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Simulation of corrosion reactions has become an important tool in the analysis of novel materials for corrosion resistant materials and applications. A number of analytical, boundary element and finite element methods currently exist in the literature, which use experimental corrosion parameters as model inputs for the extraction of simulated polarization curves, oxide growth rates, and other corrosion behaviors. Here,we propose the combination of finite element simulationwith thermodynamic data from Pourbaix diagrams to allow for the simulation of metal corrosion, where individual corrosion reactions can be monitored at the metal surface. [ABSTRACT FROM AUTHOR]

Multi-modal imaging, which visualizes changes in the structure and chemistry of the same region of interest inmaterials by combining various techniques, is becoming attractive to material scientists. Here, we describe amulti-modal approach to investigate intergranular (IG) corrosion of sensitized stainless steels using synchrotron-based nanoscale X-ray imaging with sensitivity to microstructure and chemical composition. Three-dimensional tomography of 304 stainless steel samples deteriorated by IG corrosion, was carried out using X-ray fluorescence and differential phase contrast imaging. These findings were further supported with surface imaging and chemical analysis using scanning electron microscopy and energy dispersiveX-ray spectroscopy. The combined quantitative structural and chemical analysis indicates that chromium segregates along grain boundaries, cracking is due to IG corrosion, and Cr-enrichment occurs on the cracked surfaces. Such quantitative 3D imaging of Cr23C6 nucleation at grain boundaries and Cr enriched oxides at cracked surfaces is a powerful tool to correlate IG corrosion mechanisms at nanoscale with buried grain boundary structure and alloy composition. Such understanding of IG corrosion mechanisms is critical for both the development of predictive multiscale corrosion models, and the engineering of corrosion resistant materials. [ABSTRACT FROM AUTHOR]

The corrosion behavior of single-phase Mg-Al alloys has been examined using a combination of aqueous, atmospheric and ionic liquid based techniques. Our results show preferential rapid dissolution of Mg along with redistribution and enrichment of the effectively more "noble" Al component. During aqueous free corrosion experiments immediate pH increases were measured at the solid-liquid interface in aqueous chloride. Using inductively coupled plasma mass spectroscopy the oxide/hydroxide chemical dissolution rates were determined to be 0.222 per atomic site/s for Mg2+ and 0.022 per atomic site/s for Al3+ from the elemental alloy components. Atmospheric corrosion studies measured a 60◦ contact angle decrease during 20 hour free corrosion corresponding to a small 0.04 Jm-2 reduction in the MgO/water interfacial free energy. Rotating disk electrode and ionic liquid dissolution techniques revealed mud cracking, platelet formation and nanowire morphologies that can result from selective dissolution ofMg in single-phase Mg-Al alloys. The evolution of these morphologies is described in terms of a step-flow dissolution mechanism. [ABSTRACT FROM AUTHOR]

Ti-6Al-4V alloy produced by selective laser melting (SLM) was reported to exhibit an inferior corrosion resistance compared with the traditionally processed Grade 5 alloy, due to the formation of high-energy metastable α' martensite with regard to α martensite. This work manipulates the transformation of α' martensite to α martensite by heat-treatment in SLM-produced Ti-6Al-4V alloy and studies the effect on its corrosion behavior using electrochemical tests and microstructural analysis. The electrochemical results reveal that the heat-treated SLM-produced samples exhibit a higher corrosion rate than the as-received counterparts. The microstructural characterization results show that the acicular α' martensite vanishes gradually, and a plate-shaped α phase and a lamellar α + β mixture continuously form with enhancing heat-treatment temperature, which increases the grain size. The relation between changes in grain size and corrosion resistance of SLM-produced Ti-6Al-4V has been discussed in detail. [ABSTRACT FROM AUTHOR]

Chlorosilane species are commonly used at high temperatures in the manufacture and refinement of ultra-high purity silicon and silicon materials. The chlorosilane species are often highly corrosive in these processes, necessitating the use of expensive, corrosion resistant alloys for the construction of reactors, pipes, and vessels required to handle and produce them. In this study, iron, the primary alloying component of low cost metals, was exposed to a silicon tetrachloride-hydrogen vapor stream at industrially-relevant times (0-100 hours), temperatures (550-700°C), and vapor stream compositions. Post exposure analyses including FE-SEM, EDS, XRD, and gravimetric analysis revealed formation and growth of stratified iron silicide surface layers, which vary as a function of time and temperature. The most common stratification after exposure was a thin FeSi layer on the surface followed by a thick stoichiometric Fe3Si layer, a silicon activity gradient in an iron lattice, and finally, unreacted iron. Speculated mechanisms to explain these observations were supported by thermodynamic equilibrium simulations of experimental conditions. This study furthers the understanding of metals in chlorosilane environments, which is critically important for manufacturing the high purity silicon required for silicon-based electronic and photovoltaic devices. [ABSTRACT FROM AUTHOR]

The electrochemical corrosion of the carbon-based catalyst support materials used in proton exchange membrane fuel cells (PEMFCs), especially at the cathode, has a significant impact on PEMFC lifetime. Thus, an effective and reliable method for the evaluation of the corrosion resistance of new carbon supports, as they are developed, is required. In the present work, a novel approach that allows for the ranking of carbon supports for their corrosion susceptibility has been developed, based on the testing of a conventional microporous carbon material (Vulcan carbon, VC) and two ordered mesoporous carbons (OMCs), synthesized using sucrose and anthracene as the carbon precursors. While cyclic voltammetry does reveal important information about surface area and surface oxidation changes, the charge passed during potential stepping between 0.8 and 1.4 V vs. RHE was found to be still more informative, with the cathodic charge used to continuously correct for the changing surface area of the carbon during its oxidation. Based on this approach, it was found that VC, which is the more crystalline material, is more stable to oxidation than the OMCs, as expected, while the anthracene precursor leads to a more stable OMC than when sucrose is used. [ABSTRACT FROM AUTHOR]

Rheocast AZ91 magnesium alloy was evaluated in terms of microstructure and corrosion resistance. Rheocasting leads to a globular microstructure of α-Mg spheres separated by an interconnected β-Mg17Al12 (β-phase) network. Findings revealed that early stages of corrosion were located at the center of α-Mg globules and more importantly at α-Mg/β-phase interfaces due to galvanic coupling as predicted from surface potential maps. Electrochemical, hydrogen evolution and weight loss measurements demonstrated the superior corrosion resistance of the rheocast alloy. This was attributed to an improved barrier effect of the β-Mg17Al12 phase and. possibly, to a smaller area fraction of Al-(Mn, Fe) inclusions. For long immersion times, only small attacked areas were observed which corresponded to randomly corroded α-Mg globules. [ABSTRACT FROM AUTHOR]

This work investigated the grafting of 11-(2-bromoisobutyrate)-undecyl-1-phosphonic acid (BUPA) and 1-dodecylphosphonic acid (C12PA) to form (mixed) monolayers with different proportions of BUPA and C12PA on Phynox. The role and impact of these grafted molecules have been evaluated in terms of the corrosion resistance and the feasibility to act as a suitable platform for surface initiated atom transfer radical polymerization (ATRP) of 2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate (MPC). It appeared that both molecules play an important role: BUPA to initiate the ATRP polymerization of MPC and C12PA to increase the resistance to corrosion of Phynox substrates. Moreover, the presence of C12PA in the mixed monolayer beneath the poly-2-(methacryloyloxy)ethyl 2-(trimethylammonio)ethyl phosphate (PMPC) layer has a beneficial impact in terms of corrosion resistance. [ABSTRACT FROM AUTHOR]

In this study, aluminosilicate sol-gel coatings were deposited on Type 430 stainless steel by multiple spin casting cycles. Amorphous aluminosilicate coatings, 65 nm thick, were prepared from precursor solutions with 50, 100, and 500 mmol dm-3 total concentrations of aluminum and silicon species (molar ratio of Al/Si = 1/4) by 10, 5, and 1 spin casting cycles, respectively. Although the obtained coatings had a similar composition with a molar ratio of Al/Si = 25/75, the coatings with increased density were formed by reducing the concentration of precursor solution. The pitting potentials of the coated stainless steels, measured by potentiodynamic polarization in 3.5% NaCl solution, increased remarkably (to 1.1 V vs Ag/AgCl) with a decrease in the concentration of precursor solution. Cyclic corrosion tests, consisting of 30 cycles of spraying of 5% NaCl solution at 35°C for 2 h, drying at 60°C for 4 h, and wetting at 50°C and >95% relative humidity for 2 h, revealed highly improved corrosion resistance. Layer-by-layer sol-gel deposition using diluted precursor solutions is an effective way to obtain highly protective coatings. [ABSTRACT FROM AUTHOR]

Low-temperature wafer-level Cu-to-Cu thermo-compression bonding and its reliability for hermetic sealing application have been investigated in this work. The volume of the encapsulated cavities is about 1.4×10-3 cm3 in accordance with the MIL-STD-883E standard prescribed for microelectronics packaging hermeticity measurement. The samples under test are bonded at 300 °C under a bonding force of 5500 N for 1 h in vacuum (∼2.5 × 10-4 mbar) with a 300 nm thick Cu diffusion layer and 50 nm thick Ti barrier layer which are deposited in an e-beam evaporator. The reliability test is accomplished through a temperature cycling test (TCT) from -40 to 125 °C up to 1000 cycles and a humidity test based on IPC/JEDEC J-STD-020 standard. In addition, an immersion in acid/base solution is applied to verify the corrosion resistance of the Cu frame for hermetic application. Excellent helium leak rate which is smaller than the reject limit defined by the MIL-STD-883E standard (method 1014.10) is detected for all the samples. These excellent helium leak rates show an outstanding bonding quality against harsh environment for hermetic encapsulation in 3D integration applications. [ABSTRACT FROM AUTHOR]

In this paper we present a novel method to fabricate reliable micro-electro-mechanical system (MEMS) disk resonators with high yield and good performance. The key breakthrough in the fabrication process is a novel approach to effectively restraining electro-chemical corrosion of polycrystalline silicon (polysilicon) electrically coupled with noble metals of MEMS devices by hydrofluoric acid (HF)-based solutions. In addition, a measurement architecture based on a differential readout topology is demonstrated. The differential circuit proposed here can effectively suppress noise and feed-through current by common-mode rejection of the differential amplifier. This differential amplifier circuit configuration is also used to build up a notch filter. The preliminary result about the temperature dependence of the resonance frequency is discussed, and the device failure is analysed. [ABSTRACT FROM AUTHOR]

For pure Fe, solution pH effects on pitting potential and passive film properties were examined in a borate-phosphate buffer solution using a polarization test, Mott-Schottky analysis, and a galvanostatic test. Combining the results, the relationship between the surface charge and pitting potential was presented. Passive film analyzes revealed that the most protective passive film with the lowest defect density and highest thickness was formed on Fe in the buffer solution at pH 8.5-9. From the dependency of the film thickness on the solution pH, it was concluded that the surface charge of the film was changed by the pH from positive to negative at pH 8.5-9, thus, the film dissolved via an H+-assisted reaction below pH 8.5, and via H2O-assisted reaction above pH 9. Due to the change in the film dissolution reaction, the ion accumulation in the interfacial diffuse layer was altered from cation-selectivity at pH levels lower than 8.5 to anion-selectivity at pH levels higher than pH 9. It was confirmed that the Cl- attack on the passivated Fe surface was significantly limited in the buffer solution with pH levels higher than 9 due to the formation of the anion-selective diffuse layer. [ABSTRACT FROM AUTHOR]

The effect of thiourea (TU) and saccharin (SAC) on the deposition rate, surface morphology, boron (B) content, micro-hardness, and corrosion resistance of an electroless Ni-B plating layer on AZ9ID magnesium alloy was investigated. The electroless Ni-B plating layer was characterized by scanning electron microscopy (SEM), electron probe micro-analysis (EPMA), X-ray diffraction (XRD), energy dispersive spectroscopy (EDS), Vickers hardness and electrochemical techniques in 3.5 wt% NaCI aqueous solution. The results showed that TU and SAC had different effects on the morphology and a similar influence on the particle size of the plating. TU slightly decreased the B content in the coating, while SAC had no effect. The two additives reduced the Ni-B plating rate and enhanced the corrosion resistance of the coating. Appropriate amounts of the additives improved higher micro-hardness of the plating. Elements diffusion occurred between substrate and coating during heat-treatment. After heat-treatment the deposited coating layer transformed from an amorphous structure to crystalline. [ABSTRACT FROM AUTHOR]

The rare earth metal conversion coating process is recognized for its simple electrolyte composition, which is generally considered to be environmentally friendly. In this study, cerium conversion coatings were made in a cerium nitrate/hydrogen peroxide solution on AZ31 magnesium alloys after 20 s of pickling in hydrochloric acid (HCl) or hydrofluoric acid (HF) solutions. Results show that acid pickling in HF or HCl enhanced the adhesion and corrosion resistance of the cerium conversion coating. This enhancement is due to the inhibition of the blister formation, which presumably results from the rupture of the cerium oxide layer by hydrogen bubbles. Finally, the mechanism of HF and HCl acid pickling effect on the reaction rate and defect of the cerium conversion coating was discussed in detail. [ABSTRACT FROM AUTHOR]

Nano zinc oxide-containing epoxy-based coatings were prepared by co-deposition of zinc oxide nano particles and epoxy-based cathodic electrodeposition paint. The films were exposed to UV radiation for different periods and the corrosion resistance properties of the exposed films were evaluated by electrochemical impedance spectroscopy. It was found that the nano zinc oxide stabilized coatings maintain their protective properties even after a prolonged exposure to UV light. The more prolonged retention of protection properties of the coating was assigned to the morphology of the film containing nano ZnO after exposure to UV light. Nano ZnO stabilized coatings show a uniform degradation of the film surface while non-stabilized coating exhibit deep cracks which results in deterioration of the film integrity. UV exposure of non-stabilized films was found to result in formation of deep cracks and non-uniform photodegradation in epoxy coating. [ABSTRACT FROM AUTHOR]

Chromate conversion coatings (CCCs) were synthesized on AA7075 alloy. The effects of sodium saccharin as a grain refining agent (GRA) and coating time on the coating morphology, topography, and alloy corrosion resistance were studied in this work. Morphologies and topographies of CCCs were examined using optical, scanning electron and atomic force microscopes. The corrosion behaviour was evaluated using potentiodynamic polarization and electrochemical impedance spectroscopy in 0.5 M NaCl solution. Major decreases in both coating grain size and corrosion rate occur at a GRA concentration of 1 g/l. Coating roughness increased to a limited nano-scale extent with increasing immersion time. [ABSTRACT FROM AUTHOR]

Electrochemical impedance spectroscopy was used to study the corrosion resistance of Al 7075-T6 after degreasing and one of three different alkaline activations. Electrochemical tests were conducted using an aqueous solution containing 0.35 w/v% NaCl and 0.70 w/v% (NH4)2SO4 at its natural pH of ∼5.5 or with its pH adjusted to ∼9.0. These tests showed increasing the electrolyte pH to 9.0 made the electrolyte less corrosive, which allowed impedance characterization at low frequency (1.00-0.01 Hz) after only 1500 s of stabilization prior to testing. The total impedance of the native oxide was ∼5.9 kΩ cm² and degreasing did not alter this value. Degreasing followed by activation in 5 wt % Na2CO3 or 1 wt % NaOH decreased the total impedance by ∼20% to 4.8 kΩ cm², whereas activation in 2 wt % NaOH decreased impedance by ∼30% to 4.2 kΩ cm². The decreased impedance after activation allowed a cerium-containing solution to penetrate the surface oxide and react with the substrate to form a conversion coating. Thus, increasing the electrolyte pH made the electrolyte less corrosive, which enabled characterization of the decrease in surface oxide impedance after alkaline treatments using electrochemical impedance spectroscopy. [ABSTRACT FROM AUTHOR]

The corrosion and contact resistances of coated and uncoated stainless steel grades were studied. The coatings studied were PVD CrN and arc discharge deposited Au. The samples were aged in long steady-state experiments using a multisinglecell device. MEAs and exhaust water were analyzed for accumulated iron after measurements. Iron accumulation was measured from MEAs, exhaust water and gas outlet pipes from the cells. The interfacial contact resistances were measured before and after the fuel cell experiments. Low contact resistance was achieved with all coated samples. The main accumulation site of dissolved iron was found to be the MEA and GDLs. A large variation in the corrosion results due to differences in the coating quality was observed. Some coatings with low interfacial contact resistance were found to be prone to corrosion. The CrN coating was also tested in a stack, and it performed well. It was concluded that the multisinglecell is a useful tool for screening different coatings reliably and cost-effectively. [ABSTRACT FROM AUTHOR]

Highly ordered TiO2 nanotube (TN) arrays with a regular top porous morphology were fabricated by a facile two-step electrochemical anodization in an ethylene glycol solution containing NH4F and H2O. The morphology, crystalline phase, and composition of the TN films were characterized systematically by scanning electron microscopy, x-ray diffraction, x-ray photoelectron spectroscopy, and ultraviolet-visible spectroscopy. The photoelectrochemical properties of the TNs in 0.5 M NaCl solution were evaluated through electrochemical measurements under illumination and dark conditions. The nanoporous TNs exhibited a drastically enhanced photocurrent in the UV light region. The electrode potentials of 304 stainless steel coupled with the TiO2 nanotube arrays negative shift values are no less than 354 mV under a white light irradiation. The experimental results indicated that the photoelectrochemical performance of the nanoporous-structured TNs was markedly influenced by the crystallization and the novel porous nanotubular architecture. And the nanoporous-structured TNs with a comparable high aspect ratio were able to effectively function photogenerated cathodic protection for metals under UV and visible light illumination. It is possible for such photogenerated cathodic protection to last for a period of 24 h, even in darkness. [ABSTRACT FROM AUTHOR]

The electrolytic MgO coating on Mg alloy has been carried out in 0.1 M Mg(NO3)2·6H2O aqueous solution to improve its corrosion resistance. The as-coating was Mg(OH)2 which was formed by the electrolysis, Mg2+ + 2OH¯ → Mg(OH)2, and finally transformed into MgO at 350°C. The surface morphology and phase structure were analyzed using scanning electron microscope and grazing angle X-ray diffraction. Polarization curves and immersion tests were used to evaluate the corrosion resistance of the coated specimens. More OH¯ ions were produced, and the migration of Mg2+ was enhanced at a more negative applied potential, leading to a higher nucleation rate of Mg(OH)2 on the specimen and resulting in the (001) preferred orientation. The weight gain resulted from coatings increased with increasing deposition time for the initial 40 min, and the increasing rate slowed down after 1 h due to the precipitation of Mg(OH)2 in the solution. A coating deposited at -1.8 V (Ag/AgCl) for 40 min and annealed at 400°C for 1 h was suggested to provide a more uniform and dense MgO protective coating, which results in a reduction of corrosion current density from 99.5 down to 0.2 μA/cm² and the enlarged passivation region between -1.52 and -1.25 V (Ag/AgCl) in 3.5 wt % NaCl aqueous solution, with respect to the uncoated specimen. Compared with AZ9ID magnesium alloy substrate, the corrosion resistance was improved nearly 2 orders by the electrolytic MgO ceramic coating. However, the bonding strength, 10 MPa, should be further improved to satisfy the minimum requirement, 35 MPa, for the orthopedic implants. [ABSTRACT FROM AUTHOR]

Commercially available magnesium alloy AZ31 is extensively used in structural engineering components although, like many magnesium-based materials, it suffers from poor corrosion resistance, particularly in marine environments, which limit wider application. Previously, the ionic liquid (IL) trihexyl(tetradecyl)phosphonium bis(trifluoromethanesulfonyl)amide ([P66614][NTf2]) was shown to improve the corrosion resistance of magnesium alloy AZ31 in humid environments and in the presence of chloride-containing aqueous environments. Here, we investigate the morphology and composition of the protective surface film that forms upon immersion of the Mg alloy in the IL, using grazing angle X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), time of flight-secondary-ion mass spectrometry (TOF-SIMS), solid-state NMR, and transmission electron microscopy (TEM). XRD indicates that an amorphous film is present on the surface subsequent to exposure to the [P66614][NTf2] IL, whereas XPS etching experiments indicate that the film is multilayered. The innermost layer is predominantly inorganic fluoride salts as well as native oxide/hydroxide surface species. TOF-SIMS spectra support these observations and indicate an outermost, thin, adherent layer of IL species. Multinuclear NMR spectroscopy confirms the presence of a multiphase composition as well as the presence of metal fluorides and complex organic species. The surface film appears to be of the order of 100 nm according to the TEM/energy-dispersive X-ray spectroscopy observations. [ABSTRACT FROM AUTHOR]

The CrAlN/SiNx multilayers were deposited by radio-frequency reactive magnetron sputtering. In multilayers, the SiNx layer thickness varied from 0.3 to 1 nm, and the layer thickness ratios of CrAIN to SiNx were set to be 4:0.3, 13:1, and 4:1. The effects of the SIN, layer thickness on the crystalline behavior and microstructure of the multilayers were discussed by X-ray diffraction patterns. scanning electron microscopy, and high resolution transmission electron microscopy. In addition to transforming the SiNx structure from crystalline to amorphous with thickness increase from 0.3 to 1 nm. the films were changed from a columnar microstructure to a dense one. The corrosion resistance of the coatings in 3.5 wt % NaCI solution was investigated by Tafel measurement and electrochemical impedance spectroscopy. The multilayers refined the coarse columnar structure in single-layered CrAIN, leading to a denser microstructure, and revealed lower corrosion current density and higher corrosion impedance. Additionally, the multilayer with a thickness ratio of ICrAIN to ISiNx = 13:1 was identified with a similar composition yet a denser microstructure compared to the one with an ICrAIN to lSiNx thickness ratio of 4:0.3. The multilayer with the thickness ratio of ICrAIN to ISiNx = 13:1 showed better corrosion resistance, suggesting that anticorrosion properties were dominated by microstructure rather than composition. Furthermore, the multilayer with the thickness ratio of lCrAIN to ISiNx = 4: 1 exhibited the densest micro-structure and revealed the best corrosion resistance because the amorphous SiNx layers interrupted the columnar growth and then provided no direct diffusion paths. [ABSTRACT FROM AUTHOR]

Silver-containing oxide coatings on AZ31 Mg alloys were fabricated by microarc oxidation (MAO) in AgNO3-containing sodium silicate (Na2SiO3)-based electrolyte, and their physical and chemical properties were investigated, particularly focusing on corrosion resistance and antibacterial activity. The porous oxide coatings consisting of Mg2SiO4 and MgO formed in both AgNO3-containing and AgNO3-free electrolytes and the MAO coatings were composed of a porous outer layer and a dense inner layer. MAO in AgNO3-containing electrolyte resulted in a thicker oxide coating, especially a thicker fluorine (F)-rich inner layer. Fluorine (F) was rich in the dense inner layer, and Ag was preferentially located close to the coating surface. The potentiodynamic test indicated that Ag-containing MAO coating had a more positive corrosion potential (1.42 V), lower corrosion current density (0.02 μA/cm2), and thus higher corrosion resistance (1824 kΩ cm2) compared to Ag-free MAO coatings (1 .53 V, 0.32 μA/cm2, and 131 kΩ cm2, respectively). The electrochemical impedance spectroscopy results revealed that the higher corrosion resistance of Ag-containing MAO coating was due to an order of magnitude higher resistance of the dense inner layer. Ag-containing MAO coating showed an excellent antibacterial activity over 99.9% against two strains of bacteria, Staphylococcus aureus and Escherichia coli. [ABSTRACT FROM AUTHOR]

Polyaniline has been electrodeposited on an AA 7075 alloy by a potentiostatic method, and its corrosion protection ability has been studied by Tafel polarization and electrochemical impedance spectroscopic techniques in 1% NaCI. A pure polyaniline film protects the aluminum alloy up to 70%. However, the corrosion resistance property of the polyaniline film has substantially increased to 90% by post-treatment in a cerium salt solution. X-ray photoelectron spectra studies have shown that the film formed due to the post-treatment of polyaniline with the AA 7075 alloy in the cerium salt solution is composed of both Ce3+ and Ce4+ oxides. [ABSTRACT FROM AUTHOR]

Alloy 22 (N06022) is a Ni-Cr-Mo alloy that offers an outstanding corrosion resistance in a wide variety of highly corrosive environments. In the present work, the general corrosion of alloy 22 in the passive and active states and the transition from passive and active states were studied in acidic chloride solutions at 90°C. Electrochemical studies, including electrochemical impedance spectroscopy and polarization tests, were performed using mill-annealed and thermally aged (10 h at 760°C) alloy 22 specimens. The depassivation pH (pHD) was 1.7 in deaerated conditions and PHD = 0.3 in aerated conditions. The transition from passive to active states was characterized by a 3 orders of magnitude increase in the corrosion rate (CR) and a significant increase in the interfacial capacity. The CRs obtained via electrochemical tests for mill-annealed (MA) and thermally aged alloy 22 were comparable in all the tested conditions used in the present work. lntergranular attack was observed in thermally aged alloy 22 corroding in the active state due to the presence of precipitates and adjacent depleted zones of the protective alloying elements. [ABSTRACT FROM AUTHOR]

A corrosion-resistant electrocatalyst support was prepared by overcoating high surface-area diamond powder (3-6 nm diameter, 250 m/g) with a thin layer of boron-doped ultrananocrystalline diamond (B-UNCD) by microwave plasma-assisted chemical vapor deposition. This core-shell approach produces electrically conducting (0.4-0.5 S/cm) and high surface-area (150-170 m2/g) diamond powder (B-UNCD-D). Accelerated degradation testing was performed by thermogravimetric analysis (TGA) to assess the oxidation resistance (i.e., corrosion resistance) of powder in the absence and presence of nanoscale Pt. The oxidation onset temperature for B-UNCD-D powder decreased with the Pt loading from 0 to 30 wt % (Pt/C). However, compared with the bare powder, the rate of carbon consumption was significantly greater for Pt-(XC-72) as compared to the platinized diamond powder. For example, the temperature of the maximum carbon consumption rate, Td, occurred at 426°C for Pt-(XC-72) (20% Pt/C), which was 295°C lower than the Td for bare XC-72. In contrast, Td for Pt-(B-UNCD-D, 20% Pt/C) was 558°C; a temperature that was only 62°C lower than that for bare diamond. Isothermal oxidation at 300°C for S h produced negligible weight loss for Pt-UNCD-D (20% Pt/C) while a 75% weight loss was observed for Pt-(XC-72) (20% Pt/C). The results clearly demonstrate that platinized diamond is more resistant to gas phase 6xidation than is platinized Vulcan at elevated temperatures. [ABSTRACT FROM AUTHOR]

A cobalt-based alloy, MP35N, is currently used as a conductor material for thin wires in pacemaker leads. In this study, electrochemical impedance spectroscopy and cyclic polarization measurements of the alloy in a phosphate-buffered saline solution with 100 mM H2O2 indicated a high corrosion resistance and no passivity breakdown. Scanning electron microscopy and energydispersive spectroscopy analyses showed the existence of micrometer-sized TiN particles in the microstructure. Volta potential mapping by scanning Kelvin probe force microscopy revealed that the Volta potential of the TiN particles was several tens of millivolts higher than that of the alloy matrix. By in Situ atomic force microscopy measurements in the solution, small pitlike holes were observed in the vicinity of TiN particles and in other areas after 2 weeks of exposure. However, deposition of corrosion products within the pits was observed in the following days, and the pitlike holes were sealed upon further exposure. The results indicated a negligible risk for localized corrosion of this alloy despite the TiN particles present in the microstructure. [ABSTRACT FROM AUTHOR]

The crevice corrosion performance of Alloy 22 was tested under potentiostatic polarization more positive than the repassivation potential in 4 M NaCI solution at 100°C. Under this aggressive condition, crevice corrosion initiated under the crevice contacts and four stages of corrosion behavior were observed: initiation, propagation, stifling (corrosion slowed), and arrest (corrosion stopped). During the exposure, dark green deposits were found on the uncorroded metal surface around the crevice contacts, light green precipitations were found in the test solution, and the solution color changed from clear to light green. After exposure, loose black corrosion products were found under the crevice contacts. Surface analyses at the sites of varying corrosion penetrations showed similar composition depth profiles, and the results indicated that a 3-5 nm thick, chromium-rich oxide film was formed on the alloy surface. The composition depth profiles indicated that the crevice corrosion occurred by a uniform, nonselective dissolution. Surface analysis results showed that the corrosion products in the crevice were rich in 0, enriched with Mo and W, and depleted of Ni and Cr relative to the bulk alloy. A solution analysis showed that Ni was the main element dissolved into the solution during the exposure. [ABSTRACT FROM AUTHOR]

The corrosion behavior of Ce metal and a Ce-1 wt % Ga alloy in aqueous deaerated solutions has been investigated through potentiodynamic and electrochemical impedance experiments. The solutions consist of 1-1000 mM concentrations of HCI, NaCI, H2SO4, Na2SO4, HNO3, and NaNO3. It was found that the addition of Ga is generally detrimental to the corrosion resistance of Ce, resulting in the loss of passivity and a decrease in polarization resistance. Ce metal was found to be susceptible to pitting in chloride environments. Increasing acidity was found to promote the passivity of Ce in chloride and sulfate solutions. The opposite was true in nitrate solutions. Dissolution of the Ce-Ga alloy was ohmically limited in certain solutions. The ohmic limitation was not attributable to the solution resistance. Although the addition of Ga was found to be detrimental to the corrosion resistance of Ce and Pu, Ce and Ce-Ga were found to be poor electrochemical surrogates for Pu and Pu-Ga. [ABSTRACT FROM AUTHOR]

Effects of Si on the repassivation kinetics and stress corrosion cracking (SCC) of alloy 304Si were examined by a scratch electrode technique and slow strain rate test in chloride solutions and compared with those of other stainless steels (SSs), 304 and 316L. Repassivation kinetics of these alloys and Fe-20Cr-xSi (x = 0-2) alloy were analyzed in terms of the current density, i(t), flowing from the scratch as a function of the charge density, q(t), that has flowed from the scratch. Passive film initially nucleated and grew according to the place exchange model, and then grew according to a high-field ion-conduction model in which log i(t) has a linear relationship with l/q(t) with a slope of cBV. The repassivation rate of Fe-20Cr-xSi (x = 0-2) alloys, evaluated by the cBV value, increased with an increase in Si content. Furthermore, repassivation rate decreased on the order of 304Si, 316L, and 304. The resistance to SCC of the SSs (304Si, 304, and 316L) measured in 35 wt % MgCl2 solution at 120°C was in good agreement with those predicted based on the repassivation kinetics. The beneficial effects of Si on SCC of 304Si SS appears to be associated with the enrichment of Si in the passive film. [ABSTRACT FROM AUTHOR]

The effects of cold work on the pitting corrosion resistance of a nickel-free high-nitrogen stainless steel in chloride solution have been investigated by electrochemical tests, surface chemical analysis, immersion tests, and microscopic observations. Potentiodynamic polarization revealed that pitting resistance was degraded by cold work as convinced by the decreased critical pitting potential. This could be due to a less compact and protective anodic passive film based on the results of electrochemical impedance spectroscopy, Mott-Schottky measurement, and X-ray photoelectron spectroscopy analysis. The growth of such an imperfect passive film could be attributed to a high density of deformation bands and other defects introduced by cold work. Scanning electron microscopy observation of the pitted specimens after polarization tests showed no obvious change in size and density of corrosion pits with increasing cold work level, whereas immersion tests showed varied pit density with cold work although the average size of pits did not increase linearly as a function of cold work level. The effects of cold work on the characteristics of passive films are discussed. [ABSTRACT FROM AUTHOR]

Abstract: This paper is aimed at studying single bubble growth and detachment in controlled conditions and under the action of an electric field. An experimental set-up was built, consisting mainly of a stainless steel lamina with a nucleation site etched in its center, facing the testing fluid. The required heating power was provided by an SMD microresistor, stuck by means of epoxy resin on the back side of the plate. A signal generator, connected to the resistor, allowed for heating power modulation and thus for variation of the bubble size. Two different fluids, FC-72 and HFE-7100 were tested. An external electrostatic field was applied by imposing up to 15kV dc to a ring of 4mm inner diameter suspended 3mm above the plate: in this way, a very clear axisymmetric configuration was created, suitable for two-dimensional analyses. High speed images were taken by means of a high-speed camera, operated at 1000 frames per second with a resolution of about 100pixel/mm. Images were treated with a dedicated image processing software to obtain bubble significant geometrical parameters. The preliminary results reported here show elongation of the detached bubble under the action of the electric field, confirming former results obtained with nitrogen bubbles originating from an orifice in the same liquids. The detachment volume under the action of the electric field either increases or decreases, for low and high electric permittivity fluid, respectively, evidencing the complex nature and role of the electric forces. First results under variable heat load evidence a reduction in detachment diameter. The dynamical forces outside the microlayer region seem to have a minor role, compared to the static ones, in vapor bubble growth. [Copyright &y& Elsevier]

Corrosion-resistant materials under atmospheric conditions can suffer from localized corrosion (e.g., pitting, crevice, stress-corrosion cracking). The stability of such a localized corrosion site requires that the site (anode) must dissolve at a sufficiently high rate to maintain the critical chemistry while a wetted surrounding area (cathode) provides matching cathodic current. The objective of this study was to computationally characterize the stability of such a local corrosion site and explore the effects of physiochemical parameters and electrochemical kinetics. The goal is to contribute to the establishment of a scientific basis for the prediction of the stabilization of localized attack. An analytical method for evaluating the stability of localized corrosion of corrosion-resistant alloys under thin-layer (or atmospheric) conditions is presented. The method uses input data that are either thermodynamic in nature or easily obtained experimentally. The maximum cathode current available depends on the cathode geometry, temperature, relative humidity, deposition density of salt (i.e., mass of salt per unit area of cathode), and the interfacial electrochemical kinetics. The anode demand depends on the crevice geometry, the position of attack within the crevice, and the localized corrosion stability product. By coupling these two approaches, the stability of a crevice can be determined for a given environmental scenario. The method has been applied to the atmospheric crevice corrosion of type 316L stainless steel. [ABSTRACT FROM AUTHOR]

The effect of constituent elements Tb, Dy, and Fe on corrosion of Terfenol-D (Tb0.3Dy0.7Fe1.92) was studied by potentiodynamic polarization studies in freely aerated, deaerated, and fully aerated 3.5% NaCl and 0.01 N Na2SO4 solutions. The corrosion products obtained from immersion and cyclic spray tests were characterized by Fourier transform infrared (FTIR) spectroscopy and scanning electron microscopy (SEM). The polarization behavior of Terfenol-D closely resembled that of pure iron in all environments. Characterization of spalled corrosion products after immersion testing revealed a higher rare earth (RE) content. An increase in iron content of the adherent corrosion products with increasing duration of exposure pointed Out the significant role of iron in the general corrosion processes of Terfenol-D. The polarization and characterization results have been related to the dealloying corrosion mechanism, wherein selective dissolution of REs from the surface results in corrosion from an essentially iron-enriched surface. [ABSTRACT FROM AUTHOR]

Close-packed coupled multielectrode arrays simulating a planar electrode were used to monitor the anodic current evolution as a function of position during initiation and propagation of crevice corrosion of AISI 316 stainless steel (UNS 531600) and Ni- Cr-Mo alloy 625 (UNS N06625). Scaling laws X~rit vs G and x~ vs G derived from polarization data in simulated crevice solutions guided the implementation of resealed crevices with greater spatial resolution. Xcrit and are the distances from the mouth to the location where the potential reaches two different critical values, and G is the crevice gap. Scaling laws were also used along with anodic polarization data in simulated crevice solution to predict crevice corrosion behavior of alloy 22 (UNS N06022). Crevice corrosion of AISI 316 stainless steel in 0.6 mol/L NaCI at 50°C readily initiated close to the crevice mouth (i.e., x~1 0) at modest applied potentials (e.g., Eapp 0 V5~5) and spread both inward and outside the crevice with time. Crevice corrosion initiated farther inside the crevice (i.e., ~ is large) and required higher applied potentials (e.g., E~5~ = 50 mVscs) in the case of alloy 625. The local crevice current density increased dramatically over a short period of time to reach a limiting value in the case of AISI 316; while metastable dissolution behavior over a large area was observed for alloy 625. The ramification of the larger critical depth for Ni-Cr-Mo alloys toward crevice corrosion susceptibility in the case of crevice formers of finite length is discussed. Crevice corrosion shifts to the mouth of the crevice for the less corrosion-resistant materials in crevice solutions saturated in metal salts but remains confined at a distance x.,,, for alloy 625 under the conditions tested. [ABSTRACT FROM AUTHOR]

A quantitative procedure of determination of kinetic and transport parameters for individual alloy constituents during anodic film growth on stainless steels in light reactor water is developed. It is based on in-depth compositional data for oxides obtained from ex Situ analyses using Auger electron spectroscopy and X-ray photoelectron spectroscopy. The growth of the inner compact layer is described as a sequence of interfacial reactions and transport driven by homogeneous diffusion-migration mechanism. Based on the mixed-conduction model for oxide films, a fitting procedure for the calculation of the in-depth distribution of the individual alloy constituents in the inner layer is put forward. The effects of temperature and applied potential on the kinetic and transport parameters in the inner layer are assessed. In addition, the growth of an outer layer consisting of crystallites with pores filled with electrolyte in-between is described formally as a diffusion process and the transport parameters characterizing this process are estimated. The estimates of the kinetic and transport parameters obtained are discussed in relation to the corrosion mechanism of the steel and the incorporation of electrolyte-originating species in the bilayer oxide film. Using the proposed quantitative procedure, the kinetic and transport parameters of long-term (up to 10,000 h) film growth and restructuring on AISI 304 stainless steel in simulated pressurized water ractor (PWR) with or without zinc addition are also estimated on the basis of a quantitative comparison of the model predictions and literature data on the in-depth concentration profiles of the constituent elements. The obtained values are discussed in terms of the effect of Zn on the growth rate of the inner and outer layers of the corrosion film. [ABSTRACT FROM AUTHOR]

Microchannels in stainless steel were fabricated by using solutions of various concentrations of FeCl3, HCl and HNO3 in water as etchants. This study shows that for obtaining smooth uniform channels on stainless steel substrates, an etchant consisting of FeCl3, HCl and HNO3 is necessary. An increase in the concentration of HCl in the etchant increases the etch rate as well as the etch factor but adversely affects the roughness. Addition of HNO3 is necessary to obtain smooth uniform channels. The depth and etch factor are significantly affected by the composition of etchant, operating temperature and initial width of opening. In the range of operating conditions studied, an etchant containing 10 wt% FeCl3, 10 wt% HCl and 5 wt% HNO3 at 40 °C and an initial width of 190 µm gave the best results. With this etchant, the channels were smooth and uniform without any cavities on the edges of the channels. Initial width also plays a vital role in obtaining the final desired depth and etch factor. [ABSTRACT FROM AUTHOR]

Friction stir welding of stainless steel has been modelled using a steady-state, Eulerian formulation that considers coupled viscoplastic flow and heat transfer in three dimensions. The model equations are solved using the finite element method to determine the velocity field and temperature distribution, with a modified Petrov-Galerkin employed to stabilize the temperature distribution. Strain hardening is incorporated using a scalar state variable for the isotropic strength that evolves with deformation as material moves along streamlines of the flow field. The evolution equation for the hardening is integrated along streamlines of the flow field. The influence of pin threads on the friction between the tool and the workpiece was modelled by supplementing the tangential tractions along the pin interface with axial tractions that depend on the pitch of the threads. The formulation is used to conduct a parametric study to determine the influences of various welding parameters on the flow, heating and hardening of the stainless steel. For parameters corresponding to available experimental data, comparisons are drawn between the simulation results and measured values of hardness and temperature. [ABSTRACT FROM AUTHOR]

A new variotherm molding apparatus is presented in this paper for the fabrication of high aspect ratio 316L stainless steel micro-structures using micro powder injection molding (?PIM) technology. The molding apparatus prototype includes an injection mold in which a silicon insert with an array of 24 × 24 (576) microcavities is mounted, a set of rapid tempering systems for the mold and a set of vacuum systems. The key advantage of this molding apparatus lies in the real-time monitoring and rapid adjustment of the mold cavity temperature during injection molding and part ejection, which makes molding and demolding of high aspect ratio green micro-structures possible. For example, incomplete filling occurs while injection molding micro-structures of 60 µm × height 191 µm with an aspect ratio of 3.2 using a conventional mold. In comparison, smaller micro-structures with higher aspect ratio are produced successfully in the case of the new molding apparatus, e.g. micro-structures of 40 µm × height 174 µm with an aspect ratio of 4.35 and 20 µm × height 160 µm with an aspect ratio of 8 were molded successfully. [ABSTRACT FROM AUTHOR]

The electrochemical dissolution of MnS inclusions and pit initiation processes on type 303 stainless steel were investigated by an electrochemical microcell technique. In 1 M Na2SO4, the electrochemical dissolution of MnS inclusions started at 0.1–0.3 V vs Ag/AgCI(3.33 M KCI), which was followed by the initiation of a hemispherical and smooth wall pit at MnS/matrix boundary. It was suggested that the dissolution products of MnS inclusions induced the formation of a salt film, which caused localized electropolishing. In 0.1 M NaCI, the onset potential of electrochemical dissolution of MnS inclusions was 0.3–0.4 V and the stable pit growth occurred at a potential of around 0.5 V. Field-emission scanning electron microscopy observations revealed that many metastable pits with a diameter of approximately 1 μm were formed at MnS/matrix boundary on the specimen, of which the polarization measurement was stopped immediately after stable pit initiation. From a morphological point of view, the metastable pits were found to be very similar to flat-walled etch pits. The dissolution products of MnS inclusions and chloride ions would attack the metal surface newly exposed by dissolution of the inclusions. It is proposed that the chemistry of dissolved species from MnS inclusions have a substantial influence on pit initiation at MnS inclusions. [ABSTRACT FROM AUTHOR]

Oriented Cu2O coatings were grown on polycrystalline stainless steel substrates showing that oriented crystallization can be nucleated by processes other than epitaxy. Cu2O, deposited from alkaline Cu(II) lactate bath at pH 9 switches the growth direction from [100] to [110] on varying the bath composition. On decreasing the temperature from 65 to 55°C the Orientation switches back to [100]. At pH 12 a distinctive [Ill] orientation unaffected by the bath composition was observed. This shows the importance of a solution-based chemical approach to directing oriented crystallization through a kinetic pathway. This alternative approach is based on a complex interplay of a number of factors such as the stability constant of the precursor species, solubility of the product species, and degree of supersaturation of the bath as determined by the pH, temperature, and concentration. The distinct orientations depend on the crystal energetics and can be correlated to the observed morphology, thereby establishing a direct relationship between the textural properties at the nanometer level and the morphology at the micrometer level. The coatings were characterized by powder X-ray diffraction and scanning electron microscopy. [ABSTRACT FROM AUTHOR]

The effect of magnetic fields on localized corrosion was explored for one-dimensional artificial pits that are used to simulate pitting corrosion, and for two-dimensional pits in thin metal films. It was found that the pitting dissolution of ferromagnetic electrodes was significantly affected by the presence of a magnetic field. The presence of magnetic fields can lead to local stirring in the vicinity of artificial pits in ferromagnetic metals (iron, cobalt, or nickel) and pits in FeCo thin films, through the effects of the high field gradient force and the Lorentz force, causing an increase in the diffusion-limited current when the field is applied parallel to the dissolving surface. When the field is applied perpendicular to the dissolving surface, the field gradient force draws paramagnetic corrosion products toward the metal surface, protecting the metal from dissolution. The field gradient is, however, absent for paramagnetic stainless steel artificial pits, and the Lorentz force itself (in a field of 0.35 T) is insufficient to cause stirring within the pit cavities. Fields that are changing show a considerably bigger effect than static fields. [ABSTRACT FROM AUTHOR]

Experimentally it is shown that a movable grounded metallic plate placed inside a multi-dipole magnetic cage can vary the diffused plasma parameters such as density, plasma potential and electron temperature. Plasma is solely produced in the source section of a double plasma device by a dc hot filament discharge and a low-density plasma is produced in the target section by local ionization of neutral gas by the high energetic electrons coming from the source section. A grounded movable stainless steel plate is inserted in the target section of the device. The floating potential of the plate also changes depending on the position of the plate inside the magnetic cage. [ABSTRACT FROM AUTHOR]

Grain boundary networks are engineered by increasing the fraction of boundaries which exhibit improved properties. Favourable boundaries have either low grain boundary misorientation or they are special boundaries, such as coincident site lattice boundaries. Significant improvement in properties such as corrosion resistance, critical current in superconductors and mechanical strength and toughness occur, provided percolating grain or grain boundary structures can be engineered. We develop computational models for grain boundary engineered polycrystals and demonstrate that grain boundary constraints modify the behaviour near the percolation threshold. We postulate that this is due to an enhanced clustering of weak boundaries induced by grain boundary constraints. In random grain structures the fraction of strong grain boundaries may be measured in two ways, either the length fraction, c, or the edge fraction ce. We find that grain boundary constraint shifts the length fraction threshold, c*, of Potts model polycrystals to higher values, while the edge fraction, ce*, remains almost the same in both correlated and uncorrelated grain structures. [ABSTRACT FROM AUTHOR]

The inert properties of gold make it a useful material for implants. Gold was applied as a coating on 316L stainless steel stents to improve the radiopacity and to provide better thrombogenic resistance and a lower degree of restenosis after deployment. Reports of clinical trials using gold-coated stents showed controversial results. A detailed examination of gold-coated stents was designed to understand the influence of surface conditions on the electrochemical properties in vitro. Corrosion resistance of gold-coated stents was investigated by cyclic polarization, and potentiostatic control. Surface morphologies of gold-coated stents in as-received condition, postinflated condition, and after cyclic polarization were characterized by scanning electron spectroscopy (SES). X-ray mapping identified elemental distribution. Results found severe defects in the gold-coating in the as-received condition, cracks and wrinkles on inflated gold-coated stents, and severe corrosion after cyclic polarization. Leaching of metallic ions in Ringer's solution was possible. [ABSTRACT FROM AUTHOR]

The effects of a coating of silica particles on the localized corrosion behavior of AISI 304 stainless steel (304SS) during drying of thin electrolyte layers in controlled relative humidity environments were investigated by measurements of the transients of open-circuit potential (OCP) and galvanic current. The silica coatings were composed of spherical silica particles and were deposited on 304SS by cathodic electrophoretic deposition. It was confirmed that the silica layer worked very well as a host layer to soak up electrolyte solutions and that it remained intact under wet and dry conditions. OCP and galvanic current transients indicated that the silica layer affected propagation more than initiation of pitting corrosion. The propagation of pitting corrosion for silica-coated samples was slower than for uncoated 304SS. [ABSTRACT FROM AUTHOR]

This paper presents electrochemical behavior of AISI 304 stainless steel with a silica layer in a stagnant bulk solution of 0.1 M NaCl. Layers composed of densely packed 350 nm diam silica particles were deposited cathodically on stainless steel at a constant voltage by electrophoretic deposition (EPD). Quite smooth and crack-free silica layers less than about 80 μm in thickness were obtained and the thickness of the layer depended linearly on the deposition time. It is proposed that silica layers deposited by EPD can be used as simulated particulate layers to investigate localized corrosion of corrosion-resistant alloys under atmospheric environments. Electrochemical properties of silica-coated stainless steel samples in 0.1 M NaCl were investigated. The cathodic polarization behavior depended on the thickness of the silica layer; the limiting current density for oxygen reduction reaction decreased with increasing silica layer thickness. The effect of the silica layer on anodic polarization behavior was not remarkable. [ABSTRACT FROM AUTHOR]

Phase transformations of Al2O3 films, deposited by metallorganic chemical vapor deposition from aluminium tri-isopropoxide on AISI 301 stainless steel, were investigated using an original technique of deflection associated with X-ray diffraction and electron microscopy. The samples were first oxidized at 1123 K in air to obtain a 0.9 μm thick Cr2O3 protective oxide film on one side of the samples. Then, 1 μm thick amorphous Al2O3 films were deposited on the opposite side at 823 K and 2 kPa. The deflection of such dissymmetrical samples was recorded during anisothermal treatments, consisting in slow heating to 1173 K in Ar atmosphere. The coefficient of thermal expansion of both the Cr2O3 and the amorphous Al2O3 films was determined to be 7 x 10-6 K-1 and 14.7 × 106 K-1, respectively. Crystallization kinetics of amorphous to mainly γ-Al2O3 become significant at temperatures equal or greater than 983 K. Transformation of metastable Al2O3 to α-Al2O3 is initiated below 1173 K. It is demonstrated that deflection is a powerful tool for investigating the behavior of thin films deposited on a substrate and especially to reveal transformations occurring in these films during heat-treatments. [ABSTRACT FROM AUTHOR]

To improve the corrosion protection performance of CrNx films, the relationship between the pinhole defect density of the films and the surface condition of stainless steel substrates was studied. A commercial, heated type 304 stainless steel (ss) and a high purity heated type 316L ss substrate were used. The surface of substrates was finished with wet SiC paper polishing, diamond paste polishing, or electropolishing. CrNx films 41 nm thick were formed by ion-beam-enhanced deposition. The pinhole defect density was evaluated by the critical passivation current density method. The surface roughness was examined by atomic force microscopy. The pinhole defect density of CrNx films on a commercial 304 ss substrate decreased with decreasing surface roughness of the substrate in cases of diamond paste polishing and wet SiC paper polishing. Pits were caused by electropolishing on the surface of 304 ss substrate owing to the dissolution of manganese oxysulfide inclusions, which resulted in an increase in the pinhole defect density of CrN, film. However, no pits were caused by electropolishing on a high purity 316L ss substrate and an extremely low pinhole defect density of 4.1 × 10-4 area % was obtained for CrNx film on this substrate. [ABSTRACT FROM AUTHOR]