Al-based Coatings Research Articles

Effect of Spherical WC Content on the Microstructure and Properties of SiCp Aluminium Composite Material

In this paper, SiCp aluminium matrix composites were used as the matrix, and AlSi10Mg powder, which has a relatively similar coefficient of thermal expansion to that of the matrix, was used to prepare laser cladding Al-based coatings. The results show that the optimal process parameters are P = 4400 W, Vf = 11.3 g·min−1, and VS = 1800 mm·min−1, and, although the hardness of the coatings is lower than the hardness of the substrate, it reduces the generation of defects such as cracks and porosity. With the increase in WC reinforced phase and the hardness of the coatings, wear resistance increases, the granular cytocrysts are transformed into rod-like cytocrysts, and at the same time generate the dendritic crystals, and the undergo grain refining and generate the new phases such as Al4C3, Al4SiC4. There is no obvious defect in AlSi10Mg + 40%WC coatings, the macro morphology of the coatings is good, there is no spalling in the friction wear morphology, and the wear resistance is excellent, but there are obvious cracks and obvious spalling in the coatings of AlSi10Mg + 60%WC. Compared to the matrix hardness of 171.61 HV, the hardness of the 20%WC cladding layer increased by a factor of 1.06, while the hardness of the 40%WC cladding layer increased by a factor of 1.65 and that of the 60%WC cladding layer increased by a factor of 1.8. In terms of wear, compared to a substrate wear amount of 9.36 mg, the wear for the 20%WC cladding layer was reduced to 6.13 mg (34.5% less than the substrate), for the 40%WC cladding layer it was reduced to 4.58 mg (51.06% less than the substrate), and for the 60%WC cladding layer it was reduced to 7.35 mg (21.47% less than the substrate). The quality of the coatings decreases although the hardness is higher than that of AlSi10Mg + 40%WC. The comprehensive performance of AlSi10Mg + 40%WC coatings is optimal.

Research on Thermal Properties and High Temperature Exposure Behavior of Non-Skid Coating Fabricated by Twin Wire Arc Spraying

Conventional non-skid coatings for marine construction contain polymeric materials. These materials are generally susceptible to high temperature environments because of their low thermal conductivity and thermal resistance. A metal-based non-skid coating has great potential for high temperature applications, yet, there has only been limited research. In this study, twin wire arc spray (TWAS) was used to fabricate Al and Al-3%Ti coatings on a high strength low alloyed (HSLA) steel substrate. The purpose of this study is to confirm the feasibility of TWAS Al-based coating for non-skid areas on marine construction. The static coefficient friction of TWAS Al-based coatings exhibited excellent and uniform values compared with a conventional epoxy-based non-skid coating. The specific heat and thermal conductivity of TWAS Al-based coating was measured and compared with that of the substrate. The thermal property values of the TWAS Al-based coating were reported for the first time in this study. The TWAS Al-based coating had A continuous interface with the substrate and the general microstructural features of a thermal-sprayed metal coating. After exposure to 500℃ for 24 hours, the an Fe-Al intermetallic compound and oxide were formed inside of the coating and coating-substrate interface. The adhesion strength indicated that the TWAS Al-based coating sustained its strength after the isothermal exposure test. The Vickers hardness of the TWAS Al-3%Ti coating was higher than that of the Al coating. The solid solution hardening of Ti atoms in the as-deposited coating and the precipitation hardening of the TiAl3 compound in the heat-treated coating contributed to the improvement of in Vickers hardness. Thus, the TWAS Al-3%Ti coating is proven to be a promising nonskid coating for high temperature applications.

Study on the corrosion behavior of cold sprayed aluminum-based coatings on Mg-based alloy in chloride containing solution: Effect of N2 processing gas temperature

Cold sprayed (CS) commercially pure Al-based coatings (processed at various propellent N2 gas temperatures) were applied on Mg-based alloys. The porosity percentage of the CS coatings decreased, and the flattening ratio increased as the N2 processing gas temperature reduced due to the effect of the in-situ tamping densification. This also led to the obvious reduction of wear rate of the CS Al-based coatings. In the present research, among the Al coated Mg alloys having higher general corrosion resistance (i.e., higher |Z|f=0.01 Hz and polarization resistance at the corrosion potential (Rpol)), a decrease in dislocation density and microstrain was postulated to lead to the improvement of overall pitting behavior of the CS Al-based coating (processed at the lowest N2 propellent gas temperature) after 12 days immersion in 3.5 wt% NaCl solution.

Long-Term Corrosion Behavior of Flame Sprayed Al-Based Coatings After Nano-alumina Sealing Treatment

Long-Term Corrosion Behavior of Flame Sprayed Al-Based Coatings After Nano-alumina Sealing Treatment

Microstructure and Properties of Al-Based Ceramic Coating Deposited on Magnesium Alloy Surface by Cold Spraying

In this study, pure Al and Al-Al2O3 composite coatings with a low porosity and high density were prepared on magnesium alloys by cold spraying. The surface morphology, component, hardness, interfacial bonding, wear and corrosion properties were investigated. Additionally, the relationship between the interface structure and the protective coatings’ quality was preliminarily established. Pure Al powder was used to create a coating with a homogeneous and dense microstructure. The hard-phase Al2O3 in the composite coatings was non-oxidized and would reduce the porosity of the coatings to improve their density and interfacial bonding by up to 55.82 MPa. The bonding mode of the pure Al coatings is primarily mechanical, whereas the bonding mode of the Al-Al2O3 mixed coatings is mechanical and metallurgical. The tough Al2O3 particles combined to form a layer of work-hardening reinforcement that resisted wear and effectively prevented it from spreading. The three Al-based coatings had excellent corrosion properties, as evidenced by their corrosion current being several orders of magnitude lower than that of the magnesium alloy substrates. The thick coating was significantly more corrosion-resistant than the thin coating and provided greater protection to the substrate. This study offers theoretical and technological assistance for the surface protection of magnesium alloy equipment in demanding conditions.

Comparative Research on Corrosion Resistant Non-Skid Al and Al-3%Ti Coating Fabricated by Twin Wire arc Spraying

To ensure the lifetime of marine constructions and the safety of workers and pedestrians, corrosion protective non-skid coating is an effective solution. However, the conventional polymer-based coating has some limitations. In this study, newly-suggested Al and Al-3%Ti coatings were deposited on high strength low alloyed steel substrate using twin wire arc spraying (TWAS). The static and dynamic friction coefficients of the Al-based coatings under dry and wet conditions were measured using portable friction testers. To evaluate the corrosion behavior under sea water conditions, a cyclic potentiodynamic polarization test (CPDP) and salt solution immersion test (SSIT) were performed with a 3.5% NaCl solution. To confirm the coating degradation, mechanical properties (Vickers hardness and adhesion strength) were compared before and after SSIT. The results showed that the TWAS Al-based coatings were well fabricated on HSLA steel and had the general microstructure of a thermal spray. The coatings provided excellent corrosion protection for the steel substrate and greatly increased the friction coefficient of the surface. The Vickers hardness slightly increased and adhesion strength decreased after SSIT. The microstructure observation revealed that the TWAS coatings had a bimodal structure induced by non-uniform droplet generation at the TWAS tips. After SSIT, some oxides formed on the surface and porous regions of the coatings. This indicated that the TWAS coating successfully provided corrosion protection and non-skid properties.

Surface modification on AZ31B Mg alloy for improved corrosion resistance and hardness by thermal spray aluminium coating

The recently developed thermal spray technique was used to deposit different composition of totally dense aluminium-based (Al) coating on AZ31B magnesium (Mg) alloy. The microstructure, adhesive coating, and corrosion behaviour of the materials were all thoroughly examined. The Al-coated AZ31B alloy has enhanced surface morphology and mechanical characteristics. This exceptional corrosion resistance is due to its disordered structure, consistent material composition, and the creation of a uniform passive coating on the surface, which prevents chloride ions from invading and causing additional corrosion. The high defined corrosion tests also show that the Al-based coatings are not aqueous solution permeable for the certain period immersions, indicating that the AZ31B Mg alloy substrate was protected against corrosion for a long time. Furthermore, the differences in corrosion resistances of Al-based coating was detected and explained using their distinct microstructures created during the coating deposition process. The current thermal spray technique has a lot of potential for cost-efficient and effective magnesium alloy corrosion protection, and it gives industries greater freedom in designing and using magnesium alloy products.

Effect of Hg2+ on the corrosion behavior of Al-2%Zn coatings on AA5083 in 3.5 Wt.% NaCl solution

PurposeThis paper aims to study the effect of Hg2+ on the corrosion behavior of Al–2%Zn coatings on AA5083 in 3.5 Wt.% NaCl solution.Design/methodology/approachPotentiodynamic polarization and electrochemical impedance spectroscopy are used to investigate the effect of Hg2+ on the corrosion behavior. The surface and cross-sectional morphology are characterized by scanning electron microscopy and energy dispersive spectroscopy (EDS) to further reveal the corrosion mechanism of Hg2+.FindingsThe results show that the corrosion behavior of the coating changes significantly as the concentration of Hg2+ increases from 5 to 30 μg/L. The corrosion production film can inhibit the corrosion process when Hg2+ concentration is in the range of 0.5–5 μg/L, while Hg2+ can promote the corrosion process significantly when its concentration reaches to 30 μg/L. The generation rate of dense oxide film on the coating surface is faster than dissolution rate when the concentration of Hg2+ is in the range of 0–5 μg/L, which makes the coating “self-healing” and thus slightly slows down the corrosion rate. The EDS analysis shows that excessive Hg2+ are preferentially deposited at locations with inhomogeneous electrochemical properties, which in turn accelerates corrosion.Originality/valueThe corrosion resistance of Al-based coatings is significantly affected by Hg2+ in seawater. Thus, it is important to explain the corrosion mechanism of Al–2%Zn coatings under the combined effect of Hg2+ and Cl− in 3.5 Wt.% NaCl solution.

Effect of reinforcement particles on cold-sprayed Al-based coatings

ABSTRACT In this study, malleable and heavy Ta particles were introduced into soft Al powders to prepare Al-Ta composite coatings through a low-pressure cold-spray process; for comparison, Al-A2O3 composite coatings were also deposited. The surface and cross-sectional morphologies, deposition efficiency, microstructure, hardness and composition of the coatings were investigated. The results demonstrated that the Al-Ta coatings had roughness values that were almost twice as large as those of the Al-Al2O3 coatings for the same volumetric fraction of reinforcement particles used in the feedstock. Ta particles were more effective in improving the deposition efficiency and densification than were Al2O3 particles. The formation mechanism of the Al-Ta coatings was mainly attributed to the malleable and heavy nature of Ta particles, which allowed them to bond with the formed coating and impact the coating strongly through the peening effect.

Mitigating CO2 Corrosion of Natural Gas Steel Pipelines by Thermal Spray Aluminum Coatings

Internal pipeline corrosion due to carbon dioxide (CO2) is a major challenge facing the oil and gas industry. The objective of this study was to investigate the corrosion behavior of aluminum (Al)-based alloys as sacrificial coatings to protect pipelines in a CO2-saturated aqueous electrolyte (3.5 wt% NaCl) at 4 bar CO2 partial pressure (3 bar) and 40°C. The corrosion resistance of Al-based alloys and thermal spray coatings was evaluated in an electrochemical reaction autoclave using electrochemical methods (potentiodynamic polarization, linear polarization resistance, and electrochemical impedance spectroscopy). Post-corrosion surface characterization was performed by scanning electron microscopy equipped with energy-dispersive x-ray spectroscopy. The obtained data show Al-based alloys demonstrated promising protection against CO2 corrosion with no breakaway degradation issues.

Corrosion resistance and thermal stability of sputtered Fe44Al34Ti7N15 and Al61Ti11N28 thin films for prospective application in oil and gas industry

Fe-and Al-based thin-film metallic glass coatings (Fe44Al34Ti7N15 and Al61Ti11N28) were fabricated using magnetron co-sputtering technique, and their corrosion performances compared against wrought 316L stainless steel. The results of GI-XRD and XPS analyses demonstrated amorphous structure and oxide layer formation on the surface of the fabricated thin films, respectively. The potentiodynamic (PD) polarization test in chloride-thiosulfate (NH4Cl ​+ ​Na2S2O3) solution revealed lower corrosion current (Icorr) (0.42 ​± ​0.02 ​μA/cm2 and 0.086 ​± ​0.001 ​μA/cm2 Vs. 0.76 ​± ​0.05 ​μA/cm2), lower passivation current (Ipass) (1.45 ​± ​0.03 ​μA/cm2 and 1.83 ​± ​0.07 ​μA/cm2 Vs. 1.98 ​± ​0.04 ​μA/cm2), and approximately six-fold higher breakdown potential (Ebd) for Fe- and Al-based coatings than those of wrought 316L stainless steel. Electrochemical Impedance Spectroscopy (EIS) of both films showed 4- and 2-fold higher charge transfer resistance (Rct), 7- and 2.5-times higher film resistance (Rf), lower film capacitance values (Qf) (10 ​± ​2.4 ​μS-sacm-2, and 5.41 ​± ​0.8 ​μS-sacm-2 Vs. 18 ​± ​2.21 ​μS-sacm-2), and lower double-layer capacitance values (Qdl) (31.33 ​± ​4.74 ​μS-sacm-2, and 15.3 ​± ​0.48 ​μS-sacm-2 Vs. 43 ​± ​4.23 ​μS-sacm-2), indicating higher corrosion resistance of the thin films. Cyclic Voltammetry (CV) scan exhibited that the passive films formed on the Fe- and Al-based coatings were more stable and less prone to pitting corrosion than the wrought 316L stainless steel. The surface morphology of both films via SEM endorsed the CV scan results, showing better resistance to pitting corrosion. Furthermore, the thermal analysis via TGA and DSC revealed the excellent thermal stability of the thin films over a wide temperature range typically observed in oil-gas industries.

Preparation of Al-based amorphous coatings and their properties

Al86Ni8Co1La1Y2Gd2 amorphous coatings were prepared using cold gas kinetic spray technology. The results show that Al86Ni8Co1La1Y2Gd2 amorphous coatings are achieved with the porosity about 3.2%, thickness about 893 μm, the amount of amorphous phase about 82.5%, the hardness about 300HV0.2. The corrosion potential and anti-corrosion life of 7075 T6 alloy aluminum are about −0.78 V and 72 h, respectively. The electrochemical analysis and neutral salt spray are about −0.69 V corrosion potential and 274 h anti-corrosion life for amorphous Al-based coatings, respectively. Therefore, the life of the Al-based amorphous coatings is about 3.8 times that of 7075 T6 aluminum alloy. Besides, the failure mechanism was analyzed using TEM in this investigation. In a word, Al86Ni8Co1La1Y2Gd2 coatings keep dense structure, high amorphous content, favorable amorphous phase stabilizing ability and longer anti-corrosion life. That is, Al86Ni8Co1La1Y2Gd2 coatings have better comprehensive properties. Therefore, these findings indicate that the present Al86Ni8Co1La1Y2Gd2 amorphous coatings prepared using cold gas kinetic spray technique can protect aluminum alloy very well and they can be considered to be used in aviation field.

SiCp/Al5056 Composite Coatings Applied to A Magnesium Substrate by Cold Gas Dynamic Spray Method for Corrosion Protection

Corrosion protection using cold spraying is a promising method to address the shortcomings associated with classical techniques for protecting magnesium alloys from corrosion. In this study, SiCp/Al 5056 composite coatings were prepared on a magnesium substrate using cold spraying. The effects on the microstructure and corrosion properties after adding SiC were analysed. To evaluate the durability of the cold-sprayed Al-based coatings on Mg, galvanic corrosion, immersion and thermal cycling tests were conducted. The results show that cold-sprayed aluminium coatings serve as a reliable cathode for magnesium substrates. The addition of SiC particles increases the galvanic potential and decreases the galvanic reduction current of the coating/substrate couple. The SiCp/Al 5056 composite coatings show better corrosion resistance than that of the Al 5056 coating in extended immersion tests due to the densification of the coating under the peening effect of hard particles. Moreover, SiC particles with an average size of 15.6 µm show more improvement than with SiC particles having an average size of 72.8 µm. The cold-sprayed SiCp/Al 5056 composite coating also presents excellent properties in the thermal cycling tests. After applying failure mode parameters in the thermal cycling tests, the composite coating demonstrates good adhesion as cracking was located in the Mg substrate and not at the interface.

Mechanical and corrosion properties in 3.5% NaCl solution of cold sprayed Al-based coatings

The recent development of the cold spray method has made it possible to deposit dense coating with good adhesion and with almost no change in the microstructure, which is promising in repairing damaged Al-based aircraft skin. In this work, the in-situ shot-peening-assisted low-pressure cold spray method was used to deposit Al-based dense coatings with good mechanical and corrosion protection properties on AA 2024-T3 alloy. The detailed microstructure, coating adhesion, and corrosion protection performance were systematically investigated. A dense microstructure with low porosity (<1.7%), high cohesive strength (>45 MPa) is achieved for the coatings. By comparison, Al 5083 coating exhibited the optimum mechanical properties. The Al and Al 5083 coatings reveal similar pitting resistance and repassivation ability. During long-term immersion test (>480 h) the corrosion resistance of Al 5083 coating surpassed that of CP Al coating. In conclusion, Al 5083 coating has a good combination of mechanical and anti-corrosion properties.

Carrier-microencapsulation of arsenopyrite using Al-catecholate complex: nature of oxidation products, effects on anodic and cathodic reactions, and coating stability under simulated weathering conditions

Mining activities often generate large amounts of sulfide-rich wastes containing arsenopyrite (FeAsS), which when dissolved releases toxic arsenic (As) and generates acid mine drainage (AMD) that are both disastrous to the environment. To suppress arsenopyrite dissolution, a technique that selectively coats sulfide minerals with a protective layer of Al-oxyhydroxide called Al-based carrier-microencapsulation (CME) was developed. Although a previous study of the authors showed that Al-based CME could significantly limit arsenopyrite dissolution, nature of the coating formed on arsenopyrite, including its electrochemical properties, is still not well understood. Moreover, stability of the coating once exposed to weathering conditions remains unclear. Better understanding of these important issues would greatly improve Al-based CME especially in its application to real mine wastes. In this study, nature of the coating formed by Al-based CME was investigated using SEM-EDX, DRIFTS and XPS while the electrochemical properties of the coating were evaluated by cyclic voltammetry and chronoamperometry. Meanwhile, stability of the coating was elucidated using consecutive batch leaching experiments and weathering cell tests.SEM-EDX, DRIFTS and XPS results indicate that the protective coating formed on arsenopyrite by Al-based CME was mainly composed of bayerite (α-Al(OH)3), gibbsite (γ-Al(OH)3), and boehmite (γ-AlO(OH)). These Al-based coatings, which have insulating properties, made arsenopyrite less electrochemically active. The coatings also limited the extent of both the anodic and cathodic half-cell reactions of arsenopyrite oxidation that suppressed As release and acid generation. Weathering cell tests indicated that the oxidation of CME-treated arsenopyrite was effectively limited until about 15 days but after this, it started to gradually progress with time due to the increasing acidity of the system where Al-based coatings became unstable. Nonetheless, CME-treated arsenopyrite was less oxidized based on the released amounts of Fe, As and S suppressed by 80, 60 and 70%, respectively, compared with the one treated with control.

Preparation and characterization of aluminum-based coatings deposited by very low-pressure plasma spray

Aluminum-based coatings were manufactured by the very low-pressure plasma spray, using an F4-VB plasma torch under a working pressure of 150 Pa. The morphologies and phase compositions of the resultant coatings were investigated along the radial direction of the plasma jet, which was found that the Al-based coatings exhibited three different deposition states. At the center of the plasma jet, an Al-Fe coating was formed due to the diffusion of the substrate element, which had a packed columnar microstructure that deposited by the vapor and clusters. As the radial distance increases, a pure Al coating was obtained, with a lamellar binary microstructure that mainly formed by spread liquid droplets and plenty of vapor. At the outer edge of the plasma jet, another pure Al coating was achieved, possessed a typical layer microstructure consisted of semi-molten particles, molten particles, and a little vapor. Moreover, the microhardness of the deposits was measured, respectively. The hardness of Al-Fe coating reached 448.74 ± 23.7 HV0.025, while that of pure Al coating was only 46.37 ± 3.18 HV0.025. In order to better explain the difference in coating microstructures and properties along the radial direction, a spatial distribution model for the depositions based on the melting state of Al powders was established.

Effect of CeO2 on Impact Toughness and Corrosion Resistance of WC Reinforced Al-Based Coating by Laser Cladding.

WC reinforced Al-based coating with added CeO2 was prepared on the surface of S420 steel by laser cladding. The microstructure and structure of the coatings were analyzed by scanning electron microscope, X-ray diffractometer and optical profiler. The mechanical properties and corrosion properties of the coatings were studied by microhardness tester, friction and wear tester, Charpy impact tester, and electrochemical workstation. The results show that the coating is mainly composed of Al-phase, continuous-phase, and hard reinforced-phase WC, and the coating and substrate show good metallurgical bonding. When the content of CeO2 is 1%, the fine grain strengthening effect is obvious, and the impact toughness of the coating is obviously improved. Appropriate amount of rare earth CeO2 can significantly improve the hardness of the coating. When the content of CeO2 is more than 1%, the wear resistance of the coating decreases. The coating prepared with different CeO2 content has higher impedance and corrosion resistance than that of the substrate. At 1% CeO2 content, the coating has the best corrosion resistance.

Deposition of fully dense Al-based coatings via in-situ micro-forging assisted cold spray for excellent corrosion protection of AZ31B magnesium alloy

In this work, three types of fully dense aluminum-based (Al) coatings (pure Al, AA2219 and AA6061) were deposited on AZ31B magnesium (Mg) alloy by a recently developed in-situ micro-forging assisted cold spray process. The detailed microstructure, coating adhesion and corrosion protection performance were systematically investigated. Results show that the porosities of the pure Al, AA2219 and AA6061 coatings are as low as 0.34 ± 0.11%, 0.23 ± 0.09% and 0.24 ± 0.08%, respectively. Strong adhesion strength (83.6–91.5 MPa) was achieved for the Al-based coatings due to the in-situ micro-forging induced enhanced mechanical-interlocking between Al-based coating and the magnesium alloy substrate. The corrosion current density of the AZ31B Mg alloy decreases to 1.9–5.8 μA cm−2 from 312.8 μA cm−2 after coated with the Al-based coatings. The long-term corrosion tests further indicate that the Al-based coatings are not aqueous solution permeable during the entire 1000 h immersion, thus provided robust long-term corrosion protection of AZ31B Mg alloy substrate. Moreover, the difference in corrosion resistances among the three Al-based coatings was observed and was further explained based on their unique microstructures arising from the coating deposition process. The present in-situ micro-forging assisted cold spray process shows great potential for economical and effective corrosion protection of magnesium alloy and provides more freedom for industries to design and use magnesium alloy parts.

Structure of Al-based composite coatings prepared by thermal diffusion of the arc-ion plating Al coatings

In order to improve the high-temperature oxidation resistance of the hydrogen-resistant steel, Al coatings were firstly deposited on the hydrogen-resistant steel by arc-ion plating and then the thermal diffusion treatment was used to produce the Al-based composite coatings on the hydrogen-resistant steel. The effect of thermal diffusion parameters on the structure of Al-based composite coatings was studied. The crystal structure, composition and morphology of Al-based composite coatings were analyzed by using X-ray diffraction (XRD), energy-dispersive X-ray spectroscopy (EDS), X-ray photoelectron spectroscopy (XPS) and scanning electron microscope (SEM). The results showed that the double inner diffusion layer was formed on Al coatings treated at 700[Formula: see text]C. And the single inner diffusion layer with uniform composition distribution could be formed on Al coatings treated at 950[Formula: see text]C. The Al-based composite coating prepared by thermal diffusion treatment at 950[Formula: see text]C had a dense and thick [Formula: see text]-Al2O3 surface layer, and it exhibited good high-temperature oxidation resistance.

Protective Properties of Electrochemically Deposited Al-Based Coatings on Yb0.3Co4Sb12 Skutterudite

To protect CoSb3-based skutterudite thermoelectric materials from oxidation and to suppress the sublimation of antimony in long-time service, a series of surface coatings including Al, Al-Ni, Al-Ni-Al were deposited onto Yb0.3Co4Sb12 by using an electrochemical deposition method. The thermal aging behavior for the Yb0.3Co4Sb12 samples with and without different surface coatings were investigated by accelerated thermal aging tests at 873 K. Thermoelectric properties of Yb0.3Co4Sb12 with different coatings after aging are used as the evaluation criteria for coating effectiveness. After thermal aging at 873 K for 30 days, the thermoelectric properties of Yb0.3Co4Sb12 coated with Al-Ni double-layered coating were almost undecreased, indicating that the Al-Ni coating is suitable for protecting CoSb3-based skutterudite from oxidation and for suppressing the sublimation of antimony. It is expected that this coating could improve the reliability of CoSb3-based devices and could accelerate the application of skutterudite thermoelectric generators.