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The inhibition behavior of 1H-benzotriazole on corrosion of mild steel and Aluminum alloy 1050 in single and couple modes was investigated in sea water by immersion, Tafel polarization and electrochemical impedance spectrometry methods. The results indicated that an increase in inhibitor concentration cause to enhance in inhibition efficiency for both MS and AA1050 in single mode. In this case, the use of 0.01 M BTA caused to 50 and 70 percent reduction in corrosion rate of mild steel and AA 1050, respectively. BTA adsorbed on both MS and AA1050 surfaces physically according to the Langmuir adsorption isotherm. BTA was adsorbed on mild steel surface chemically when mild steel coupled to AA1050 which in turn caused the corrosion rate of mild steel to reduce more than 95 percent with respect to reference sample.   

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In the present work, the application of 8-hydroxyquinoline (8-HQ) as a ferric ion sensitive indicator, in epoxypolyamine coating was investigated. Having turn-on mechanism and showing no prematurely fluorescence when mixed with the coating precursors make 8HQ useful for detecting undercoating corrosion of St-37 which is covered by epoxy coating. The effect of different concentrations of 8HQ(0.05,0.1,0.5,1w.t%) in epoxy coating, on corrosion detection, optical, electrochemical and adhesion properties of applied coating were studied respectively by fluorescence microscopy, UV- Visible spectroscopy, electrochemical impedance spectroscopy and Pull-off methods. In the process, the sample with 0.1w.t% of 8HQ not only, showed acceptable corrosion detection performance, but also was good in optical, electrochemical and adhesion properties.

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The electrochemical behavior of specified aluminium alloys, due to their usage in cathodic protection systems and batteries such as aluminium batteries, has always been considered. The aim of this study was to design an aluminium alloy for use as an anode in aluminium batteries with saline electrolytes. Aluminium alloy with Al-Mg-Sn-Ga structure was made by stir casting technique and corrosion behavior of this alloy was evaluated using different techniques. Microstructural studies were made using optical microscopy and scanning electron microscopy. It is known that the tin particles may be either in solid solution or may be segregated as second phase particles or intermetallic compounds in the alloy and cause the active dissolution of alloy exhibiting anodic behavior. The results of immersion, open circuit and closed circuit potentials, hydrogen evolution, polarization, electrochemical impedance spectroscopy and anodic efficiency tests showed that in chloride containing mediums, alloy had an anodic behavior.

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In this study, plates of 304 stainless steel and st37 steel were welded together by friction stir welding which has been set at a welding speed of 50 and 100 mm/min and tool rotational speed of 400, 600 and 800 rpm in order to study the effect of parameter variations on micro structure and corrosion resistance.  Samples were cut from the cross section of the joint and metallographic imaging was performed after etching. For the corrosion resistance evaluation, samples were immersed in Ferric Chloride and acetic acid 2M and then were studied by macroscopic imaging and stereograms also Tafel polarization and electrochemical impedance spectroscopy (EIS) tests have been performed in 3.5% NaCl solution in order to verify weight loss results. The results showed that the corrosion rate of the St37 base metal is more than other parts of the joint. On the other hand, all parts of stainless steel 304 was galvanically protected. The best corrosion resistance among all the weld areas were determined for the weld at the tools rotational speed of 800 rpm due to minimum grain growth by heating.

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In most oil and gas industry, the corrosion rate of metals is accelerated by the presence of sulfur containing ions such as H2S species. In this study, acidic sour water corrosion of API 5L Gr.B carbon steel in oxygen-free Na2SO4+Na2S solution in the presence different concentrations of bisN-(3-nitrobenzyl) benzamide as corrosion inhibitor at temperature of 25˚C were investigated by electro impedance spectroscopy and potentiodynamic polarization technique. Potentiodynamic polarization curves showed that the inhibitor decreased the corrosion rate of API 5L carbon steel by postponing hydrogen evolution. The results showed that the inhibition efficiencies of carbon steel increased significantly with the increase of concentration of inhibitor. The inhibition efficiencies, calculated from impedance results, show the same trend as those obtained from polarization measurements.

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Corrosion of reinforced concrete structures is one of the major factors in creating intensive damages in concrete structures installed in south region of Iran. This phenomenon has been in the focus of many studies recently. Since during corrosion assessment stage there is a difference between results of accelerated and field tests, it is necessary to conduct field evaluation survey in this regard. In the current article corrosion behaviour of reinforced concrete cylinders, containing micro silica, corrosion inhibitors and without any additive were studied using Electrochemical Impedance Spectroscopy (EIS). The samples were exposed to corrosive environment in Northern margin of Persian Gulf in a corrosion research center for 8 years. Analysis of observed spectra in terms of modified Randles circuit appeared to be a reasonable approximation. In addition micro silica added samples have 1.8 and 13.4 times better charge transfer resistance comparing to the corrosion inhibitor added and without any additive samples, respectively

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Electroless deposition of Ni-P coating on AZ31 magnesium alloy was carried out after forming conversion coating on the samples by immersing in saturated NaHCO3 solution. Effect of changing immersion time in NaHCO3 solution on surface morphology, chemical composition and phase structure of coatings were studied by SEM/EDS and XRD analyses. Hardness and corrosion resistance of the coatings were studied by microhardness test and polarization test in 3.5 wt.% NaCl solution. The results indicated significant effect of pre-treatment process on morphology and therefore corrosion resistance of Ni-P coated samples. By increasing conversion film formation time to optimum time, smooth and compact Ni-P morphology was obtained. Corrosion potential was nobler for Ni-P coatings in comparison with Magnesium alloy substrates and electroless Ni-P coating improved corrosion resistance of the substrate. In addition the microhardness of the Ni-P alloy coatings was examined and Ni-P coatings enhanced hardness, significantly. Increasing the conversion film formation time to a certain amount resulted in a better morphology of the Ni-P films with less porosity and thus better corrosion resistance. Any increase in conversion film formation time more than the optimum amount led to a lower corrosion resistance.

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In this paper, the effect of cerium chloride with solution features of immersion time=15 minutes, concentration of cerium=5 gr/lit, pH =5.5 at room temprature  on the anti-corrosion behaviour of zirconium- coated steel in optimized condition with immersion time = 90 seconds,0.01 molar H2ZrF6 and pH= 4 was investigated.The results of EIS test showed that the corrosion resistance of steel without coating, with zirconium conversion coating and with zirconium-cerium conversion coating was 520, 1150 and 2400 Ω/cm 2 respectively. DC polarization test showed that the corrosion current density decreasd from 8.2 to 1.6 µA/cm2 .The addition of 200 ppm nickel sulphate to the cerium conversion solution increased the corrosion resistance of Zr-modified steel to 3300 Ω/cm 2 .

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Conversion Coatings Based on Rare Earth Elements From an Environmental Standpoint are a Good Alternative for Chromate Conversion Coatings. There are a lot of Cracks in the Structure of These Coatings and Because of This the Main Foible of These Coatings is Undesirable Anti-Corrosion Properties. Different Additives Have Been Used in the Formulation of These Coatings to Improve the Properties. In This Study, at First the Formulation of an Eco-Friendly Cerium Based Conversion Coating is Optimized. In the Next Step, the Effect of Presence of Polyvinyl Alcohol (PVA) as an Eco-Friendly Additive on the AntiCorrosion and Morphological Properties of the Coating on a Steel Substrate is Investigated. DC Polarization, SEM, EDS, XRD and Contact Angle Tests Have Been Utilized to Analyze the Samples. The Results Show that the Presence of PVA in the Coating Formulation Reduces the Number of Cracks in the Structure of the Coating and Leads to Formation of a Coherent and Corrosion Resistant Coating. Consequently, it Can be Said that Polyvinyl Alcohol (PVA) Acts as an Inhibitor on the Steel Substrate and By Means of Creating Complexes in the Anodic and Cathodic Areas may Improve the Anti-Corrosion Properties of the Cerium Based Conversion Coating. Based on the Results, the Lowest Corrosion Rate is Related to the Conversion Coating Containing the Maximum Concentration of Poly Vinyl Alcohol.

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In this study, Zinc-Nickel electrophosphate coating was applied on galvanized steel. microstructure, corrosion resistance and porosity of coating were characterized using scanning electron microscopy, polarization test and electrochemical method respectively, Zn-Ni electrophosphate coating was applied on galvanized steel substrate using cathodic electrochemical method at different operation times, the result of this study indicated that, by using cathodic electrochemical method, coating with the desired properties can be obtained at low temperature bath. Result of microscopic study indicated that, in low operation time, the surface of the substrate not fully covered by phosphate crystals, consequently, coating with poor corrosion resistance can be obtained, also at the high operation time, excessive growth of phosphate crystals leads to high porosity in the coating. Therefore, by increasing the operation time from 20 min to 40 min the corrosion current density increase from 0.68µA/cm2 to 2.54 68µA/ cm2 consequently, the optimized time for obtaining the coating with desired properties is 20 minutes. Also the deposition mechanism of Zn-Ni electrophosphate coating was investigated in this study.

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Due to the formation of porous oxide on the steel surface it can't directly use by PEO procedure. Therefore, in this research, hot diPping process (at 750°C and 5 min) was used to deposit Al coating on steel substrate. Plasma electrolytic oxidation (PEO) was aPplied on the obtained aluminized coating to measure its resistance to corrosion attack. SEM was used to evaluate the microstructure of PEO coatings deposited on aluminized steel by different aPplied Voltages. XRD was also used to analyze the phases on PEO coatings generated by aPplied different Voltages. Corrosion behavior of the coatings was also investigated using polarization tests in 3.5% NaCl solution. Results in indicated that the coated samples prepared at 400 Volts developed a coatings with porosity of  about 4.86% and a thickness of  30 μm had a corrosion current density of 2.88 ×10-8 A/cm2  which in comparison to that of coated samples produced at Voltages of 350 and 450 Volts with corrosion current densities of 1.04×10-7 A/cm2 and
 2.18×10-7 A/cm2  respectively showed an improvement of 1.98 to 2.5 times in corrosion resistance

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The cladding of plain carbon steel with stainless steel is desired in industry because increase of corrosion resistance and reduction of economic costs. The cladding using tungsten electrode arc welding and shielding gas is in more attention due to unique features such as high quality and good adhesion to the base metal. In this study ER309L austenitic stainless steel was used as the primary layer and E316L as the final layer, on the SA516- Gr70 steel as well as the effect of heat input at four heat level (574.5 j/mm, 609, 673, 743.5) was investigated. The ferrite was measured by a ferrite meter and Cr-Ni equivalent chart. From these results the amount of ferrite was higher at minimum heat input with respect to other heat inputs. The corrosion resistance of the samples was evaluated. According to the results, it was observed that increasing the heat input reduced the corrosion resistance and the highest corrosion resistance was observed at minimum heat input (574.5 j /mm).

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Using fluoride mouth washes is recommended to protect the teeth during orthodontic treatment. Therefore it is important to investigate the effect of fluoride ion on the pitting corrosion of orthodontic archwires. The aim of this study is to investigate the effect of fluoride ion on the corrosion behaviour of NiTi and NiTiNb orthodontic archwires in chloride solution by means of potentiodynamic and potentiostatic polarysation techniques. Results revealed that NiTi orthodontic wire is susceptible to pitting corrosion in chloride solution. Fluoride ion was found to have an inhibition effect and its addition increases the pitting potential for NiTi wire. The pitting potential increases also by increment in the F-/Cl- concentration ratio. NiTiNb orthodontic archwire shows passivity behaviour in sole fluoride solutions; however, its pitting corrosion was observed in solution containing both chloride and fluoride ions.

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The study employed sequential DC plasma electrolytic oxidation on morphology and behavior of coatings on CP titanium. The coatings formed in two steps first in silicate, next in calcium phosphate. The influence of second step coating in silicate and calcium  phosphate electrolytes on morphology, phase structure and corrosion behavior were studied using SEM followed by EDS, XRD and polarization. Due to low thickness coating in silicate electrolyte and increasing applied Voltage, coatings formed in calcium phosphate have a low size porosity compare to coating formed in silicate electrolyte and in turn revealing an improvement in corrosion resistance. Unlike coatings formed first in calcium phosphate then in silicate electrolyte, the size of porosity increased and corrosion resistance has been decreased.

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Well-known corrosion and wear resistance of electroless nickel phosphorus (NiP) coatings led studies on upgrading of mechanical and chemical properties and feasibility of its application in different industries. In this study, the effect of coating applying time on corrosion and wear resistance of the electroless nickel phosphorus-nano graphene oxide composite coating (NiP/GO) on st37 steel substrate was studied, comparing the simple electroless nickel phosphorus coatings. According to the polarization and electrochemical impedance spectroscopy results, NiP/GO deposit possessed more corrosion resistance than NiP coatings and the appropriate coating time was 60 minutes. The results also revealed that the presence of graphene oxide in nickel phosphorus coatings and increasing of coating applying time causes increasing of the coating microhardness by 279.8 HV and the friction coefficient by 19.33%.

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Plasma electrolytic oxidation was employed for producing alumina, alumina/titania composite and alumina/ titania composite coatings containing sodium tungstate additive. These coatings were produced in a silicatebased electrolyte on 7075 aluminum alloy using unipolar and bipolar waveforms with anodic/cathodic duty aspect ratios of 1 and 0.5. The results showed that the morphology of the coatings surfaces depends on the used waveform. By increasing the cathodic duty cycle, pancake-like morphology was converted to crater-like one. The incorporation of TiO2 nano-particles into the coatings, led to the widening the micro-pores when unipolar waveforms were used. The results revealed that the incorporation of TiO2 nano-particles doesn’t depend on the used waveforms. Titania nano-particles were incorporated into the coatings via a physical entrapping mechanism, while the adsorption mechanism of tungstate ions was electrophoretic. The corrosion resistance of the coatings was increased by increasing the cathodic duty cycle. Furthermore, the use of titania nanoparticles led to a reduction of corrosion resistance and the use of tungstate additive in bipolar waveform compensated the reduced resistance. The corrosion currents recorded 3, 5 and 3 nano-amperes for simple, composite and additive contained composite coatings respectively.

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In this study, the ion beam sputtering method was used to deposit the optimized ZrN coating with 1 μm thickness on AZ91 magnesium alloy at 400 °C and then the HA coatings were created on them at temperatures of
 150 °C, 200, 250, 300, and 350 °C for 360 minutes. The profilometry and indentation methods for thickness and film adhesion evaluation showed that, from 150 to 300 °C the thickness decreases from 8.1 μm to 3.3 μm and dp/dr ratio increases  from 0.07 to 0.2 kg/μm. The analysis of the x-ray diffraction pattern by Williamson - Hall method showed that, by increasing the temperature to 300 °C the grain growth is dominated therefore the grain size reaches to 0.36 μm, but with increasing the temperature to 350 °C, grain size decreases to 0.12 μm. The potentiodynamic polarization test showed that, all coated samples have corrosion potential close to AZ91 about 1.54 Volt vs. SCE and the corrosion current density in the deposited samples at 300°C showed the minimum current density about 0. 33 μA/cm2.

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In this study two step method was used in order to fabricate superhydrophobic surface with high corrosion resistance and chemical stability on Ti substrate. At first shot peening treatment was applied on Ti surface and then etching operation was carried out on it. Finally, silane operation was done on Ti surface in order to reduce the surface energy. The effect of shot peening treatment on wettability, corrosion behavior and long term chemical stability of fabricated superhydrophobic surface was studied. The results indicated that, the network fiber structure is in nanometer scale which bonded with functional group of methyle tricolor silane on Ti substrate. Corrosion resistance of superhydrophobic surface was analyzed by immersion, potentiodynamic polarization and EIS test in 3.5%wt NaCl solution. Also long tern stability of fabricated coating was studied by immersion in 3.5%wt NaCl solution for different times. The results showed that the highest contact angle of 159° was obtained for pre- shot peened samples. The corrosion resistance evaluation studies also indicate the high corrosion resistance of pre shot peened sample. Also the surface with high corrosion resistance indicate highest chemical stability and contact angle.

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In this study stress corrosion cracking behavior of X70 pipeline steel after shielded metal arc welding has been investigated. For this purpose, the alloy was welded by low, medium and high rates of heat input. Microstructures of specimens were studied using light and electron microscopes. Stress corrosion cracking susceptibility was evaluated using slow strain rate tests in C2 simulated soil solution in free corrosion potential. Scanning electron microscopy was used to examine the fracture surfaces. Corrosion of different areas of weld was evaluated by potentiodynamic polarization test method. Results showed that by increasing heat input, tensile strength and hardness of welded metal reduces, larger heat affected zone (HAZ) is produced and the grain size is increased. Slow Strain Rate Test (SSRT) results showed that increasing the welding heat input will reduce the susceptibility to SCC. SEM images obtained from samples confirmed brittle fracture of specimens tested in the corrosive environment. It was also observed that the produced cracks might grow in transgranular mode. Potentiodynamic polarization tests showed the lowest rate of anodic dissolution for welded samples with higher heat inputs. Overall, results showed that by reducing heat input the susceptibility to SCC increases; this is due decrease in areas which are sensitive to crack growth and initiation.

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In this study, the effect of processing time on microstructure and corrosion behavior of coatings fabricated by plasma electrolytic oxidation (PEO) on pure titanium substrate was investigated. All PEO processes were performed in aluminate based electrolyte and under constant applied voltage (420 V) and at three times (180, 240 and 300 s). By studying the surface morphology of coatings, it was found that the coating formed at 180 s had the most compact and uniform structure with smallest micropores and the least porosity. The XRD pattern of this coating showed that the coating is composed of rutile, anatase and TiAl2O5 phases. Also, studying the corrosion behavior of coatings with potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) tests in 3.5 wt.% NaCl solution proved that the coating formed at 180 s exhibited the most noble corrosion potential, the lowest corrosion current density and  the most polarization resistance and so the best corrosion resistance among all samples.