Corrosion Rate Of Alloy Research Articles

Influence of pickling time on electroless Ni–P coating on magnesium alloy

AbstractIn this study, a simple pickling process in H3PO4 and NH4HF2 solution was used for electroless Ni–P plating on AZ61 magnesium alloy. It is found that the corrosion rate of magnesium alloy during pickling significantly decreased because NH4HF2 was added into H3PO4 pickling solution. Ni–P coating plated only with pickling process shows poor adhesion because of the low F/O ratio of the substrate surface. However, F/O ratio, adhesion, and corrosion resistance of Ni–P coating are obviously enhanced after pickling followed by activation. The optimal pretreatment process is pickling for 120 s and activation for 4 min, under which the Ni–P coating has an optimum F/O ratio of 1.8 and the coating gets a dense structure, better adhesion, and higher corrosion resistance.

Synergistic interactions between wear and corrosion of Ti-16Mo orthopedic alloy

In this study, corrosion, wear, and tribocorrosion of Ti-16Mo alloy manufactured by powder metallurgy (PM) in phosphate-buffered saline are investigated. The results indicate that the corrosion rate of Ti-16Mo alloy increases about 100 times from 0.00009 mm/yr to 0.00851 mm/yr under the tribocorrosion condition. Also, corrosion accelerates wear loss, and wear increment rate due to the corrosion (4.7715 mm/yr) of Ti-16Mo alloy is about 40% of pure mechanical wear rate (11.78 mm/yr). Compared with as-cast pure Ti (23.70999 mm/yr) and Ti-6Al-4 V (17.12003 mm/yr), Ti-16Mo alloy exhibits the lowest materials loss of 16.56001 mm/yr making it become a promising alloy for bone-tissue applications.

A comparative study of chemical and physical properties of copper and copper alloys affected by acidic, alkaline and saline environments

Chemical and physical behavior including corrosion performance, thermal conductivity and visual color change of the copper-based alloys brass and bronze have been studied prior and after corrosion in acidic, alkaline and saline media. The concentrations of 0.5 M H2SO4, 0.5 M NaOH and 0.5 M NaCl were used in which copper and copper-alloy samples were immersed and left to corrode at room temperature for 28 days. The experiments were performed prior and after corrosion, using conventional gravimetric measurements accompanied with measurements of thermal conductivity, microstructure and optical properties. The color change of different samples was also studied through tristimulus color parameter (L*, a* and b*) values. It is concluded that the corrosion rate of copper and copper alloys is greater in acidic than in salt and alkaline media. This is due to the extent of disruption of the passive film formed on the surfaces. In the cases of alkaline and salt media, the passive films on the surface remain stable to a large extent. Small increase of thermal conductivity takes place due to formation of a very thin film of oxide and hydroxide bonded to the surface. The environment also affects the color of copper and copper alloys by chemical changes like oxidation and formation of different intermetallics on the surfaces. A microstructural study of experimental materials confirms that corrosion after 28 days results in formation of pores on the surfaces in acidic environment, and passive film that grows thicker on the surfaces in alkaline and saline environments. Aluminum oxide that is more stable than zinc oxide causes better anti-corrosion performance and minimal color variation of bronze compared to brass, especially in acidic environment.

Influence of Calcium Scaling on Corrosion Behavior of Steel and Aluminum Alloys.

Calcium scaling is a serious problem encountered in the oil and gas industry because it is common that brines produced alongside oil and gas exhibit high concentrations of calcium ions, among others, which is expensive to remedy. The precipitation of calcium salts on the internal wall of the pipelines may occur because of the physical and chemical changes as fluids are produced from downhole to surface facilities. Although different researchers have address scaling and corrosion in the oil and gas industry, there are few reports in the literature relating the corrosion and scaling phenomena simultaneously. Despite there being indications that scales may produce corrosion problems, affecting the mechanical integrity of the infrastructure, there is minimal research in the literature addressing such relations. Previous studies presented aluminum alloys as excellent and reliable materials for applications in the petroleum industry, such as drilling activities. In this work, we evaluate the corrosion behavior of steel and aluminum alloys under highly scaling environments using supersaturated brines. Our results show that the presence of calcium carbonate and calcium sulfate as a scaling environment increases the corrosion rates for aluminum alloys and carbon steel; however, the same environments do not affect the corrosion behavior of stainless steel.

Formation and In Vitro Evaluation of a Deep Eutectic Solvent Conversion Film on Biodegradable Magnesium Alloy.

The chemical conversion films from deep eutectic solvents (DESs) have recently been shown to reduce the corrosion rate of magnesium alloys, which are recognized as a kind of promising materials applied in the human body. However, the biocompatibility of the conversion films has not been investigated. This study proposes an uncommon DES system composed of lithium chloride and urea to fabricate the chemical conversion films on Mg and its alloy. The fabrication process of the conversion film is facile, which is performed by the heat treatment of the substrate in the DES at about 200 °C for 30 min. It is found that the thermal decomposition of the DES can release hydrogen, which diffuses into the Mg substrate to form MgH2-based conversion films. The DES conversion film possesses a porous structure on pure Mg, whereas it becomes dense on the alloy with some cracks. X-ray photoelectron spectroscopy shows that MgCO3 and oxides also exist in the DES conversion films, which depends on the substrate. Electrochemical corrosion test and in vitro biocompatibility tests, including hemolysis, cytotoxicity, antibacterial, and cytoskeleton staining experiments, are performed in a simulated body environment, which shows that the corrosion resistance and biocompatibility of the substrates have been improved significantly. We expect that the DES heat treatment method will be applied to the fabrication of corrosion-resistant and biocompatible surfaces for biodegradable Mg alloys.

Box-Behnken design to enhance the corrosion resistance of high strength steel alloy in 3.5 wt.% NaCl solution

Recently, the production of green corrosion inhibitors and green inhibition strategies is highly demanded in the field of science and technology due to the growing demand of green chemistry. Usage of plant extracts as metallic corrosion inhibitors has attracted considerable attention in the last few decades. Plant products are perfect green candidates for replacing traditional toxic corrosion inhibitors. Reduced environmental risk, lower cost, widespread availability and high corrosion inhibition efficiency make plant extracts ideal candidates for the substitution of costly and harmful traditional synthetic corrosion inhibitors. An aqueous extract of plant material Henna (Lawsonia Inermis) powder was used as a corrosion inhibitor to control the corrosion of high strength steel immersed in an aqueous solution containing 35000 ppm Cl − , by electrochemical methods in the absence and presence of the inhibitor. Lawsone is the principal constituent of this plant extract. This has excellent efficiency in inhibition and displays excellent IE at neutral pH. Electro-chemical experiments such as potentiodynamic polarization and impedance were used to describe the mechanistic aspects of corrosion inhibitions. Box-Behnken method was used to investigate the effect of key parameters (i.e. concentration of inhibitors, temperature, and speed of rotation) on the efficiency of inhibition and corrosion rate of high strength steel alloy in 3.5 wt.% NaCl solutions. From electrochemical measurements and statistical analysis, it was found that the efficacy of inhibition improves with higher inhibitor concentration, low rotation speed and low temperature. The Lawsonia Inermis extracted demonstrated strong corrosion inhibition in saline media for high strength steel alloy and reached 81.68.

Electrochemical Impedance Spectroscopy for the Measurement of the Corrosion Rate of Magnesium Alloys: Brief Review and Challenges

From a technological point of view, measurement of the corrosion rate of magnesium (Mg) and its alloys is critical for lifetime predictions of Mg-based structures and for comparative assessments of their corrosion protection ability. Whilst weight loss, hydrogen evolution, and polarization curves methods are frequently used for measuring the corrosion rate, the determination of values by electrochemical impedance spectroscopy (EIS) is relatively scarce and has only been realized recently. This technique seems to be the most suitable for monitoring corrosion rate values due to its “non-destructive” character, its reproducibility, and its reliable determination of small corrosion rates, much lower than those measured by other techniques. This review aims to picture the state-of-the-art technique of using EIS for measuring the corrosion rate of Mg. This paper starts by introducing some fundamental aspects of the most widely used methods for monitoring the corrosion rate of Mg/Mg alloy and continues by briefly explaining some of the fundamental concepts surrounding EIS, which are essential for the user to be able to understand how to interpret the EIS spectra. Lastly, these concepts are applied, and different approaches that have been proposed to obtain quantitative values of corrosion rate since the 1990s are discussed.

Experimental Investigation and Optimization of Wire Electrical Discharge Machining for Surface Characteristics and Corrosion Rate of Biodegradable Mg Alloy

Wire electrical discharge machining (Wire EDM) is a spark erosion process that modifies the surface characteristics by creating overlapped craters and oxides on the machined surface. This oxide and metamorphic layer can be advantageous for Mg alloy in terms of improved corrosion resistance and osteoblast activities. In the current work, face-centered central composite design has been used to carry out the experiments on Wire EDM to study the influence of process parameters and to generate the correlation between input parameters and performance characteristics of ZM21 Mg alloy. Performance characteristics chosen for Mg alloy machining are cutting speed, surface roughness and corrosion rate. To identify the important input parameters and a numerical model that fits the response characteristics, analysis of variance has been used. Using a scanning electron microscope (SEM), it has been found that Wire EDM resulted in overlapped craters and formation of µ-cracks on the machined surface, influenced by discharge energy developed across the electrodes. SEM and XRF (x-ray fluorescence) analysis confirm the formation of a metamorphic layer on the machined surface which leads to corrosion resistance improvement as compared to polished ZM21 Mg alloy. Under response surface methodology, desirability function was utilized to obtain the optimal solutions for multi-response characteristics which were validated experimentally and the sample machined at optimal setting shows improved surface morphology with an oxide layer having uniform nanoscale structure. Electrochemical impedance spectroscopy analysis (for 7 days) shows an increasing trend of corrosion resistance for machined samples, which supports the application of Wire EDM for Mg alloy implants.

Corrosion behavior of AZ91D magnesium alloy in distilled water

The corrosion of AZ91D magnesium alloy has received extensive attention due to the continuous expansion of its application field in recent years. However, the corrosion of AZ91D magnesium alloy in distilled water is relatively few. In this paper, the corrosion behavior of AZ91D magnesium alloy was studied in distilled water by electrochemical tests in combination with weight loss and surface analysis methods. The results indicated that the corrosion rate of AZ91D magnesium alloy increased with the increase of temperature and immersion time. The increase of the corrosion rate of AZ91D magnesium alloy with the increase of immersion time might be attributed to the damage of the structure of corrosion product film by hydrogen evolution, significantly accelerating the anodic process of AZ91D magnesium alloy. It was interesting that, in distilled water, the EIS of AZ91D magnesium alloy excluded an inductive arc in the low frequency region, which indicated that there was no the adsorption and desorption of aggressive ions or the damage and repair of film. The corrosion product film of AZ91D magnesium alloy in distilled water was composed of a compact inner corrosion product film and a loose outer corrosion product film.

The Effect of Zirconium Addition on Corrosion Behavior of Zn-Zr Alloys as Biodegradable Orthopedic Implant Application

In this work, corrosion behaviour of zinc-based alloys with addition of 0.5%, 1%, and 2% of zirconium for biodegradable material as orthopaedic implant were investigated. The potentiodynamic polarization method is carried out to determine the corrosion resistance and corrosion rate of each composition in order to observe the effect of zirconium addition in a Kokubo simulated body fluid solution. The result showed that the addition of 0.5% and 1% of zirconium would decrease the corrosion rate of Zn-xZr alloys corresponding to 0.079 mm/year and 0.116 mm/year whereas the 2% addition would increase the rate to 0.188 mm/year due to the formation of Zr-rich precipitates inside the alloys. The passivation zone on the polarization curve showed the formation of the protected thin layer on the surface of the alloys which caused the corrosion rate to decrease, therefore confirmed the degradable ability of the Zn-xZr alloys. In general, the corrosion rates of Zn-xZr alloys were higher than Fe-based alloys and lower than Mg-based alloys. Moreover, the corrosion rates were much lower than the maximum rate of 0.4 mm/year for biodegradable implants so Zn-xZr alloys were suitable as biodegradable material implant for orthopaedic application.

In Vitro Degradation, Hemocompatibility, and Cytocompatibility of Nanostructured Absorbable Fe-Mn-Ag Alloys for Biomedical Application.

The addition of noble elements such as Ag was shown as a successful method to accelerate the corrosion rate of absorbable Fe-based alloys. One major concern of Ag addition is its effect on hemocompatibility and biocompatibility. In this study, in vitro degradation and surface analysis of Fe-30Mn-xAg (x = 0, 1, and 3 wt %) alloys as well as their effects on hemocompatibility and cell viability of human umbilical vein endothelial cells (HUVECs) were investigated. The static degradation rate of the alloys was 4.97, 4.69, and 4.49 mg/cm2 for Fe-30Mn, Fe-30Mn-1Ag, and Fe-30Mn-3Ag, respectively. The surface analysis after degradation showed that γ-FeOOH was formed on Fe-30Mn-3Ag, while α-FeOOH was more dominant on Fe-30Mn and Fe-30Mn-1Ag. As γ-FeOOH is more soluble than α-FeOOH, it assists further degradation of Fe-30Mn-3Ag alloy. The high amount of Ag, which induced the hemolysis ratio, however, inhibited coagulation by decreasing the platelet adhesion. Fe-30Mn-1Ag and Fe-30Mn-3Ag alloys show an improved cell viability as compared to that of Fe-Mn alloy. Shear yield strength and shear elastic modulus of the samples after immersion tests were increased, while the ultimate shear strength was not affected. On the basis of the acceptable hemolysis rate, low platelet adhesion, acceptable cell viability, and appropriate mechanical properties after degradation, Fe-30Mn-1Ag can be considered as a suitable blood-contacting Fe-based absorbable alloy.

Characterization of AZ31-NbC surface composite fabricated by friction stir processing

Abstract AZ31D magnesium alloy is widely used in automotive, aircraft, and aerospace applications because of its high strength to weight ratio. However, the softness of the alloy results in higher wear rate and the high activity results in higher corrosion rate. With an aim of reducing the wear rate and corrosion rate of AZ31 alloy, surface composite of AZ31 alloy is fabricated by reinforcing niobium carbide (NbC) by friction stir processing. The microstructure and dispersion of the reinforcements in AZ31-NbC surface composite is analysed by optical microscopy. In addition, the microhardness and tribological characteristics of the developed AZ31-NbC surface composite are investigated. The results demonstrated an increase in microhardness (23.2 %) and the decrease in wear rate (15.6 % for a normal load of 2 kg) in the developed AZ31-NbC surface composite with respect to the base material. The immersion corrosion test was performed to analyse the corrosion rate of the developed AZ31-NbC surface composite in simulated sea water environment (3.5 wt % NaCl solution). The results indicate that the corrosion rate of the developed AZ31-NbC surface composite is higher than that of base material. A comprehensive analysis on the wear and corrosion mechanism of the developed AZ31-NbC surface composite is presented.

The corrosion behavior of M5 (Zr–1Nb-0.12O) alloy in 360 °C water with dissolved oxygen

The corrosion behavior of M5 alloy in 360 °C/20 MPa water with 1.5 ppm dissolved oxygen (DO) was studied. The test was conducted by using a circulating autoclave loop system. The results indicated that DO accelerated the corrosion of M5 alloy in high temperature water. The corrosion behavior of β-Nb phase in the barrier layer and the post-transition layer in oxygenated water is completely different from that in deoxygenated water. For materials exposed to oxygenated water, β-Nb phases are sequentially oxidized to crystalline NbO (Nb2+) and crystalline NbO2 (Nb4+), then part of it is completely oxidized to Nb2O5 (Nb5+) in the barrier layer. In the post-transition layer, these crystalline oxidation products of β-Nb phase change to amorphous state, wherein Nb is totally oxidized to Nb5+ state. In the outer layer, the dissolution of β-Nb oxide is not completed when exposed to oxygenated water for even 100 days. Oxygenated water can accelerate corrosion of β-Nb SPPs, which could be responsible for high corrosion rate of Nb-containing Zr alloy in DO water.

Effects of 405 stainless steel on crevice corrosion behavior of Alloy 690 in high-temperature pure water

Effects of 405 stainless steel (405 SS) on crevice corrosion behavior of Alloy 690 in high-temperature pure water were investigated. Results revealed that the corrosion rate of Alloy 690 was low within the crevice. It was likely attributed to the fact that a Cr-rich inner oxide film and a Ni-rich layer beneath this oxide film formed upon Alloy 690, inhibiting the diffusion of oxygen towards the oxide/matrix interface. Moreover, the Fe2+ ions dissolved from 405 SS consumed most of oxygen, leading to less oxygen participating in the oxidation of Alloy 690. In addition, it was found that Fe concentration continuously decreased from the surface of the inner oxide film to the oxide/matrix interface of Alloy 690 within the crevice, which was probably due to the diffusion of Fe2+ ions dissolved from 405 SS into the inner oxide film.

Study on Corrosion Resistance of Zn-Al Alloy Coated with Zeolitic Imidazolate Framework-67 Film in 3.5 wt.% NaCl Solution

A zeolitic imidazolate framework-67 (ZIF-67) film was prepared on the surface of a Zn-Al alloy via a secondary seeded growth method. The thickness, adhesion and hydrophobicity of the film were evaluated by coating thickness test, the cross-cut test and water contact angle measurements, respectively. The phase composition and surface morphology of the synthesized film were investigated by x-ray diffraction, energy-dispersive spectroscopy and scanning electron microscopy, respectively. Potentiodynamic polarization measurements and electrochemical impedance spectroscopy were employed to evaluate the corrosion properties of the ZIF-67 film-coated Zn-Al alloy in 3.5 wt.% NaCl static solution. The compact, hydrophobic and adhering ZIF-67 films (the thickness of 15.0 ± 1.4 µm) were successfully coated on Zn-Al alloy surface. The Icorr of the Zn-Al alloy-coated ZIF-67 film decreased two orders of magnitude in comparison with that of the Zn-Al alloy substrate. The ZIF-67 film decreases the corrosion rate of Zn-Al alloy, and has good corrosion resistance characteristics. The obtained results indicated that the hydrophobic ZIF-67 film has the potential application for the protection of Zn-Al alloy in 3.5 wt.% NaCl solution.

Formulation of corrosion rate of magnesium alloys using microstructural parameters

Up to the date of writing this article, a quantitative analysis between corrosion rate and combined microstructural parameters including composition, grain size, and precipitations has not been reported. Hence, a literature review was carried out on these parameters to understand the quantitative effect of each one on the corrosion rate of Mg and Mg alloys. Moreover, using the available data in the literature and several experimental results, a new model was developed to predict the corrosion rate, through microstructural parameters. This model suggests that by using ultra-fined grains, alloying compounds with low Volta-potential difference relative to the matrix and a low fraction of secondary phase, a very low corrosion rates of materials are achievable.

Beneficial effects of Cr addition on the nanocrystalline Si and B modified Co-Zr permanent magnetic alloys

Co-Zr alloys with Si and B modifications show potential for rare earth-free permanent magnets. In this work, Cr was employed for improving the hard magnetic properties of melt-spun Co78-xZr16CrxSi3B3 (x = 0, 1, 2, 3, and 4) alloys. Their phase constitution, microstructure, and properties have been investigated. The results show that Cr addition can suppress the formation of the soft magnetic FCC-Co phase. The coercivity increased almost linearly with increasing Cr addition, accompanied by decreasing remanence. A high coercivity of 7.7 kOe was obtained in the alloy with 4 at.% Cr substitution for Co, manifesting a 67% coercivity enhancement from 4.6 kOe of the Cr-free alloy. Cr atoms were found to partially substitute Co atoms in the Co-Zr-Cr-Si-B alloys. The size of nanograin decreased with Cr addition alloys, partly due to the precipitation of the secondary Cr phase. After Cr addition, the enhanced positive peak in Henkel plots and the closed recoil loop indicate the improved exchange coupling and consistent magnetic reversal. The alloys with x = 0 and 4 exhibited much lower absolute values of coercivity temperature coefficient, 0.183%/℃ and 0.251%/℃, respectively, and one or two orders of magnitude smaller corrosion current density than that of melt-spun Nd-Fe-B alloys, demonstrating that Co-Zr based alloys have not only excellent thermal stability but also good corrosion resistance. In addition, Cr substitution can further reduce the corrosion rate of Co-Zr alloys in the 3.5 wt% NaCl solution.

Corrosion behaviours of Ti6Al4V-Mg/Mg-Alloy composites

The effect of coupling of unalloyed Mg and Mg-alloys (AZ91 and WE43) with Ti6Al4V alloy on corrosion and degradation behaviours of produced composites has been investigated in simulated body fluid (SBF) by hydrogen evolution, and surface and electrochemical characterization techniques. Combining of unalloyed Mg with Ti6Al4V intensified galvanic corrosion and catastrophic failure occurred by initiation of microcracks formed by sudden hydrogen gas evolution. In contrast to other composites, Ti6Al4V-AZ91 composites, containing new TiAl3 interface layer formed during composite production, preserved their mechanical integrities due to lowest corrosion and degradation rate of AZ91 alloy.

The Effect of Trivalent Chromium Process on Al-Zn-In Pigments in Epoxy Primer on the Corrosion Protection of AA2024-T3

Active metal pigments in metal-rich coatings are oxidized preferentially and provide sacrificial protection to more-noble metallic substrates. Al-rich primer (AlRP), which contains pigment particles made from an active aluminum alloy (Al-5Zn-0.02In), uses this mechanism to provide a chromate-free epoxy primer system. To address the high self-corrosion rate of active aluminum pigments, the active aluminum pigment particles are pretreated using trivalent chromium process (TCP). In this study, the effects of different TCP treatment times were evaluated, and coating protection properties were studied. Potentiodynamic polarization tests were performed in aerated 0.1 M NaCl solution for a TCP-treated bulk active aluminum alloy and for AA2024-T3. The potentiodynamic polarization curves show that the corrosion potential of the bulk active aluminum alloy is about 500 mV lower than that of AA2024-T3. Therefore, bulk active aluminum alloy is a candidate alloy for cathodic protection of AA2024-T3. In addition, the TCP treatment reduces the corrosion rate of the bulk active aluminum alloy by one order of magnitude. AlRP-coated AA2024-T3 panel samples were scribed and exposed in corrosion chambers, and the cross section of each coating was evaluated by scanning electron microscopy and energy dispersive x-ray spectroscopy mapping. The accelerated corrosion exposure results show that AlRP coatings containing TCP-treated particles provided better protection to the scribe than the one with bare pigment particles. The adhesion of the AlRPs based on pull-off adhesion tests was similar regardless of the TCP treatment time of the pigments, but the adhesion of AlRP was reduced in comparison to a neat epoxy coating.

Basic characterization of new Ti-Mn-Zr alloys

Beta titanium alloys (β-Ti) have been a subject of great interest since the 1980s. In this study, the microstructure, mechanical and corrosion behavior of new low-cost β-type Ti-14Mn-xZr (x = 0, 3 and 6 wt%) alloys are studied. The novel alloys were fabricated by arc melting followed by annealing treatments at 900 °C for 6 hrs then quenched in ice water to achieve good homogenization. The microstructure, mechanical properties, and corrosion properties of the alloys were investigated. The XRD patterns show a single β phase in all alloys and confirmed by the microstructural analyses. Both the compression strength and the hardness of the alloys were increased by increasing the Zr-content in the alloy due to the solid solution strengthening as well as the higher β-phase stability. Also, Zr addition decreased the corrosion rate of TiMnZr alloys.