Positive Shift In Corrosion Potential Research Articles

Flexible carbon-coated FeNi alloy/PDMS nanocomposites toward a multifunctional high-performance electromagnetic absorber

The increasing prevalence of electromagnetic wave technology has raised concerns regarding electromagnetic pollution and its potential hazards. Microwave absorbing materials (MAMs) have emerged as an effective solution for capturing and dissipating electromagnetic waves. This study presents a novel approach for developing flexible microwave absorbers by dispersing carbon-coated FeNi alloy nanoparticles (FeNi@C NPs) into a polydimethylsiloxane (PDMS) matrix. The unique contributions lie in the mass production of (FeNi)@C NPs through the arc plasma and controlled making of (FeNi)@C/PDMS nanocomposites for practical electromagnetic wave (EMW) absorption/shielding application. Simultaneously, the formation mechanism of (FeNi)@C NPs is illustrated in detail by real-time optical emission spectroscopy. The obtained (FeNi)@C/PDMS nanocomposites show multifunctionality such as hydrophobicity and mechanical performance, rendering them suitable for applications in lightweight flexible electronics, wearable devices, and stealth technology. Through adjustments in the contents of (FeNi)@C fillers, the (FeNi)@C/PDMS nanocomposites exhibit excellent microwave absorption capacity. At a mass ratio of 15% of (FeNi)@C NPs, the minimum reflection loss is −33.51 dB at a thickness of 2.3 mm with an effective absorption band of 4.96 GHz. This enhanced performance is attributed to the synergistic effects of magnetic and dielectric loss, multiple reflection/scattering, conduction loss, and suitable impedance matching. Furthermore, the (FeNi)@C/PDMS nanocomposites demonstrate remarkable corrosion resistance, exhibiting a positive shift in corrosion potential to −0.18 V compared to bare aluminum (−0.83 V), along with a corresponding protection efficiency of 98.78%. In conclusion, this study provides a validated strategy for the fabrication of EMW absorption nanocomposites consisting of magnetic nanoparticle fillers and polymer matrix, highlighting their potential for application in intricate environments.

Corrosion inhibition of 8-HQ for AA5052 in 3 wt% NaCl solution in presence of trace Cu2+ ions: Electrochemical/surface studies, DFT/MD modeling

In this paper, the effect of Cu2+ ions on corrosion inhibition of 8-hydroxyquinoline (8-HQ) for AA5052 aluminum alloy in the simulated seawater solution has been studied by weight loss experiments, electrochemical measurements and surface analysis. 8-HQ inhibits the corrosion of AA5052 aluminum alloy in 3 wt% NaCl solutions very well, resulting in a positive shift in corrosion potential. The 0.01 mg/L of Cu2+ ions can deteriorate the corrosion inhibition of 8-HQ at low concentrations. This behavior is interpreted on the basis of deposition of copper by displacement on the defects of the corrosion inhibition film of 8-HQ. When the concentration of 8-HQ reached 5 mg/L, the presence of 0.01 mg/L Cu2+ ions increase the corrosion inhibition efficiency of 8-HQ by 6.27%. 8-HQ shows efficient inhibition at a relative high concentration, suggesting that the chelate formed by Cu2+ ions and 8-HQ can repair the defects of the 8-HQ inhibitive film on aluminum surface. The complex film would suppress the partial cathodic reaction and lead to the improved corrosion inhibition.

Polythiophene (PTh)-TiO2-Reduced Graphene Oxide (rGO) Nanocomposite Coating: Synthesis, Characterization, and Corrosion Protection Performance on Low-Carbon Steel in 3.5 wt % NaCl Solution.

The ternary nanocomposite polythiophene (PTh)-TiO2-reduced graphene oxide (rGO) (PTh-TiO2-rGO) was synthesized by chemical oxidative polymerization with FeCl3 used as the oxidizing agent. Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), Raman spectroscopy, scanning electron microscopy (SEM), and transmission electron microscopy (TEM) were used to characterize the synthesized nanocomposite, followed by its casting on a low-carbon steel (LCS) substrate using N-methyl-2-pyrrolidone (NMP) as a solvent and an epoxy resin and triethyl tetraamine as a binder and curing agent, respectively. Anticorrosion properties of the PTh-TiO2-rGO nanocomposite in 3.5 wt % NaCl solution were established using open-circuit potential (OCP), electrochemical impedance spectroscopy (EIS), potentiodynamic polarization (PDP), salt spray test, immersion test, contact angle (CA) measurements, water uptake test, and SEM. Additionally, PTh and PTh-TiO2 were separately synthesized, characterized, and subjected to anticorrosion tests following identical synthesis routes for comparison purposes. The results of the investigations demonstrated that the PTh-TiO2-rGO nanocomposite coating provides superior protection in 3.5 wt % NaCl solution compared to pure PTh and PTh-TiO2 coatings, which are evident from its lowest corrosion current density (I corr) (0.570 × 10-6 A cm-2), highest positive shift in corrosion potential (E corr) (-0.578 V), highest impedance and phase angle (3.56 × 103 Ω cm2 and 70°, respectively), highest hydrophobicity (CA 94°), and highest protection efficiency (99%). These results show that the proposed nanocomposite coating provides better corrosion protection in a 3.5 wt % NaCl solution than other coatings.

Facile fabrication of superhydrophobic coatings with superior corrosion resistance on LA103Z alloy by one-step electrochemical synthesis

Superhydrophobic coatings are effective in avoiding corrosion of substrates due to their special wetting properties. The present work dispenses with the need for complex pre-treatments and post-modification with low surface energy substances. A facile and rapid one-step electrochemical synthesis method was used to prepare a superhydrophobic coating of [CH3(CH2)12COO]2Ca with excellent corrosion resistance on the surface of LA103Z alloy. The corrosion behavior of the coated alloy in 3.5 wt% NaCl solution was investigated using electrochemical techniques. The results show that a uniform and relatively thick surface is an effective barrier to the penetration of corrosive liquids. The best corrosion resistance of the coated samples was achieved at an electrochemical synthesis time of 30 min, with a positive shift in corrosion potential and a significant reduction in corrosion current density.

Preparation of medical Mg\u2013Zn alloys and the effect of different zinc contents on the alloy

In recent years, along with the development and application of magnesium alloys, magnesium alloys have been widely used in automotive, aerospace, medicine, sports, and other fields. In the field of medical materials, magnesium not only has the advantage of light weight, high strength, and a density similar to that of human bone, but also has good biocompatibility and promotes the growth of human bone. However, the mechanical properties and corrosion resistance of magnesium alloys need to be further improved to meet the requirements for human biodegradable implants. In this study, three alloys (mass fractions: Mg–10Zn, Mg–20Zn, and Mg–30Zn (wt.%)) were prepared using powder metallurgy by homogeneously mixing powders of the above materials in a certain amount with magnesium as the substrate through the addition of zinc elements, which also have good biocompatibility. The effect of zinc on the microstructure, mechanical properties, wear performance, and corrosion resistance of magnesium–zinc alloys was studied when the zinc content was different. The results show that compared with the traditional magnesium alloy using powder metallurgy, prepared magnesium alloy has good resistance to compression and bending, its maximum compressive stress can reach up to 318.96 MPa, the maximum bending strength reached 189.41 MPa, and can meet the mechanical properties of the alloy as a human bone-plate requirements. On the polarization curve, the maximum positive shift of corrosion potential of the specimens was 73 mv and the maximum decrease of corrosion-current density was 53.2%. From the comparison of the above properties, it was concluded that the three prepared alloys of which Mg–20% Zn had the best overall performance. Its maximum compressive stress, maximum bending strength, and corrosion-current density reached 318.96 MPa, 189.41 MPa and 2.08 × 10−5 A·cm−2 respectively, which are more suitable for use as human implant bone splints in human-body fluid environment.The mechanical properties of the sintered Mg–Zn alloys were analyzed using powder-metallurgy techniques, and their microstructure, micromotion wear properties, electrochemical corrosion properties and composition of the physical phases were analyzed and discussed.

Anodic dissolution of aluminum in AlCl3-[BzMIM]Cl ionic liquid

• The anodic dissolution behaviors of aluminum in AlCl 3 —1-benzyl-3-methylimidazolium chloride ionic liquid were studied for the first time. • The mechanism of passivation generation was explained in detail, and the passivation products were identified. • The corrosion behaviors of aluminum in AlCl 3 -[BzMIM]Cl ionic liquid were analyzed by electrochemical tests. • To provide the theoretical basis for the extraction of aluminum from AlCl 3 -[BzMIM]Cl ionic liquid. The anodic dissolution behaviors of aluminum in AlCl 3 -[BzMIM]Cl (1-benzyl-3-methylimidazolium chloride) ionic liquid was investigated using coulometric weight loss experiments, linear sweep voltammetry, potentiodynamic polarization and electrochemical impedance spectroscopy. The results showed that passivation occurred during the anodic dissolution of aluminum, and the passivation film was identified as the formation of AlCl 3 precipitates and local solidification of electrolyte on the electrode surface. The potentiodynamic polarization analysis showed that an increase in temperature caused a positive shift in corrosion potential ( E corr ), an increase in corrosion current density ( i corr ) and a decrease in polarisation resistance ( R P ). Impedance measurements indicated that the anodic dissolution process of aluminum in AlCl 3 -[BzMIM]Cl ionic liquids consisted of charge transfer, confinement of the passivated film on the electrode surface and diffusion-induced Warburg impedance.

Improving the tribological and anti-corrosion property of the WS2 film through Ta doping

The easy oxidation and poor corrosion resistance of the sputtered WS2 film would limit its application in spacecraft due to the sharp deterioration of lubricity resulting from the contact with the marine atmosphere inevitably with the increasing space launch from sea or seaside. In this study, the active metal Ta was skillfully introduced into the WS2 film through co-sputtering of the WS2 and Ta targets. The influence of the doped Ta related microstructure regulation on the tribological and anti-corrosion properties of the prepared composite films was investigated. It showed that the incorporation of the active Ta would activate the residual O atoms to form Ta2O5 phase while making the WS2 phase partly oxidized to form the WSxOy and WO3. WS2–Ta composite films with low Ta content exhibited low friction coefficient and long wear life more than 3 times of that for pure WS2 film. In addition, the corrosion resistance of WS2–Ta film was improved by a positive shift of corrosion potential in salt spray with increasing the Ta content, originating from the passivation effect of the Ta2O5 phase and the WSxOy phase in the film as well as the dense structure.

Corrosion Inhibition Properties of Sulfonated Polyaniline-Poly(Vinyl Alcohol) Composite on Mild Steel

In this work, we demonstrate water based corrosion inhibition properties of engineered sulfonated polyaniline molecules on poly(vinyl alcohol), PANI-PVA, for mild steel. The corrosion-inhibition performances were evaluated using potentiodynamic polarization in salty corrosive 3 % NaCl solution. The anti-corrosion coating based on these composite materials display barrier properties against corrosion causing agents and show corrosion protection efficiency of 84.39 %, compared with uncoated. The material showed lower value of corrosion current (Icorr) that is 2.56 μA cm-2 and positive shift in corrosion potential (Ecorr), -0.426 V, in comparison with uncoated steel. Open circuit potential (OCP) Studies and electrochemical impedance (EIS) were also carried out to check the corrosion protection ability of the material. OCP studies, Nyquist plot and Bode plots showed that the synthesized PANI-PVA possess corrosion protection ability on mild steel against the corrosive species.

Synthesis and Properties of Mg-Mn-Zn Alloys for Medical Applications.

The magnesium alloys Mg-0.5Mn-2Zn, Mg-1.0Mn-2Zn, and Mg-1.5Mn-2Zn (wt.%) with potential biomedical applications, synthesized by powder metallurgy, were investigated to evaluate the influence of manganese content on their microstructure, mechanical properties, and corrosion resistance. The results show that Mg-Mn-Zn alloys prepared by powder metallurgy reached the maximum compressive stress of 316 MPa and the maximum bending strength of 186 MPa, showing their good resistance to compression and bending, and meeting the mechanical properties required for the human bone plate. With an increase in manganese content, the corrosion resistance improved. In the polarization curve, the maximum positive shift of corrosion potential was 92 mV and the maximum decrease of corrosion current density was 10.2%. It was concluded that, of the alloys tested, Mg-1.0Mn-2.0Zn (wt.%) had the best overall performance, and its maximum compressive stress force and corrosion current density reached 232.42 MPa and 1.32 × 10−5 A·cm−2, respectively, being more suitable for service in human body fluids.

Effect of Ce addition on microstructure, mechanical properties and corrosion behavior of Al-Cu-Mn-Mg-Fe alloy

The effects of rare earth Ce on the microstructure, mechanical properties and corrosion behavior of Al-Cu-Mn-Mg-Fe alloys were investigated by means of microstructure analysis, tensile test and electrochemical corrosion test. The research shows that the Al-Cu-Mn-Mg-Fe alloy after low temperature heat treatment mainly contains the S (Al2CuMg) phase, the T (Al20Cu2Mn3) phase, the Al6 (Mn, Fe) phase and the Al7Cu2Fe phase, and the rare earth Ce makes the alloy form the new rare earth phase Al8Cu4Ce. The appearance of this phase has a significant refinement effect on the Al6 (Mn, Fe) phase. Compared with Ce-free, the yield strength and tensile strength of Al-Cu-Mn-Mg-Fe alloy with 0.254 ωt% Ce increased by 7% and 15%, respectively, and the elongation increased from 3.1% to 4.8%. It also has better corrosion resistance, which is represented by the decrease of corrosion current density and positive shift of corrosion potential in Tafel measurement in solutions of different concentrations, and the increase of corrosion impedance in electrochemical impedance spectroscopy test, especially the corrosion current density was reduced by 6.06 μA cm−2 in 3.5% NaCl solution.

Determination of Iron Valence States Around Pits and the Influence of Fe3+ on the Pitting Corrosion of 304 Stainless Steel.

Potassium ferricyanide and potassium ferrocyanide were used to observe and monitor the pitting corrosion of 304 stainless steel (SS) at anodic polarization in situ. The results show that there are Fe3+ ions around the corrosion pit when pitting occurs on 304 SS in NaCl aqueous solution. The effect of Fe3+ surrounded pits on the pitting corrosion was also studied by testing the electrochemical behavior of 304 SS in different Fe3+/Fe2+ solutions. The presence of Fe3+ leads to the positive shift of corrosion potential and the increase of corrosion rate of 304 SS. There are two possible reasons for this phenomenon. On the one hand, Fe3+ hydrolysis results in the decrease of pH value of solution. At the same iron ion concentration, the higher the Fe3+ ion concentration, the lower the solution pH value. On the other hand, Fe3+ may reduce on the electrode surface. The decrease of solution pH and the reduction of Fe3+ resulted in the acceleration of the corrosion rate.

Role of nano ZnO particles in the electrodeposition and growth mechanism of phosphate coatings for enhancing the anti-corrosive performance of low carbon steel in 3.5% NaCl aqueous solution

In this work, nano ZnO powders were used in the electrodeposition of zinc phosphate coatings to mitigate the detrimental effects of corrosion on low carbon steel. Our results showed that nano ZnO powder promotes the formation of hopeite (Zn3(PO4)2·4H2O) and phosphophyllite (Zn2Fe(PO4)2·4H2O) phases which are the main constituents of phosphate conversion coatings. The surface morphology, chemical composition, the growth process and anticorrosive performance of these coatings are examined using SEM, EDS, XRD and electrochemical measurements. Electrochemical characterization results suggest, nano ZnO incorporated phosphate coatings exhibit a lower corrosion rate (∼1.89 mpy) in 3.5% NaCl solution against normal zinc phosphate coatings (∼5.68 mpy) which is well supported by microstructural examination. It is believed that positive shift in corrosion potential and marked reduction in the current density helps in the formation of compact coatings with full crystalline surface coverage suggesting the corrosion protection mechanism offered by these coatings is a diffusion controlled process.

The Effect of Rhenium Addition on Microstructure and Corrosion Resistance of Inconel 718 Processed by Selective Laser Melting

In this study, the effect of rhenium addition (2, 4, and 6 wt pct) and building orientation (0 and 90 deg) on the microstructure and corrosion resistance of Inconel 718 (IN718) alloy processed by selective laser melting (SLM) was investigated. Microstructure characterization showed that the as-built IN718-Re alloys consist of columnar grains growing parallel to the building direction (Z-axis). Each columnar grain was characterized by a fine columnar/cellular dendritic substructure with Nb- and Mo-rich Laves phases and MC-type carbides embedded in the interdendritic spaces. Rhenium addition segregated to γ phase dendrites which resulted in an increase of the columnar/cellular substructures width with increasing Re content. Due to a strong microstructure anisotropy of SLM-processed IN718-Re alloys, the corrosion properties were examined for mutually perpendicular planes: XY (90 deg samples) and XZ (0 deg). The presence of rhenium enhanced the corrosion resistance of IN718 alloy in 0.1 M Na2SO4 and NaCl solutions at both exposed planes. The corrosion current density was significantly reduced for IN718-Re alloys and increasing Re content correlated with a more positive shift in corrosion potential. Moreover, the XY plane possessed better corrosion resistance than the XZ plane due to the higher fraction of laser overlapping areas observed for the XZ plane.

Potentiodynamic polarization studies of the pitting corrosion resistance and passivation behavior of P4 low carbon mold steel in chloride and acid chloride solution

Potentiodynamic polarization studies and open circuit potential measurement of P4 low carbon mold steel (P4LC) was performed to assess its pitting corrosion resistance in specific concentrations of chloride and acid chloride solutions. Results showed the corrosion rates of P4LC were generally higher in the acid chloride media. P4LC displayed significant pitting resistance, independent of chloride concentration in the chloride media. The chloride attack was determined to be the consequence of film breaking and penetration mechanism. Delayed passivation coupled with metastable pitting activity occurred at the anodic region of the polarization plot in the acid chloride solution and beyond a certain chloride concentration in the acid chloride solution, passivation behavior of the steel was completely absent due to the combined electrochemical action of and Cl− ions. O2 reduction was the dominant cathodic in the chloride solution while H2 evolution was the dominant reaction in the acid chloride media. Data from open circuit potential analysis shows the oxide film formed on P4LC in the chloride solution was sustainable from the positive shift in corrosion potential while in the acid chloride solution the corrosion potential were more electronegative. The morphology of P4LC showed the presence of deep elliptical corrosion pits at low chloride concentration while at higher chloride concentration fewer but larger pits in the form of vertical grain attack were visible. The morphology of P4LC from the acid chloride solution showed the presence of large number of deep elliptical corrosion pits coupled with a more deteriorated surface.

Enhanced corrosion protection performance with MWCNT dispersed epoxy coating prepared under supercritical CO2 assistance

The corrosion protection performance of epoxy coatings could be enhanced by incorporation of nanofillers such as MWCNT. However, a homogeneous dispersion of MWCNT in epoxy polymer is still a teasing challenge. Herein, we report an environmentally benign single‐step supercritical CO2 processing method to improve the dispersion of MWCNT in epoxy matrix in order to achieve an effective anticorrosive coating. The executed approach provides a cluster‐free uniform distribution of MWCNT in epoxy matrix as characterized with UV‐visible spectroscopy, Fourier transforms infrared spectroscopy, X‐ray diffraction, and surface analysis. The anticorrosive characteristics of MWCNT/epoxy coating were studied in NaCl as well as in photodegraded dye medium through electrochemical impedance spectroscopy (EIS) and potentiodynamic polarization measurements. We observed the remarkable corrosion of model metal substrate in photodegraded dye medium besides NaCl medium. In both mediums, the protection efficacy of MWCNT/epoxy coating was deduced from the stable impedance arcs in Nyquist plot and increased impedance modulus. The electrochemical impedance spectra were best fitted with equivalent circuits showing the higher values of pore resistance. Also, the MWCNT/epoxy coating exhibited a positive shift of corrosion potential and possessed a lower corrosion rate as compared with neat epoxy coating. More direct evidence of the excellent barrier properties for MWCNT/epoxy coating was visualized in SEM images. The obtained results implied that the superior dispersion of MWCNT into epoxy matrix significantly reduces the porosity of coating and inhibits the permeability of corrosive ions. We expect supercritical CO2 assisted dispersion method can offer an efficient, cost‐effective, and industrially viable route to develop high performance protective coatings for varied commercialized applications.

Comparison of Anticorrosion Studies of Titanium Dioxide andNickel Oxide Thin Films Fabricated by Spray Coating Technique

The titanium dioxide and nickel oxide nanoparticles are synthesized by chemical precipitation method. The as prepared nanoparticles of titanium dioxide and nickel oxide are coated on steel substrate (304L SS) using spray coating technique. The corrosion resistance of 304L SS substrates spray coated with nanostructured titanium dioxide (TiO2) and Nickel oxide (NiO) in 3.5% NaCl is studied from Tafel polarization curve and electrochemical impedance spectra. The polarization curves of coated 304L SS substrates showed positive shift in corrosion potential with respect to that of bare. The Nyquist plot of the coated films confirmed that the coatings have improved the corrosion resistance of 304L SS substrate. The variation of impedance with frequency of the coated 304L SS before and after salt spray test shows that NiO and TiO2 films are quite stable in salt environment. There is no much change in surface morphology and surface roughness of films after corrosion test and this further confirm the film stability in corrosive environment. The absence of crack in AFM images of films subjected to load shows that the films are quite tough. The non-existence of rust in coated substrate exposed to salt environment (5% NaCl at 30°C) for 390 hrs confirms that the films can act as anticorrosive coating for 304L SS substrate in adverse salt environment.

Electrodeposition of Adherent Polypyrrole Film on Titanium Surface with Enhanced Anti-corrosion Performance

A method of producing extremely adhesive polypyrrole film on Titanium (Ti) substrate was investigated. The Ti substrate was chemically pretreated and then modified by polydopamine (PDA), the polypyrrole film synthesized by electrochemical method on the treated Ti substrate displayed good adhesion and enhanced anticorrosion performance. The study of the corrosion process was conducted through open circuit potential, tafel polarization and alternating current impedance test. The adhesive polypyrrole film coated titanium showed higher positive shift in corrosion potential and lower corrosion rate, indicating the great enhanced anti-corrosion performance.

Electrochemical deposition of Mg(OH)2/GO composite films for corrosion protection of magnesium alloys

Abstract Mg(OH) 2 /graphene oxide (GO) composite film was electrochemical deposited on AZ91D magnesium alloys at constant potential. The characteristics of the Mg(OH) 2 /GO composite film were investigated by scanning electron microscope (SEM), energy-dispersive X-ray spectrometry (EDS), X-ray diffractometer (XRD) and Raman spectroscopy. It was shown that the flaky GO randomly distributed in the composite film. Compared with the Mg(OH) 2 film, the Mg(OH) 2 /GO composite film exhibited more uniform and compact structure. Potentiodynamic polarization tests revealed that the Mg(OH) 2 /GO composite film could significantly improve the corrosion resistance of Mg(OH) 2 film with an obvious positive shift of corrosion potential by 0.19 V and a dramatic reduction of corrosion current density by more than one order of magnitude.

Improved Surface Properties of AZ31 and AZ91 Mg alloys Due to Electron Beam Liquid Phase Surface Treatment

Electron beam alloying (EBA) was applied to improve the surface properties of AZ31B and AZ91D magnesium alloys. Three Al-based additives with different Si contents (0, 12, and 30 wt.%) were pre-deposited on the Mg substrates by atmospheric plasma spraying (APS) and cold gas spraying (CGS). Spraying temperatures above (APS) and below (CGS) the melting point of the oxidation-sensitive Al-based sprayed material caused different amounts of oxide in the coatings, resulting in varying layer qualities. EBA layers using the CGS deposition technique are more homogeneous and reached hardness values up to 200…220 HV0.1. Potentiodynamic polarization tests in 0.001 M NaCl solution showed, compared to the base material, a positive shift in corrosion potential up to 400 mV for EBA layers using AlSi30, with a reduction in corrosion current density of more than 3 times compared to the untreated base materials. The coefficient of wear for all EBA layers reached a minimum at an applied load of 25N and was reduced by 50% in comparison to the base material.

Surface treatment of iron by electrochemical oxidation and subsequent annealing for the improvement of anti-corrosive properties

Corrosion resistance of iron oxides on iron foils prepared by anodization, annealing or a combination of both was characterized by electrochemical methods. Even though iron oxide film with a thickness of more than 2μm could be prepared by single anodization, corrosion resistance deteriorated because the oxide film was in the amorphous phase and contained many defects. Corrosion resistance of iron oxides was also not enhanced by single annealing. Conversely, combination of anodization and subsequent annealing led to a positive shift of the corrosion potential in the Tafel plot, indicating that corrosion resistance was improved. Formation of thicker oxide during anodization was associated with a more positive shift in corrosion potential after annealing. Electrochemical impedance spectroscopy showed that the slowest charge transfer was observed in oxide films grown by a combination of anodization and annealing. We found that the optimum annealing temperature of anodic films in terms of the most positive shift of Ecorr was 500°C.