Influence of potential on the structure and properties of microarc oxidation coating on Mg alloy

2008 ◽  
Vol 55 (5) ◽  
pp. 264-269 ◽  
Author(s):  
Deng Shu‐hao ◽  
Yi Dan‐qing ◽  
Gong Zhu‐qing ◽  
Su Yu‐chang
Keyword(s):  
Corrosion Resistance ◽  
Microarc Oxidation ◽  
Oxidation Potential ◽  
Structure And Properties ◽  
Micro Hardness ◽  
External Layer ◽  
X Ray Diffraction ◽  
Content Type ◽  
Constant Potential ◽  
Composition Structure

PurposeTo obtain an optimized microarc oxidation (MAO) coating on magnesium alloy from an environmentally‐friendly electrolyte free of Cr6 +  and PO43− and to investigate the influence of oxidation potential on the morphology, composition, structure, and other properties such as micro‐hardness and corrosion resistance.Design/methodology/approachA constant potential regime was applied to produce the coatings and scanning electron microscopy, energy dispersive spectroscope, X‐ray diffraction, hardness testing and electrochemical methods were used to study coating properties.FindingsThe results clearly show that oxidation potential plays an important role in the formation of coating structure and properties. The MAO coating is smooth and white and consists of two layers. The external layer is loose and porous and enriched in Al and Si. Moreover, the content of Al and Si increase with operated potential. The inner layer is compact and the content of Al and Si are lower than are those of the external layer. The coating is composed of several phases: the main phase is MgAl2O4/MgO, and the minor phase is Al2O3/SiO2 when the potential is higher. The micro‐hardness of the coating obtained a maximum at a potential of 45 V, as does the corrosion resistance.Originality/valueThis paper provides information relating to MAO technology and the morphology, structure and properties of MAO coatings.

Appraisal on corrosion performances of CrNi, TiAlN/CrNi and CrNi–Al2O3–TiO2 coatings on H13 hot work mold

2020 ◽  
Vol 67 (2) ◽  
pp. 150-157
Author(s):  
Kong Dejun ◽  
Li Jiahong
Keyword(s):  
Corrosion Resistance ◽  
Salt Spray ◽  
Test Chamber ◽  
Electrochemical Corrosion ◽  
Optical Microscope ◽  
Electrochemical Performances ◽  
X Ray Diffraction ◽  
H13 Steel ◽  
Content Type ◽  
Electrochemical Corrosion Resistance

Purpose The purpose of this paper is to evaluate the salt spray corrosion (SSC) and electrochemical corrosion performances of CrNi, TiAlN/NiCr and CrNi–Al2O3–TiO2 coatings on H13 steel, which improved the corrosion resistance of H13 hot work mold. Design/methodology/approach CrNi, TiAlN/NiCr and CrNi–Al2O3–TiO2 coatings were fabricated on H13 hot work mold steel using a laser cladding and cathodic arc ion plating. The SSC and electrochemical performances of obtained coatings were investigated using a corrosion test chamber and electrochemical workstation, respectively. The corrosion morphologies, microstructure and phases were analyzed using an electron scanning microscope, optical microscope and X-ray diffraction, respectively, and the mechanisms of corrosion resistance were also discussed. Findings The CrNi coating is penetrated by corrosion media, producing the oxide of Fe3O4 on the coating surface; and the TiAlN coating is corroded to enter into the CrNi coating, forming the oxides of TiO and NiO, the mechanism is pitting corrosion, whereas the CrNi–Al2O3–TiO2 coating is not penetrated, with no oxides, showing the highest SSC resistance among the three kinds of coatings. The corrosion potential of CrNi coating, TiAlN/CrNi and CrNi–Al2O3–TiO2 coatings was –0.444, –0.481 and –0.334 V, respectively, and the corresponding polarization resistances were 3,074, 2,425 and 86,648 cm2, respectively. The electrochemical corrosion resistance of CrNi–Al2O3–TiO2 coating is the highest, which is enhanced by the additions of Al2O3 and TiO2. Originality/value The CrNi, TiAlN/CrNi and CrNi–Al2O3–TiO2 coatings on H13 hot work mold were firstly evaluated by the SSC and electrochemical performances.

Electrochemical behavior and corrosion resistance of electrodeposited nano-particles Zn-Co-Fe alloy

2015 ◽  
Vol 63 (1) ◽  
pp. 29-35 ◽  
Author(s):  
Mortaga Abou-Krisha ◽  
Fawzi Assaf ◽  
Omar Alduaij ◽  
Abdulrahman G Alshammari ◽  
Fatma El-Sheref
Keyword(s):  
Corrosion Resistance ◽  
Ternary Alloy ◽  
Binary Alloys ◽  
Linear Sweep Voltammetry ◽  
Nano Particles ◽  
X Ray Diffraction ◽  
Surface Appearance ◽  
Content Type ◽  
X Ray ◽  
Anticorrosion Properties

Purpose – The purpose of this study was to compare the electrodeposition behavior and corrosion resistance of ternary and binary alloys. Design/methodology/approach – Potentiodynamic polarization resistance measurement and anodic linear sweep voltammetry techniques were used for the corrosion study. The surface morphology and chemical composition of the deposits were examined using scanning electron microscopy and atomic absorption spectroscopy, respectively. The phase structure was characterized by X-ray diffraction analysis. Electrodeposition behavior was carried out using cyclic voltammetry and galvanostatic techniques. Findings – It was found that the obtained ternary alloy exhibited better corrosion resistance and a more-preferred surface appearance compared to the binary alloys that were electrodeposited under similar conditions. Research limitations/implications – The ternary alloy showed better anticorrosion properties compared to binary deposits that were electroplated successfully from the plating baths. The Zn-Co-Fe alloy could be used advantageously in industry because the ternary alloy exhibits the collective properties of the binary alloys in one alloy via the electrodeposition of Zn-Ni-Co alloy. Social implications – Increasing the corrosion resistance implies to social economic increases. Originality/value – To date, the electrodeposition of Zn-Co-Fe alloy was studied in only a small number of articles. It was found that the presence of Co or Fe could provide a useful coating on the steel that would reduce its susceptibility to corrosion attack.

Effect of MgO on the Composition, Structure and Properties of Alite-Calcium Strontium Sulphoaluminate Cement

2010 ◽  
Vol 168-170 ◽  
pp. 472-477
Author(s):  
Chao Nan Yin ◽  
Ling Chao Lu ◽  
Shou De Wang ◽  
Ya Ming Chen
Keyword(s):  
Mass Fraction ◽  
Cement Clinker ◽  
Structure And Properties ◽  
X Ray Diffraction ◽  
Cement Production ◽  
X Ray ◽  
Sulphoaluminate Cement ◽  
Suitable Amount ◽  
Early Strength ◽  
Composition Structure

The influence of MgO on the composition, structure and properties of alite-calcium strontium sulphoaluminate cement were investigated by means of X-ray diffraction, SEM–EDS and light analysis. The results show that when the mass fraction of MgO is 1~5%, the early strength of cement can be enhanced significantly. The optimal content of MgO in the cement clinker is 2% and the compressive strengths of the cement at 3, 28 d are 64.3, 103.6 MPa respectively. A suitable amount of MgO can promote the formation of C1.5Sr2.5A3 , while the formation of C1.5Sr2.5A3 can be hindered if the content of MgO is excessive. The existence of MgO can improve the formation of C3S, increasing the mechanical property of the cement. Compared with the Portland cement, alite-calcium strontium sulphoaluminate cement has a higher capacity to dissolve MgO, which indicates that low-quality high-magnesium limestone can be efficiently used in the cement production.

Study On the Corrosion Resistance Properties of the Ceramic Coating Obtained Through Microarc Oxidation on the Aluminium Alloy Surface

2007 ◽  
Vol 353-358 ◽  
pp. 1733-1736 ◽  
Author(s):  
Fei Chen ◽  
Hai Zhou ◽  
Chen Chen ◽  
Fan Xiu Lu ◽  
Fan Xiu Lu
Keyword(s):  
Corrosion Resistance ◽  
Aluminium Alloy ◽  
Ceramic Coating ◽  
Microarc Oxidation ◽  
Electrochemical Corrosion ◽  
Nacl Solution ◽  
X Ray Diffraction ◽  
Micro Arc Oxidation ◽  
Coating Formation ◽  
Α Al2o3

Oxidation ceramic coating was directly synthesized on LY12 aluminium alloy by micro-arc oxidation (MAO) process in Na2SiO3 electrolyte solution with the Na2WO4-KOH-Na2EDTA addition. The corrosion resistance of the coating was tested using CS300P electrochemical corrosion workshop in 3.5% NaCl solution. Using the scanning electron microscopy (SEM) and X-ray diffraction (XRD), the cross-section microstructure, the surface morphology and the phase structure of the micro-arc oxidation ceramic coating were analyzed. The results showed that the corrosion resistance of the micro-arc oxidation ceramic coating in 3.5% NaCl solution was enhanced remarkably, the corrosion velocity was obviously slowed down. The thickness of micro-arc oxidation ceramic coating was about 11μm. The final phases in the coating were found to be α-Al2O3 and γ-Al2O3. The mechanism of the oxidation ceramic coating formation was investigated too.

scholarly journals Influence of Cu2+ Ions on the Corrosion Resistance of AZ31 Magnesium Alloy with Microarc Oxidation

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2647
Author(s):  
Madiha Ahmed ◽  
Yuming Qi ◽  
Longlong Zhang ◽  
Yanxia Yang ◽  
Asim Abas ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Photoelectron Spectroscopy ◽  
Microarc Oxidation ◽  
Mg Alloy ◽  
Cell Counting ◽  
Cytotoxicity Test ◽  
X Ray Diffraction ◽  
Corrosion Properties ◽  
X Ray ◽  
Az31 Mg Alloy

The objectives of this study were to reduce the corrosion rate and increase the cytocompatibility of AZ31 Mg alloy. Two coatings were considered. One coating contained MgO (MAO/AZ31). The other coating contained Cu2+ (Cu/MAO/AZ31), and it was produced on the AZ31 Mg alloy via microarc oxidation (MAO). Coating characterization was conducted using a set of methods, including scanning electron microscopy, energy-dispersive spectrometry, X-ray photoelectron spectroscopy, and X-ray diffraction. Corrosion properties were investigated through an electrochemical test, and a H2 evolution measurement. The AZ31 Mg alloy with the Cu2+-containing coating showed an improved and more stable corrosion resistance compared with the MgO-containing coating and AZ31 Mg alloy specimen. Cell morphology observation and cytotoxicity test via Cell Counting Kit-8 assay showed that the Cu2+-containing coating enhanced the proliferation of L-929 cells and did not induce a toxic effect, thus resulting in excellent cytocompatibility and biological activity. In summary, adding Cu ions to MAO coating improved the corrosion resistance and cytocompatibility of the coating.

Titanium fabricated by selective laser melting: microstructure, wear and corrosion behavior in different orientations

2021 ◽  
Vol ahead-of-print (ahead-of-print) ◽  
Author(s):  
Yabao Hu ◽  
Hanning Chen ◽  
Xiaodan Liang ◽  
Jianbo Lei
Keyword(s):  
Corrosion Resistance ◽  
Wear Mechanism ◽  
Mechanical Anisotropy ◽  
Corrosion Mechanism ◽  
Micro Hardness ◽  
Evolution Mechanism ◽  
Content Type ◽  
Influence Mechanism ◽  
Wear And Corrosion ◽  
Wear And Corrosion Resistance

Purpose Studies on titanium implants have shown that the mechanical properties of the parts are affected by the microstructure characteristic derived from the manufacturing process. The properties of different orientations of specimens under the same process parameters will be different, which should be considered in the application of bone implants. This paper aims to understand the influence of microstructure on micro-hardness, wear and corrosion resistance in different orientations. Design/methodology/approach The authors manufactured titanium parts and carried out micro-hardness, wear tests and electrochemical corrosion of different orientations under the same process conditions. Then, finally studied the evolution mechanism of the microstructure in different orientations and its influence mechanism on wear and corrosion mechanism. Findings The melting method makes the grains on the surface in XY orientation finer. The wear mechanism of XY orientation is abrasive wear, that of XZ and YZ orientations are adhesive wear. During corrosion, XY orientation forms a stable passivation film earlier. Compared with XZ and YZ orientations, XY orientation has higher micro-hardness, better wear and corrosion resistance. Originality/value In this paper, the microstructure, wear and corrosion resistance of selective laser melted parts were discussed and the differences in different orientations under the same experimental conditions were discussed. The evolution mechanism of the microstructure in different orientations and its influence mechanism on wear mechanism and corrosion mechanism was studied. The mechanical anisotropy of selective laser melted components was discussed.

An investigation of corrosion resistance of HVOF coated ASME SA213 T91 boiler steel in an actual boiler environment

2017 ◽  
Vol 64 (5) ◽  
pp. 499-507 ◽  
Author(s):  
Varinder Pal Singh Sidhu ◽  
Khushdeep Goyal ◽  
Rakesh Goyal
Keyword(s):  
Corrosion Resistance ◽  
Original Research ◽  
Ambient Conditions ◽  
X Ray Diffraction ◽  
Hvof Spraying ◽  
Boiler Steel ◽  
Content Type ◽  
Boiler Environment ◽  
Spraying Process ◽  
Minimum Resistance

Purpose This paper aims to use the high-velocity oxy fuel (HVOF) spraying process for depositing 93(WC–Cr3C2)–7Ni, 75Cr3C2–25NiCr, 83WC–17CO and 86WC–10CO–4Cr coatings on ASME SA213 T91 to study the corrosion resistance of these coatings in an actual boiler environment. Design/methodology/approach The HVOF spraying process was used for depositing 93(WC–Cr3C2)–7Ni, 75Cr3C2–25NiCr, 83WC–17CO and 86WC–10CO–4Cr coatings on ASME SA213 T91. All the coatings obtained are found to be uniform, dense and having thickness between 200 and 250 μm. All the coatings were exposed in an actual boiler environment at 900°C temperature for 10 cycles. Each cycle consisted of 100 h heating followed by 1 h cooling at ambient conditions. X-ray diffraction, scanning electron microscopy and energy-dispersive spectroscopy techniques were used to analyse corrosion products. Findings All the coated samples were found to be having higher corrosion resistance than the uncoated samples. Among coated specimens, 93(WC–Cr3C2)–7Ni coating has shown maximum and 75Cr3C2–25NiCr coating has shown minimum resistance to corrosion. Originality/value This paper is original research.

Structure and Properties of Microarc Oxidation Films on Zinc-Containing Aluminum Alloy

2007 ◽  
Vol 546-549 ◽  
pp. 1145-1148 ◽  
Author(s):  
Wen Bin Xue ◽  
Xiao Ling Wu ◽  
Jian Cheng Du ◽  
Xi Jin Li ◽  
Hua Tian
Keyword(s):  
Corrosion Resistance ◽  
Microarc Oxidation ◽  
X Ray Diffraction ◽  
Amorphous Sio2 ◽  
Oxidation Treatment ◽  
Cu Alloy ◽  
Wear And Corrosion ◽  
Protective Films ◽  
Composition Profiles ◽  
Α Al2o3

The wear and corrosion protective films were synthesized on the LC4 Al-Zn-Mg-Cu alloy by microarc oxidation (MAO) technique in an alkali-silicate electrolyte. The microstructure and composition profiles were investigated by scanning electron microscopy and energy dispersive spectroscopy, and the phase structure was performed by X-ray diffraction. The corrosion resistance of coated LC4 alloy was evaluated using potentiodynamic polarization curves. The MAO film consists of γ-Al2O3, α-Al2O3 and amorphous SiO2 phases. The film up to 210 μm contains two layers. The Si element from electrolyte enriched in the outer layer film. After microarc oxidation treatment, the microhardness and corrosion resistance of LC4 alloy were improved significantly.

The influence of hexamethylenetetramine on the structure and corrosion resistance of phosphate coating on AZ31 magnesium alloy

2016 ◽  
Vol 63 (3) ◽  
pp. 161-165 ◽  
Author(s):  
Jiansan Li ◽  
Yali Li ◽  
Yanqin Chen ◽  
Jiawei Sun ◽  
Chunxiao Wang ◽  
...  
Keyword(s):  
Corrosion Resistance ◽  
Magnesium Alloys ◽  
Design Methodology ◽  
Energy Dispersive Spectrometry ◽  
Electrochemical Impedance ◽  
Phosphate Coating ◽  
X Ray Diffraction ◽  
Content Type ◽  
X Ray ◽  
Phosphate Coatings

Purpose This paper aims to report the influence of hexamethylenetetramine (HMTA) on phosphate coatings formed on AZ31 magnesium alloys. Design/methodology/approach These phosphate coatings were obtained by immersing magnesium alloys in phosphate baths with HMTA. The morphology and composition of the phosphate coatings were investigated via scanning electron microscopy, energy dispersive spectrometry and X-ray diffraction. Findings The phosphate coatings were mainly composed of CaHPO4·2H2O. The HMTA concentration in the phosphate bath influenced the crystallization and corrosion resistance of the phosphate coating. Originality/value The polarization curve shows that the anti-corrosion qualities of the phosphate coating were optimal when the HMTA concentration was 1.0 g/L in the phosphate bath. Electrochemical impedance spectroscopy (EIS) shows that the electrochemical impedances increased gradually when the HMTA concentration varied from 1.0 to 3.0 g/L.

Effects of Hypophosphate Concentrations on the Characteristics of Micro-Arc Oxidation Coatings Formed on Biomedical NiTi Alloy

2011 ◽  
Vol 314-316 ◽  
pp. 240-244
Author(s):  
Ji Lin Xu ◽  
Jun Ming Luo ◽  
Fu Liu
Keyword(s):  
Surface Roughness ◽  
Corrosion Resistance ◽  
Bonding Strength ◽  
Niti Alloy ◽  
Microarc Oxidation ◽  
X Ray Diffraction ◽  
Micro Arc Oxidation ◽  
Surface Morphologies ◽  
Hank’S Solution ◽  
Better Than

Microarc oxidation coatings on biomedical NiTi alloy were prepared in aluminate electrolytes with and without hypophosphate addition. The effect of hypophosphate concentrations on the characteristics of micro-arc oxidation coatings has been studied. The compositions and surface morphologies of the coatings prepared in different hypophosphate concentrations were determined by energy dispersive spectroscopy (EDS), X-ray diffraction (XRD) and scanning electron microscopy (SEM). Surface roughness (Ra) and bonding strength of the coatings were measured by surface roughmeter and a direct pull-off test, respectively. The corrosion resistance of the coatings was evaluated in Hank’s solution using potentiodynamic polarization tests. The results show that all of the coatings exhibit a typical porous surface structure and mainly consist of γ-Al2O3 crystal phase. With increasing the hypophosphate concentrations, the elemental contents of Ni, Ti and P increase while Al decreases; the pore sizes and surface roughness of the coatings decrease firstly, reaching a minimum value at 0.01mol/L, and then increase; at the same time, the bonding strength increases up to 60MPa, and then decreases. The corrosion resistance of the coatings decreases with the increase of the hypophosphate concentrations, but all of the coated samples is better than that of the uncoated NiTi alloy.

Sign in / Sign up

Export Citation Format

Share Document