Effect of Deposition Time on the Morphological Features and Corrosion Resistance of Electroless Ni-High P Coatings on Aluminium (original) (raw)
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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 ...
Surface and Coatings Technology, 2007
Amorphous Ni-P layers with 8-10 wt.% phosphorus were deposited by sodium hypophosphite onto AlMg2 type aluminium alloy substrates after different pre-treatments. Prior to the electroless nickel-phosphorus (ENP) deposition in an acetate and lactic acid based nickel bath, the widely applied Zn (zincate) or Ni displacement (Ni strike) pre-treatments for aluminium substrates as well as a non-conventional surface conditioning one (soaking in a warm solution containing only hypophosphite and lactic acid) were all tested and their effects evaluated on the corrosion and other properties of the Ni-P layers developed right afterwards. The surface morphology and structure of the ENP layers were characterized by scanning electron microscopy and X-ray diffraction analysis. Polarization resistances were measured in 0.5 mol dm − 3 Na 2 SO 4 solution at pH 3. Compared to the direct electroless plating on the bare aluminium alloy AlMg2, it was found, that the hypophosphite adlayer (hypophosphite immersion pre-treatment) have also increased the corrosion resistance as the displacement pre-coatings, but without decreasing the deposition rate unlike conventional displacement methods. In the studied ENP deposition systems the decrease of corrosion rate could mainly be attributed to the lower microporosity and smoother morphology of the nickel-phosphorus coatings.
Electroless ternary nickel alloy using hypophosphite ion as reducing agent was done on pure Fe substrate (Fe 99.5%) with Zn or Cu as additive. The effect of plating bath pH on nickel alloy deposit composition was studied using Scanning Electron Microscope (SEM), Energy Dispersive Analysis X-ray (EDAX) and X-ray Diffraction (XRD). Polarization curve measurements were used to evaluate the deposits corrosion properties. The phosphorous content in the deposit decreased as plating bath pH increased. Zn and Cu content also decreased as plating bath pH increase. The phosphorous content in deposit has significant effect on corrosion behavior of the deposits. The addition of Zn and Cu has effect on corrosion behavior of the deposits.
Mechanical Characterization of Electrodeposition of Ni-P Alloy Coating
Journal of Nano-and electronic Physics, 2020
The electrodeposition process plays a crucial role in the formation of thin films on materials, in particular, the electrodeposition of nickel-phosphorus because of its important properties. In this study, NiP coatings were deposited on X52 steel substrates by electrodeposition technique from a solution containing nickel sulfate, sodium hypophosphite (NaH2PO2). Composition, surface morphology, and mechanical properties of the NiP deposits were studied using SEM, EDAX, the Vickers method, weight loss and potentiodynamic polarization techniques. The effects of the current density were investigated on the surface morphology, phosphorus content, microhardness and corrosion of the coatings. It was observed that both the phosphorus content and microhardness are dependent on the current density. Results demonstrate that the morphology of the electrodeposited NiP alloys shows that the grains are spherical in nature for all the samples. It has been observed that the influence of current density on the P content of the deposit is an inverse relation with phosphorous content and also the as-plated coatings at current density of 5 Am − 4 exhibit the superior microhardness. Corrosion tests show that 5 Am − 4 is the best current density value which gives the best protection coating against corrosion.
Deposition of electroless Ni–P graded coatings and evaluation of their corrosion resistance
Surface & Coatings Technology, 2006
Electroless Ni–P coatings provide high hardness and excellent resistance to wear and abrasion. The present work aims to study the formation of electroless Ni–P graded coatings, with varying nickel and phosphorus contents of the individual layers and to evaluate their corrosion resistance by polarization and electrochemical impedance spectroscopic studies. The possibility of preparing electroless Ni–P graded coatings by sequential immersion in three different plating baths is discussed. The study reveals that electroless Ni–P graded coatings offer better corrosion resistance than non-graded Ni–P coatings.
Surface & Coatings Technology, 2007
The corrosion protection performance of electroless deposited nickel-phosphorus (Ni-P) alloy coatings containing tungsten (Ni-P-W) or nano-scattered alumina (Ni-PAl 2 O 3) composite coatings on low carbon steel was studied. The effect of heat treatment on the coating performance was also studied. The optimum conditions under which such coatings can provide good corrosion protection to the substrate were determined after two weeks of immersion in 3.5% NaCl solution. Electrochemical impedance spectroscopy (EIS) and polarization measurements have been used to evaluate the coating performance before and after heat treatment. The NiP -W coatings showed the highest surface resistance compared with NiP -Al 2 O 3 and NiP. The surface resistance of NiP -W coatings was 12.0 × 10 4 Ω cm 2 which is about the double of the resistance showed by NiP -Al 2 O 3 (7.00 × 10 4 Ω cm 2) and twenty times greater than the surface resistance of NiP (0.78 × 10 4 Ω cm 2). XRD analysis of non-heat-treated samples revealed formation of a protective tungsten phosphide phase. Heat treatment has an adverse effect on the corrosion protection performance of tungsten and alumina composite coatings. The surface resistance decreased sharply after heat treatment.
International Journal of Electrochemical Science, 2016
Electrochemical behavior of electroless nickel phosphorus (EN-P) coated aluminum 6061 alloy combination in different zincating conditions have been evaluated. The effect of the zincate additives (anionic surfactant sodium dodecyl sulfate (SDS) and copper sulfate) on structure and morphology of zincating and electroless EN-P deposition have been studied. Corrosion performance of the prepared samples was studied by polarization and electrochemical impedance spectroscopy (EIS). Scanning electron microscope (SEM), Energy dispersive X-ray spectroscopy (EDS) and X-ray diffraction (XRD) analysis were used for studying surface morphology and chemical composition of coatings. According to the obtained results, the zincate solution containing copper sulfate and SDS surfactant indicated the fast deposition of Zn and dense nucleation with small Zn particles at the surface. This Zn films resulted in dense and small grains of EN-P deposition with smooth surfaces.
Ni-P coatings electroplating - A review, Part I: Pure Ni-P alloy
arXiv: Applied Physics, 2018
In the electroplating industry Ni-P coatings are extensively employed owing to their excellent properties which enable substrate protection against corrosion and wear. Depending on their composition and structure, as-plated deposits demonstrate good mechanical, tribological and electrochemical features, catalytic activity but also beneficial magnetic characteristics. With subsequent thermal treatment hardness of Ni-P metal-metalloid system can approach or be even higher than that of hard Cr coatings. The purpose of this paper is to provide a general survey of the research work dealing with the electrodeposition of Ni-P binary alloy coatings. Proposed phosphorus incorporation mechanisms, Ni-P alloy microstructure before and after thermal treatment, its mechanical, tribological, corrosion, catalytic and magnetic properties are considered, so are the key process variables influencing phosphorus content in the deposits and the roles of the main electrolytic bath constituents. Findings o...
Effects of Current Density on Ni–P Coating Obtained by Electrodeposition
METALLOFIZIKA I NOVEISHIE TEKHNOLOGII, 2021
In this work, NiP coatings are deposited on the steel substrate by electrodeposition from a solution containing nickel sulfate and sodium hypophosphite (NaH 2 PO 2). The effect of the current density on the morphology, phase structure, microhardness, and corrosion performance of the NiP coatings are studied. Scanning electron microscopy and energy dispersive X-ray analysis and X-ray diffraction are used to study the morphological, composition and phase structure. The corrosion performance of the coatings is evaluated by weight loss, electrochemical impedance spectroscopy and Tafel polarization. Results showed that the morphology of the electrodeposited NiP alloys coatings has spherical grains for all the samples, and the Ni 3 P phases are formed all over the microstructure of the coatings. It is observed that the phosphorus content and microhardness are dependent on the current density. The corrosion tests show that 5 A⋅dm −2 current density is the optimal value which gives the best protective coating against corrosion. It also exhibits superior microhardness originated from the higher Ni 3 P amount.