Calculation of Oxygen Diffusion Coefficients in Oxide Films Formed on Low-Temperature Annealed Zr Alloys and Their Related Corrosion Behavior

The growth of oxide film, which results from the inward oxygen diffusion from a corrosive environment, is a critical consideration for the corrosion resistance of zirconium alloys. This work calculates the oxygen diffusion coefficients in the oxide films formed on zirconium alloys annealed at 400~500 °C and investigates the related corrosion behavior. The annealed samples have a close size for the second-phase particles but a distinctive hardness, indicating the difference in substrate conditions. The weight gain of all samples highly follows parabolic laws. The weight gain of the sample annealed at 400 °C has the fastest increase rate at the very beginning of the corrosion test, but its oxide film has the slowest growth rate as the corrosion proceeds. By contrast, the sample annealed at 500 °C shows the lowest weight gain but the highest corrosion rate constant. Such a corrosion behavior is attributed to the amount of defects existing in the oxide film formed on the annealed samples; fewer defects would provide a lower fraction of short-circuit diffusion in total diffusion, resulting in a lower diffusion coefficient of oxygen in the oxide film, thereby producing better corrosion resistance. This is consistent with the calculated diffusion coefficients of oxygen in the oxide films: 3.252 × 10−11 cm2/s, 3.464 × 10−11 cm2/s and 3.740 × 10−11 cm2/s for the samples annealed at 400 °C, 450 °C, and 500 °C, respectively.

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Effect of Bi Addition on the Corrosion Behavior of Zirconium Alloys

Volume 1: Plant Operations, Maintenance, Engineering, Modifications, Life Cycle and Balance of Plant; Nuclear Fuel and Materials; Radiation Protection and Nuclear Technology Applications ◽

10.1115/icone21-15460 ◽

2013 ◽

Cited By ~ 1

Author(s):

M. Y. Yao ◽

B. X. Zhou ◽

Q. Li ◽

W. P. Zhang ◽

L. Zhu ◽

...

Keyword(s):

Solid Solution ◽

Corrosion Resistance ◽

Corrosion Behavior ◽

Mass Fraction ◽

Zirconium Alloys ◽

Deionized Water ◽

Second Phase ◽

Micro Structure ◽

Second Phase Particles ◽

Structure Observation

In order to investigate systematically the effect of Bi addition on the corrosion resistance of zirconium alloys, different zirconium-based alloys, including Zr-4 (Zr-1.5Sn-0.2Fe-0.1Cr), S5 (Zr-0.8Sn-0.35Nb-0.4Fe-0.1Cr), T5 (Zr-0.7Sn-1.0Nb-0.3Fe-0.1Cr) and Zr-1Nb, were adopted to prepare the zirconium alloys containing Bi of 0∼0.5% in mass fraction. These alloys were denoted as Zr-4+xBi, S5+xBi, T5+xBi and Zr-1Nb+xBi, respectively. The corrosion behavior of these specimens was investigated by autoclave testing in lithiated water with 0.01 M LiOH or deionized water at 360°C/18.6 MPa and in superheated steam at 400 °C/10.3 MPa. The micro structure of the alloys was examined by TEM and the second phase particles (SPPs) were analyzed by EDS. Micro structure observation shows that the addition of Bi promotes the precipitation of Sn as second phase particles (SPPs) because Sn is in solid solution in α-Zr matrix in Zr-4, S5 and T5 alloys. The concentration of Bi dissolved in α-Zr matrix increase with the increase of Nb in the alloys, and the excess Bi precipitates as Bi-containing SPPs. The corrosion results show that the effect of Bi addition on the corrosion behavior of different zirconium-based alloys is very complicated, depending on their compositions and corrosion conditions. In the case of higher Bi concentration in α-Zr, the zirconium alloys exhibit better corrosion resistance. However, in the case of precipitation of Bi-containing SPPs, the corrosion resistance gets worse. This indicates that the solid solution of Bi in α-Zr matrix can improve the corrosion resistance, while the precipitation of the Bi-containing SPPs is harmful to the corrosion resistance.

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Homogenization and Growth Behavior of Second-Phase Particles in a Deformed Zr–Sn–Nb–Fe–Cu–Si–O Alloy

Metals ◽

10.3390/met8100759 ◽

2018 ◽

Vol 8 (10) ◽

pp. 759 ◽

Cited By ~ 6

Author(s):

Liang-Yu Chen ◽

Peng Sang ◽

Lina Zhang ◽

Dongpo Song ◽

Yan-Qiu Chu ◽

...

Keyword(s):

Ostwald Ripening ◽

Short Circuit ◽

Zirconium Alloys ◽

Lattice Diffusion ◽

Growth Behavior ◽

Homogeneous Distribution ◽

Second Phase ◽

Deformation Degree ◽

Linear Distribution ◽

Second Phase Particles

Homogeneous distribution of fine second-phase particles (SPPs) fabricated by cycles of deformation and annealing in zirconium alloys is a critical consideration for the corrosion resistance of fuel claddings. Different deformation degrees of zirconium alloys would result in distinctive microstructures, leading to a distinct growth of SPPs during subsequent annealing. Unfortunately, the homogenization and growth behavior of SPPs in deformed zirconium alloys have not been well studied. In this work, a β-quenched Zr–Sn–Nb–Fe–Cu–Si–O alloy was rolled and annealed at 580 °C or 680 °C. The morphologies, distributions, and sizes of SPPs resulting from the different processing procedures were investigated. A linear distribution of SPPs is found in the β-quenched sample. Afterward, SPPs grow and are randomly distributed during heat treatment as the deformation degree or annealing time (or temperature) increases. The homogenization and growth of SPPs are attributed to the Ostwald ripening mechanism that is governed by lattice diffusion and short-circuit diffusion. The sample with a higher deformation degree is speculated to have a larger number of defects that provide more shortcuts for the mass transfer of SPPs, thereby facilitating a homogeneous distribution of fine SPPs during annealing.

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Study on Corrosion Behavior of Ultrafine-Grained Ti-6Al-7Nb Fabricated by Equal Channel Angular Pressing

Metals ◽

10.3390/met10070950 ◽

2020 ◽

Vol 10 (7) ◽

pp. 950 ◽

Cited By ~ 1

Author(s):

Zequn Yu ◽

Yuecheng Dong ◽

Xin Li ◽

Jingzhe Niu ◽

Igor Alexandrov ◽

...

Keyword(s):

Corrosion Resistance ◽

Oxide Film ◽

Equal Channel Angular Pressing ◽

Corrosion Behavior ◽

Photoelectron Spectroscopy ◽

Electrochemical Impedance ◽

Electrochemical Measurement ◽

Coarse Grained ◽

Angular Pressing ◽

Ultrafine Grained

The aim of this study was to investigate the corrosion resistance of ultrafine-grained (UFG) Ti-6Al-7Nb fabricated by equal channel angular pressing (ECAP) and coarse-grained (CG) Ti- 6Al- 7Nb. The microstructure of each specimen was investigated by the electron backscattered diffraction (EBSD) method. The corrosion behavior of each specimen was determined by electrochemical measurement in Ringer’s solution. The surface corroded morphologies and oxide film formed on Ti-6Al-7Nb alloy after electrochemical measurement were investigated by scanning electron microscope (SEM) and X-ray photoelectron spectroscopy (XPS). EBSD investigation shows that the grain size of UFG Ti-6Al-7Nb decreased to ~0.4 µm, accompanied by low angle grain boundaries (LAGBs) accounting for 39%. Potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) results indicated that UFG Ti-6Al-7Nb alloy possessed a better corrosion resistance. The surface corroded morphologies revealed many small and shallow corrosion pits, which can be attributed to the good compactness of the oxide film and a rapid self- repairing ability of the UFG Ti-6Al-7Nb alloy.

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Effect of ECAP Pass on Corrosion Behavior of High-Al Content Magnesium Alloys

Materials Science Forum ◽

10.4028/www.scientific.net/msf.747-748.270 ◽

2013 ◽

Vol 747-748 ◽

pp. 270-275

Author(s):

Qiang Fan ◽

Wei Liang ◽

Li Ping Bian ◽

Man Qing Cheng

Keyword(s):

Corrosion Resistance ◽

Corrosion Behavior ◽

Performance Test ◽

Corrosion Current ◽

Second Phase ◽

Al Content ◽

Microstructure Observation ◽

Angular Pressing ◽

The Matrix ◽

High Al Content

In view of low strength and poor corrosion resistance of Mg alloys, a Mg-12Al-0.7Si alloy was designed, fabricated and subjected to equal channel angular pressing (ECAP) in order to refine the microstructure. Microstructure observation and electrochemical performance test were conducted to investigate the influence of the microstructural variation subjected to multi-pass ECAP processing on the corrosion behavior of the alloy. The results showed that both α-Mg matrix and β-Mg17Al12of the alloy were significantly refined after processing for different passes (2,4,6,8) through route BC, and the 4-pass ECAPed alloy in 3.5% NaCl solution presents the lowest weight loss, lower corrosion current and higher corrosion potential in the polarization curves. The reason for high corrosion resistance of 4-pass ECAPed alloy and the effects of grain size of the matrix and the particle size, distribution of second phase and dynamic precipitates on corrosion behavior of the alloy were discussed.

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Corrosion Behavior of High-Strength Low-Alloy Steel in High-Temperature Water with Zinc and Aluminum Simultaneous Injection

CORROSION ◽

10.5006/3545 ◽

2020 ◽

Vol 76 (10) ◽

pp. 918-929

Author(s):

Shenghan Zhang ◽

Chenhao Sun ◽

Yu Tan

Keyword(s):

Oxide Film ◽

Corrosion Behavior ◽

Electrochemical Impedance ◽

Oxide Films ◽

High Strength ◽

Corrosion Current ◽

Pressurized Water ◽

Simultaneous Injection ◽

Primary Water ◽

Photocurrent Measurement

Oxide films were formed on A508-3 steel in simulated pressurized water reactor (PWR) primary water at the temperature of 561 ± 1 K for 168 h with zinc and/or aluminum injection. Corrosion behaviors of oxide films were analyzed by electrochemical polarization, electrochemical impedance spectroscopy, Mott-Schottky plots, photocurrent measurement, scanning electronic microscopy, and x-ray diffraction. The results showed that zinc and aluminum simultaneous injection technology decreased the corrosion current density, increased the impedance value, made the oxide film more compact, and affected the semiconductor properties of the oxide film. The increase in zinc concentration improved the corrosion resistance to some extent. ZnAl2O4 phase, with extremely low solubility and high stability, had been detected in the oxide film; this substance changed the composition of the oxide film and affected the corrosion behavior of A508-3 steel.

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Effect of fluoride on the thickness, surface roughness and corrosion resistance of titanium anodic oxide films formed in a phosphate buffer solution at different applied potentials

Research Society and Development ◽

10.33448/rsd-v9i11.10689 ◽

2020 ◽

Vol 9 (11) ◽

pp. e95791110689

Author(s):

Gláucia Domingues ◽

Michele de Almeida Oliveira ◽

Nayne Barros Gonzaga Ferreira ◽

Bhetina Cunha Gomes ◽

Elivelton Alves Ferreira ◽

...

Keyword(s):

Surface Roughness ◽

Corrosion Resistance ◽

Oxide Film ◽

Phosphate Buffer ◽

Electrochemical Impedance ◽

Oxide Films ◽

Phosphate Buffer Solution ◽

Buffer Solution ◽

Titanium Film ◽

Small Surface

The anodizing process and anions type present in the electrolyte during anodic oxidation are important parameters to improve oxide biocompatibility. From these parameters, it is possible to control the thickness and surface roughness of the oxide film. This control is of major importance, once blood clots can be avoided when the oxide film on the metal substrate has a small surface roughness (Ra ≤ 50 nm). In this paper, the thickness, surface roughness, and corrosion resistance of the anodized titanium film were studied in a phosphate buffer solution containing fluoride anions (0.6 w.t % NaF), at 20 V, 40 V, 60 V, and 80 V, using atomic force microscopy (AFM), spectroscopic ellipsometry (SE), and electrochemical impedance spectroscopy (EIS) techniques. It was observed that thickness and roughness tend to increase as the applied potential rises. For oxides grown in the solution without NaF, the growth rate is roughly 1.3 ± 0.2 nm/V. Surface roughness generally presents the same behaviour. Moreover, EIS and SE thickness measurements agree at 20 V and 60 V but disagree at 80 V. This may be associated with a possible dielectric breakdown at 80 V. The oxide film formed at 60 V showed the best corrosion resistance in relation to the other studied potentials. Globular structures were also observed using AFM on surfaces at 40 V, 60 V, and 80 V, which suggests oxide film nucleation. Oxide films formed in solution with NaF presented lower thickness, excellent corrosion resistance, and low surface roughness (Ra ≤ 50 nm).

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Effect of Sulfur and Chlorine on Fireside Corrosion Behavior of Inconel 740 H Superalloy

High Temperature Materials and Processes ◽

10.1515/htmp-2016-0186 ◽

2018 ◽

Vol 37 (3) ◽

pp. 245-251 ◽

Cited By ~ 2

Author(s):

Lu Jin-tao ◽

Li Yan ◽

Yang Zhen ◽

Huang Jin-yang ◽

Zhu Ming ◽

...

Keyword(s):

Corrosion Resistance ◽

Oxide Film ◽

Corrosion Behavior ◽

Flue Gas ◽

Coal Ash ◽

Corrosion Process ◽

Fireside Corrosion

AbstractFireside corrosion behavior of Inconel 740H superalloy was studied at 750 °C in simulated coal ash/flue gas environments by means of XRD, SEM and EDS. The results indicated that the corrosion behavior was strongly related to the SO2 levels and was significantly affected by NaCl additions. In presence of the atmospheres with 0.1 % SO2, the alloy exhibited the highest corrosion resistance due to formation of a stable and dense Cr2O3 film. In presence of the atmosphere with 1.5 % SO2, however, a non-coherent and porous Cr2O3 film was formed. The thickness of film and internal sulfides were substantially increased. The NaCl additions significantly accelerated the corrosion process. A non-protective outer oxide film was formed, composed by multiple layers with serious inner sulfide and spallation. The depths of internal oxidizing and sulfuration zones were significantly increased. The mechanism of ash corrosion formation was also discussed.

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Influence of Rare Earth Element (Y) on Microstructure and Corrosion Behavior of Hot Extrusion AZ91 Magnesium Alloy

Materials ◽

10.3390/ma13163651 ◽

2020 ◽

Vol 13 (16) ◽

pp. 3651 ◽

Cited By ~ 1

Author(s):

Yanan Cui ◽

Yonghai Wang ◽

Zhongyu Cui ◽

Wenlong Qi ◽

Jidong Wang ◽

...

Keyword(s):

Corrosion Resistance ◽

Rare Earth ◽

Corrosion Behavior ◽

Rare Earth Element ◽

Earth Element ◽

Volume Fraction ◽

Reduction Rate ◽

Mg Alloy ◽

Second Phase ◽

Az91 Magnesium Alloy

The influence of rare earth element (RE) Y on the microstructure and corrosion behavior of extruded AZ91 Mg alloy was surveyed via morphology characterization and corrosion performance measurements. The results indicate the corrosion resistance of the transversal section of AZ91 Mg alloy containing Y was improved compared with AZ91 Mg alloy without Y. The corrosion resistance of the longitudinal section of AZ91 Mg alloy with Y was lower than that of AZ91 Mg alloy without Y. The change of corrosion resistance can be attributed to the dispersion and volume fraction of the second phase, the effect of cathodic reduction rate, and the refined second phase.

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Surface Corrosion Resistance in Turning of Titanium Alloy

International Journal of Corrosion ◽

10.1155/2015/823172 ◽

2015 ◽

Vol 2015 ◽

pp. 1-8 ◽

Cited By ~ 8

Author(s):

Rui Zhang ◽

Xing Ai ◽

Yi Wan ◽

Zhanqiang Liu ◽

Dong Zhang ◽

...

Keyword(s):

Corrosion Resistance ◽

Oxide Film ◽

Film Thickness ◽

Titanium Alloys ◽

Oxygen Concentration ◽

Oxide Films ◽

Surface Oxidation ◽

Implant Surface ◽

Surface Corrosion ◽

Oxide Film Thickness

This work addresses the issues associated with implant surface modification. We propose a method to form the oxide film on implant surfaces by dry turning to generate heat and injecting oxygen-rich gas at the turning-tool flank. The morphology, roughness, composition, and thickness of the oxide films in an oxygen-rich atmosphere were characterized using scanning electron microscopy, optical profiling, and Auger electron spectroscopy. Electrochemical methods were used to study the corrosion resistance of the modified surfaces. The corrosion resistance trends, analyzed relative to the oxide film thickness, indicate that the oxide film thickness is the major factor affecting the corrosion resistance of titanium alloys in a simulated body fluid (SBF). Turning in an oxygen-rich atmosphere can form a thick oxide film on the implant surface. The thickness of surface oxide films processed at an oxygen concentration of 80% was improved to 4.6 times that of films processed at an oxygen concentration of 21%; the free corrosion potential shifted positively by 0.357 V, which significantly improved the corrosion resistance of titanium alloys in the SBF. Therefore, the proposed method may (partially) replace the subsequent surface oxidation. This method is significant for biomedical development because it shortens the process flow, improves the efficiency, and lowers the cost.

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