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.     

EIS study on passive films of AISI 304 stainless steel in oxygenous sulfuric acid solution

Electrochemical impedance spectroscopy (EIS) and Kramers–Kronig (K–K) transforms were made on American Iron and Steel Institute (AISI) 304 stainless steel (SS) in naturally aerated sulfuric acid solution at room temperature. The K–K relations testify that the systems under investigation comply with the linearity, causality, and stability constraints of linear system theory (LST) and thereby validate the EIS data. The polarization resistance decreased with removing of passive film and pitting formed in the passive layer, due to layer thinning or pitting caused by chloride. The impedance data for 304 SS with passive films can be accurately modeled using individual components of the equivalent circuits. The polarization resistances (Rp) of the 304 SS can be confirmed by Nyquist plots and estimated from the anodic polarization curves. The reaction model of the dissolution‐passivation process of 304 SS in acid solution is proposed. Copyright © 2009 John Wiley & Sons, Ltd.     

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.     

The influence of Cu on the electrochemical behaviour of 304 stainless steel in 0.1M H3PO4 solution

The effect of different Cu addition on the electrochemical and passivation behaviour of the 304 series stainless steel in 0.1 M phosphoric acid solution was evaluated by the potentiodynamic measurements and electrochemical impedance spectrum (EIS). The effect of Cu on chemical composition of the passive film formed in the solution was also studied by X‐ray photoelectron spectroscopy (XPS). The results indicated that Cu did not appreciably improve the corrosion resistance of the passive film, but enhanced the passivation, lowered the critical and passive current density. The passive and critical current density decreased with Cu content increased. The presence of Cu in the passive film affects passive film stability. Cu can modify the proportion of Cr element in the passive film, and also change the components of Fe in the passive film. Copyright © 2012 John Wiley & Sons, Ltd.     

Hydrogen effects on microstructural evolution and passive film characteristics of a duplex stainless steel

We revealed the effects of hydrogen on the microstructural evolution and passive film properties of a 2205 duplex stainless steel by the joint use of electron backscatter diffraction (EBSD), electron channeling contrast imaging (ECCI), X-ray photoelectron spectroscopy (XPS) and electrochemical measurements. The microstructural analysis results show that effects of hydrogen on the two phases are different: (i) in austenite, stacking faults are induced by hydrogen, and (ii) in ferrite, hydrogen causes an increase of the dislocation density. The XPS analysis revealed that hydrogen reduced the occurrence of Cr₂O₃ and nitrogen in the passive film, leading to the reduction of their overall thickness. Furthermore, for the first time we demonstrated that the hydrogen release time plays an important role in the electrochemical behavior of the hydrogen charged steel.     

不锈钢载波钝化膜的半导体性质

运用交流阻抗法和光电化学法研究了不锈钢载波钝化膜层的半导体性质。讨论了交流阻抗测试中扰动频率的变化对Mott-Schottky曲线的影响，讨论了不锈钢载波钝化膜的n/p型、杂质施主密度和平带电位等半导体性质，同时结合光电化学法对交流阻抗测试结果进行了验证分析，实验结果认为不锈钢载波钝化膜层具有与直流钝化膜层相似的半导体性质，并通过膜层的组成结构对其半导体性质作了分析。     

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.     

Studying the fine microstructure of the passive film on nanocrystalline 304 stainless steel by EIS,XPS, and AFM

The fine microstructure of the passive films on nanocrystalline (NC) and coarse crystalline (CC) 304 stainless steels (SSs) in 0.5 M H₂SO₄ were investigated by electrochemical impedance spectroscopy (EIS), X-ray photoelectron spectroscopy (XPS), and atomic force microscopy (AFM). The results indicate that the passive film on both CC and NC SSs exhibits a two-layer microstructure consisting of a compact inner layer and a porous outer layer. Some hydrated compounds (HC) were present in the porous outer layer of NC SS but not CC SS in 0.5 M H₂SO₄ solution. The pores in the outer layer of the NC SS were observed to be in the nanoscale by AFM. HC filling of the pores in the passive film on NC SS may occur due to capillary forces endowed by the nanosize pores. XPS analysis of the passive films on both CC and NC SSs, however, does not show such a composition difference which is attributed to dehydration occurring in the XPS vacuum chamber. Both the inner and outer layers of the NC SS were determined by EIS analysis to be more compact and protective than the corresponding films on CC SS as evidenced by the lower Q value, higher n, and much higher R value in the corresponding layer.     

Corrosion resistance of amorphous AlPO4 coating in salty atmospheres

The objective of the present study was to introduce a cost-effective and environmentally friendly coating to improve the corrosion resistance of the structures located in salt water. The coating solution, based on amorphous aluminum phosphate composition, was synthesized by sol–gel process and applied to AISI 304 stainless steel by dip coating technique. X-ray diffraction, scanning electron microscopy, and energy dispersive X-ray spectroscopy analyses were employed to investigate the phase composition and morphology of the coating. Corrosion behavior of the uncoated and coated samples was investigated using standard salt spray test, potentiodynamic polarization, and electrochemical impedance spectroscopy (EIS) in 3.5 wt.% NaCl solution. Salt spray test results for the bare substrate revealed a corrosion rate of six-time greater than that of the coated surface after 168 hr exposure time. Electrochemical test results declared that the amorphous AlPO₄ coating decreased the corrosion current density of the AISI 304 stainless steel by 10 orders of magnitude. Furthermore, according to the corresponding EIS measurements, the coated surface exhibited a superior anti-corrosion performance than uncoated sample. Overall, the results declared that the amorphous AlPO₄ coating could be a good choice for surface protection of stainless steel against electrochemical corrosion in salty environments.     

Corrosion protective ability of electrodeposited ceria layers

It has been ascertained that the electrochemically deposited thin films of cerium oxides, containing mainly CeO₂ and also some insignificant amount of Ce₂O₃, are acting as an effective cathodic coating, leading to restoration of the passive state of the studied stainless steel (OC 404) samples. This effect is associated with a strong shifting of the stationary corrosion potential of the steel in positive direction, moving over from potentials characteristic of corrosion in active state to potentials falling within the zone of passivity. In this respect, another basic purpose of the investigations was the elucidation of the mechanism of action of the cerium oxide film and in particular collecting experimental evidence for the supposition about the occurrence of an efficient depolarization reaction of CeO₂ reduction (resulting in a state of passivity—improved ability of self-passivation) instead of hydrogen depolarization reaction. For this purpose, we considered also the decrease in the surface concentration of ceria in the passive layer under the conditions of the actual corrosion process (self-dissolution) of the stainless steel by means of XPS, SEM, ICP-AES, and gravimetric analyses. A decrease in the surface concentration of CeO₂ (Ce⁴⁺) has been observed, which is known to be chemically inert in acidic media. The obtained results prove the occurrence of an effective cathodic process of Ce⁴⁺ (CeO₂) reduction into Ce³⁺ (soluble in acids Ce₂O₃ ) in the superficial oxide film.     

Nanoindentation studies and modeling of surface layers on austenitic stainless steels by extreme electrochemical treatments

The nanoindentation studies were performed on two austenitic stainless steels, AISI 304L and 316L. The steel samples have undergone two different electrochemical treatments, standard (EP50) and a high‐current density electropolishing (EP1000). Firstly, the observations of the steels' surfaces were done with the optic images of the AISI 304L and 316L SS after these two treatments displayed. Presented in the paper results have shown clearly that the high‐current density close to 1000 A/dm² allows for obtaining the passive nanolayers with other mechanical properties than those obtained after a standard electropolishing (EP50). The prediction of these results has been confirmed by the preliminary XPS studies allowing for modeling of the steels' surface layers. The main finding of the study is revealing a new method of electrochemical treatment (EP1000) allowing to obtain the reduced Young's modulus of the stainless steels lower than that obtained after EP50. This feature is of high importance regarding the use of these steels as biomaterials. Copyright © 2015 John Wiley & Sons, Ltd.     

Investigation on Electronic Property of Passive Film on Nickel in Bicarbonate/Carbonate Buffer Solution

The electronic properties of passive film formed on nickel in bicarbonate/carbonate buffer solution were studied by electrochemical impedance spectra (EIS) and Mott‐Schottky plot. The film composition was analyzed by X‐ray photoelectron spectroscopy (XPS). The results showed that passive film exhibited p‐type semi‐conductive character, and the acceptor density (N_A) decreased with increasing potential, prolonging time, decreasing temperature, increasing pH value and decreasing chloride/sulfur ions concentration. The transfer resistance and film resistance increased with the above factors changing. XPS results showed that passive film was composed of NiO and a little amount of Ni₂O₃.     

Comparative XPS analysis of passive layers composition formed on AISI 304 L SS after standard and high‐current density electropolishing

In the paper, there are described chemical compositions of passive surface layers formed on AISI 304 L (EN 1.4307) stainless steel after standard (EP50; i = 50 A/dm²) and high‐current density (EP1000; i = 1000 A/dm²) electropolishing. For the studies, a mixture of orthophosphoric and sulfuric acid electrolyte in proportion 1:4 was used. The survey and high‐resolution spectra of Cr 2p, Fe 2p, S 2p, P 2p, Ni 2p and C 1s are presented. On the basis of the obtained results it was noted that the chromium‐to‐iron ratio (Cr/Fe) after EP50 was about 3.5 times higher than that after EP1000 treatment. The phosphorus‐to‐sulfur ratios after EP50 and EP1000 electropolishing were 0.13 and 0.3, respectively, and nickel to the sum of chromium and iron coefficient (Ni/Cr + Fe) for both electrochemical polishing was equal to 0.04. Copyright © 2014 John Wiley & Sons, Ltd.     

Mixed oxide semiconductors based on bismuth for photoelectrochemical applications

The structural and photoelectrochemical properties of mixed oxide semiconductor films of Bi-Nb-M-O (M = Al, Fe, Ga, In) were studied in order to explore their use as photoanodes in photoelectrochemical cells. These films were prepared on AISI/SAE 304 stainless steel plates by sol–gel dip-coating. The films were characterized by scanning electron microscopy—energy dispersive spectroscopy (SEM-EDS), X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS), and their photoelectrochemical properties were studied by open circuit potential (OCP) measurements, linear sweep voltammetry (LSV), and cyclic voltammetry (CV). SEM micrographs show homogeneous and rough films with agglomerates on the surface. EDS analyses show that the films are composed of Bi, Nb, and M, and the agglomerates are mainly composed of Bi. XRD analyses show a predominant crystalline phase of bismuth(III) oxide (Bi₂O₃) and a secondary phase composed of Bi-M mixed oxides. It is noteworthy that there was no identified niobium-based crystalline phase. XPS results reveal that the films are composed by Bi(III), Nb(V), and M(III). CV results show that the electrochemical behavior is attributed only to the semiconductor films which indicate a good coating of the stainless steel support. OCP measurements show that all the films have n-type semiconductor properties and exhibited photoresponse to the visible light irradiation. LSV results show that the application of a potential higher than +0.1 V enhances the photocurrent which can be attributed to an improved charge carrier separation. The results indicate that these materials can be used in photoelectrochemical cells.     

摩擦条件下硫脲对1Cr18不锈钢电化学行为的作用

控制金属材料的腐蚀或磨损有三种方法：１）合理选用耐蚀金属材料（包括开发新材料或对材料进行适宜的表面强化处理;２）改善金属材料服役的介质环境（包括合理使用缓蚀剂）;３）采取电化学保护措施．由于在腐蚀介质中工作的各种摩擦副往往受腐蚀与磨损的协同作用而发生...     

Medicago sativa as a green corrosion inhibitor for 1018 carbon steel in 0.5 M H2SO4 solution

A study on the use of the methanol extract of Medicago sativa as a green corrosion inhibitor for 1018 carbon steel in 0.5?M of sulfuric acid has been carried out by using potentiodynamic polarization curves, electrochemical impedance spectroscopy and gravimetric tests. Testing temperatures were 25°C, 40°C and 60°C. Results showed that M. sativa is a good corrosion inhibitor, with its efficiency increasing with its concentration and with time, but decreasing with the temperature. M. sativa forms a passive film on top of the steel with a passive current density and pitting potential values lower than that for uninhibited solution, and remained on the steel for 8–12?h. This film formed by iron ions and heteroatoms present in OH^? and amine groups from the extract are adsorbed on the steel and form a protective film on to the steel.     

Protective coatings based on Mn-Co spinel for current collectors of solid oxide fuel cells

The method of electrostatic spray pyrolysis was designed to apply protective coatings based on Mn-Co spinel to ferrite stainless steels (Crofer22APU and 08Kh18T1). The comparative thermogravimetric (TG) studies of ferrite stainless steels with and without protective coatings were carried out. The electrochemical characteristics of protective coatings exposed to long current loading were studied. The formation processes of Cr₂O₃ oxide films were studied at the contact of ferrite stainless steel with La_0.8Sr_0.2MnO₃ ionic and electronic conductor. The coatings of Mn-Co spinel were shown not preventing formation of continuous oxide film on the stainless steel surface.     

XPS depth profile study of porous zirconia films deposited on stainless steel by spray pyrolysis: the problem of substrate corrosion

Zirconia (ZrO₂) films of tissue‐like structure and narrow pore size distribution have been deposited by spray pyrolysis using aqueous zirconyl chloride octahydrate (ZrOCl₂·8H₂O) precursor solutions. Stainless‐steel sheets, protected or unprotected by a ZnO barrier layer, have been used as the substrate material held at 473 K. The ZnO barrier layers have been deposited on the stainless steel held at 523 K by spray pyrolysis using a zinc acetate precursor. Their property of corrosion protection to stainless steel has been proved by electrochemical polarization measurements in 0.5 M NaCl solution. A complementary study of XPS (depth profiling, mapping) and x‐ray diffraction has shown that the unprotected steel substrates were corroded during ZrO₂ film post‐annealing in air at T ≥ 773 K, whereas steel substrates protected with a compact barrier layer of crystalline ZnO before ZrO₂ film deposition did not show surface corrosion even after annealing up to 997 K. Copyright © 2004 John Wiley & Sons, Ltd.     

水热法制备TiO_2纳米线薄膜的光生阴极保护性能

应用水热法在钛箔表面制备TiO2纳米线薄膜,采用场发射扫描电子显微镜、X射线衍射和紫外-可见分光光度法对薄膜进行表征,用电极电位和电化学阻抗谱考察TiO2光生阴极保护性能.结果表明:薄膜由纵横交错的锐钛矿型TiO2纳米线组成,纳米线的直径约10nm.在150℃下反应6h生成的TiO2纳米线薄膜在0.3mol·L-1 Na2SO4溶液和0.3mol·L-1 Na2SO4+0.5mol·L-1 HCOOH混合溶液中对与TiO2薄膜耦连的403不锈钢均有良好的阴极保护效应.TiO2膜所在溶液中含有HCOOH时,可使耦连的403不锈钢在0.5mol·L-1 NaCl溶液中电极电位负移约545mV,界面反应电阻显著变小,表明电解质溶液加入HCOOH可以增强TiO2纳米线薄膜对403不锈钢的光生阴极保护效应.     

Dynamic electrochemical impedance spectroscopy measurements of passive layer cracking under static tensile stresses

Electrochemical impedance spectroscopy allows the examination of corrosion susceptibility and resistance for different construction materials, in particular the determination of the properties of their passive films. This technique makes possible the analysis of electrochemical processes in time domain, including rapid phenomena such as changes in the properties of passive films, but it has never been used for passive layer cracking examination. In many cases, fracture of the passive film under tensile stresses leads to stress corrosion cracking. Therefore, investigations of passive layer cracking on austenitic stainless steels under tensile stresses facilitate the understanding of the mechanism of stress corrosion cracking in these common engineering materials. The effect of static tensile stresses on the passive film cracking behaviour of type 304L stainless steel immersed in 0.5 M NaCl solution at room temperature has been investigated. This paper presents the impedance spectra obtained for 304L stainless steel samples at different potential values.Contribution to the 3rd Baltic Conference on Electrochemistry, Gdansk-Sobieszewo, Poland, 23–26 April 2003Dedicated to the memory of Harry B. Mark, Jr. (28 February 1934–3 March 2003)