Corrosion Resistance Of Films Research Articles

Influence of Dy in solid solution on the degradation behavior of binary Mg-Dy alloys in cell culture medium

Rare earth element Dy is one of the promising alloying elements for magnesium alloy as biodegradable implants. To understand the effect of Dy in solid solution on the degradation of Mg-Dy alloys in simulated physiological conditions, the present work studied the microstructure and degradation behavior of Mg-Dy alloys in cell culture medium. It is found the corrosion resistance enhances with the increase of Dy content in solid solution in Mg. This can be attributed to the formation of a relatively more corrosion resistant Dy-enriched film which decreases the anodic dissolution of Mg.

蒸気コーティング法によるMg–6Al–1Zn–2Ca合金への耐食性皮膜の作製

Corrosion resistant films were prepared on flame-resistant Mg–6Al–1Zn–2Ca (in mass%) alloy by steam coating using ultra pure water as steam source. The prepared films were characterized using SEM, XRD, and FT-IR. Corrosion resistance of the film was estimated by polarization curve measurement in 5 mass% NaCl aqueous solution. All XRD patterns of the films coated Mg–6Al–1Zn–2Ca alloy revealed that all films were composed of crystalline Mg(OH)2 and Mg–Al layered double hydroxide (LDH). FT-IR spectra showed that the Mg–Al LDH had carbonate- and nitrate-ions in the interlayer. Potentiodynamic polarization curves of the film prepared at 433 K for 6 h indicated that the corrosion current density decreased by more than four orders of magnitude as compared to that of the uncoated Mg–6Al–1Zn–2Ca alloy.

PREPARATION OF GRAYISH BLACK FILM ON AM50 MAGNESIUM ALLOY BY CHEMICAL CONVERSION–MICRO-ARC OXIDATION

The grayish black film was prepared on AM50 magnesium alloy with a new method which combined chemical conversion with micro-arc oxidation (MAO). The optimum formula of chemical conversion was obtained by L9(34) orthogonal test. Meanwhile, the morphology, structure, composition and corrosion resistance of films were analyzed by scanning electron microscopy (SEM), energy spectrum analysis (energy dispersive X-ray spectroscopy (EDS)), X-ray diffraction (XRD), electrochemical tests and CuSO4 drip experiment. The results indicated that Mo element was introduced into the MAO film by chemical conversion pretreatment. The surface of composite film was smooth and compact. The main phase composition of the composite film were SiO2, Mo9O[Formula: see text], MgSiO[Formula: see text] Mg2SiO4 and Mo9O[Formula: see text] was identified to be responsible for giving color to the film. The corrosion resistance of the grayish black film was improved obviously.

Synergy between molybdenum and nitrogen on the pitting corrosion and passive film resistance of austenitic stainless steels as a pH-dependent effect

This paper brings up some insights upon the pH dependence of the synergistic effect of Mo and N on the localized corrosion resistance of austenitic stainless steels. The objective of this work is to study the synergetic effect of Mo and N additions on corrosion and passive film properties of austenitic grades. A comparison between Mo containing (3 wt% Mo); Mo and N containing (3 wt% Mo and 0.1% N) and free Mo or free Mo and N grades of highly controlled laboratory heats was done considering their localized corrosion resistance and oxide film formation in different aggressive conditions, from neutral to alkaline pH. The passive layer was characterized by EIS and XPS analyses. The combined effect of Mo and N on the pitting potential was confirmed to be synergistic, and not just the addition of their individual effects. Moreover, this effect was found to be pH-dependent, being very positive in acid to neutral conditions whereas it was almost inexistent in high pH.

Corrosion resistance and characterization studies of calcium series chemical conversion film via green pretreatment on magnesium alloy

Purpose Magnesium alloys, although valuable, are reactive and require protection before its application in many fields. The purpose of this study was to evaluate a novel anticorrosive chemical conversion film on AZ80 magnesium alloy by environmental-friendly calcium series surface pretreatment. Design/methodology/approach The corrosion resistance of the film was evaluated by potentiodynamic polarization and electrochemical impedance spectroscopy in 3.5 Wt.% NaCl solution. The surface morphologies, microstructure and composition of the film were investigated by scanning electron microscopy and energy-dispersive spectroscopy. Findings The corrosion current density of the calcium series film decreased by more than one order of magnitude as compared to that of the AZ80 magnesium alloy. The conversion film presented dry-mud morphology, and its thickness was estimated to be approximately 4 μm. The conversion film was highly hydrophilic, and the organic coating adhesion on treated AZ80 surface was approximately 13.5 MPa. Originality/value Excellent performance of the calcium-based chemical conversion film on Mg alloy was obtained, which does not contain heavy metals or fluorides and completely conforms to European RoHS (Restriction of Hazardous Substances) standard.

Design of a Multitask Reactive Distillation with Intermediate Heat Exchangers for the Production of Silane and Chlorosilane Derivates

Silane and chlorosilanes are essential materials for manufacturing silicon solar cells, glass microscope slides, oxidation masks, and corrosion-resistant films among other products. Monochlorosilane (SiH3Cl) and dichlorosilane (SiH2Cl2) are produced on a large scale as intermediates in the synthesis of silane (SiH4) by disproportionation of trichlorosilane (SiHCl3). However, seldom are they isolated due to the highly integrated nature of silane production, and the high commercial demand for silane relative to monochlorosilane and dichlorosilane. This study proposes a multitask reactive distillation (MTRD) column with intermediate heat exchangers that has the flexibility to switch between the production of SiH4, SiH3Cl, and SiH2Cl2 from the SiHCl3 disproportionation. Because the reactive distillation that separates SiH4 uses an expensive refrigerant, intermediate heat exchangers are installed to reduce the cost and energy consumption of expensive refrigerants in the optimized MTRD. Process simulation and m...

Oxide Scale Analysis of the Carbon Steel Exposed to Bentonite after Electrochemical Test

Introduction Geological disposal is the most realistic method in high-level radioactive waste (Hereafter HLW) in Japan. To consider long-term stability for geological disposal, several types of material Engineer barrier with host rock is studied. In such studies, the combination of carbon steel and bentonite is proposed one of idea for use. Carbon steels show uniform corrosion in many cases1. Magnetite scale is formed on carbon steel when it is exposed to low-oxygen partial pressure. And the Magnetite scale may serve as corrosion resistant film. Corrosion under film, however, is known even if the film is a paint film2. Therefore we have to investigate the long-term corrosion tendency of carbon steel. For this purpose, the electrochemical test for accelerated corrosion. Experimental A sample composed of SS400 class carbon steel (ISO 630 equivalent) and bentonites (Kinigel V1: 21% pts. Mass% water and 1.6g/cm3 dry density) is prepared. Two carbon steel plates having t=2mm thickness and 60mm diameter are emplacement between both ends of bentonite column. One is used for a working electrode and the other is used for a counter. The sample is surrounded by an acrylic container to limit the oxygen diffusion. This is a model of HLW disposal container into the underground. Regarding oxide scale of the surface carbon steel, it is remained considering to in its natural state for Overpack made of carbon steel before the disposal. For measuring the potential of sample, we used the silver-silver chloride electrode. At first, a polarization test is carried out. Scanned overvoltage is -250mV to 250mV. The scan rate was 1mV/s3. After that, we carried out +100mV electrolysis of the same sample for 13 days. After electrolysis3, we analyzed the steel/ bentonite interface with SEM, EDX and Raman Spectroscopy. Results and Discussion The corrosion potential measured by polarization test was -0.6VvsSSE3. This is the mixed potential of steel and scale. Hara and co-researchers report that the corrosion potential of iron in supernatant of bentonite water solution is -0.4VvsSSE and that of magnetite, main composition of the oxide scale, is -0.8VvsSSE4. Therefore the potential we obtained is the mixed potential of iron and magnetite. After electrolysis test, we obtained that the steel corroded under the oxide scale confirmed3. The interface of dummy canister shows same as the electrolysis test This corrosion phenomenon was also found at Engineer barrier experiment test in Switzerland for study HLW disposal5. Those results indicate that at least a part of the inner steel metal is connected to outside bentonite and corroded at mixed potential of magnetite and steel. This means that the steel metal may be a sacrifice anode. The scale is confirmed to be FeOOH by micro Raman spectroscopy. The scale is trivalent iron. In the other case of a lab experiment, Hara et al. 4, carbon steel (SM400B) with Fe3O4 film into bentonite (Kunigel V1) showed that the corrosion product was a mixture of FeCO3 and Fe2(OH)2CO3. At first stage, Fe3O4 film-coated carbon steel in compressed bentonite is reacting as the self-reduction reaction. Next step, this reaction is a trigger to destroy Fe3O4. As a result, the internal iron is corroded and bivalent iron is created. The difference of corrosion product, trivalent or bivalent iron, is determined by the presence of the internal state oxygen during the test. As the next step, the authors are planning to make a lab test under the conditions of oxygen and total current density controlled. Reference E. McCafferty, Introduction to Corrosion Science, Chapter1,Springer (2010)Y. Akage, H.Saito, ECS transactions, 50(50),pp.7-11(2013)H.Saito, M. Uyama,et.al., 67th ISE Proseeding (now printing)T.Tsushima, N.Hara, K.Sugimoto,Zairyo-to-Kankyo,52,pp545-553(2003) in JapaneseNagra Grimsel Test Site HP (FEBEX-DP), http://www.grimsel.com/gts-phase-vi/febex-dp/febex-dp-introduction

A study on corrosion resistant graphene films on low alloy steel

Graphene nanosheets were produced after synthesizing graphene oxide via Hummer’s method and a modified Hummer’s method. The obtained graphene after reduction was dispersed in 1-propanol to get a coating solution. Mild steel coupons were coated with the graphene solution via dip coating method. Corrosion studies were carried out at different environments like water (pH 6.0), HCl (0.1 N), NaCl (3.5 wt%) and NaOH (1 M). Tafel analysis showed a reduction in the corrosion rate up to 99 % after three layer deposition with the graphene developed using the modified Hummer’s method. X-ray diffraction and Raman Spectroscopy confirmed the presence of graphene.

Inhibition of the Corrosion of Aluminum Alloy by a Composition of Ion-Exchange Pigments

It is shown that natural zeolites of the clinoptilolite-type modified with zinc cations serve as efficient corrosion inhibitor for aluminum alloys in the media of weakly acid atmospheric precipitations. The combination of Zn-zeolite with polystyrene-divinylbenzene resin modified with phosphate anions improves its protective properties due to the formation of corrosion-resistant films on the surfaces of alloys. Zinc-modified zeolite and its composition with phosphate-containing anion-exchange resins represent promising inhibiting pigments for paint-and-lacquer coatings on aluminum alloys.

Effect of SiO2 Sol Sealing on Corrosion Resistance of Anodic Films of AZ31 Mg Alloy

Silica sol was used to seal the pores of anodic oxide film of AZ31 magnesium alloy. The effect of the immersion time, the calcinating temperature and the immersion times on morphology and corrosion resistance of the film was discussed. Scanning electron microscope (SEM) was employed to characterize the surface morphology of the composite film, and potentiodynamic polarization curves were used to analyze the corrosion behaviors. The surface composition of the sealed anodic films was studied by energy dispersion spectroscopy (EDS) and X-ray photoelectron spectroscopy (XPS). It has been found that the corrosion resistance of anodic film is improved by sealing by silica sol. When the dipping time is 1.5 min and the calcination temperature is 350 °C, the corrosion resistance of the film is the best. Times of dipping and calcination have a greater influence on the performance of the film. When the dipping-calcination is 7 times, the film has a good corrosion resistance. After sealing, silica sol is adsorbed on inner pores and outside pores of the anodic oxidation film.

Effects of Solute Zn on Corrosion Film of Mg–Sn–Zn Alloy Formed in NaCl Solution

The effects of solute Zn on the corrosion resistance and surface film of Mg–5Sn single-phase alloy were investigated. The corrosion resistance of alloy decreased with increasing Zn content. The surface film formed on the Mg–Sn–Zn ternary alloy in NaCl solution had three layers and mainly contained Mg(OH)2 and MgO. The pore defect density of film outer layer increased with the addition of Zn, which could enable more chloride ions to penetrate into the surface layer and form a film. MgCl2(H2O)6, which can readily dissolve in aqueous solutions and accelerate film dissolution, was present in the middle and inner layers. The film/substrate interface and inner film layers of the Mg–Sn–Zn were both enriched with elements Sn and Zn owing to the selective corrosion of active Mg atoms. The enriched Zn could be responsible for the decreased protectiveness of film and for the decreased corrosion resistance of alloy.

An Ultrathin Corrosion-Resistant Film on a Steel Surface Formed by Dipping in a Tungstate Solution

An Ultrathin Corrosion-Resistant Film on a Steel Surface Formed by Dipping in a Tungstate Solution

Influence of Dispersoids on Corrosion Behavior of Oxide Dispersion-Strengthened 18Cr Steels made by High-Energy Milling

Corrosion behavior of 18Cr ferritic steel with and without yttria produced by high-energy milling followed by hot extrusion was studied in 3.5% NaCl solution using electrochemical and immersion techniques. The cyclic polarization study showed that pitting corrosion is predominant in all the materials. The pitting rate is higher in yttria dispersed steels and also increases with milling time. Impedance analysis revealed the formation of better corrosion resistance film on the surface of the steel without yttria. Potentiodynamic polarization studies indicated that the corrosion rate decreased up to 48 h of exposure time and increased beyond 48 h. The increase in corrosion rate beyond 48 h is due to the porous passive film. The corrosion behavior of all the materials in immersion studies followed the same trend as observed in electrochemical studies. Even though the corrosion rate of yttria dispersed 18Cr ferritic steel is less than that of the base material, the difference is marginal. The presence of dispersoids appears to promote nucleation of pits when compared to the steel without the dispersoids.

Effect of treatment time in the Mg(OH)2/Mg–Al LDH composite film formed on Mg alloy AZ31 by steam coating on the corrosion resistance

Abstract The corrosion resistant films were fabricated on Mg alloy AZ31 substrates by steam coating method using Al(NO 3 ) 3 ·9H 2 O aqueous solution as a steam source. The treatment temperature was maintained at 433 K, while the treatment time was varied at 3, 5, 7 and 9 h. X-ray diffraction (XRD) analysis demonstrated that the coated films were composed of a mixed structure of Mg(OH) 2 and Mg–Al layered double hydroxide (Mg–Al LDH) phases. As revealed by the scanning electron microscopy (SEM) observation, the surface of coated films had a good uniformity of changing treatment times. The deposition rate increased exponentially with increasing treatment time. Fourier transform infrared (FT-IR) spectra showed that carbonate and nitrate ions were co-existed in the interlayer of Mg–Al LDH. The potentiodynamic polarization curves of the film coated for 7 h exhibited the lowest corrosion current density, which was almost four orders of magnitude lower than that of bare AZ31. The enhanced corrosion resistance was well consistent with the increase of Mg–Al LDH content in the films.

Influence of Ag content on the antibacterial properties of SiC doped hydroxyapatite coatings

The main goal of the paper is to enhance the resistance to the bacteria of the hydroxyapatite deposited on Ti6Al4V alloy substrate. Hydroxyapatite coatings, enriched with SiC and Ag, were prepared and investigated for this paper. SiC was added to enhance film corrosion resistance, while by Ag addition the improvement of the antibacterial properties was foreseen. The coatings, with different Ag contents, were deposited on Ti6Al4V alloy substrates by co-sputtering of hydroxyapatite, SiC and Ag targets, using a magnetron sputtering system. The films were characterized in terms of elemental and phase composition, texture, morphology, corrosion resistance and antibacterial activity (Staphylococcus aureus MRSA, Staphylococcus aureus ATCC 29213, Streptococcus pyogenes ATCC 19615, Salmonella Typhimurium ATCC 14028), by EDS, XRD, FTIR, SEM and AFM techniques, electrochemical tests and antimicrobial tests. The influence of the Ag content on the film properties was also analysed. The antibacterial efficacies of hydroxyapatite versus Gram-positive bacteria are demonstrated if a small amount of Ag was added in their structure. The hydroxyapatite with Ag content less than 1at% proves to have a good resistance to the bacteria attack, even if the content is reduced.

Vertical Graphene Growth from Amorphous Carbon Films Using Oxidizing Gases

Amorphous carbon thin films are technologically important materials that range in use from the semiconductor industry to corrosion-resistant films. Their conversion to crystalline graphene layers has long been pursued; however, typically this requires excessively high temperatures. Thus, crystallization routes which require reduced temperatures are important. Moreover, the ability to crystallize amorphous carbon at reduced temperatures without a catalyst could pave the way for practical graphene synthesis for device fabrication without the need for transfer or post-transfer gate deposition. To this end we demonstrate a practical and facile method to crystallize deposited amorphous carbon films to high quality graphene layers at reduced annealing temperatures by introducing oxidizing gases during the process. The reactive gases react with regions of higher strain (energy) in the system and accelerate the graphitization process by minimizing criss-cross-linkages and accelerating C–C bond rearrangement at de...

Aluminum titanium oxide alloys: Deposition of amorphous, transparent, corrosion-resistant films by pulsed DC reactive magnetron sputtering with RF substrate bias

Optically transparent and mechanically flexible encapsulation films are desirable for advanced optoelectronic devices. Among many variations of encapsulation, ternary metal oxide films present good optical and mechanical properties. In this study, aluminum titanium oxide (Al1−xTixOy) films were deposited with a range of Ti/(Ti+Al) molar fractions (x) using pulsed DC magnetron sputtering with RF substrate bias. Subsequently, the films were subjected to an Accelerated Weathering Environment (AWE) test at 220°C, 1.6atm and ~100% RH for 3h. Optical, chemical, and morphological analyses revealed that there exists a range of Ti/(Ti+Al) molar fraction (x=0.4–0.7) where films withstood the test, maintaining their optical, chemical, and morphological integrities. The study suggests that encapsulation films with continuously and spatially varying refractive index can be available by varying x within this range, forming encapsulation with broadband, wide angle antireflective coatings.

Composite film of magnesium alloy chemical conversion microarc oxidation

The dark composite ceramic film was prepared on AZ91D magnesium alloy with a new method which combined chemical conversion with microarc oxidation. Using L16 (45) orthogonal test to optimise the optimum technological conditions of the chemical conversion treatment fluid. The surface morphologies, chemical composition and structure of the film were examined by SEM and XRD. The corrosion resistance performances of the films were investigated by electrochemical measurements (in 3·5 wt-%NaCl aqueous solution). The results showed Zn element was introduced into the microarc oxide ceramic films by chemical conversion pretreatment. The main composition of composite ceramic film was ZnO, ZnO2 and Mg3 (PO4)2 and the surface of the composite ceramic film was smooth, compact and even dark. The saline soaks experiment (72 h) and electrochemical analysis showed corrosion resistance of ceramic film was improved obviously. Adding glycerin can make microarc oxidation reaction more stable and ceramic film of the discharge apertures was smaller. This further increased the density of the film layer and improved the corrosion resistance of the film.

On the Characteristics and Corrosion Resistance of Anodic Alumina Films Prepared in Sulfuric Electrolyte with Different Additives

The characteristics including surface morphology, phase constitution, thickness and the corrosion resistance of the porously anodic films prepared in the sulfuric electrolyte with different additives at 35°C were investigated by SEM, EDS, XRD and electrochemical polarization method in this paper. The additives are organic acids, polyhydric alcohols and rare earth (REE) salts. A porous anodic film with about 20 nm holes in diameter can be obtained by additives into the sulfuric electrolyte. The main chemical compositions of the anodic films are Al, O elements, and a small amount of S. The film after boiling water sealing is composed of boehmite (Al2O3·H2O) and alumina (Al2O3) phases. The compactness and the thickness of the anodic films can be improved by the coupling effect of the additives, which increases the corrosion resistance of the film. The effect of additives on morphologies and corrosion resistance is discussed.

Corrosion Resistance of Aluminum Films Electroplated on Steel from Chloroaluminate Ionic Liquids Containing Toluene as a Co-Solvent

Aluminum is a widely used material for corrosion resistant coatings. From a thermodynamic perspective, it is a very active metal. However, its excellent corrosion resistance stems from the formation of a robust, self-healing ~50 nm thick barrier film of Al2O3, which is formed spontaneously upon exposure to air at ambient temperature. Unfortunately, it is established that aluminum cannot be plated from aqueous solutions under normal conditions because hydrogen is evolved before most Al(III) species are reduced to Al. A number of commercial Al plating processes have been developed. Typically, these processes are based on pyrophoric mixtures of AlCl3 or AlBr3 with LiAlH4 dissolved in suitable organic solvents, such as ethers or mixtures of substituted benzenes.The first report in which a room-temperature haloaluminate ionic liquid was used to plate Al appeared in 1948.1 Although moisture-sensitive themselves, such ionic liquids, particularly those based on mixtures of AlCl3 and quaternary ammonium chloride salts, have many safety and convenience advantages over the currently used commercial Al plating baths. In this work, we report the pulsed-current plating of Al on steel substrates from the Lewis acidic AlCl3-1-ethyl-3-methylimidazolium chloride (EtMeImCl) ionic liquid with and without organic co-solvents. Compared to DC methods, pulsed-current techniques can produce electrodeposited metals with smaller grain size and greater brightness, as well as less internal stress and correspondingly greater corrosion resistance.Some preliminary results for Al films electrodeposited on steel from this ionic liquid are shown in Figs. 1 and 2. The surface morphology and corrosion resistance of these films were interrogated with optical microscopy and electrochemical impedance spectroscopy (EIS) in aqueous NaCl, respectively. Micrographs of typical Al electrodeposits (Fig. 1) indicate that their surface morphologies changed significantly with changes in t on and t off. For example, the grain size of the Al film prepared with t on = 0.25 s is much smaller than that for deposits prepared with t on =1 s. Figure 2 shows complex plane impedance plots resulting from EIS experiments. These plots show at least one time constant. A circuit model for an electrode coated with an inert porous layer2 was fitted to the data in Fig. 2 to extract information about the pore resistance (R p) of the coating. The pore resistance reflects the corrosion resistance of the electrodeposited films. Figure 2 shows that the best results were obtained for t on = 0.25 s and t off = 0.50 s in agreement with the results obtained by microscopy. It was generally found that films with the best corrosion resistance were obtained with smaller values of t on. Optimization of the parameters for the pulse plating of Al will be discussed with respect to the surface structure, grain size, corrosion resistance, and brightness of the deposits. References 1F. H. Hurley, U.S. Pat. 2,446,331 (1948). 2M. E. Orazem and B. Tribollet, Electrochemical Impedance Spectroscopy, (New Jersey: John Wiley and Sons, 2008). Acknowledgement This work was funded by the Strategic Environmental research and Development Program (SERDP) through contract DE-AC05-00OR22725 to Oak Ridge National Laboratory.