Corrosion properties of micro- and nanocomposite copper matrix coatings produced from a copper pyrophosphate bath under pulse current

The aim of this work was the deposition of copper matrix composites under direct and pulse current at different frequencies and the evaluation of their protective properties, in the frame of the research domain of the production of metal matrix composite coatings.The deposits were produced using copper pyrophosphate bath in which 20 g/l of either micro- (mean diameter 2 μm) or nano- (mean diameter 45 nm) SiC particles have been added. A squared current waveform was used with the frequencies 0.01, 0.1, 1, and 10 Hz for the pulse current deposition.The microstructure of all deposits, both on the top surface and in cross section, was studied by Scanning Electron Microscopy. The SiC content was evaluated by EDXs in the case of the micro-composite deposits and by Glow Discharge Optical Emission Spectroscopy for the nanocomposite ones. The protective properties were examined by potentiodynamic measurements in different corrosive environments and by salt spray exposure combined with Electrochemical Impedance Spectroscopy measurements.Both the nanoparticles incorporation and the use of pulse current lead to a noticeable grain refinement and thus to a corrosion resistance increase. The nanocomposite deposits present the highest resistance to both uniform and localized corrosion, strongly correlated to their compact structure. The micro-composite deposits produced under direct current present gaps between the particles and the copper matrix, which lower the corrosion resistance. The use of the pulse current managed to partially close these gaps and increase the corrosion resistance to values similar to those of the pure copper deposits.     

Electrochemical codeposition of PMMA particles with zinc

Zinc matrix composite coatings containing polymethyl methacrylate (PMMA) particles were electrodeposited from an aqueous acidic (pH 2.0 and 4.0), lignosulfonate solution of zinc sulfate on low-carbon steel substrates, under galvanostatic, either constant or pulse current, plating conditions at current densities of 2 and 20 A dm⁻². The effect of particle inclusion on the deposit electrocrystallization was investigated by X-ray diffraction and scanning electron microscopy. The observed dependence of the PMMA content of the deposits on bath pH and applied current density was illustrated in terms of the particle surface charge variation and their interaction with the growing metal phase. The corrosion resistance of the composite coatings was evaluated by Tafel analysis.     

Co-electrodeposition and characterization of Cu-Si3N4 composite coatings

Smooth copper coatings containing well-distributed silicon nitride particles were obtained by co-electrodeposition in acidic sulfate bath. The cathodic current density did not show significant influence on incorporated particle volume fraction, whereas the increase of particle concentration in the bath led to its decrease. The increase of stirring rate increased the amount of embedded particles. The microhardness of the composite layers was higher than that of pure copper deposits obtained under the same conditions due to dispersion-strengthening and copper matrix grain refinement and increased with the increase of incorporated particle volume fraction. The microhardness of composites also increased with the increase of current density due to copper matrix grain refining. The composite coatings presented higher strength but lower ductility than pure copper layers. Pure copper and composite coatings showed the same corrosion resistance in 0.5 wt.% H₂SO₄ solution at room temperature.     

Effect of the plating parameters on the electrodeposition of Ni matrix coatings containing Ti nanoparticles

This work focuses on the production of electrodeposited nickel matrix composite coatings containing Ti nanoparticles and on the modification of the process parameters in order to maximise the codeposited particles content as well as obtaining a uniform distribution along the coating thickness. The deposition was carried out using a Ni sulphamate plating bath with different amounts of Ti nanoparticles. The plating parameters such as current density, current type (direct, DC, or pulsed, PC) and the use of ultrasound during the deposition have been modified. The specimens produced have had their microstructure, chemical composition and microhardness analysed. It was found that the increase of the particle concentration in the plating bath up to 40?g?L^?1 leads to an increase of the amount of codeposited particles. The use of ultrasound prevents agglomeration of the particles, leads to a more uniform distribution and increases the Ti content. However, it induces microstructural defects in the matrix. These defects can be limited by increasing the current density or by using pulsed current.     

Synthesis and mechanical properties of nickel‐titania composite coatings

Nickel‐titania composite coatings were prepared under direct current conditions by codeposition of nano titania particles (21 nm) and nickel from a nickel Watts type bath. Current density, concentration of titania particles, effect of agitation, and ultrasonic waves were investigated and the optimum values of these parameters for reaching to maximum vol% of titania particles in the coating were determined. Microhardness of these coatings was investigated by Vickers method and their morphological properties and chemical composition were studied by SEM and EDS analysis, respectively. The results showed that optimal values of current density, concentration of particles, and agitation rate exist that maximum percent of particles codeposited in the coating. Also it is demonstrated that using the ultrasonic waves dramatically decrease the agglomeration of particles in the coating.     

Fabrication and Characterization of Ni-Al_2O_3 Nano-Composite Coatings by Sediment Co-Deposition

Ni-Al2O3 nano-composite coatings were fabricated by sediment co-deposition (SCD) from Watt’s type electrolyte containing nano-Al2O3 particles without any additives. For comparison, Ni-Al2O3 nano-composite coatings were prepared by conventional electro-plating (CEP) under experimental conditions. Effects of process parameters, such as nano-Al2O3 concentration in plating solution, current density, stirring rate, and bath temperature, on nano-Al2O3 content in composite coatings were investigated. The distribut...     

Electrodeposition and characterization of Cu-Nb composite coatings

Copper coatings containing well-distributed Nb particles were obtained by co-electrodeposition in an acidic sulfate bath. Nb particle concentration in the bath was the most significant factor for the incorporation of Nb particles in copper, followed by stirring rate, whereas current density presented low significance. High Nb particle concentration and low stirring rate led to a higher incorporated Nb particle content. The microhardness of the composite layers was higher than that of pure copper deposits obtained under the same conditions due to copper matrix grain refinement and increased with the increase of both current density and incorporated Nb particle volume fraction. The corrosion resistance of Cu-Nb composites in 0.5 wt.% H₂SO₄ solution at room temperature was higher than that of pure copper and increased with the increase of the Nb content.     

Electrodeposition and characterization of Ni-TiB2 composite coatings

Nickel-titanium diboride (Ni-TiB₂) composite coatings were successfully fabricated by pulse electrodeposition techniques from nickel sulfamate bath containing dispersed submicron TiB₂ particles. The effect of TiB₂ codeposition on the morphological, microstructural, microhardness and anti-corrosive properties of the composite coatings have been investigated by using scanning electron microscopy coupled with energy dispersive spectroscopy system, X-ray diffraction (XRD), vickers microhardness, and electrochemical impedance spectroscopy (EIS) techniques. Incorporation of TiB₂ particles into the nickel matrix has modified the regular crystal growth of nickel. The XRD patterns revealed that the preferred (100) crystallite orientation of pure nickel has been modified into mixed orientations by the enhancement of (111) and attenuation of (200) diffraction intensities by the incorporation of TiB₂ particles into the nickel matrix. Vickers microhardness of the Ni-TiB₂ composite coating is found to be increased which is nearly 3 times higher than pure nickel coating. The results obtained by polarization curves and EIS analysis in 3.5 wt% NaCl solution have shown the improved corrosion resistance properties of Ni-TiB₂ composite coating over pure nickel electrodeposit.     

Effect of applied current on the electrodeposited Ni-Al2O3 composite coatings

Nano-sized Al₂O₃ ceramic particles (50 nm) were co-deposited with nickel using electrodeposition technique to develop composite coatings. The coatings were produced in an aqueous nickel bath at different current densities and the research investigated the effect of applied current on microstructure and thickness of the coatings. The variation in some mechanical properties such as hardness, wear resistance, and the adhesive strength of the composite coatings is influenced by the applied current and this was also studied. The morphology of the coatings was characterized by scanning electron microscopy and energy dispersive X-ray spectroscopy. The hardness, wear resistance, and bond strength of the coatings were evaluated by Vickers micro-hardness test, pin-on-disc test, and tensile test, respectively. Results showed that the Al₂O₃ particles were uniformly distributed in the coatings, and the coatings deposited at a current density of 0.01 A/cm² was most favorable in achieving a maximum current efficiency which causes the co-deposition of a maximum amount of Al₂O₃ particles (4.3 wt.%) in the coatings. The increase in Al₂O₃ particles in the coatings increased the mechanical properties of the Ni-Al₂O₃ composite coatings by grain refining and dispersion strengthening mechanisms.     

Corrosion behaviour of electrodeposited Ni/Al2O3 composite coating covered with a NaCl salt film at 800 °C

The electrodeposited Ni/Al₂O₃ composite coatings were prepared by direct current (DC), pulse current (PC) and pulse reversal current (PRC) deposition, respectively. The corrosion behaviour of electrodeposited Ni/Al₂O₃ composite coatings covered with NaCl salt films at 800 °C in air was investigated by SEM/EDX, XRD and thermogravimetric analysis. It is found that corrosion of the three types of coatings is seriously aggravated with a present NaCl salt film, and a corrosion layer with a poor adherence to the matrix has been formed. Furthermore, chlorine enrichment at the interface between the matrix and the corrosion product has been observed. The corrosion resistance of the three types of coatings has improved with the increase of Al₂O₃ content. The corrosion resistance of the Ni/Al₂O₃ composite coatings prepared by PRC deposition is the best, and that by DC deposition is the worst. The corrosion mechanism of Ni/Al₂O₃ composite coatings will also be discussed.     

NiP/SiC composite coatings: the effects of particles on the electrochemical behaviour

NiP/SiC (17 at.% P) composite coatings were prepared by electrodeposition from a Brenner type plating bath containing SiC particles. Cyclic voltammetry and immersion time were used to evaluate the electrochemical behaviour of these coatings.The results showed that the presence of SiC particles in NiP alloy increased corrosion properties, because the exposed area of the metallic matrix was reduced due to its recovering by SiC particles. However, the current densities developed by the NiP/SiC composite coatings increased with increasing amount of incorporated particles, and such effect is more remarkable for small particles, after heat treatment and when the systems are polarized.     

电沉积制备Ni/nano-WC复合镀层的工艺及机理研究

采用脉冲电沉积法制备了纳米WC强化镍基复合镀层。探究了不同表面活性剂（十二烷基硫酸钠）添加量以及WC粉的湿磨预处理对Ni/nano-WC复合镀层表面形貌、颗粒分布、微观结构以及显微硬度的影响。表面活性剂的添加和对WC湿磨处理有助于细化镀层晶粒,得到WC颗粒分布均匀的致密镀层。镀层中WC含量以及镀层的显微硬度随着表面活性剂的添加量的增加而增加,但过量会使效果变差,理想的SDS添加量为0.15g/l,湿磨10h。     

Production of electroplated Co-Al2O3 nanocomposites by pulse reverse plating (PRP) and anionic surfactant

Nanocomposite Co-Al₂O₃ electrodeposited coatings have been produced for the first time by pulse reverse plating (PRP) in conjunction with an anionic surfactant, sodium dodecylsulphate (SDS), by a similar method used for Co – IF WS₂ deposition in previous work. The influence of two parameters on nanocomposite composition and morphology was investigated in this study: the SDS content of the bath was varied (from 0 to 0.8?g L^?1) as well as the length of the cathodic pulse, from t_c?=?30?s to 120?s. In addition, the composites were also produced by direct current (DC) for comparison. Co-PTFE nanocomposites were also considered using the same approach. The coatings were characterised microstructurally by SEM, EDX, XRD, and mechanically with a Knoop microhardness test. For Co-Al₂O₃, the alumina particle content is high for PRP coatings compared to those produced by DC; a higher particle content was achieved at lower t_c. Increasing SDS led to a peak in the particle content, followed by a reduction in the particle content with further increase in the SDS concentration. Cathode efficiency decreased with increasing t_c, but is higher compared to the DC coatings. Particle surface coverage for both nanocomposites per pulse cycle follows a pattern for the PRP coatings with varying SDS content that is different to that achieved with DC coatings. Increasing particle content led to a decrease in crystallite size, which indicated that the particle inclusion led to grain size refinement. However, analysis of the hardness tests showed that the Al₂O₃ particles predominantly provide dispersion strengthening.

For Co-PTFE the PRP mechanism was shown to be ineffective in producing composite coatings. This is thought to be due to the larger size of the particle.     

The influence of pulse parameters on Zn-Ni alloy coatings plated on AZ91 magnesium alloy

The influence of pulse parameters on zinc-nickel coatings plated on AZ91 magnesium alloy is investigated by scanning electron microscopy (SEM) and X-ray diffraction (XRD). The particles of zinc-nickel alloy plated on AZ91 magnesium alloy become smaller and the surface roughness decreases with the increase of current density and frequency. However, long plating times and a high ratio of t_on/t_off have decremental effects on the particles and surface roughness. The contents of crystal phases of zinc-nickel alloy coatings are higher under pulse current deposition than under direct current. The frequency, current density, plating time and ratio of t_on/t_off have different impacts on the thickness and Ni content of zinc-nickel coatings.     

Effect of surfactant on the co-electrodeposition of the nano-sized ceria particle in the nickel matrix

The nickel–ceria (Ni–CeO₂) nanocomposite coatings have been pulse electrodeposited from a Watts-type electrolyte containing nano-sized CeO₂ particles produced by high-energy ball milling technique (HEBM). Sodium Lauryl Sulphate (SLS) has been added in the electrolyte as a cationic surfactant. The effects of the surfactant on the zeta potential, co-deposition and distribution of ceria particles in the nickel matrix and hardness of composite coatings have been investigated. Experimental results show that the addition of SLS up to 0.10 g/l increases the amount of co-deposited ceria particles in the nickel matrix and microhardness of the nanocomposite. However, when the amount of SLS in the electrolyte is more than 0.1 g/l, there is a tendency to form agglomerates of ceria particles in the nickel matrix resulting no further increase in hardness of the Ni–CeO₂ nanocomposite coatings.     

Ni-Co/ZrO2复合共沉积过程的电结晶行为

为了研究Ni-Co-ZrO_2复合镀层电结晶初期的共沉积行为,在酸性氨基磺酸盐体系中采用阴极扫描伏安和计时电流等电化学测试方法,通过电化学反应动力学参数计算揭示Ni-Co-ZrO_2复合镀层成核机理。结果表明:Ni-Co合金镀液中ZrO_2纳米粒子的添加使共沉积电位正移,降低了阴极极化度。Ni-Co合金和Ni-Co-ZrO_2复合镀层的形核/生长过程符合受扩散控制的Scharifker-Hill瞬时成核模型,在低负电位下,Ni-Co-ZrO_2复合镀层成核弛豫时间减少,成核速率更高,电极表面吸附的ZrO_2纳米粒子促进了基质金属的成核及生长;高负电位下,复合镀层体系的峰值电流略低于合金体系,且成核速率降低,ZrO_2纳米粒子在电极表面表现出空间位阻效应,抑制了基质金属的电结晶过程。     

不同纳米WS2含量Ni-P-Ti N-WS_(2)复合化学镀层的制备及其摩擦学性能EI北大核心CSCD

Ni-P-TiN化学复合镀层具有比Ni-P镀层更高的硬度和耐磨性,但其表面粗糙度大,与对偶件之间的摩擦因数高,应用潜力受到限制。通过在化学镀液中添加不同用量的纳米WS_(2)颗粒和固定用量的TiN颗粒,在低碳钢表面制备Ni-P-TiN-WS_(2)复合镀层。采用X射线能谱仪(EDS)、扫描电子显微镜(SEM)和X射线衍射仪(XRD)对镀层的化学成分(质量分数)、表面形貌及微观结构进行表征,并利用球盘式摩擦磨损试验机测试复合镀层的摩擦磨损性能。结果表明:纳米WS_(2)颗粒与纳米TiN颗粒的共沉积可使镀层表面更加致密、平整。随着镀液中纳米WS_(2)用量的增加,复合镀层的硬度先减小后增大,与氮化硅陶瓷球的摩擦因数则先升后降,磨损率显著下降,耐磨性增强。镀液中纳米WS_(2)粉末的用量为2.5 g/L时复合镀层的摩擦学性能最佳。纳米WS_(2)颗粒的加入及用量优化可显著改善复合镀层的综合性能,可为发展高耐磨低摩擦因数的先进涂层提供借鉴。     

Zinc–nickel alloy coatings electrodeposited from a chloride bath using direct and pulse current

Zinc–nickel alloys were electrodeposited on steel from chloride bath by direct and pulse current. Some electric variables (average current density, pulse frequency, duty cycle) and some important bath conditions (ratio of Ni²⁺/Zn²⁺ in bath, temperature) on chemical compositions, current efficiency, microhardness and surface appearance of coatings were studied. At low current densities, transition from anomalous to normal co-deposition was observed for both direct and pulse current. Pulse current seems to increase brightness of the coating and to decrease the precipitation of zinc hydroxide at the cathode surface. In addition, applied pulse current increases the percentage of nickel in deposits. Pulse frequency and duty cycle had little effect on the chemical composition of deposits. The polarization curve of zinc–nickel deposition with pulse current is shifted to positive potentials in comparison with direct current curves. The temperature of the plating bath had a very strong effect on the composition of the deposits. This is primarily the result of intrinsically slow nickel kinetics. The hardness of Zn–Ni alloy coatings (approx. 220 VHN) was greater than the hardness of zinc coating (approx. 161 VHN). The hydroxide suppression mechanism for Zn–Ni co-deposition has been confirmed.     

Influence of SiO2 particles on zinc–nickel electrodeposition

Abstract

Zinc–nickel/SiO₂ electrodeposits have been produced from an acid sulphate bath. The complimentary (mutual) codeposition behaviour of SiO₂ and nickel was observed. The presence of SiO₂ in the zinc–nickel bath appears to change the alloy deposition behaviour. Rate of nickel deposition was considerably increased with SiO₂ particles in the bath. Similarly, nickel ions were found to enhance the rate of SiO₂ incorporation. The effect of particle size studied revealed that the rate of incorporation of larger (2 μm) particles was higher than that of the smaller (20 nm) particles. Changes in hydrodynamic conditions of the composite bath seem to influence the mass transport of nickel ions hence there is a notable increase in the rate of nickel deposition and SiO₂ incorporation. Morphological studies show that the presence of SiO₂ in the bath seems to have a marked effect on the morphology and microstructure of the zinc–nickel coatings. Cathodic polarisation studies carried out during electrodeposition show a decrease in cathodic current densities with increasing SiO₂ concentration in the bath.     

Formation Routes of Nanocomposite Coatings in Detonation Spraying of Ti3SiC2-Cu Powders

In thermally sprayed coatings, nano-sized features of the microstructure may be either inherited from the nanostructured agglomerates of the feedstock powder or form as a result of rapid cooling of molten particles upon deposition. Applying a process of the computer-controlled detonation spraying (CCDS) to Ti₃SiC₂-Cu composite powders produced by high-energy mechanical milling, we show that both routes are possible depending on the spraying conditions. When the nanostructure of the Ti₃SiC₂-Cu coating is inherited from the feedstock powder—under very mild conditions of detonation spraying, which exclude melting, so is the phase composition of the coating. In higher-temperature conditions of spraying, a significant fraction of the copper matrix melts and the interaction between Ti₃SiC₂ and Cu occurs. The TiC _x -Cu(Si) coatings that form show crystallites of both phases in the nano-range. In this case, rapid solidification of the molten fraction of the particles is responsible for the formation of the coatings with a nanostructured matrix. Due to the flexibility of the CCDS process, conditions of spraying were found such that a composite coating with very fine crystallites of the Cu(Si) matrix (30 nm) and a hardness of 273 HV could be obtained.