Corrosion Film Research Articles

Localized corrosion of magnesium alloys potentially applicable for medical implants: fundamental aspects

A comparative analysis of the corrosion activity of bioresorbable MA8 magnesium alloy (Mg– Mn – Ce system) in a medium for cultivation of mammalian cells (minimum essential medium, MEM) and 0.83 wt. % aqueous NaCl solution was performed. The development of the corrosion process on the surface of a magnesium alloy in two media was established using local scanning electrochemical methods (scanning vibrating electrode technique and scanning ion-selective electrode technique), traditional electrochemical methods (potentiodynamic polarization, electrochemical impedance spectroscopy) and hydrogen evolution measurements. The protective properties of the corrosion film formed on the alloy in MEM, as well as during exposure to NaCl solution, were established. The composition of the layer of corrosion products formed on the magnesium alloy in MEM was studied using confocal Raman spectroscopy, X-ray diffraction analysis, scanning electron microscopy, and energy dispersive X-Ray analysis. Calcium-phosphate compounds are the main products formed on the surface of a magnesium alloy during immersion in MEM. The model of corrosion mechanism of magnesium alloy in MEM, which includes three stages of the development of surface film, is proposed. The formation on the magnesium alloy in MEM of corrosion product layer, including magnesium-substituted hydroxyapatite, stabilizes the local pH below 9.0, which along with the presence of organic acids, does not allow increasing the pH during corrosion. A diagram that allows one to determine the possible reactions occurring on the surface of a magnesium alloy in MEM and the thermodynamic probability of the formation of chemical compounds based on the values of the local pH is designed. The obtained results indicate the prospect of using bioresorbable magnesium implants in surgery.

Damage analysis of rotation speed on corrosion film of 3Cr steel in the CO2 environment with silty sand

The 3Cr steel used as the tubing has serious corrosion damage in a flowing CO2 environment with silty sand. Hence, the investigation for the influence of flow velocity on the corrosion behavior of 3Cr steel has an important and practical significance. It could not only unveil the corrosion damage mechanism of the steel under dynamic conditions, but also provide a theoretical basis for the corrosion protection of the tubing. In this paper, the effect of flow velocity on the corrosion film of 3Cr steel in a CO2 environment with silty sand was investigated by adjusting rotation speed. The results revealed that the corrosion resistance of 3Cr steel was first reduced, followed by enhancing and then reduced as the rotation speed increased. There was a critical rotation speed for the transformation of corrosion mechanism of 3Cr steel, i.e., 600 r/min. When the rotation speed was lower than the critical speed, the mass transfer process of corrosive medium dominated the corrosion resistance of 3Cr steel, and silty sand participated in the formation of corrosion film. The increasing rotation speed accelerated the mass transfer process, which first reduced and then improved the corrosion resistance. When the rotation speed was higher than the critical speed, the shear stress of silty sand played a predominant role. At the same time, silty sand impinged on the corrosion film, and then destroyed the stability of the film, leading to a significant decrease of the corrosion resistance. Silty sand changed from participating in the corrosion film to destroying the corrosion film with increasing rotation speed.

Effect of simultaneous application of ultrasonic vibrations during laser surface melting on electrochemical properties of 2024 aluminum alloy

In the present investigation, effect of laser melting with and without simultaneous application of ultrasonic vibrations on electrochemical properties of 2024 aluminum alloy is investigated. The electrochemical behavior of the laser melted specimens was studied using open-circuit and potentiodynamic polarization measurements. Subsequently, investigation of the corrosion films was performed using scanning electron microscopy. It was observed that the laser melted specimens exhibited significant improvement in open circuit potential (both with and without simultaneous ultrasonic vibration application). The open circuit potential of the laser melted specimen without ultrasonic vibrations was observed to be more stable compared to the laser melted specimen with ultrasonic vibrations. It was observed that the corrosion mechanism undergoes a transition from pitting to uniform corrosion in the laser treated specimen, particularly in the laser melted specimen without ultrasonic vibrations. However, the extensive agitations due to ultrasonic vibrations in the melt pool appear to restrict Cu migration to grain boundaries that result in porous and relatively inefficient passive layer formation in laser processed samples with application of ultrasonic vibrations. This behavior was also observed in the potentiodynamic polarization studies that showed that the laser melted specimen without ultrasonic vibrations exhibited lower corrosion current and corrosion rate compared to the laser melted specimen with ultrasonic vibrations as well as the as received substrate. Copyright © 2017 VBRI Press.

In vitro degradation behavior of novel Zn–Cu–Li alloys: Roles of alloy composition and rolling processing

Zn–alloys are considered to be promising biodegradable materials due to suitable degradation rates. In this paper, novel Zn–Cu–Li alloys with layered CuZn4 structure were achieved. The corrosion properties of newly developed biodegradable Zn–Cu–Li alloys in simulated body fluid was studied. Results indicated that the cold-rolled alloys presented a relatively uniform corrosion mode, although early corrosion occurred preferentially at phase boundaries. Galvanic corrosion and corrosion product films jointly determined the later corrosion process. Cu improved the corrosion potential and film properties in its solid solution state, induced galvanic corrosion, and provided a physical barrier to corrosion by forming CuZn4 phase. Rolling accelerated the initial corrosion rate by enhancing the matrix electrochemical activity, while it contributed to uniform corrosion by improving the CuZn4 phase shape. Finally, cold-rolled Zn–4Cu–0.02Li possessed the best corrosion resistance and mechanical properties combination among the prepared alloys, with a yield strength of 256 MPa, an ultimate strength of 342 MPa, a fracture elongation of 39.8 %, and a corrosion rate of nearly 55 μm/year.

The anisotropy electrochemical corrosion behavior of Ni-based single crystal superalloy on different crystal planes: An investigation from the film growth aspect

The electrochemical corrosion and passivation behaviors of DD5 Ni-based single crystal superalloy with different crystal orientations were compared. The corrosion resistance and film growth behaviors of three different oriented samples were evaluated by using electrochemical techniques. The compositions of passive film and the corrosion morphologies on various crystal planes were revealed by X-ray photoelectron spectroscopy (XPS) and scanning electron microscopy (SEM). The electrochemical processes on the sample surfaces were further analyzed based on the surface energy and the point defect model (PDM). The results revealed that the dissolution rates of the three tested planes lie in the order of (011) < (001) < (111), and the passive film grows faster and denser on the plane with higher surface energy. The presence of Cr2O3 and the enrichment of MoO3 in the passive film can enhance the corrosion resistance of (011) plane. Our results can provide an in-depth understanding of the correlations between the surface energies, the film growth behaviors, and the electrochemical corrosion behaviors of planes with different crystal orientations.

Microstructures and corrosion behavior of HVOF‐sprayed WC‐12%Cr3C2‐6%Ni coatings before and after sealing

AbstractThe WC‐12%Cr3C2‐6%Ni coatings are prepared by high‐velocity oxygen‐fuel spraying technology on 42CrMo steel substrate, and then the sealing treatment is carried out by sol‐gel aluminum phosphate inorganic sealing agent. The composition, phase structure, morphologies, and porosities of the coatings are characterized by energy dispersive spectrometer (EDS), X‐ray diffraction, scanning electron microscope (SEM), and metallographic gray‐scale methods. Results show that the corrosion current density and corrosion rates of WC‐12%Cr3C2‐6%Ni coatings in different media are lessened by the aluminum phosphate sealing treatment, which can improve the corrosion resistance of the coating. The corrosion rates of unsealed and sealed coatings immersed in 3.5% Na2SO4 solution at 35℃ for 28 days are 0.99 and 0.38 g·m–2·h–1, and the porosity of the coatings is significantly decreased by the aluminum phosphate sealing treatment, which is lower than 2%. During the immersion corrosion, the sealed and unsealed coatings surface form oxide films with different compositions, which can slow down the corrosion along the normal direction of the coating surface in the process of continuous destruction and regeneration, and no obvious coating/substrate interface corrosion occurs.

Stress corrosion cracking of A517 steel in marine environments

PurposeThe purpose of this study is to develop the existence and mechanism of stress corrosion cracking (SCC) for A517 steel in marine environments.Design/methodology/approachSlow strain rate test (SSRT) and constant load tests were used to investigate the SCC susceptibility of A517 steel. In addition, the additive stresses caused by the corrosion film and hydrogen entering into steel were applied to reveal the fundamental mechanism of the SCC.FindingsThe SCC susceptibility increased due to anodic dissolution and additive stress caused by the corrosion-produced film under anode polarization. Furthermore, the SCC susceptibility increased with increasing cathodic polarization, which is due to the increased additional stress caused by hydrogen entering into the steel. However, when the cathode polarization further increased, the additional stress remained due to the constant hydrogen content, thus the SCC susceptibility did not vary. Moreover, the SCC susceptibility of A517 steel under an alternate immersion environment (AIE) was lower than that under a full immersion environment and the steel under the AIE with 0.5 W/D had the lowest SCC susceptibility.Originality/valueThe stress corrosion behaviors of A517 in marine environments under various conditions were systematically analyzed.

Effects of minor RE (Y, La) on microstructure and corrosion behavior of TX31 alloys

The effects of minor RE (Y, La) on microstructure and corrosion behavior of TX31 alloys are systemically investigated. The results show that the CaMgSn phase of TX31-RE alloys is an outstanding thermally stable phase. The addition of little Y, La of the alloys after homogenization does not form new phases. Meanwhile, the minor Y, La can refine the dendritic structure in the TX31 alloys. The Y, La elements can reduce the corrosion rate and increase the corrosion film resistance of the TX31 alloys. The corrosion resistance of La-containing TX31 alloy is better than that of Y-containing TX31. The corrosion of the alloys is typical pitting corrosion because of the potential difference between CaMgSn phases and Mg matrix. The corrosion products are mainly Mg(OH)2, Ca(OH)2, MgO, and SnO2. The RE (Y, La) forms the RE oxide/hydroxide and also promotes the formation of a small amount of CaO. The RE oxide/hydroxide and CaO fill the holes in the metal hydroxides (Mg(OH)2 and Ca(OH)2) films and weaken the penetration rate of Cl−, which improves the corrosion resistance of the RE-containing TX31 alloys.

Bioactivity and &amp;lt;italic&amp;gt;in&amp;lt;/italic&amp;gt; &amp;lt;italic&amp;gt;vitro&amp;lt;/italic&amp;gt; degradation behavior of MgZnCa thin-film metallic glass

<p indent="0mm">Magnetron sputtering was used to prepare MgZnCa thin-film metallic glass (MG), and a single roller melt-spinning method was used to prepare amorphous MgZnCa ribbon. Potential polarization curves of MgZnCa amorphous ribbon and bulk high-purity magnesium (HP Mg) in simulated body fluids were compared using electrochemical tests. The corrosion resistance of MgZnCa MG is found to be significantly better than that of HP Mg, which is mainly attributed to its higher corrosion potential and lower corrosion current density. Immersion experiments, hydrogen evolution experiments, X-ray diffraction, Raman spectroscopy, and scanning electron microscopy were used to analyze the structure and composition of MgZnCa thin-film MG (TFMG) before and after corrosion, showing that the release rate of hydrogen was the fastest in the first hour, with active magnesium and calcium on the film’s surface preferentially dissolved. Furthermore, the appearance of a zinc-rich phase in the corrosion film and the increase in local pH promotes the precipitation of phosphate, which can improve the corrosion resistance of MgZnCa MG. <italic>In</italic> <italic>vitro</italic> experiments show that the 25% concentration extract obtained after soaking the MgZnCa MG has higher cell viability and lower apoptosis rate than the control medium, indicating that the MgZnCa MG is biocompatible. Therefore, with excellent corrosion resistance and biocompatibility, MgZnCa MG can be used as bioactive coatings on the surface of biologically inert materials.

Corrosion inhibition of amino acids for 316L stainless steel and synergistic effect of I− ions: Experimental and theoretical studies

AbstractThe inhibition effect of amino acids l‐lysine (Lys) and l‐arginine (Arg), which serve as inhibition films for corrosion of 316L stainless steel in 0.5 M NaCl solution, is studied by electrochemical measurements. The adsorption of the inhibitor molecules on the steel surface is studied by Fourier transformed infrared spectroscopy (FTIR) and surface‐enhanced Raman spectroscopy (SERS), accompanied by the characterization of the metal surface by scanning electron microscopy (SEM). All in all, Lys or Arg can obviously restrain the corrosion of 316L steel, while the inhibition efficiency is even higher with the assistance of I− ions. Arg always has better inhibition performance than Lys regardless of the addition of I− ions. FTIR and SERS confirm the adsorption of amino acids on the metal surface; at the same time, the morphology and protection effect of the inhibition films is clearly illustrated via SEM images. Thanks to all experimental measurements as mentioned above and theoretical calculations, a mechanism model is proposed to simulate the corrosion inhibition process of amino acids and the synergistic effect of I− ions on 316L steel.

Corrosion and passivation behavior of laser powder bed fusion produced Ti-6Al-4V in static/dynamic NaCl solutions with different concentrations

In this work, the corrosion and passivation behavior of Ti-6Al-4V produced by laser powder bed fusion (L-PBF) were investigated in different concentration of NaCl solutions under static and dynamic conditions. Oxide films including TiO2, Ti2O3, TiO were formed on L-PBF-produced Ti-6Al-4V. The film thickness increased under both test conditions with increasing the Cl− concentration, and the film contained more TiO2 in dynamic conditions under the same Cl− concentration. The mechanism of the corrosion behavior and film growth under different Cl− concentration and electrolyte conditions were discussed by the relevant electrochemical and surface characteristic measurements, e.g. Mott-Schottky analysis, X-ray photoelectron spectroscopy.

Mechanistic insights into selective oxidation and corrosion of multi-principal element alloys from high resolution and in situ microscopy

Multiple principal element alloys (MPEAs) have drawn significant recent interest from the metallurgical research community. These novel alloys have the potential to replace traditional alloys with a range of tailored mechanical properties, corrosion resistance, and radiation tolerance enabled by complex compositions. The broad alloy design space of MPEAs presents a great opportunity to discover new forms of oxidation and corrosion resistance in extreme environments that break away from conventional alloy design criteria. However, understanding the oxidation and corrosion response of MPEAs can be a challenging task due the complex compositional, structural, and chemical state changes occurring in the oxide or corrosion film and at its interface with the base alloy. This perspective discusses the utility of high resolution and in situ microscopy techniques for revealing unique aspects of MPEA oxidation and corrosion behavior at the atomic and near atomic scales. Challenges of studying oxidation and corrosion response of these alloys and several open questions are presented.

Effect of sulfide on corrosion behavior of stainless steel 316SS and Hastelloy C276 in sub/supercritical water

Stainless steel 316SS and Hastelloy C276, as the representatives of iron-based and nickel-based alloy, respectively, were employed to explore the corrosion properties under reducing subcritical and supercritical water containing sulfide. Experiments were executed at a pressure of 25 MPa, temperatures of 350 °C–520 °C, and sulfur concentrations of 1000 and 5000 ppm for 80 h. An isothermal equilibrium phase diagram involving the oxidation/sulfidation products of Fe, Cr, and Ni, was established by theoretical calculation in supercritical water system at 520 °C, in order to predict the corresponding products under various conditions and assist the discussion on corrosion mechanism. The results show that whether in subcritical water or in supercritical water, 316SS always exhibited better corrosion resistance relative to C276. In subcritical water at 350 °C, a portion of corrosion film peeled off from 316SS specimen, while numerous pores or cracks appeared on the surface of scale for C276. Under supercritical water at 520 °C, a compact scale grown on 316SS sample surface was composed of Fe3O4, FeCr2O4, and FeS. For C276, a duplex-layer scale formed on alloy surface. However, due to the higher content of Ni in C276, Ni-sulfide channels through the inner layer were developed, accelerating the sulfidation corrosion of alloys. Overall, the high-temperature alloys with high Cr content and low Ni/Cr ratio can be considered as the candidate material of equipment in supercritical water gasification of sulfur-containing coal.

Effects of Ga addition on the corrosion behaviours of high strain rate rolled Mg–Ga alloy sheets

ABSTRACT The effects of Ga addition (1, 2, 3 and 5 wt-%) on the corrosion behaviour of high strain rate rolled Mg–Ga alloys are firstly investigated by weight loss measurement and electrochemical testing. Solute Ga atoms can reduce the corrosion potential but improve the corrosion resistance of the alloy with the Ga content lower than 3 wt-%. The Mg–3Ga alloy sheet is the most corrosion-resistant with the weight loss rate of 0.52 mg cm−2 day−1 for 7 days immersion in 3.5% NaCl solution. The corrosion resistance improvement can be ascribed to the enhanced compactness of the corrosion film associated with Ga addition. The Ga addition affects the DRX degree, but the DRX degree is not the crucial factor in the corrosion of the alloys. The Mg5Ga2 dynamic precipitates are detrimental to the corrosion resistance of the Mg–Ga alloys and play a relatively important role in the corrosion of the Mg–5Ga alloy.

The corrosion behavior and film properties of Al-containing high-entropy alloys in acidic solutions

Aluminum has shown promising application in reducing the high-entropy alloys’ weight and enhancing their mechanical properties. In this work, the impact of solid-solution aluminum on the corrosion behavior and film properties of FeCoCrNiAlx (x = 0.1, 0.3) high-entropy alloy in 0.5 M H2SO4 and 0.5 M HCl solutions was investigated by electrochemical measurement, Auger electron spectroscopy, and X-ray photoelectron spectroscopy. The results demonstrate that both of the high-entropy alloys exhibit an equiaxed grain structure with numerous annealing twins. FeCoCrNiAl0.3 alloy still remains the stable FCC substrate without any second phase precipitates. The increasing aluminum content can improve the corrosion resistance of FeCoCrNiAlx by simultaneously increasing Cr oxide content in the passive film and making it thicker in the H2SO4 solution. Nevertheless, the effect is negative in the HCl solution because chloride ions are inclined to combine with the Al-containing metastable ion complexes, which accelerates the dissolution of HEA.

Effects of Zn Addition on Microstructure, Mechanical, and Corrosion Properties of the As-Solutionized Mg-5Ga Alloy

The work uses the optical microscopy (OM), scanning electron microscopy (SEM), tensile testing, immersion testing, and electrochemical measurement to analyze the effects of the Zn addition (0, 0.3, 0.6, 0.9 and 1.2 mass%) on microstructure, mechanical, and corrosion performance of the as-solutionized Mg-5Ga alloy. The addition of Zn can bring about finer grain size, higher tensile strength, and bigger breaking elongation in the Mg-5Ga alloy. The as-solutionized Mg-5Ga-1.2Zn alloy shows optimal comprehensive mechanical performance with the ultimate tensile strength of 260 ± 2.4MPa and ultra-high plasticity (the breaking elongation of 40.3 ± 0.3%). Grain refinement and solution strengthening are mainly conducive to the improvement in strength. Moreover, adding Zn element enhances anticorrosion property of the as-solutionized Mg-5Ga alloy, wherein the as-solutionized Mg-5Ga-0.9Zn alloy has the optimal anticorrosion property in 3.5% NaCl solution, in close relation with finer grain size and more protective corrosion film.

Role of Ca2+ in the CO2 corrosion behavior and film characteristics of N80 steel and electroless Ni–P coating at high temperature and high pressure

The effects of Ca2+ on the CO2 corrosion behavior and film characteristics of N80 carbon steel and electroless Ni–P coating at high temperature and high pressure were investigated by immersion tests, in-situ electrochemical measurements, surface characterization techniques and water chemistry analysis. The results demonstrate that the corrosion of N80 steel is significantly influenced by Ca2+ concentration, however Ni–P coating exhibits exceptional corrosion resistance regardless of Ca2+ concentration. The microstructure and compactness of FeCO3 corrosion film is altered with the increased incorporation of Ca2+, thereby affecting the electrolyte penetration and the corrosion rate consequently. The added Ca2+ also impacts the water chemistry of the aqueous phase, postponing the FeCO3 precipitation. Meanwhile, the superb corrosion resistance of Ni–P coating is owing to the protection of the formed NiO/Ni(OH)2 film and the absence of scale formation.

Correlation between Corrosion Films and Corrosion-Related Defects Formed on 316 Stainless Steel at High Temperatures in Pressurized Water

The correlation between corrosion films and corrosion-related defects formed on 316 austenitic stainless steel exposed to 300 °C/10 MPa water for 50 h, 100 h, 200 h and 500 h was characterized by x-ray absorption spectroscopy, grazing incidence x-ray diffraction, scanning electron microscopy/energy-dispersive x-ray spectroscopy and positron annihilation spectroscopy. The corrosion results showed that the oxide films formed were composed of hematite (Fe2O3/Cr2O3) and spinel (FeCr2O4). At the initial corrosion stage, the deposition of these oxide films was accompanied by the formation of abundant corrosion-related defects. As the corrosion duration increased, the formation of more spinel in the oxide films led to a decrease in the density of corrosion-related defects.

Influence of microstructure on the corrosion behavior of super 13Cr martensitic stainless steel under heat treatment

The effect of microstructure on the corrosion characteristics of super 13Cr martensitic stainless steel (S13Cr MSS) under heat treatment was investigated. The results revealed that the Ni enriched reversed austenite content in the tempered steel increased as the tempering temperature increased. No Mo-rich intermetallic compounds and reversed austenite were found in the quenched steel. The Mo-rich intermetallic compounds adversely affected the protective properties of the corrosion film because the Mo-depleted regions adjacent to the compounds had approximately 7 mV Volta potential lower than steel matrix, destroying the corrosion film stability. However, the reversed austenite benefitted on the corrosion film due to it inhibiting further corrosion of S13Cr MSS and enhancing the corrosion film stability. Accordingly, the quenched steel without Mo-rich intermetallic compounds had the highest corrosion resistance and the corrosion resistance of the tempered steel increased with an increasing tempering temperature.

Microporous micro-arc oxidation/bis-[3-triethoxysilylpropyl]tetrasulfide/graphene composite film with improved corrosion protection properties on aluminum alloy

Micro-arc oxidation, bis-[3-triethoxysilopropyl] tetrasulfide and reduced graphene oxide composite film was prepared on AA 6061 using a combination of micro-arc oxidation and self-assembly. The morphological、chemical characteristics、corrosion resistance and film formation mechanism of the composite film were studied. The results showed that a complete and dense composite film was formed on the surface of aluminum alloy, which may be due to the formation of Al–O–Si, Si–O–Si and Si–O–C chemical bonds on aluminum alloy by self-assembly doping technology. The composite film effectively prevented the corrosive medium from contacting the aluminum alloy, thus protecting the aluminum alloy substrate.