Chromium Electroplating of Aluminium Alloys Using Electroless Nickel as Underlayer (original) (raw)
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Corrosion resistance of electrodeposited Ni–Al composite coatings on the aluminum substrate
Materials & Design, 2011
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Journal of Materials, 2013
High phosphorus Ni-P alloy was deposited on aluminium substrate using electroless deposition route. Using zincating bath, the surface was activated before deposition. Deposition time was varied from 15 minutes to 3 hours. Deposit was characterised using scanning electron microscope with energy dispersive spectroscope, X-ray diffraction, and microhardness tester. The corrosion resistance was measured using Tafel extrapolation route. The medium was aqueous 5% HNO3 solution. The analysis showed that the deposit consisted of nodules of submicron and micron scale. The predominant phase in the deposit was nickel along with phosphides of nickel. Compared to substrate material, deposit showed higher hardness. With increase in deposition time, the deposit showed more nobleness in 5% HNO3 solution and nobleness reached a limiting value in 1 hour deposition time.
Preparation and Study on Nickel Coated Aluminium through Electroless Deposition Technique
2016
In this study we made an attempt to prepare nickel (Ni) coated aluminium (Al)via electroless deposition technique for the formation of a thin metallic nickel film coating on pure sintered aluminium substrate which was developed by powder metallurgy route.The metal film of nickel was deposited on the metal surface of aluminium from an aqueous electrolytic solution of nickel chloride as a source ofnickel. This electroless deposition process involves without additional external electrode or any electric current passingthrough it.The surface structure of sintered aluminium is changed as a consequence of several interactions between sintered aluminium and aqueous electrolytic solution of nickel chloride carried on room temperature. In this experiment the influence of process parameter like temperature was also observed. The prepared nickel coated aluminium samplewas analyzed for their phases by XRD analysis. Changes of surface morphology after electroless deposition on aluminium substrat...
2018
The purpose of this investigation is to explore the relationship between various zincating treatments and coating adhesion. A modification on the conventional single zincating process has been made by extending the duration, with an objective to enhance the non-homogeneous deposition of zinc particles on the aluminium alloy 7075 (AA7075) substrate. To compare the impact of various zincating treatments on the coating adhesion, a double zincating process at various durations were also applied in this study. A scanning electron microscopy (SEM), atomic force microscopy (AFM) and energy dispersive analysis of x-rays (EDX) were used to characterize the microstructural changes and composition of AA7075 during various zincating treatments at various durations. A scratch tester was used to investigate the coating adhesion of nickel deposits. A strong relationship between zincating duration and surface morphology of the zincated substrate has been observed in SEM results. The adhesion betwee...
Journal of Metallurgy, 2015
The effects of temperature, pH, and time variations on the protective amount and quality of electroless nickel (EN) deposition on cast aluminium alloy (CAA) substrates were studied. The temperature, pH, and plating time were varied while the surface condition of the substrate was kept constant in acid or alkaline bath. Within solution pH of 5.0–5.5 range, the best quality is obtained in acid solution pH of 5.2. At lower pH (5.0–5.1), good adhesion characterised the EN deposition. Within the range of plating solution pH of 7.0 to 11.5, the highest quantity and quality of EN deposition are obtained on CAA substrate in solution pH of 10.5. It is characterised with few pores and discontinuous metallic EN film. The quantity of EN deposition is time dependent, whereas the adhesion and brightness are not time controlled. The best fit models were developed from the trends of result data obtained from the experiments. The surface morphologies and the chemical composition of the coating were ...
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2014
Coating systems protect metal substrates from environmental corrosion attack. However, although having good performances, the presence of specific metal ions in their composition represents a potential source of environmental contamination. The necessity to conciliate corrosion protection with environmental impact is, thereby, primary. This work was designed to study the performance of low environmental impact coating systems (surface pre-treatment and primer), such as those free from hexavalent chromium (Cr VI), layered on different substrates of aluminium alloy [Al 7075 (T6) unclad and Al 2024 (T3) unclad] usually utilized in aerospace applications. Substrate surfaces were first treated by environmentally friendly Cr-free products. Successively, on pre-treated substrates, Cr-free epoxy primers were applied. The capability to protect substrates from corrosion phenomena was evaluated following exposure of 4 groups of samples to in situ marine atmosphere at the Experimental Marine St...
Surface Modification of Al Alloy 2014 by Electrochemical Deposition of Ni
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Surface and Coatings Technology, 2019
Low corrosion protection performances of Trivalent Chromium Process (TCP) coatings with reference to Chromium Conversion Coatings (CCC) deposited on aluminium alloys can be overcome by application of post-treatment processes. This work shows the effect of post-treatment bath (containing hydrogen peroxide and lanthanum salt) on the chemical composition, structure and the corrosion performances of TCP coating deposited on AA 2024-T3 aluminium alloy. Different times of post-treatment bath were applied on the TCP coating and the samples were analyzed by Time-of-Flight Secondary Ion Mass Spectrometry (ToF-SIMS), X-ray Photoelectron Spectroscopy (XPS) and Glow Discharge-Optical Emission Spectrometry (GD-OES). The ToF-SIMS and GD-OES depth profiles show that the post-treatment time has no influence on the thickness of the TCP coating and on its bi-layered structure. It is composed of an outer layer, rich in zirconium and chromium oxides and an inner layer rich in aluminium oxides and oxy-fluorides. 3D ToF-SIMS images reveal an enrichment of Cr and Zr-like species over the surface of intermetallic particles with reference to alloy matrix, whereas a homogenous distribution of La is observed. The analysis of in-depth distribution shows that La is present principally in the outer part of the TCP coating. The La concentration increases with increasing post-treatment time. The effect of post-treatment time on protection was evaluated by Electrochemical Impedance Spectroscopy (EIS) and Linear Sweep Voltammetry (LSV) in a 0.001 M NaCl + 0.1 M Na 2 SO 4 electrolyte. The increased posttreatment time enhances the cathodic inhibition against oxygen reduction. The post-treatment provides improved coating homogeneity and sealing properties.
Wear behavior of Ni-P and Al 2 O 3 electroless nano coating on aluminium alloy
Electroless Nickel (ENi-P) is the major evolving surface coating technique employed in today's industries. This covering is the decision for some design applications with different actual attributes of EN coatings, for example, hardness, wears opposition, covering consistency and erosion obstruction. The major advantages of ENi-P and Al 2 O 3 coatings are uniform coating thickness, improved wear and corrosion resistance, hardness, ability to deposit on surface activated non conductors etc. Typical anionic surfactant and various passive chemical additives and nano additives such as Al 2 O 3 were added to the EN bath. Coating was carried out on Al LM6 alloy specimens. In this research work, Sodium Lauryl Sulphate (SLS) surfactant along with nano additives such as Al 2 O 3 was added to the ENi-P bath. The effect of surfactant along with nano additives on surface properties such as corrosion resistance, wear properties, surface roughness, micro hardness and microstructure of electroless nickel-phosphorus and Aluminum oxide coating was investigated. The surface roughness of the coated specimens was measured using stylus instrument, microhardness was measured using vicker's hardness tester, microstructure was studied using Scanning Electron Microscope (SEM) and wear test was measured using Pin on disc machine. The result obtained from the above tests clearly indicates that the surfactant and passive additives improves the surface finish, microhardness, and microstructure and wear rate of ENi-P and Al 2 O 3 coatings significantly.