A comparison between the corrosion behavior of nanostructured copper thin films deposited on oxidized silicon and copper sheet in alkaline media

Copper thin films were deposited on oxidized silicon at a substrate temperature of 70 °C and 150 °C using EB-PVD technique. The morphology and crystal orientation of the deposited film were investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD), respectively. Corrosion behavior of films was studied through electrochemical impedance spectroscopy (EIS), potentiodynamic polarization, immersion test, and cathodic chronopotentiography. Additionally, the crystalline structure of corroded samples immediately after polarization was examined by XRD. Corrosion current density for copper deposits was higher than copper sheet by polarization tests, while the data obtained by the EIS technique emphasized higher corrosion current density for copper sheet. However there was a conflict between polarization and EIS data, the other results obtained by immersion and cathodic chronopotentiography tests proved that the corrosion resistance of copper deposits was higher than copper sheet in the same alkaline media, which can be attributed to chemical composition and higher thickness of the passive layer formed on copper deposits. On the other hand, breakdown potential (E_bp) for copper sheet was about 0.3 V_SCE, while a distinct E_bp was not found for copper deposits. This was a sign of higher stability of the passive layer formed on copper deposits. The XRD patterns of samples immediately after polarization showed a higher content of Cu(OH)₂ on copper deposits in comparison with copper sheet. The stable morphology formed on the surface of copper after polarization was monoclinic CuO, which is assumed to have a significant effect on copper protection in alkaline media. This morphology was more compact on copper deposits in comparison with copper sheet. This was due to higher ability of deposits to react with hydroxyl ions.     

Electrochemical study on hot corrosion of Si-modified aluminide coated In-738LC in Na2SO4-20 wt.% NaCl melt at 750 °C

The corrosion performance of the slurry Si-modified aluminide coating on the nickel base superalloy In-738LC exposed to low temperature hot corrosion condition has been investigated in Na₂SO₄-20 wt.% NaCl melt at 750 °C by combined use of the anodic polarization and characterization techniques.The coated specimen showed a passive behavior up to −0.460 V vs. Ag/AgCl (0.1 mol fraction) reference electrode, followed by a rapid increase in anodic current due to localized attack in the higher potential region. In the passive region, the anodic dissolution of constituents of the coating occurred through the passive film, probably SiO₂, at slow rate of 20-30 μA/cm². The passive current for the Si-modified coating was two orders of magnitude smaller than that for bare In-738LC, which is known as Cr₂O₃ former in this melt. This indicates that the SiO₂ film is chemically more stable than Cr₂O₃ film under this condition. However, pitting-like corrosion commenced around −0.460 V and proceeded at the high rate of 100 mA/cm² in the higher potential region than +0.400 V. The corrosion products formed on the coating polarized in different anodic potentials were characterized by SEM, EDS and XRD. It was found from the characterization that oxidation was dominant attack mode and no considerable sulfidation occurred at 750 °C. The SiO₂ oxide was not characterized in the passive region because the thickness of the passive film was extremely thin, but was detected as the primary oxide in the localized corrosion region, where the selective oxidation of Al was observed by further progress of the corrosion attack front into the inner layer of coating.     

X-ray photoelectron spectroscopic analyses of corrosion products formed on rock bolt carbon steel in chloride media with bicarbonate and silicate ions

The passivation behavior of Yucca Mountain Repository rock bolt carbon steel in deaerated 3.5% NaCl solution containing SiO₃²⁻ and HCO₃⁻ ions was investigated by potentiodynamic polarization, electrochemical impedance spectroscopy, scanning electron microscopy, and X-ray photoelectron spectroscopic methods. Polarization results indicate that combinations of silicate and bicarbonate anions decrease the passive current density and raise the pitting potential. XPS results indicate the enrichment of silica at passive potentials and the formation of mixed FeCO₃ and silica film at lower potentials. This change in film composition was responsible for the changes in corrosion rate at lower and higher potentials. XPS results also support the thermodynamic data with regard to the occurrence of second oxidation peak observed in the polarization curves to be due to the oxidation of FeCO₃ to Fe₂O₃.     

Temperature effect in the corrosion resistance of Ni-Fe-Cr alloy in chloride medium

The corrosion susceptibility of alloy 33 in 0.5 mol/L sodium sulphate solutions containing or not 0.1 mol/L sodium chloride was tested at three different temperatures: 22 °C, 40 °C and 60 °C. Electrochemical studies were performed using corrosion potential measurements (E_corr) as well as potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) techniques. Corrosion potential measurements showed that alloy 33 was passivated by a previously air formed film which was not destroyed during immersion in both solutions. No corrosion was observed during these tests although the temperature affected the film. Potentiodynamic polarization experiments showed that at high anodic potentials the previous film was broken up, and localized corrosion occurred in both solutions and at the three temperatures tested. Electrochemical impedance spectroscopy tests confirmed the presence of a stable passive film on the alloy surface at open circuit potential. Mott-Schottky analysis indicated that the passive film is an n-type semiconductor due to the presence of point defects of donor species, such as oxygen vacancies and interstitial metallic cations. As the potential increases the Cr(III) present in the barrier layer oxidizes producing Cr(VI) soluble species. The dissolution creates metallic cation vacancies that are acceptor species and the film changes from n-type to p-type semiconductor. The passive film rupture and the following localized attack are related to the drastic oxidative dissolution of the film at high anodic potentials, independent of its p-nature, chloride presence or increased temperature.     

Corrosion behavior of Ti-Mo alloys cold rolled and heat treated

Corrosion behavior of (α + β) Ti-10Mo and β Ti-20Mo (mass%) alloys cold rolled and solution heat treated was investigated by studying the anodic polarization curves at 310 K in 5 mol% HCl solution to determine the potential use of those alloys in biomedical applications. The anodic films formed on the surfaces of the alloys were examined using X-ray photoelectron spectroscopy analysis and scanning electron microscopy. The results reveal that both of the Ti-Mo alloys cold rolled and solution treated exhibit a passive behavior in 5% HCl solution, which is attributed to the passive film formation of a mixture of MoO₃ and TiO₂. The cold rolling process does not influence the formation of passive films on the Ti-Mo alloys although it slightly increases the passive current densities. The corrosion resistance of the Ti-Mo alloys increases with Mo content and both of the Ti-Mo alloys exhibit better corrosion resistance than commercial pure Ti—the currently used metallic biomaterial.     

Electrochemical behavior of Ni3Al-based intermetallic alloys in NaOH

The corrosion behavior of Ni₃Al-based intermetallic alloys in a 0.5 M NaOH solution was studied at 25 °C. The open circuit potential, cathodic and anodic potentiodynamic polarization, Tafel plots and linear polarization resistance measurements were used to characterize the corrosion behavior. For the Ni₃Al(B, Zr) alloy, potentiodynamic polarization curves showed a wide passive region that can be found between about ?0.220 V_SCE and 0.520 V_SCE. On the other hand, a narrow passive region, in the range of potentials from about ?0.180 V_SCE to 0.180 V_SCE, was observed for the Ni₃Al(B, Zr, Cr, Mo) alloy. Chromium, as an alloying element in the Ni₃Al(B, Zr, Cr, Mo) alloy, contributes to transpassive dissolution of the passive film at much lower anodic potentials and remarkably reduces the passivation region. The experiments indicated also that damaged passive films on alloys repairs itself and pits do not initiate. The surface of both alloys and passive films possess extremely high corrosion resistance in a studied solution. However, Tafel and linear polarization tests revealed that freshly exposed surfaces of the Ni₃Al(B, Zr) alloy exhibited better corrosion resistances than the Ni₃Al(B, Zr, Cr, Mo) alloy. Both methods, used for the determination of corrosion rates gave very similar results. The calculated corrosion rates are about 2.8 ·10^?3 and 6.0·10^?3 mm year^?1 for the Ni₃Al(B, Zr) alloy and B, respectively.     

Characterization of Corrosion Product Layers from CO2 Corrosion of 13Cr Stainless Steel in Simulated Oilfield Solution

The influence of temperature and flow rate on the characterization and mechanisms of corrosion product layers from CO₂ corrosion of 13Cr stainless steel was carried out in simulated oilfield solution. Cyclic potentiodynamic polarization method as well as weight loss tests in autoclave were utilized to investigate pitting corrosion behavior at various temperatures. Weight loss tests were performed at 100 and 160 °C under dynamic and static flow conditions. At the same time, the significant pitting parameters such as E _corr, E _pit, E _pp, ∆E, and I _pass in cyclic polarization curves at various temperatures were analyzed and compared for revealing the pitting behavior of 13Cr stainless steel. The surface measurement techniques such as SEM, XRD, and XPS were used to detect the corrosion product layers. The results showed that both temperature and flow rate had significant effects on characterization of corrosion product layers or passive films formed on 13Cr stainless steel in CO₂ corrosion system. At high temperature, lots of pits were formed at the localized corrosion areas of metal surfaces. Corrosion rates under the condition of 5 m/s were higher than those under the static condition regardless of the test temperatures.     

Eis and XPS study of surface modification of 316LVM stainless steel after passivation

The effects of surface finish, nitric acid passivation and ageing in air on corrosion resistance of 316LVM stainless steel in 0.5% H₂SO₄ have been investigated by EIS, potentiodynamic polarization measurements and XPS. The results indicate that a smoother surface exhibits to a higher corrosion resistance. The effectiveness of the passivation treatment strongly depends on nitric acid concentration, passivation time and temperature. The passivation treatment significantly increases the corrosion resistance due to a high Cr content in the passive film and increased film thickness. Ageing after passivation increases the corrosion resistance whereas ageing before passivation has little effect.     

The stability of passive film growth on copper in anaerobic sulphide solutions

The corrosion behaviour of oxygen-free copper in anoxic 0.1?M NaCl?+?2?×?10^?4?M Na₂S·9H₂O solution (pH?=?9.0) was investigated under potentiostatic polarisation for different times. Electrochemical methods, including electrochemical impedance spectroscopy, Mott–Schottky analysis, localised electrochemical impedance spectroscopy (LEIS) and scanning electron microscopy observations, were conducted. The results indicated that the corrosion resistance of oxygen-free copper decreased with increasing applied potential, whereas it increased with increasing polarisation time. The passive film growth kinetics obeyed a logarithmic law (lnD?=?alnt?+?b, where D is the layer thickness, b is a constant taken as the initial growth rate, t is the polarisation time and a is the time exponent). Subsequent to the formation of a compact and coherent passive film, the thicker the film was, the more difficult for ion to migrate, which further resulted in a slower film growth rate. The passive film displayed p-type semiconductor behaviour and the acceptor density (cation vacancy) was approximately 10²² to 10²³?cm^?3. The LEIS results showed that the passive film achieved relative stability after 24?h of immersion under natural conditions, which was longer than the duration of potentiostatic polarisation (4?h at ?0.6?V_SCE).     

The nature of the copper sulfide film grown on copper in aqueous sulfide and chloride solutions

In this paper, the properties of copper sulfide films formed both anodically and naturally in deaerated/anoxic aqueous sulfide and chloride solutions were investigated using a series of electrochemical and surface analytical techniques. A combination of cyclic voltammetric, corrosion potential (E_corr), and cathodic stripping voltammetric experiments showed that the sulfide film growth kinetics and film morphologies were controlled by the supply of SH⁻ from the bulk solution to the copper surface. There was no passive barrier layer observed on the copper surface under either electrochemical or corrosion conditions. The film morphology was dependent on the type and concentration of anions (SH⁻, Cl⁻) present in the solution. Scanning electron microscopy on both surfaces and focused ion beam-cut cross-sections showed the growth of a thin, but porous, base layer of chalcocite (Cu₂S) after short immersion periods (up to 2 hr) and the continuous growth of a much thicker crystalline outer deposit over longer immersion periods (≥36 hr), suggesting a solution species transport-based film formation process and the formation of an ineffective thin “barrier-type” layer on copper.     

Corrosion behavior of glassy Ni55Co5Nb20Ti10Zr10 alloy in 1 N HCl solution studied by potentiostatic polarization and XPS

Corrosion resistance of glassy Ni₅₅Co₅Nb₂₀Ti₁₀Zr₁₀ (at.%) alloy in 1 N HCl solution was investigated with respect to the electrochemical behavior and the compositions of the passive film and the underlying alloy surface just below the passive film. The potentiostatic polarization curve indicated that the alloy was spontaneously passivated with a low passive current density of the order of 10⁻³ A m⁻². The quantitative X-ray photo-electron spectroscopy (XPS) analysis revealed that the thickness of the surface film increased linearly with an anodizing ratio of 1.5 nm V⁻¹. The high corrosion resistance of the glassy alloy was due to the formation of niobium, titanium and zirconium-enriched passive film. The growth mechanism of the passive films is also discussed.     

Phosphate ions used as green inhibitor against copper corrosion in tap water

Three dosages of ions are evaluated as corrosion inhibitors of copper in artificial tap water by measuring the corrosion potential, polarization resistance, electrochemical impedance and reflectance spectra. The water is moderately hard, highly carbonated and chloride-rich. The results show that the surface film is composed by Cu₂O. When the inhibiting agent is added, the film becomes thicker, denser and more compact. This behaviour is attributed to CuO incorporating into the passive layer. The optimal dosage of inhibitor is 10 mg l⁻¹ P when the polarization resistance increases three times. The inhibitor retards the pit initiation, without hindering pit growth.     

Corrosion inhibition of 70Cu–30Ni alloy in LiBr + ethylene glycol + H2O mixtures by inorganic compounds

The corrosion inhibition of a 70 wt% Cu–30Ni alloy in a 55 wt% lithium bromide (LiBr) + ethylene glycol + H₂O by inorganic inhibitors has been evaluated at different temperatures by using electrochemical techniques. Inhibitors used included lithium chromate (Li₂CrO₄), lithium molybdate (LiMoO₄), and lithium nitrate (LiNO₃), in a concentration of 5 ppm at 25, 50, and 80 °C. Employed techniques included potenthiodynamic polarization curves, linear polarization resistance, and potentiostatic measurements. Results have shown that the alloy had an active–passive behavior at 25 and 50 °C, and the passive film properties were improved with the addition of inhibitors, whereas at 80 °C the inhibitors did not have any effect. Similarly, in general terms, the best corrosion performance at 25, 50, and 80 °C was obtained by adding Li₂CrO₄, LiNO₃, and LiMoO₄, respectively. However, the alloy was not susceptible to pitting corrosion in presence of inhibitors but it was highly susceptible towards pitting type of corrosion in absence of inhibitors.     

Mott–Schottky analysis of passive films on Cu containing Fe–20Cr–xCu (x = 0, 4) alloys

Effect of copper on the defect density of Fe–20Cr–xCu (x?=?0, 4) stainless steel alloys was investigated in deaerated pH 8·5 borate buffer solution at room temperature using Mott–Schottky analysis. Mott–Schottky analysis revealed that the addition of copper increased the acceptor density (N_A, V_Cr^?3), i.e. decreased the Cr⁺³ content of the passive film. Also the donor densities, shallow donor (N_D1, V_O⁺²) and deep donor (N_D2, V_Cr⁺⁶), of the passive films formed were increased. XPS analysis confirmed the decrease in Cr content and enrichment of copper in the passive film of Cu containing alloys, which ultimately dictated their lower corrosion resistance, i.e. decreased film protectiveness and stability.     

Corrosion and anodic oxidation of copper in 1-butyl-3-methylimidazolium bromide–copper(II) bromide ionic liquid

Using the gravimetric and polarization methods, the corrosion behavior of copper in 1-butyl-3-methylimidazolium bromide (BMImBr) ionic liquid in its pure state and with additions of CuBr₂ (from 0.4 to 1.2 mol kg^–1) has been investigated. It is found that the corrosion in naturally aerated BMImBr ionic liquid is accompanied by oxygen depolarization. Copper dibromide in BMImBr–CuBr₂ ionic liquid plays the role of an oxidant, and the rate of copper corrosion in this case is higher by about an order of magnitude than for the pure ionic liquid. The method of cyclic voltammetry shows that the anodic dissolution of copper in BMImBr–CuBr₂ ionic liquid proceeds via the EC mechanism. It is shown that the chemical-reaction rate of dissolving the surface layer and the rate of copper corrosion (according to gravimetric and polarization data) are comparable. Copper corrosion in the studied ionic liquid is accompanied by the effect of surface polishing, as is confirmed by the atomic force microscopy and profilography.     

The role of Ce ions in electrochemical corrosion of 304 SS in Ce(NO<Subscript>3</Subscript>)<Subscript>3</Subscript>.6H<Subscript>2</Subscript>O

Effects of temperature and potential on the electrochemical corrosion behavior of alloy AISI 304 (UNS S30400) Stainless steel were investigated in 3 wt.% cerium nitrate (Ce[NO₃]₃.6H₂O) solution. With an increase in electrolyte temperature from ambient temperature to 90°C, the corrosion potential of the alloy shifted towards the noble direction, and the resistance to polarization increased due to the formation of Ce-oxide on the electrode surface. The oxide films formed at the open circuit potential (OCP) and a passive potential of 0.4 V_SCE were examined by x-ray photoelectron spectroscopy (XPS). The oxide film formed at 50°C and a passive potentialof 0.4 V_SCE consists of mixed oxides of Ce and Cr, whereas that at OCP consists of only Cr oxide. The formation of Cr oxides on the electrode surface was primarily due to the nitrate (NO₃ ⁻) ions in Ce(NO₃)₃.6H₂O electrolyte.     

Effect of temperature on anodic behavior of 13Cr martensitic steel in CO2 environment

The corrosion behavior of 13Cr martensitic stainless steel in a CO₂ environment in a stimulated oilfield was studied with potentiodynamic polarization and the impedance spectra technique. The results showed that the microstructure of the surface scale clearly changed with temperature. This decreased the sensitivity of pitting corrosion and increased the tendency toward general (or uniform) corrosion. The capacitance, the charge transfer resistance, and the polarization resistance of the corrosion product scale decrease with increasing temperature from 90 to 120 °C, and thus the corrosion is a thermal activation controlled process. Charge transfer through the scale is difficult and the corrosion is controlled by a diffusion process at a temperature of 150 °C. Resistance charge transfer through the corrosion product layer is higher than that in the passive film.     

High temperature corrosion properties of ionic liquids

The corrosion behaviour of several metals and metal alloys (copper, nickel, AISI 1018 steel, brass, Inconel 600) exposed to a typical ionic liquid, the 1-butyl-3-methyl-imidazolium bis-(trifluoromethanesulfonyl) imide, ([C₄mim][Tf₂N]), has been investigated by electrochemical and weight-loss methods. Corrosion current densities have been determined by extrapolation from Tafel plots and by polarization resistance measurements and 48 h immersion tests were performed at 150, 250, 275 and 325 °C. Room temperature results show low corrosion current densities (0.1-1.2 μA/cm²) for all the metals and alloys investigated. At 70 °C, the corrosion current for copper dramatically increases showing a strongly dependence on temperature. At 150 °C copper shows significant weight-loss while nickel, AISI 1018, brass and Inconel do not. At higher temperatures (?275 °C), the copper sample crumbles and localized corrosion occurs for the other metals and alloys.     

The effect of chromate in the corrosion behavior of duplex stainless steel in LiBr solutions

The electrochemical behavior of duplex stainless steel (DSS) in LiBr media was investigated by anodic cyclic polarization curves and AC impedance measurements. The effect of bromide concentration and chromate presence in the solutions on the corrosion behavior of DSS was studied. It was found, by cyclic polarization curves analyses, that there was different pitting susceptibility of passive films formed on DSS depending on the chromate/bromide ratio: pitting corrosion susceptibility highly decreased from a chromate/bromide ratio lower than 0.01.The comparative investigations carried out in LiBr and LiBr + 0.032Li₂CrO₄ verify the assumption that the halide ions facilitate inhibitor adsorption. The addition of halides increased inhibition efficiency to a considerable extent. Passive film becomes more resistant when bromide concentration increases, although film thickness decreases.     

H2S溶液中316L不锈钢TIG焊接头的腐蚀性能

文中通过极化曲线、交流阻抗、Mott-Schottky曲线、浸泡腐蚀试验等方法对316L奥氏体不锈钢TIG焊接头各区域在不同浓度H₂S溶液中的耐蚀性能进行了研究.极化曲线及交流阻抗结果表明,随着溶液中H₂S浓度的升高,焊接接头各区域的耐蚀性明显降低.另一方面对于相同浓度的H₂S溶液,316L基体的耐蚀性最好,其次是热影响区,焊缝区的耐蚀性最差.Mott-Schottky曲线结果表明,焊接接头在H₂S溶液中的表面钝化膜形成p-n结结构,掺杂浓度高达1022 cm-3,且掺杂浓度随H₂S浓度升高而增大,致使钝化膜防护性能降低.