Electroless deposited Ni–P alloys: corrosion resistance mechanism

Exploration of the Corrosion Behavior of Electroless Plated Ni-P Amorphous Alloys via X-ray Photoelectron Spectroscopy

A Ni-P amorphous alloy was deposited on a low carbon steel substrate via electroless plating. Further, the prepared samples were crystallized under the high temperature with a range from 200 °C to 500 °C in air for 1 h. The crystallization process was studied via XRD, AFM, and XPS, and anodic electrochemical behavior was investigated by potentiostatic methods in a 3.5 wt% NaCl solution. The experimental results indicate that the diffusion, dissolution, and enrichment of the component elements in the Ni-P alloy are essential during crystallization because the various corrosion behaviors corresponding to Ni and P are directly affected. More importantly, under the 400 °C treatment, H₂PO_2^- was enriched in the alloy, which effectively hinders the anodic dissolution of nickel and forms a complete adsorption layer on the surface of the alloy. Our results demonstrate that P can effectively block the anodic dissolution of Ni during the corrosion process, and the crystallization process can effectively promote the surface enrichment of P to improve the corrosion resistance of the coating.

Full Optimization of an Electroless Nickel Solution: Boosting the Performance of Low-Phosphorous Coatings

Univariate and multivariate optimizations of a novel electroless nickel formulation have been carried out by means of the Taguchi method. From the compositional point of view, adjustment of the complexing agent concentration in solution is crucial for fine-tuning free Ni²⁺ ions concentration and, in turn, the mechanical properties of the resulting coatings. The Ni (II) concentration and the pH are the main parameters which help restrict the incorporation of phosphorous into the Ni layers. On the other hand, the stirring rate, the pH and the reducing agent concentration are the most influential parameters for the corrosion resistance of the coatings. Multivariate optimization of the electrolyte leads to a set of optimized parameters in which the mechanical properties (hardness and worn volume) of the layers are similar to the optimal values achieved in the univariate optimization, but the corrosion rate is decreased by one order of magnitude.

In situ embedding dual-Fe nanoparticles in synchronously generated carbon for the synergistic integration of magnetic resonance imaging and drug delivery

In situ incorporating versatile magnetic iron nanoparticles into ordered mesoporous carbon (OMC) by means of synthetic methodology for functional integration is a great challenge. Inspired by the phenomenon of uniovular twins in nature, a homometallic [Fe₉(μ₃-O)₄(O₃PPh)₃(O₂CCMe₃)₁₃] ({Fe₉P₃}) cluster was synthesized and used as the ovulum to in situ produce dual-Fe nanoparticle (γ-Fe₂O₃ and Fe(PO₃)₃)-functionalized OMC (dual-Fe/OMC). In vitro magnetic resonance imaging (MRI) studies showed a longitudinal relaxation (r ₁) and transverse relaxation (r ₂) of 9.74 and 26.59 mM^-1 s^-1 with a r ₂/r ₁ ratio of 2.73 at 0.5 T. The MRI performances were further examined by mouse model with a subcutaneous HeLa tumor. In addition, the low cytotoxicity, considerable loading capacity and delivery of doxorubicin hydrochloride (DOX) were also studied in vitro. These results demonstrate the feasibility of the concept of uniovular twins in the one-pot preparation of dual-Fe/OMC for functional integration.

Molecular dynamics simulations of amorphous Ni-P alloy formation by rapid quenching and atomic deposition

A combined experimental and simulation study is carried out to compare the properties of amorphous Ni_100-x P _x alloys obtained by electroless deposition and rapid melt-quenching. The onset of crystallization of experimental electroless deposited amorphous films is measured by differential scanning calorimetry experiments. Classical molecular dynamics simulations using Embedded Atom Model-based interactions are performed to obtain glassy Ni-P by melt-quenching the liquid with various quenching rates, as well as via low-energy chemical deposition to mimic experimental electroless deposition. It is shown that the deposited amorphous and glassy states display similar short-range order. The amorphous deposit corresponds to a glassy state obtained with a cooling rate of 10⁹ K s^-1, indicating that deposition yields generally more relaxed amorphous structures. The appearance of phosphorus-enriched surface on the simulated deposited thin film, comparable to experimental observations, is discussed.

Nanostructure of Surface Films on Ni18P Alloy in Sulfate Solutions by the Maximum Entropy Method

NiP alloys are very often used in industry, due to their outstanding performance in corrosion and wear. Alloys with high phosphorus content (≥16 atom % P) are amorphous and show high corrosion resistance in both neutral and acidic solutions irrespective of the presence of chloride ions. The reason for this behavior is attributed to the formation of a "P-enriched surface layer" whose exact nature is still under debate. In this work, an iterative algorithm based on the application of maximum entropy method on nondestructive angle-resolved X-ray photoelectron spectroscopy data has been applied to the investigation of the surface layer grown on Ni18P alloys following mechanical polishing and anodic polarization in sulfate solutions. The results show that the outermost region of the examined alloy has a complex layered structure: (1) an uppermost hydrocarbon contamination layer about 1 nm thick, which includes also adsorbed water; (2) a nickel (poly)phosphate layer of about 1 nm; (3) a highly phosphorus-enriched interface being about 2 nm thick with a marked phosphorus concentration gradient, from 70 to 20 atom %; and (4) bulk alloy with the stoichiometric composition. These findings, together with the chemical state of the different phosphorus compounds, allow us to conclude that the high corrosion and wear resistance of NiP alloys might be ascribed to the presence of a thin, self-repairing nickel (poly)phosphate layer grown on a strongly P-enriched interface. Because the Auger parameter of P at the interface is similar to that of elemental P, it might be also concluded that the interface is enriched in elemental phosphorus.

Investigation of the Corrosion Behavior of Electroless Ni-P Coating in Flue Gas Condensate

The corrosion behavior of Ni-P coating deposited on 3003 aluminum alloy in flue gas condensate was investigated by electrochemical approaches. The results indicated that nitrite acted as a corrosion inhibitor. The inhibiting effect of nitrite was reduced in solutions containing sulfate or nitrate. Chloride and sulfate accelerated the corrosion of Ni-P coatings greatly. This can provide important information for the researchers to develop special Ni-P coatings with high corrosion resistance in the flue gas condensate.

Electroless Nickel Deposition: An Alternative for Graphene Contacting

We report the first investigation into the potential of electroless nickel deposition to form ohmic contacts on single layer graphene. To minimize the contact resistance on graphene, a statistical model was used to improve metal purity, surface roughness, and coverage of the deposited film by controlling the nickel bath parameters (pH and temperature). The metalized graphene layers were patterned using photolithography and contacts deposited at temperatures as low as 60 °C. The contact resistance was 215 ± 23 Ω over a contact area of 200 μm × 200 μm, which improved upon rapid annealing to 107 ± 9 Ω. This method shows promise toward low-cost and large-scale graphene integration into functional devices such as flexible sensors and printed electronics.

Electroless Deposition of Ni-Cu-P Coatings Containing Nano-Al2O3Particles and Study of Its Corrosion Protective Behaviour in 0.5 M H2SO4

Ni-Cu-P/nano-Al2O3composite coatings are prepared on mild steel from an alkaline electroless plating bath containing different concentrations of Al2O3nanoparticles. The protective effect of codeposited nanoparticles on the corrosion behaviour of the coatings is studied in 0.5 M H2SO4solution. The electrochemical methods, that is, electrochemical noise (ECN), electrochemical impedance spectroscopy (EIS), and polarization measurements, are used to characterize the corrosion properties of the coatings. The results show that the inclusion of nanosized particles leads to significant improvement of corrosion resistance of the coatings. The highest corrosion resistance is obtained at 20 ppm of nanoparticles concentration in the plating bath. The ECN measurements results are in good agreement with results obtained from two other electrochemical methods after trend removal. The SEM images prove that nano-Al2O3particles were embedded in the Ni-Cu-P matrix and are dispersed uniformly on the coating surface.

Characterization and corrosion behavior of Co and Co–P coatings electrodeposited from chloride bath

Co–P coatings with low and high phosphorous contents are electrodeposited using direct current (DC) and pulse current (PC) methods from cobalt chloride baths.

Corrosion Resistance of Electroless Ni-Cu-P Ternary Alloy Coatings in Acidic and Neutral Corrosive Mediums

Electroless Ni-Cu-P alloy coatings were deposited on the ordinary steel substrate in an acidic hypophosphite-type plating bath. These coatings were characterized by a scanning electron microscope (SEM) and an X-ray diffraction. The micrograph shows that coating presents a nodular aspect and is relatively homogeneous and very smooth. The EDX analysis shows that the coating contains 12 wt.% of phosphorus element with a predominance of nickel element. In addition, the anticorrosion properties of the Ni-Cu-P coatings in 1 M HCl, 1 M H2SO4, and 3% NaCl solutions were investigated using Tafel polarization curves, electrochemical impedance spectroscopy, and SEM/EDX analysis. The result showed a marginal improvement in corrosion resistance in 3% NaCl solution compared to acidic medium. It also showed that the corrosion mechanism depends on the nature of the solution.