are 0.081 and 0.034mm/y. The distillates exhibit mixed type inhibition performance in both acids. However, polarization plots displayed cathodic passivation effect at higher distillate concentration in H₂SO₄ while cathodic-anodic passivation plots were observed at all distillate concentrations in HCl solution. Corrosion potential plots from open circuit measurement at specific distillate concentrations were significantly electropositive compared to the non-inhibited steel which was electronegative. Inhibition effect of the distillates occurred through chemisorption adsorption mechanism with Gibbs free energy values greater than $-$40KJ/Mol, in agreement with Langmuir isotherm model. Optical images of the non-inhibited steel displayed a severely degraded exterior which significantly contrast the protected exterior of the inhibited steel.

Corrosion resistance of A36 carbon steel was assessed in 0.5M H₂SO₄ and HCl media in the presence of specific concentrations of Commiphoramyrrha (CM), Cymbopogon (CP) essential oil extracts and their combined admixture (CMCP). Values from potentiodynamic polarization showed CM extract reacted poorly in both acids at low concentration, but effectively at higher concentrations with optimal performance of 89.76% and 92.83%. CP extract generally performed effectively with inhibition values above 90%. CMCP performed very poorly in H₂SO₄ compared to its performance in HCl which was generally above 80% inhibition efficiency. The oil extracts exhibited mixed-type inhibition effect coupled with dominant anodic shift in corrosion potential and similar anodic slope configuration at all extract concentrations. ATR-FTIR spectra plots showed that most of the identified functional groups within the extract molecules generally adsorbed unto the A36 steel surface. Curves from open circuit potential analysis showed CM extract in H₂SO₄, and CP extract in H₂SO₄ and HCl solution significantly decreased the thermodynamic tendency of A36 steel to degrade. The curves of other extracts displayed significant time and extract concentration dependent active–passive transition behavior. Optical images of the unprotected steel exhibited severe general and localized surface deterioration compared to the inhibited steel with significantly protected morphology. Weight-loss analysis showed the effective protection effect of CP extract in both acids and CMCP in H₂SO₄ is independent of time and concentration from the onset of exposure compared to their remaining counterparts whose performance significantly varies over time and is concentration dependent. X-ray phase identification diagrams and identified patterns list revealed the presence of FeO(OH) on the steel surface without oil extracts while the phase compounds identified in the presence of the extracts are FeNi and Fe₃C.

In this study, CrNi alloyed coating was deposited on Q235 low carbon steel by arc-added glow plasma depositing technique in order to increase the corrosion resistance property. It was found that the CrNi alloyed coating was composed of face-centered cubic Cr0.7Ni2.9Fe0.36 phase. The EDS results indicated that 7.3 $\mu$m coatings were prepared which was bonded metallurgically with the substrate. The salt spray corrosion test result showed that the corrosion product film of coating was dense while the corrosion film of carbon steel was multilayered in morphology. The corrosion product film of CrNi coating reduced the corrosion rate. However, the corrosion product of Q235 with loose multi-layer structure increased corrosion process. The erosion corrosion properties of carbon steel and coating were tested in NaCl solution with different flowing speed through electrochemical test methods. The erosion corrosion results showed that the corrosion rate of carbon steel was increased in flowing NaCl solution. The corrosion product of CrNi coating could protect inner material in NaCl solution at flowing speed of 2 m·s${}^{-1}$ to 6 m·s${}^{-1}$.

The problem of scattering of electromagnetic waves is one of the most essential problems of electromagnetic theory and presents a significant interest in both theoretical and practical applications (e.g. telecommunications, electromagnetic interaction, biomedicine, remote sensing, etc.) The solution to such a problem involves the computation of surface or spatial current density on scatterers followed by the computation of scattering field (near or far) as well as various other parameters (i.e. scattering cross section). For real scatterers the scattered field is also a function of their electrical characteristics beyond all other parameters that are involved in such problems. This paper investigates the impact of the electrical characteristics of several materials to the scattered electromagnetic field.

The inhibitive synergistic effect between a cationic dimeric surfactant, 1,2-ethane-bis(dimethyl dodecylammonium bromide) (designed as 12-2-12), and halide ions (X^-) for the corrosion inhibition of A3 carbon steel in 1 M HCl solution was investigated by polarization curve and weight loss methods. The inhibition system composed by 12-2-12 and X^- is efficient. The percentage inhibition efficiency (η%) for each inhibition system increased with increasing KX concentration. The optimum dosage is around 0.1~1mM of halide salts in the presence of 12-2-12. And the inhibition efficiency (η) increased according to the order: 12-2-12/I^- >12-2-12/Br^- >12-2-12/Cl^-. The maximum inhibition efficiency of 12-2-12/I^- approached 99.3% when KI concentration reached a limiting value at 0.1mM.