Corrosion Resistance Of Cr Research Articles

Microstructure and properties of AlCrxFeNi1.2Cu0.8 high-entropy alloys at high temperature

With the development of space technology, high-temperature resistant materials have become one of the hot spots in space research. The research of new high-temperature materials has become the key to breakthrough in aviation field. Research on microstructure and properties of AlCrxFeNi1.2Cu0.8 high-entropy alloys at high temperature (900, 1000 and 1100°C) were studied in this paper. After high-temperature annealing, the structural stability of alloys is maintained and the microstructure of alloys is dendrite. The grains are refined with the increase of Cr content. The alloy exhibits excellent comprehensive mechanical properties after heat treatment. The compressive strength of the alloy is above 1000 MPa and the plasticity of the alloy is above 10%. The alloy changes from brittle to tough with the increase in temperature. The hardness of Cr1.25 specimen is doubled after annealing, and the corrosion resistance of Cr 0.5 specimen is the best.

Improvement in Corrosion Resistance and Interfacial Contact Resistance Properties of 316L Stainless Steel by Coating with Cr, Ti Co-Doped Amorphous Carbon Films in the Environment of the PEMFCs.

In order to obtain films with high corrosion resistance and excellent interfacial contact resistance (ICR) on 316L stainless steel used for bipolar plates in proton-exchange membrane fuel cells (PEMFCs), Cr, Ti co-doped amorphous carbon films were prepared on 316L stainless steel. The preparation method for the coating was magnetron sputtering. The doping amount of the Ti element was controlled by a Cr target and a Ti target current. The change in the structure and properties of the coating after the change from Cr single-element doping to Cr and Ti co-doping was studied. The change rule of the structure and properties of the coating from Cr single-element doping to Cr and Ti co-doping was studied. An increase in the Ti content led to a decreased grain boundary, a flatter surface, and a higher sp2-hybridized carbon content. TiC and CrC nanocrystals were formed in the amorphous carbon structure together. The amorphous carbon films doped with Cr and Ti simultaneously achieved a low ICR and high corrosion resistance compared with single-Cr-doped amorphous carbon. The enhanced corrosion resistance was attributed to the decreasing grain boundary, the formation of the TiC crystal structure, and the smaller grain size. The best performance was obtained at a Ti target current of 2A. Compared with bare 316L stainless steel, the corrosion resistance of Cr, Ti co-doped amorphous carbon (Icorr = 5.7 × 10-8 A/cm2, Ti-2 sample) was greatly improved. Because Ti doping increased the content of sp2-hybridized carbon in the coating, the contact resistance of the coating decreased. Moreover, the interfacial contact resistance was 3.1 mΩ·cm2 in the Ti-2 sample, much lower than that of bare 316L stainless steel. After the potentiostatic polarization test, the coating still had excellent conductivity.

Corrosion resistance of Cr(III) passivated zinc electrodeposits

Corrosion resistance of Cr(III) passivated zinc electrodeposits

Fundamental understanding on the microstructure and corrosion resistance of Cr-(Cr, Al)2O3 composite coatings in-situ synthetized by reactive plasma spraying

Three composite coatings were prepared with Al-Cr2O3-Al2O3 composite powders feedstocks by in-situ reactive plasma spraying, and the microstructures and corrosion resistances were studied. The results show that the CAC-1 coating is the hypoeutectic microstructure consisting of large-size Cr particles and the eutectic structure, the CAC-2 coating presents a typical eutectic microstructure [nano-Cr + (Cr, Al)2O3], and the CAC-3 coating is the hypereutectic microstructure which is composed of (Cr, Al)2O3 solid solution and eutectic structure. The corrosion resistance of the coating is closely related to the microstructure and defects of the coating. The surface of the nano-Cr particles in the CAC-2 coating can form a stable Cr(OH)3 film, which hinders the further contact with the electrolyte, thereby improving the corrosion resistance of the coating itself. In addition, the uniform and dense microstructure also leads to the least coating defects, further improving the corrosion resistance of the coating. While the surface product film of large-size Cr particles in the CAC-1 coating cannot exist stably, causing the Cr to continue to dissolve until it peels off. The coating itself has the highest porosity, so the coating has the worst corrosion resistance. The CAC-3 coating mainly exhibits the characteristics of ceramic coating due to the limited eutectic structure contained. Due to the unevenness of the microstructure, the coating has more defects, resulting in lower corrosion resistance than the CAC-2 coating.

Corrosion Resistance of Cr–Co Alloys Subjected to Porcelain Firing Heat Treatment—In Vitro Study

The procedure of ceramics fusion to cobalt–chromium (Co–Cr) base dental crowns affects their corrosion behavior and biological tolerance. This study’s purpose was to comparatively evaluate the effect of heat treatment (HT) applicable for dental ceramics firing on the corrosion properties among Co–Cr base alloys fabricated via different methods: casting (CST), milling soft metal and post sintering (MSM), and selective laser melting (SLM). All specimens were subjected to a heat treatment corresponding to a full firing schedule. The microstructure and elemental composition of oxidized surfaces were investigated by scanning electron microscopy and energy dispersive spectroscopy. Corrosion properties were examined by electrochemical potentiodynamic polarization tests. The values of jcorr, Ecorr, Rp, and breakdown potential Ebr were estimated. The oxide layers formed during the HT process corresponded to the composition of the original alloys’ structure. Among the thermal treated alloys, SLM showed the highest corrosion resistance, followed by the MSM and CST. This may be attributed to uniform distribution of alloying elements in homogenous structure and to the reduced porosity, which enhances corrosion resistance and decreases the risk of crevice corrosion. The overall corrosion behavior was strongly influenced by the segregation of alloying elements in the microstructure, thus, is directly determined by the manufacturing method.

Oxidation Behavior of an Austenitic Steel (Fe, Cr and Ni), the 310 H, in a Deaerated Supercritical Water Static System

The aim of this work was to study the corrosion behavior of a Fe-Cr-Ni alloy (310 H stainless steel) in water at a supercritical temperature of 550 °C and a pressure of 250 atm for up to 2160 h. At supercritical temperature, water is a highly aggressive environment, and the corrosion of structural materials used in a supercritical water-cooled nuclear reactor (SCWR) is a critical problem. Selecting proper candidate materials is one key issue for the development of SCWRs. After exposure to deaerated supercritical water, the oxides formed on the 310 H SS surface were characterized using a gravimetric analysis, a metallographic analysis, and electrochemical methods. Gravimetric analysis showed that, due to oxidation, all the tested samples gained weight, and oxidation of 310H stainless steel at 550 °C follows parabolic rate, indicating that it is driven by a diffusion process. The data obtained by microscopic metallography concord with those obtained by gravimetric analysis and show that the oxides layer has a growing tendency in time. At the same time, the results obtained by electrochemical impedance spectroscopy (EIS) measurements indicate the best corrosion resistance of Cr, and (Fe, Mn) Cr2O4 oxides developed on the samples surface after 2160 h of oxidation. Based on the results obtained, a strong correlation between gravimetric analysis, metallographic analysis, and electrochemical methods was found.

Effects of mass ratios on salt spray corrosion and electrochemical corrosion behaviors of laser cladded Cr–Ni coatings

Purpose The purpose of this paper is to improve the salt spray corrosion and electrochemical corrosion performances of H13 hot work mould steel, Cr–Ni coatings with the different Cr and Ni mass ratios are fabricated using a laser cladding (LC), which provides an experimental basis for the surface modification treatment of H13 steel. Design/methodology/approach Cr–Ni coatings with the different Cr and Ni mass ratios were firstly fabricated on H13 hot work mould steel using a laser cladding (LC). The salt spray corrosion (SSC) and electrochemical corrosion performances of Cr–Ni coatings in 3.5 Wt.% NaCl solution were investigated to analyze the corrosion mechanism, and the effect of mass ratios of Cr and Ni on their corrosion mechanism was discussed. Findings The laser cladded Cr–Ni coatings with the different Cr and Ni mass ratios are composed of Cr–Ni compounds, which are metallurgically combined with the substrate. The SSC resistance of Cr–Ni coating with the Cr and Ni mass ratios of 24:76 is the highest. The electrochemical corrosion resistance of Cr–Ni coating with the Cr and Ni mass ratio of 24:76 is the best among the three kinds of coatings. Originality/value In this study, the corrosion resistance of laser cladded Cr–Ni coatings with the Cr and Ni mass ratios of 17: 83, 20: 80 and 24: 76 was first evaluated using salt spray corrosion (SSC) and electrochemical tests, and the effect of mass ratios of Cr and Ni on their corrosion mechanism was discussed.

Microstructure evolution, wear and corrosion resistance of Cr[sbnd]C nanocomposite coatings in seawater

CrC nanocomposite coatings were deposited by multi-arc ion plating with various argon/acetylene mixtures. The XRD, XPS and HRTEM characterization suggest that the coatings consist of a carbide phase and an amorphous carbon-rich phase. The carbide phase is shown to be CrC with a fcc NaCl (B1) structure. Experiment findings and theoretical calculations reveal phase segregation of sp2-carbon from carbides in which the excess amounts of carbon are incorporated. Nanoindentation, scratch test and Rockwell indentation were performed to investigate the toughness and adhesion ability. A significant improvement of adhesion and toughness is achieved by increasing C content at the expense of hardness. The wear resistance of CrC coatings is controlled by the friction rather than hardness. Compared to dry friction, lower friction coefficients but higher wear rates were obtained under seawater condition. The corrosion behavior of CrC nanocomposite coatings with different C % was determined by potentiodynamic polarization test and electrochemical impedance spectroscopy (EIS). The coatings with higher Cr content display excellent anti-corrosion properties in seawater.

Corrosion resistance of Cr–C–W alloys produced by electrodeposition

Cr–C–W coatings were deposited from organo-aqueous solutions containing dimethylformamide by electrolysis. The obtained deposits were studied by the modern physical methods: X-ray photoelectron spectroscopy (XPS), X-ray diffraction (XRD), time-of-flight secondary ion mass spectrometry (SIMS), and inductively coupled plasma atomic emission spectroscopy (ICP-AES). The corrosion of Cr–C–W electrolytic deposits was studied in the solutions of sulfuric acid, sodium chloride, and hydrochloric acid. Cr–C–W coatings demonstrated higher corrosion resistance compared with chromium deposits. It was suggested that the decrease of the corrosion rate is caused by the formation of the thin layer enriched with tungsten and its oxides at the surface of the Cr–C–W alloy. This assumption was confirmed by both XPS and SIMS.

The Study about Property of Corrosion Resistance of AlCoCrTiNiCu_x High-Entropy Alloys

The paper had studied the property of corrosion resistance of AlCoCrTiNiCu_x high-entropy alloys by using the way of loss-weight. The results found that the function of corrosion resistance of Cr, Ni, and Ti is very good and the property of corrosion resistance of AlCoCrTiNiCu_x high-entropy alloys is reduced with increasing the content percentage of Cu, but the content percentage of chemical compounds on metal is increased.

The effect of chromic sulfate concentration and immersion time on the structures and anticorrosive performance of the Cr(III) conversion coatings on aluminum alloys

The main purpose of this study is to develop trivalent chromium, Cr(III), conversion coatings on aluminum alloys. The influence of Cr(III) concentration and immersion time on structures and anticorrosive performance of the coatings has been investigated. Corrosion behaviors of the coatings were evaluated in a 0.5 M H 2SO 4 aqueous solution at room temperature using potentiodynamic polarization. The structure and valence state of the coatings were examined by scanning electron microscopy (SEM), transmission electron microscopy (TEM), and X-ray photoelectron spectroscopy (XPS). The addition of Cr(III) ions to the conversion bath considerably changes structures and compositions of the coatings. The coatings with Cr oxides possess a denser and thinner structure. Moreover, the corrosion resistance of Cr(III) coatings tends to decline with increasing immersion time due to the dissolution of coatings in the dipping period. According to XPS analysis, the Cr(III) conversion coatings are composed of Cr 2O 3, Cr(OH) 3, Al 2O 3, Al(OH) 3, ZrO 2, Zr(OH) 4, AlF 3, and ZrF 4, but no hexavalent chromium component in the coatings. The result indicates that the coatings prepared in the solution with 0.01 M Cr(III) for 5 min have the smoothest and densest structure and the best anticorrosive performance among all of conversion coatings in this work.

Morphology and corrosion resistance of Cr(III)-based conversion treatments for electrogalvanized steel

The effectiveness of Cr(VI)-based passivation treatments is well accepted but there are many problems with regard to their environmental suitability. Because these compounds are carcinogenic and toxic, eco-friendly systems capable of replacing them are being evaluated. In this work, the corrosion behavior in 0.5 M NaCl solution of zinc coatings deposited from a free-cyanide alkaline bath and treated with Cr3+ based passivation coatings were characterized through DC and EIS techniques. The salt spray test as well as studies of the surface structure and chemical composition were also performed. From these analyses it was inferred that (1) the green-colored Cr3+ passivated coatings provide better corrosion resistance than the yellow- and blue-colored coatings, and (2) together with an adequate painting system, they could be a less polluting and less toxic alternative to traditional chromate coatings.

Corrosion resistance of Cr(III) conversion treatments applied on electrogalvanised steel and subjected to chloride containing media

The corrosion resistance of pure zinc coatings can be improved through the application of suitable chemical passivation treatments. Hexavalent chromium compounds have widely been used to formulate conversion layers providing better anticorrosive protection as well as anchorage properties to painting systems. However, taking into account that they are produced using hazardous chemical compounds, the development of alternative and “green” technologies with equivalent protective performance is a paramount purpose of many R&D laboratories working around the world. In the present paper, the corrosion behavior of zinc coatings obtained from free-cyanide alkaline baths and later subjected to a Cr 3+ based passivation treatment, with and without a sealing treatment, was studied. The experimental work involved electrochemical impedance spectroscopy measurements in 0.5 M NaCl solution, surface microstructural and morphological characterization by electronic microscopy as well as chemical analysis by EDXS. The salt spray test was also performed. The analysis and interpretation of all the data coming from this battery of tests allowed inferring that both the Cr 3+ based conversion treatment + adequate sealer presented a good corrosion resistance and, therefore, they could be used as neither a polluting nor toxic alternative to the traditional chromate coatings.

Influence of SiC + WC addition to Cr(VI) bath on corrosion behaviour of coatings in sulphate solution

Cr–WC–SiC coatings were deposited from Cr(VI) baths containing a mixture of both WC and SiC particles in the ratio of 1 : 1. X-ray photoelectron spectroscopy data indicated relatively low percentages of both WC (about 2˙68–2˙85 at.-% of W4f) and SiC (0˙16–0˙45 at.-% of Si2p) particles in the top layers of the Cr–WC–SiC coatings. However, these particles have some effect on the morphology and corrosion properties of the Cr coating. Protective properties of the coatings obtained were studied at different exposure times of samples in sulphate solution (pH=2˙8), using the electrochemical impedance spectroscopy method (EIS). Equivalent circuits, based on the electrophysical model describing the electrochemical corrosion at the coated surface, were proposed. The simulation of EIS data with the proposed equivalent circuit models made it possible to reveal the details of the corrosion processes occurring at coated systems (steel/Cr–WC–SiC coatings) immersed in the sulphate solution. Based on EIS data, diffusion in the coating was found to be a significantly controlling factor in the corrosion process for the system under investigation. The electrochemical impedance spectroscopy tests indicated a better corrosion resistance of Cr–WC–SiC coating than that of Cr. Analysis of the EIS data suggests that the enhanced corrosion resistance of Cr–WC–SiC coating was due to the microstructural features of these coatings, presumably containing smaller pores than Cr coating.

Corrosion behaviors of Cr(N,O)/CrN multi-layered coatings by cathodic arc deposition

Cr(N,O)/CrN based coatings were produced in the form of double-layered and four-layered structures, by the cathodic arc deposition process. These coatings were deposited onto tool steel substrates. The phase structure and morphology of coatings were observed by utilizing XRD, XPS and SEM. The corrosion behavior of these coatings was investigated using polarization tests, carried out in the solution of 1 M H 2SO 4 solution. The SEM surface topography showed a smoother surface of the four-layered Cr(N,O)/CrN coating compared to that of CrN and Cr(N,O)/CrN double-layered coatings. The corrosion resistance of Cr(N,O)/CrN four-layered coatings with thinner thickness was better than that of CrN single-layered and Cr(N,O)/CrN double-layered coatings, since pinholes in the coatings were effectively blocked by multi-layered structure.

Corrosion behaviour of Cr coatings deposited from Cr(III) formate-urea electrolytes

Chromium coatings were electrodeposited from trivalent chromium electrolytes with optimised additions of complexing agents to produce a good decorative appearance. The effect of hydrazine and hydroxylaminophosphate on the corrosion behaviour of Cr deposited from Cr(III) formate-urea electrolyte has been studied. The corrosion behaviour of the coatings was studied through the modelling of EIS spectra, recorded at different times of exposure to an acidic sulphate solution (pH 2·6), using various equivalent circuit models. The parameters obtained for circuit elements reflecting the corrosion behaviour of the samples at the solution/electrode interface were interpreted and correlated with the microstructure of coatings. The data obtained suggest the presence of open pores in the coatings from the onset of immersion. The samples plated in the basic formate-urea bath showed the highest corrosion rate, while the samples plated in the formate-urea bath containing hydrazine showed the lowest one. The enhanced corrosion resistance of Cr coating deposited in the presence of hydrazine may result from the change in microstructure, namely the size and number of pores (i.e. the porosity).

Corrosion behaviors of Cr(N,O)/CrN double-layered coatings by cathodic arc deposition

In this study, the Cr(N,O)/CrN double-layered coatings on tool steel were deposited using cathodic arc deposition process. CrN layer was first deposited on tool steel as an interlayer to ensure better adhesion. Then Cr(N,O) was deposited as a surface layer. The Cr(N,O) composition was varied by changing the O 2/N 2 flow ratios during the coating process. The phase structure, chemical composition, and morphology of coatings were observed by utilizing X-ray diffractometer, Auger electron spectrometer and AFM. The corrosion behavior of coatings was investigated using polarization and immersion tests. Polarization test of coatings was carried out in the solution of 3.5 wt.% NaCl. For immersion test, Cr(N,O)/CrN double-layered coatings were exposed under H 2SO 4 environment for 26 h. The results showed that the corrosion resistance of Cr(N,O)/CrN double-layered coatings with thinner thickness with thinner thickness was better than that of CrN single layer since pinholes of coatings was inhibited by double layer structure.

Study of corrosion resistance of chromium-nickel steel in calcium - hypochlorite solution. Part 1. Steels uranus b6

Corrosion resistance of Cr - Ni (special steels) specimen is tested by electrochemical methods, numerical method of linear polarization and polarization resistance method in calcium-hypochlorite (Ca(OCl)2) solutions. With increasing of Ca(OCl)2 concentration, pH value of the solution increases, as well as active chlorine concentration and corrosion activity of the medium. According to the quantitative method of the corrosion resistance determination it can be concluded that the steels tested in 1 wt % Ca(OCl)2 solution are resistant, in 10 wt % solution constant, and in 50 wt % suspension less resistant. URANUS B6 showed the best corrosion resistance of all tested chromium - nickel steels in all tested corrosion mediums.

貴金属（Pd, Ru）添加クロム基合金の硫酸中における腐食

Cr exhibited much better corrosion resistance to H2SO4 and HCl than those of Fe-Cr alloys and Ti at low temperature and low concentration. Because a wide passive potential range with a low passive current was observed for Cr in H2SO4 and HCl solutions. However Cr was severely corroded in high temperature or concentrated conditions. The corrosion resistance of Cr was improved by adding noble metals such as Pd and Ru.The corrosion behavior of Cr-Pd and Cr-Ru alloys in H2SO4 solutions was investigated by measurement of the polarization curves, the change in corrosion potential with time and the average corrosion rate. And then, surface filmes of Cr-based alloys immersed in H2SO4 have been studied by means of AES and ESCA.The corrosion resistance of Cr-based alloys in H2SO4 was improved by adding noble metals such as Pd and Ru. The addition of Pd and Ru to Cr increased the cathodic current, and decreased the anodic dissolution current in the active state. Accordingly the corrosion potential of the alloys shifted to the noble direction and the alloys were easily passivated. And the addition of Ru is more effective than that of Pd at a high temperature up to 400 K.The composition of the surface films formed on Cr-Ru and Cr-Pd immersed in H2SO4 were Cr oxide such as Cr2O3. Ru and Pd were concentrated in these films. SO2−4 existed in the surface oxide films. Pd in the surface oxide films exist in the form of Pd0, and Ru in the form of Ru2+. The effect of the Pd addition on the corrosion behaviour of Cr is caused mainly by cathodic depolarization, while the effect of the Ru addition is caused by cathodic depolarization and improvement of the passive films on Cr.

Structure and properties of cold-worked stainless steels

1. Cold plastic deformation by 15–30% increases the strength of Cr−Mn and Cr−Ni steels by 25–30%. The strength of the Cr−Mn steels after deformation is 50% higher than that of Cr−Ni steel. 2. Cold plastic deformation (up to 20% for Cr−Mn steel and up to 17% for steel Kh18N10T) increases the time to cracking, while larger deformation reduces the resistance of the steels to corrosion cracking in boiling 42% MgCl2. The time to cracking of Cr−Mn steel after deformation and passivation is two to three times higher than that of steel Kh18N10T. 3. The resistance to corrosion cracking is highest for the steel with an evenly distributed three-dimensional dislocation network. This structure occurs in steel Kh18N10T after 12–17% deformation, and in Cr−Mn steel after 17–22% deformation. 4. The good mechanical and technological properties, low cost, and high corrosion resistance of Cr−Mn steel can be utilized for heavy-duty fasteners and threaded connectors and other parts operating in corrosive media with chloride ions as a replacement for Cr−Ni steels of the 18/10 type.