Tribo-corrosion behavior of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel

In this investigation , Zn-Ni-Cu and Zn-Ni-Cu-TiB₂ were coated on a mild steel specimen using a high velocity oxy fuel thermal spray (HVOF) process. The surface morphology and coated powder distribution of coated specimens were characterized using scanning electron microscope (SEM), energy dispersive spectroscopy (EDS), and X-ray-Elemental mapping. The pin-on-disc (ASTM G99-17) method was used to examine the wear resistance of the coated and uncoated mild steel specimens. Both coated Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on mild steel saw reduced wear volume loss than uncoated mild steel. The coated samples of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on Mild Steel were put through a scratch test to determine the adhesion strength of the coating with the substrate. The adhesion strength of coated Zn-Ni-Cu and Zn-Ni-Cu TiB2 mild steel was higher than that of untreated mild steel, indicating a solid link between the coating and substrate and minimal delamination. Using the Vickers hardness test to measure the hardness caused by the coating, it was shown that coated samples of Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel had significantly higher hardness than uncoated mild steel. Using ASTM G1-03 and ASTM G-31 standards, a 0.2 M HCl immersion cycle test was conducted for 28 days to test the corrosion resistance of coatings in an acidic media (672Hrs). When compared to Zn-Ni-Cu and Zn-Ni-Cu-TiB2 coated mild steel, the weight loss for the uncoated mild steel was significantly larger. Additionally, XRD examination showed that coated samples had less rust on their surface than uncoated samples. Both Zn-Ni-Cu and Zn-Ni-Cu-TiB2 on Mild Steel were anti-corrosive, as evidenced by increased corrosion potential and reduced corrosion current density when compared to uncoated mild steel, according to electrochemical impedance spectroscopy (EIS)/Tafel study in 0.2 MHCl. The outcomes of each test were very encouraging and demonstrated the durability of these coatings against wear and corrosion.     

Two layered silica protective film made by a spray-and-dip coating method on 304 stainless steel

The silica coating has attracted much attention because of its superior corrosion resistance with almost no harm to human health and to the environment. In this study, a two layered silica film was tried to get an enhanced corrosion resistance. The silica film was prepared on the hairline finish 304 stainless steel surfaces by-a-spray- and subsequent-dip-coating process. The spray coating solution was prepared by mixing sodium silicate solution, silica colloid, tetraethyl orthosilicate (TEOS), methyltriethoxysilane (MTES), ethanol, and distilled water. Then the solution was sprayed onto the stainless steel surface, and was dried and heat treated. The dip coating solution was prepared by a simple mixing of TEOS and acidic water into ethanol, and the prior spray coated sample was dipped into the solution. The outer dip coated layer was intended to cover spray coated rough and porous layer and hence to enhance the corrosion resistance. A homogeneous and crack free surface was successfully obtained after the dip coating. The prepared silica film was characterized using scanning electron microscopy, potentiodynamic polarization scan, and electrochemical impedance spectroscopy. The two layered film showed an enhanced corrosion resistance. The enhancement was attributed to a protecting effect of the dip coated layer where the diffusion of ionic species was successfully impeded.     

EIS monitoring study of the early microbiologically influenced corrosion of AISI 304L stainless steel condenser tubes in freshwater

This study examined the early stages of tarnishing of American Iron Steel Institute (AISI) 304L austenitic stainless steel (SS) condenser tubes in contact with running freshwater from the Tagus River in Spain. The immersion time of the tubes was 569 days. Tarnishing originated by biofouling was assessed using electrochemical impedance spectroscopy (EIS), scanning electron microscopy (SEM), and X-ray photoelectron spectroscopy (XPS) analyses in conjunction with argon ion sputtering. The EIS diagrams showed a semicircle that was better defined as the experimental time increased, indicating the decreasing tarnishing resistance of the immersed specimens. The EIS results were validated using Kramers–Kronig relationships. SEM micrographs of biofouling indicated that the number of microorganisms on the SS surfaces increased with immersion time. According to the XPS spectra, the main elements deposited on the tarnished AISI 304L SS layer were calcium, phosphorus, and nitrogen. A mechanism of biofouling and microbiologically influenced corrosion behavior of AISI 304L SS condenser tubes in freshwater is proposed.     

Preparation,Characterization, and Evaluation of the Anticorrosion Performance of Submicron/Nanocarbon from Jute Sticks

Jute stick, one of the most commonly and abundantly available agricultural waste product, was converted to a value-added submicron/nano jute carbon by using pyrolysis and high-energy ball milling techniques. The submicron/nano jute carbon was characterized using FE-SEM, TEM, EDS, XRD, XPS and Raman spectroscopy. The anticorrosive performance of the submicron/nano jute carbon was investigated through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP) and salt spray techniques, on mild steel plates coated with a mixture of epoxy resin and the submicron/nano jute carbon. The electrochemical impedance of the steel coated with the composite coating was two orders of magnitudes higher than that of the specimen coated with neat epoxy. Consequently, the corrosion rate of specimens coated with composite coating was 13–20 times higher than that of steel coated with neat epoxy coating. The salt spray results also indicate an improvement in the corrosion resistance performance of the composite coating compared to the neat epoxy. The uniform distribution of the submicron/nano jute carbon particles in the epoxy resin improved the denseness of the composite coating by acting as a barrier against the diffusion of chloride, moisture, and oxygen, thus, improving the corrosion resistance of the developed coating.     

A study on the electrochemical polymerization, characterization, and corrosion protection of o-toluidine on steel

Poly(o-toluidine) (POT) coatings were electrochemically synthesized on 304 stainless steel using cyclic voltammetric method. These coatings were characterized by Fourier transform infrared spectroscopy, UV–vis absorption spectroscopy, and cyclic voltammetry. The corrosion performance of POT coating in aqueous 3 wt% sodium chloride was assessed by the electrochemical techniques such as open circuit potential measurements, potentiodynamic polarization technique, cyclic potentiodynamic polarization measurements, and electrochemical impedance spectroscopy. The results reveal that POT coating on 304 stainless steel prevents general and localized corrosion, and reduces the exchange current density almost by a factor of 45 than bare 304 stainless steel.     

Impact of sensitization on dissolution process of AISI 304 stainless steel during intergranular corrosion evaluated using DEIS technique

The paper presents the results of instantaneous impedance changes measurements vs. reactivation potential performed by means of dynamic electrochemical impedance spectroscopy (DEIS) technique for AISI 304 stainless steel (SS) dissolution process during intergranular corrosion (IG) in 0.5 M H₂SO₄ + 0.01 M KSCN solution. With the use of DEIS method, it was possible to estimate dynamic changes of the examined system’s impedance in conditions of proceeding IG process. Furthermore, the paper proposes an alternative way of evaluating AISI 304 stainless steel dissolution rate during intergranular corrosion based on approximation to theory of iron dissolution in sulfuric acid medium. Simultaneously, based on the DEIS measurements, information about the degree of sensitization of the examined material were obtained. Performed research revealed the advantages of the DEIS technique over the classical double-loop electrochemical potentiokinetic reactivation tests when investigating intergranular corrosion process.     

Electrochemical and XPS studies on corrosion behaviours of AISI 304 and AISI 316 stainless steels under plastic deformation in sulphuric acid solution

The corrosion behaviours of austenitic stainless steels were investigated by electrochemical methods under plastic deformation with constant strain in the naturally aerated 0.5 M H₂SO₄ + 0.2 M KCl solution at room temperature. The work addresses the influence of plastic deformation and molybdenum element on the corrosion resistance of austenitic stainless steels in the test solution. Electrochemical impedance spectroscopy presents the decreasing charge transfer resistance (R_t) and polarization resistance (R_p) values with the immersion time for AISI 304 stainless steel under constant strain deformation, and the increasing R_t and R_p values with the immersion time for AISI 316 stainless steel. The analysis of the chemical composition of the corrosion products was carried out by XPS. Molybdenum addition in AISI 316 stainless steel affects significantly the corrosion resistance because of its high ability to form Mo (VI) and MoCl₅ insoluble compounds in acid medium. Copyright © 2011 John Wiley & Sons, Ltd.     

Effect of thermal annealing of poly(3-octylthiophene) films covered stainless steel on corrosion properties

The effect of thermal annealing of poly(3-octylthiophene) (P3OT) coatings on the corrosion inhibition of stainless steel in an NaCl solution was investigated. P3OT was synthesized by direct oxidation of the 3-octylthiophene monomer with ferric chloride (FeCl₃) as oxidant. P3OT films were deposited by drop-casting technique onto 304 stainless steel electrode (304SS). 304SS coated with P3OT films were thermally annealed during 30 h at different temperatures (55°C, 80°C, and 100°C). The corrosion resistance of stainless steel coated with P3OT in 0.5 M NaCl aqueous solution at room temperature was investigated by using potentiodynamic polarization curves, linear polarization resistance, and electrochemical impedance spectroscopy. The results indicated that the thermal treatment at 80°C and 100°C of P3OT films improved the corrosion resistance of the stainless steel in NaCl solution; the speed of corrosion diminished in an order of magnitude with regard to the 304SS. In order to study the temperature effect in the morphology of the coatings before and after the corrosive environment and correlate it with corrosion protection, atomic force microscopy and scanning electron microscopy were used. Morphological study showed that when the films are heated, the grain size increased and a denser surface was obtained, which benefited the barrier properties of the film.     

High temperature oxidation resistance and corrosion properties of dip coated silica coating by sol gel method on stainless steel

Silica coating for the protection of stainless steel (SS) surfaces was prepared using tetraethoxysilane and methyltriethoxysilane as precursors via an acid-catalysed (H₂SO₄) sol?Cgel method and was deposited on ferritic SS AISI 430 by dip coating. The surface morphology was studied using a scanning electron microscope equipped with energy-dispersive X-ray, phase analysis was carried out by X-ray diffraction, and isothermal oxidation was carried out at 800?°C for 200?h. Corrosion properties were examined by electrochemical impedance spectroscopy and resistance polarization methods in an aqueous medium containing 3.5?wt?% NaCl. The results indicated that silica coating improved high-temperature oxidation resistance of AISI 430 in chloride media.     

电镀锌钢硅烷-有机膦酸复合钝化膜的制备及性能表征

利用N-(β-氨乙基)-γ-氨丙基三甲氧基硅烷(AAPTMS)、γ-(2,3-环氧丙氧基)丙基三甲氧基硅烷(GPTMS)和1-羟基亚乙基-1,1-二膦酸(HEDP),在电镀锌钢基体上制备了一种新型硅烷-有机膦酸复合钝化膜.X射线光电子能谱、傅立叶变换红外光谱以及中性盐雾试验、动电位极化曲线和电化学阻抗谱测试表明:该复合钝化膜主体结构由Si—O—Si、Si—O—P等组成;120 h中性盐雾试验后白锈面积小于5%,达到铬酸盐彩色钝化膜水平;且其腐蚀反应呈现更为明显的阳极扩散控制特征,属于物理阻挡机制.     

Synthesis and Properties of Cerium and Titanium Oxide Thin Coatings for Corrosion Protection of 304 Stainless Steel

Powders and thin coatings of ceria and titania were synthesized from aqueous and solvent-based precursors. Thin coatings were deposited on polished 304 stainless steel coupons by dipping them in the appropriate sol-gel oxide precursors. The coatings were subsequently densified and crystallized at several hundreds of degrees. It was possible to obtain dense titania coatings by applying thin coatings of cerium dioxide prior to titania on stainless steel substrates. Underlayer ceria coatings proved to be pivotal in obtaining dense titania coatings and preserving the integrity of the stainless steel while going through the high temperature treatments. The effect of processing parameters such as the atmosphere of heat-treatment, and temperature on the microstructure and crystal structure of the films and powders of ceria and titania was investigated. X-ray diffraction was used to identify the crystal structure of films and powders upon heat-treatment. Electrochemical measurements in NaCl, and analytical techniques such as SEM and EDX were used to evaluate the corrosion performance and pitting morphology of coated samples. A composite coating of ceria and titania was able to prevent crevice corrosion and increase the pitting resistance of the 304 stainless steel relative to the uncoated substrate.     

An Electrochemical Study on the Corrosion Inhibition of Stainless Steel by Polyaniline Film

Polyaniline(PANI)film was electrosynthesized on 304 stainless steel by cyclic voltammetry using aqueous oxalic acid as supporting electrolyte.The potential sweep rates were changed to achieve the PANI film with different thickness and structures.Protective properties of the PANI film for corrosion of stainless steel in 3% NaC1 aqueous solution were investigated by monitoring potentiodynamic polarization curves and electrochemical impedance spectroscopy(EIS).The results showed that the PANI film which was formed with lower sweep rate led to more positive shift of corrosion potential and greater charge transfer resistance,reflecting higher inhibition for corrosion of the stainless steel.     

Electrochemical behavior of Ni-Al-Fe alloys in simulated human body solution

An investigation about the corrosion resistance of Ni-Al-Fe intermetallic alloys in simulated human body fluid environments has been carried out using electrochemical techniques. Tested alloys included 57 (wt%) Ni-(20 to 30) Al-(12 to 23) Fe using the Hank's solution because the high corrosion resistance provided by protective Al₂O₃ external layer. For comparison, AISI 316L type stainless steel has also been used. Electrochemical techniques included potentiodynamic polarization curves, electrochemical impedance spectroscopy, and electrochemical noise measurements. The different techniques have shown that these alloys showed a similar or higher corrosion resistance than conventional AISI 316L type stainless steel, and this corrosion resistance decreased as the Al content in the alloy increased. The alloys were susceptible to pitting type of corrosion on the interdendritic Ni-rich phases.     

Structure,hydrophilicity and corrosion resistance of sol–gel derived Ag-containing TiO2 film on plasma nitrided 316L stainless steel

Pure and Ag-containing TiO₂ films (Ag/Ti = 3.3 at.%) are coated on plasma nitrided 316L stainless steel by sol–gel method for biomedical applications. The addition of Ag does not cause obvious change in TG–DSC curves of the dried gels. The rough surface generated by plasma nitriding and the addition of Ag improve structural integrity of the TiO₂ films. X-ray diffraction reveals N loss and oxidation of the nitride layer during calcination treatment, and peaks of Ag or its oxides are not detected. X-ray photoelectron spectroscopy analysis indicates that Ag presents as metallic state in the film. Water contact angles of the coating samples decrease with UV irradiation treatment. The potentiodynamic polarization tests in a Ca-free Hank’s balanced salt solution show that the TiO₂ coated samples have decreased corrosion resistance due to N loss and oxidation of the nitride layer. The methods for crystallization of TiO₂ gel layers with minimized or avoided structural changes of the nitride layer will be tried in order to improve corrosion resistance of the duplex treated 316L stainless steel.     

Effect of sulfate and dissolved hydrogen on oxide films on stainless steel in high-temperature water

In the present paper, we focus on the influence of sulfate ion impurity and dissolved hydrogen on the protective ability of the oxide film on stainless steel in high-temperature water. For the purpose, the electrical and electrochemical properties of oxide films formed on AISI 316L NG in simulated boiling water reactor crack conditions (10 ppm sulfate purged with N₂ + 0.01 or 0.5% H₂) were characterized by in situ electrochemical impedance spectroscopy (EIS). In addition, the surface and in-depth composition of the oxide films has been estimated by ex situ Auger electron spectroscopy (AES). The quantitative assessment of the protective ability of the oxide is based on an interpretation of the electrochemical impedance data per the mixed-conduction model. A novel procedure for the estimation of kinetic and transport parameters that involves comparison of the model equations to both EIS and AES results is proposed and tested. Based on the parameter values, the effect of sulfate and dissolved hydrogen on the processes of film growth and dissolution is discussed in view of an approach to the initiation of stress corrosion cracks.     

Structural and electrochemical characterization of sputter-deposited nitrided NiCr alloys

Nickel-based coatings are potential candidates for the protection of electrochemical dissolution of steel surfaces. Such coatings, elaborated by magnetron sputtering in a nitrogen atmosphere, offer good corrosion protection, good adherence as well as stability for metallic structures. NiCr alloys with almost constant composition have been deposited with different nitrogen contents on stainless steel and carbon steel surfaces. The coating uniformity, homogeneity, composition and crystallinity have been studied by scanning electron microscopy, energy-dispersive X-ray spectrometry, atomic force microscopy and X-ray diffraction techniques. The corrosion degradation behavior of all the samples was tested in NaCl and NaCl and CO₂ mixture exposures using electrochemical impedance spectroscopy measurements. Nitrided NiCr alloys on a stainless steel substrate resulted with better adhesion than carbon steel, by delaying the corrosion mechanism when exposed to NaCl and CO₂ solution. A comparison of the corrosion resistive behavior of the substrates (stainless steel, carbon steel) and the coatings is made by using the electrical capacitance concept from a double-layer model for the coating–metal interface.     

Poly(3-octylthiophene) and polystyrene blends thermally treated as coatings for corrosion protection of stainless steel 304

The effect of thermal annealing of poly(3-octylthiophene) (P3OT) and polystyrene (PS) blend coatings on the corrosion inhibition of stainless steel in a 0.5 M NaCl solution was investigated. P3OT was synthesized by direct oxidation of the 3-octylthiophene monomer with ferric chloride (FeCl₃) as oxidant. Stainless steel electrodes with mirror finish were coated with P3OT/PS blend by drop-casting technique. In order to study the temperature effect on the function like physical barrier against the corrosive species of P3OT/PS polymeric blend, the coatings were thermally annealed at three different temperatures (55?°C, 80?°C, and 100?°C). The corrosion behavior of P3OT/PS-coated stainless steel was investigated in 0.5 M NaCl at room temperature, by using potentiodynamic polarization curves, linear polarization resistance (LPR), and electrochemical impedance spectroscopy. The LPR values indicated that, at 100?°C, P3OT/PS coatings showed a better protection of the 304 stainless steel in 0.5 M NaCl; the corrosion rate diminished in two orders of magnitude with regard to the bare stainless steel. The superficial morphology of the coatings before and after the corrosive environment was researched by atomic force microscopy, optic microscopy, and scanning electronic microscopy. Morphological study showed that the increased temperature benefited the integration of the two polymeric phases, which improved the barrier properties of the coatings. The coating/metal adhesion and the coating thickness were evaluated. The temperature increases the adhesion degree coating/substrate; thus, the coating annealed at 100?°C showed the best adhesion.     

Investigation of Glass-Like Sol-Gel Coatings for Corrosion Protection of Stainless Steel Against Liquid and Gaseous Attack

Glass-like sol-gel coatings have been investigated as corrosion protective coatings on stainless steel. Magnesium- and borosilicate coatings with thickness of about 100–700 nm and methyl-modified SiO2 coatings with a thickness of about 2 m were deposited on stainless steel plates by dip-coating. The coatings were densified between 400°C and 500°C in different atmospheres (N2, air) for 1 h. The corrosion protection against gaseous attack was investigated by accelerated corrosion tests, at 800°C in air for 1 h. A corrosion protection factor was calculated from the relation Fe/Fe2O3, determined by XRD on the surface of coated and uncoated samples. Methyl-modified SiO2 coatings showed a protection factor, which was 2 orders of magnitude higher than for the other coatings. Electrochemical investigations were performed on samples submerged in a NaCl solution for 200 h. The corrosion propagation, polarization resistance and impedance vector were measured. For accelerated corrosion tests, polarization intensity curves were determined for high potentials of up to 1 V. Again excellent results were obtained for the methyl-modified SiO2 coatings, which remained passive for 200 h. Results of the salt spray corrosion test, however, showed no corrosion protection by the sol-gel coatings. After 2000 h in the salt spray chamber the steel was corroded and the coatings peeled off. It is concluded that for the further development of these coatings an improved interfacial passivation will be required.     

再生水环境中304不锈钢生物膜腐蚀电化学特征

研究了以再生水作为循环冷却系统补水的北京某热电厂冷却塔底粘泥中分离纯化培养出来的硫酸盐还原菌(SRB)生长特性.采用原子力显微镜(AFM)、扫描电镜(SEM)、能谱分析仪(EDS)和电化学交流阻抗(EIS)方法研究了304不锈钢(SS304)表面生物膜特征及其主要成分和不锈钢/生物膜界面电化学行为.结果显示,再生水环境下304不锈钢表面形成的生物膜是由吸附的SRB菌体及以含碳有机物为主的胞外聚合物和FeS腐蚀产物构成.浸泡前期(前7 d)SS304电极表面阻抗值主要由SS304表面钝化膜的贡献;浸泡后期(14 d后),电极体系阻抗值由不锈钢表面钝化膜和生物膜共同贡献.     

EIS and XPS studies on passive film of AISI 304 stainless steel in dilute sulfuric acid solution

Electrochemical impedance spectroscopy and XPS studies on AISI 304 stainless steel in naturally aerated 0.5 M H₂SO₄ solution were carried out at room temperature. The valuable model of the metal/solution interphase was established, and the reliable equivalent electrical circuits in the solution were presented. The analysis of the chemical composition of passive film on AISI 304 stainless steel was carried out by XPS. The passive film of AISI 304 stainless steel is composed of oxyhydroxides, Fe₂O_3, FeO, Cr₂O₃, NiO, sulfate, sulfite, and sulfide (FeS, NiS). It is reported that the ferrous sulfide film formed on AISI 304 stainless steel in the dilute sulfuric acid solution. The possible process in which sulfuric acid is reduced to sulfite and sulfide is proposed. The galvanic interaction of sulfide inclusions with the base alloy is introduced. Copyright © 2011 John Wiley & Sons, Ltd.