Passive Oxide Film Research Articles

Influence of Mn-Ni alloying elements on surface film and pitting resistance of Cr-Mn austenitic stainless steels

This research focused on surface film and corrosion resistance of three commercial type 200 austenitic stainless steels including L4, L1 and LH with different Mn/Ni mass ratio in Chinese market. X-ray photoelectron spectrum (XPS) results showed that Fe, Cr and Mn oxide layer thickness and passive film thickness were reduced as Mn/Ni mass ratio increased. Mn enrichment was only found in LH passive film. Mn oxide percentage in LH passive film was also the highest. These disadvantages deteriorated pitting resistance of LH, which was proved by anodic polarization result. Mn/Ni mass ratio should not be higher than 1.7 to ensure good corrosion resistance and low raw material cost.

Corrosion Behavior of Fe-Mn-Si-Cr-Ni-Co Shape Memory Stainless Steel in Highly Oxidizing Medium

A study was conducted on the corrosion behavior and characteristics of the passive oxide film of Fe-Mn-Si-Cr-Ni-(Co) shape memory stainless steels (SMSS) in a concentrated nitric acid (HNO3) solution, based on potentiodynamic polarization, scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) analyses. The results indicated that Fe-Mn-Si-Cr-Ni-(Co) SMSSs exhibit a passive behavior similar to that of 304L austenitic stainless steel (304L SS). However, unlike 304L SS, their high silicon (Si) content renders them insensitive to intergranular attack in highly oxidizing environments. The XPS analysis also indicated that Si appears to be the main element responsible for the high protectiveness afforded by the passive film formed on Fe–Mn–Si–Cr–Ni–Co SMSS.

A Comparative Study on the Corrosion Performance of Ni47Ti49Co4 and Ni51Ti49 Shape Memory Alloys in Simulated Saliva Solution for Dental Applications

In this study, the corrosion behavior of Ni47Ti49Co4 shape memory alloy (SMA) was investigated in simulated saliva solution with the binary alloy Ni51Ti49 as a reference. The surface morphology and the chemical composition of the oxide films were characterized by scanning electron microscopy and X-ray photoelectron spectroscopy before and after immersion in the test solutions, respectively. The results showed that the ternary alloy was less affected by the test solution, owning to the formation of passive layer composed mainly of the oxides of titanium and cobalt in several oxidation states. Cyclic voltammetry, electrochemical impedance spectroscopy and potentiodynamic polarization measurements affirmed that the passive oxide film significantly improved the corrosion resistance of Ni47Ti49Co4 SMAs as demonstrated by the smaller corrosion current density, larger resistance and smaller capacitance. Consequently, alloying with cobalt, which has paramount importance in enhancing the passive layer, expands the use of Ni47Ti49Co4 SMAs in dental work as new nitinol alloys with high corrosion resistances.

H2SO4수용액에서의 주조용 알루미늄 합금들의 부식거동

The corrosion behavior of aluminum alloys in the <TEX>$H_2SO_4$</TEX> solution was investigated based on potentiodynamic techniques. Electrochemical properties, such as corrosion potential(<TEX>$E_c$</TEX>), passive potential(<TEX>$E_p$</TEX>), corrosion current density(<TEX>$I_c$</TEX>), corrosion rate(mpy), of Al-Mg-Si, Al-Cu-Si and Al-Si alloys were characterized at room temperature. Passive aluminum oxide film, which including <TEX>$Al_2(SO_4)_3$</TEX> and <TEX>$3Al_2O_34SO_38H_2O$</TEX>, were uniformly formed on the surface via the reaction of Al with <TEX>$SO{_3}^{2-}$</TEX> or <TEX>$SO{_4}^{2-}$</TEX> ions in the <TEX>$H_2SO_4$</TEX> solution and the dependence of the corrosion behavior on the alloying element was discussed. The selective leaching of alloy element increased with increasing Cu content in the aluminum alloys.

Effect of Ta on the electrochemical behavior of new TiMoZrTa alloys in artificial physiological solution simulating in vitro inflammatory conditions

The present study explores the microstructural characteristics and electrochemical responses of different TiMoZrTa alloys designed for biomedical implantation. The alloys corrosion resistance (potentiodynamic polarization and electrochemical impedance spectroscopy) was determined in acidified Ringer's solution at 37 °C. The pH was adjusted to 3.6 in order to reproduce the pathological state. The new materials formed spontaneously a passivation oxide film on their surface, and they remained stable for polarizations up to +1.0 VSCE. No evidence of localized breakdown of the oxide layers was registered even when higher positive polarizations than those encountered in the human body were applied.

Comparison of auxiliary cathode and conventional plasma nitriding of gamma-TiAl alloy

Effect of auxiliary cathode (ACN) and conventional plasma nitriding (CPN) processes on surface modification of gamma-TiAl has been investigated. Both processes were done at temperature of 800 °C under gas ratio of N2/H2 = 1. The process duration was selected to be 3, 6 and 9 h for ACN, while it was 10, 20 and 30 h for CPN. Characterizations of the microstructure, phases, elemental distribution and hardness were performed using FESEM, XRD, GDOES, RBS and microhardness tests. Ti2AlN and TiN phases were detected as the main nitride compounds in both processes. Passive oxide films disrupted diffusion of nitrogen atoms in CPN process; hence a narrow nitrided zone was formed due to this surface oxidation. Higher ion intensity and oxidation protection emphasized the ACN process. The thicker and more uniform compound layers with more surface hardness were achieved using the auxiliary cathode. About 70% of nitriding process time was saved by ACN, in comparison with the CPN process.

Experimental investigation into fabrication of microfeatures on titanium by electrochemical micromachining

Titanium machining is one of the challenging tasks to modern machining processes. Especially fabricating microfeatures on titanium appear as a potential research interest. Electrochemical micromachining (EMM) is an effective process to generate microfeatures by anodic dissolution. Machining of titanium by anodic dissolution is different than other metals because of its tendency to form passive oxide layer. The phenomenon of progression of microfeature by conversion of passive oxide layer into transpassive has been investigated with the help of maskless EMM technique. Suitable range of machining voltage has been established to attain the controlled anodic dissolution of titanium by converting passive oxide film of titanium into transpassive with nonaqueous electrolyte. The experimental outcomes revealed that the micromachining of titanium with controlled anodic dissolution could be possible even at lower machining voltage in the range of 6–8 V. This work successfully explored the possibility of generation of microfeatures on commercially pure titanium by anodic dissolution process in microscopic domain by demonstrating successful fabrication of various microfeatures, such as microholes and microcantilevers.

Surface characterization and cytotoxicity analysis of plasma sprayed coatings on titanium alloys

In the realm of biomaterials, metallic materials are widely used for load bearing joints due to their superior mechanical properties. Despite the necessity for long term metallic implants, there are limitations to their prolonged use. Naturally, oxides of titanium have low solubilities and form passive oxide film spontaneously. However, some inclusion and discontinuity spots in oxide film make implant to adopt the decisive nature. These defects heighten the dissolution of metal ions from the implant surface, which results in diminishing bio-integration of titanium implant. To increase the long-term metallic implant stability, surface modifications of titanium alloys are being carried out.In the present study, biomimetic coatings of plasma sprayed hydroxyapatite and titanium were applied to the surface of commercially pure titanium and Ti6Al4V. Surface morphology and surface chemistry were studied using scanning electron microscopy and X-ray photoelectron spectroscopy, respectively. Cyclic potentiodynamic polarization and electrochemical impedance spectroscopy were carried out in order to study their electrochemical behavior. Moreover, cytotoxicity analysis was conducted for osteoblast cells by performing MTS assay. It is concluded that both hydroxyapatite and titanium coatings enhance corrosion resistance and improve cytocompatibility.

Analysis of the relationship between electrolyte characteristics and electrochemical machinability in PECM on invar (Fe-Ni)fine sheet

Pulsed electrochemical machining (PECM) has been conducted for invar (Fe-Ni) fine sheet consisting of 64 % Fe ions and 36 % Ni ions. Solutions of sodium chloride (NaCl), acetic acid (CH3COOH), sodium nitrate (NaNO3), and sodium nitrite (NaNO2) mixed with sodium tartrate (C4H4Na2O6) were used as an electrolyte. First, the electrical conductivities of all electrolytes have been measured. As the concentration of each electrolyte increased, the electrical conductivities of electrolytes increased except for the acetic acid. The electrochemical machinability has been investigated using four types of electrolytes. The results of PECM show that the electrolyte which has the high electrical conductivity value leads to the low electrochemical machinability. The pulse waves which indicate the electrical characteristics during the PECM has been observed and it is confirmed that the passivating oxide film occur in PECM. To compare the capability of changing in transpassive state, the anode surface has been investigated. This study presents the relationship between electrical conductivity and electrical machinability. Moreover, the capacity of changing in transpassive state has been investigated as compared with four types of electrolytes. This study shows the possibility of applying invar fine sheet in PECM and contributes to determining the electrolyte for the process.

Effect of aqueous‐based cathode slurry pH and immersion time on corrosion of aluminum current collector in lithium‐ion batteries

Corrosion of aluminum can occur during the manufacturing of lithium‐ion batteries when using aqueous‐based cathode slurries. In exposure tests, the alkaline pH value of aqueous‐based cathode slurries and immersing time were revealed as the principle factors that control the corrosion of aluminum during the cathode manufacturing process. The nickel manganese cobalt oxide active material used in the slurry does not have a direct impact on corrosion of the aluminum current collector. The initiation and evolution of localized corrosion on aluminum are closely related to the formation of galvanic cells between aluminum matrix and intermetallic particles. X‐ray photoelectron spectroscopy results confirmed that the pH of cathode slurry was the only factor that alters aluminum surface composition, during which the oxide passive film was gradually degraded into hydroxide. Electrochemical characterizations showed that aluminum electrodes gave remarkably different response to the different pH of test solutions. The time‐pH‐variant electrochemical response was ascribed to the change of passive film and electric double layer properties.

Formation of a Passive Oxide Film on Indium Electrode in Aqueous Solutions

The formation and growth of an oxide film on indium electrode immersed in sodium borate solutions has been followed and discussed using potential measurements under open-circuit conditions. The effect of concentration, pH and temperature of solution are also investigated. It is found that, the rate of oxide film growth follows a direct logarithm law, as evident from the linear relationship between the open-circuit potential and the logarithm of immersion time. The rate of oxide film growth decreases by increasing the pH of solution and by raising the solution temperature. The free activation energy of oxide film growth is determined and found to be 8.88kJ/mole, indicating that the process of oxide film growth is under diffusion control.

Ellipsometric study of passive and anodic oxide films formed on Ti and Nb electrodes

&lt;p class="PaperAbstract"&gt;&lt;span lang="EN-US"&gt;Electrochemical formation of passive films and active/passive transition on Ti and Nb metal surfaces in various concentrations of H&lt;sub&gt;2&lt;/sub&gt;SO&lt;sub&gt;4&lt;/sub&gt; and KOH solutions was investigated using potentiostatic and cyclic voltammetry methods. By simultaneous electrochemical and in-situ ellipsometric measurements the coefficients of film thickness growth of passive films in the potential region from -1.5 V to 4 V were determined. Results indicate the strong influence of the concentration and electrolyte nature to the active/passive transitions and stability of passive films. The influence of cathodic pre-treatment on the passive films dissolution and appearance of the reactivation peaks during the reverse potential cycling were shown. By multiple cycle sequences in which the final anodic potential was gradually enlarged, the barrier properties of passive films on investigated electrodes were confirmed. The electrochemical and ellipsometric data showed that the passive films formed on Nb electrode are more resistant that passive films formed on Ti electrode, especially in higher concentrations of investigated aggressive solutions.&lt;/span&gt;&lt;/p&gt;&lt;br /&gt;

Corrosion studies using potentiodynamic and EIS electrochemical techniques of welded lean duplex stainless steel UNS S82441

The corrosion characterisation of lean duplex stainless steel (1.4662) UNS S82441 welded joints using the potentiodynamic test and electrochemical impedance spectroscopy in 1M NaCl solution are discussed. The influence of autogenous TIG welding parameters (amount of heat input and composition of shielding gases like Ar and Ar–N2 and an Ar–He mixture), as well as A-TIG welding was studied. The influence of welding parameters on phase balance, microstructural changes and the protective properties of passive oxide films formed at the open circuit potential or during the anodic polarisation were studied.From the results of the potentiodynamic test and electrochemical impedance spectroscopy of TIG and A-TiG, welded joints show a lower corrosion resistance compared to non-welded parent metal, but introducing heat input properly during welding and applying shielding gases rich in nitrogen or helium can increase austenitic phase content, which is beneficial for corrosion resistance, and improves surface oxide layer resistance in 1M NaCl solution.

Electrochemical corrosion behavior and elasticity properties of Ti–6Al–xFe alloys for biomedical applications

The present study is to investigate the microstructural characteristics, electrochemical corrosion behavior and elasticity properties of Ti–6Al–xFe alloys with Fe addition for biomedical application, and Ti–6Al–4V alloy with two-phase (α+β) microstructure is also studied as a comparison. Microstructural characterization reveals that the phase and crystal structure are sensitive to the Fe content. Ti–6Al alloy displays feather-like hexagonal α phase, and Ti–6Al–1Fe exhibits coarse lath structure of hexagonal α phase and a small amount of β phase. Ti–6Al–2Fe and Ti–6Al–4Fe alloys are dominated by elongated, equiaxed α phase and retained β phase, but the size of α phase particle in Ti–6Al–4Fe alloy is much smaller than that in Ti–6Al–2Fe alloy. The corrosion resistance of these alloys is determined in SBF solution at 37°C. It is found that the alloys spontaneously form a passive oxide film on their surface after immersion for 500s, and then they are stable for polarizations up to 0VSCE. In comparison with Ti–6Al and Ti–6Al–4V alloys, Ti–6Al–xFe alloys exhibit better corrosion resistance with lower anodic current densities, larger polarization resistances and higher open-circuit potentials. The passive layers show stable characteristics, and the wide frequency ranges displaying capacitive characteristics occur for high iron contents. Elasticity experiments are performed to evaluate the elasticity property at room temperature. Ti–6Al–4Fe alloy has the lowest Young's modulus (112GPa) and exhibits the highest strength/modulus ratios as large as 8.6, which is similar to that of c.p. Ti (8.5). These characteristics of Ti–6Al–xFe alloys form the basis of a great potential to be used as biomedical implantation materials.

Surface chemical state of Ti powders and its alloys: Effect of storage conditions and alloy composition

High affinity of titanium to oxygen in combination with the high surface area of the powder results in tremendous powder reactivity and almost inevitable presence of passivation oxide film on the powder surface. Oxide film is formed during the short exposure of the powder to the environment at even a trace amount of oxygen. Hence, surface state of the powder determines its usefulness for powder metallurgy processing. Present study is focused on the evaluation of the surface oxide state of the Ti, NiTi and Ti6Al4V powders in as-atomized state and after storage under air or Ar for up to eight years.Powder surface oxide state was studied by X-ray photoelectron spectroscopy (XPS) and high resolution scanning electron microscopy (HR SEM). Results indicate that powder in as-atomized state is covered by homogeneous Ti-oxide layer with the thickness of ∼2.9nm for Ti, ∼3.2nm and ∼4.2nm in case of Ti6Al4V and NiTi powders, respectively. Exposure to the air results in oxide growth of about 30% in case of Ti and only about 10% in case of NiTi and Ti6Al4V. After the storage under the dry air for two years oxide growth of only about 3-4% was detected in case of both, Ti and NiTi powders. NiTi powder, stored under the dry air for eight years, indicates oxide thickness of about 5.3nm, which is about 30% thicker in comparison with the as-atomized powder. Oxide thickness increase of only ∼15% during the storage for eight years in comparison with the powder, shortly exposed to the air after manufacturing, was detected.Results indicate a high passivation of the Ti, Ti6Al4V and NiTi powder surface by homogeneous layer of Ti-oxide formed even during short exposure of the powder to the air.

Aging of Passive Oxide on SUS304 Stainless Steel in a Sulfuric Acid Solution

The passive oxide film on SUS 304 stainless steel (SS) was studied in a 0.1 mol dm−3 sulfuric acid solution as a function of passivation time. The passive oxide films were measured by ellipsometry and X-ray photoelectron spectroscopy (XPS). A Mott-Schottky plot of the film capacitance was employed to determine the donor density in the n-type semiconducting oxide film, and current measurements of the Fe3+/Fe2+ redox couple were employed to investigate the electronic transfer process on the passive oxide film. The passive oxide consists of Cr-Fe-Ni oxides in which enrichment of Cr to 57 mol% occurs as the potential increases. During the aging of the passive oxide at 0.6 V vs. Ag/AgCl/saturated KCl (SSC) for 43 ks, the current decreased from 30 μA cm−2 at 10 s to 0.025 μA cm−2 at 43 ks, and the Cr ratio in the oxide increased from 49 to 57 mol% with an increase in the O2– ratio. Notably, the film thickness remained nearly constant at 1.3 nm during the aging process. Enrichment of the Cr content resulted in a decrease in the donor density of the n-type semiconducting passive oxide and the inhibition of electronic charge transfer from/to the Fe3+/Fe2+ redox couple in the electrolyte.

Different mechanisms of bone formation of preosteoblast on metals in vitro

Different mechanisms of bone formation of preosteoblast on metals in vitro

Anodic Film Growth of Titanium Oxide Using the 3-Electrode Electrochemical Technique: Effects of Oxygen Evolution and Morphological Characterizations

In the present study, potentiodynamic polarization scans followed by potentiostat anodizing tests have been employed to generate the anodic oxide films on commercially pure Ti in 1 M sulfuric acid and 1 M phosphoric acid. The highly stable single-barrier anodic films with a growth ratio of ∼1.5 nm V−1 (sulfuric acid) or ∼1.7 nm V−1 (phosphoric acid) were generated at the anodic voltages from 10 V to 60 V. During the potentiostatic anodizing, the anodic film was formed after the growth of the passive oxide film in the potentiodynamic polarization stage. Oxygen evolution proceeded within both the polarization and the anodizing stages, resulting in the suppression of the current efficiency for the growth of anodic films. The oxygen bubbles were induced by the amorphous-to-crystalline transition within the anodic film, leading to the formation of blister textures. Significant rupture of the anodic film was found that started at 20 V of the anodizing processes in the sulfuric acid; conversely, the significant rupture was started at 50 V in the phosphoric acid. The XRD results indicated that the degree of amorphous-to-crystalline transition in the anodic film formed in the phosphoric acid was less than the film formed in the sulfuric acid. The phosphate titanium oxide layers detected by XPS in the phosphoric acid indicated that more degrees of the amorphous-to-crystalline transition might be inhibited compared with the sulfated titanium oxides found in the sulfuric acid.

The role of indium in the activation of aluminum alloy galvanic anodes

Despite six decades use of aluminum as a galvanic (sacrificial) anode, there remains a need for a better understanding of the underlying mechanisms for enhancing its efficient performance in cathodic protection systems. A few mechanisms have been proposed for the role of indium in the activation of Al‐Zn‐In anodes and there appears to be no general agreement on whether this element plays its depassivating role by modifying the bulk microstructure of the anode, chemical composition of its surrounding electrolyte or directly through doping the structure of the passive oxide film. These mechanisms have been critically reviewed to achieve a more comprehensive understanding of the role of indium in such applications. Moreover, the novel solidification processing called controlled diffusion solidification (CDS) has been introduced as an efficient way to surmount the poor castability of the anode alloy without any need for the addition of elements with detrimental effects on the electrochemical properties of the anode.

Dynamic hydrogen generation phenomenon of aluminum fed liquid phase Ga–In alloy inside NaOH electrolyte

Reaction between aluminum and water offers a simple way for hydrogen generation. However, the passive oxide film subsequently formed on Al would become a major obstacle for its continuous reaction. Gallium was proved to be an effective way to remove the passive oxide film through penetrating into Al granules, which fosters the reaction between Al and water. However, fabrications of Al–Ga alloy so far are generally highly time and energy consuming. Here, unlike the existing strategies of using solid state Al-rich alloys for the reaction system, the liquid phase alloy was introduced and prepared to develop an extremely simple source for hydrogen generation where the mass percentage of Al can be less than 1%. Such conceptual innovation would help maintain the alloy in liquid state which thus allows for rather convenient operation. To probe into the methodology, the dynamic hydrogen generation phenomenon of such Al-fed liquid phase GaIn alloy inside NaOH electrolyte was disclosed. According to the experimental observations, the hydrogen was generated mainly at the interface between the liquid metal and the Petri dish rather than the liquid metal-electrolyte interface. Homogenous hydrogen generation only takes place at the liquid–solid interface while heterogeneous hydrogen generation from the moving accumulated Al granules happens on all surfaces. The present finding is expected to open a new way towards low cost and straightforward hydrogen generation. It would also help better understand the mechanisms lying behind as well as the dynamic traveling behaviors of the aluminum powered gallium alloy machine.