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I am a PhD Researcher that focuses on characterising the microstructural behaviour of superalloys.

PINBOARD SUMMARY

Discover the science behind improving material properties through electroless deposition.

In 10 Seconds? The primary purpose of a coating is to provide a protective barrier to enhance the substrates mechanical or chemical properties – coatings can also be deposited upon metallic substrates for decorative purposes. However, this pinboard will focus on improving the materials properties.

Two main research fields within electroless deposition are enhancing wear and corrosion resistant coatings – ultimately because the cost of maintenance due to wear or corrosion in industry is massive.

Don’t believe it? Just take a look at the selection of pinned articles. They ultimately all look at improving the materials properties by add ceramic particles to the plating solution – and one particular paper looks at Nano-sized ceramic particles as opposed to micron as the norm.

What is the plating solution? This is the solution that the substrate is placed in to be coated. The plating solution will most commonly consist of nickel & (low, medium or high) phosphorus (with the addition of ceramic particles) – however, there are other solutions available depending on the properties required. The grade of phosphorus is important; this is because different levels of phosphorus offer different benefits, for e.g. low = excellent for wear resistance, medium = good combination for wear & corrosion resistance & high = excellent corrosion resistance.

How does the coating deposit onto the substrate?

For a successful deposition process, the most important parameter is the temperature of the plating bath - the optimum temperature range is between 89 & 91oC. Temperature must not fall below this range, however, plating does begin at 850C.

Fundamentally, the nickel ions within the plating solution are reduced, due to the reaction with the sodium hypophosphate. Once the nickel ions have been reduced, they are then attracted to the metallic substrate that is fully immersed in the bath, producing the thin film of nickel-phosphorus. Crucially, the nickel ions are only attracted to the metallic substrate due to it being previously activated by a catalyst prior to immersion. If ceramic particles are added to the plating solution, they are basically dragged along by the nickel ions.

8 ITEMS PINNED

Electroless Nickel Phosphorus Plating on AZ31

Abstract: One of the major drawbacks to using magnesium parts in automotive applications is poor corrosion resistance, which can be improved with a nickel-boron coating placed on a nickel-phosphorus coating, which, in turn, is placed on a phosphate-permanganate conversion-coating layer produced on the magnesium alloy AZ31. This work reports on the determination of the optimum kinetic parameters for producing a coherent nickel-phosphorus coating using an electroless-procedure phosphate-permanganate conversion-coating layer and for studying the effects of the experimental variables of the electroless plating process on the phosphorus content, surface morphology, and structure of the electroless nickel-phosphorus (EN-P) coatings produced. Measurements of the plating rate as a function of experimental variables such as the compositions of the plating bath constituents, temperature, and pH were implemented using the weight-gain method; the phosphorus content of the EN-P coatings was measured using energy-dispersive spectroscopy (EDS) analysis. The surface morphology of the coating was examined using a scanning electron microscope (SEM); X-ray diffraction (XRD) was used to characterize the structure of each coating. An empirical rate law was determined for EN-P plating on a phosphate-permanganate conversion coating. It is found that the deposition rate of the EN-P coating increases by increasing the deposition temperature, the concentration of free nickel ions, and the concentration of hypophosphite ions in the plating bath. In addition, the deposition rate decreases by increasing both the plating bath pH and the concentration of citric acid in the plating bath.

Pub.: 21 Feb '09, Pinned: 19 Apr '17

Improvement of the erosion-corrosion resistance of magnesium by electroless Ni-P/Ni(OH)2-ceramic nanoparticle composite coatings

Abstract: In this study, Ni-P/Ni(OH)2-ceramic nanoparticle composite coatings were directly deposited onto commercially pure magnesium in order to improve its resistance to erosion-corrosion damage. The effect of three incorporated ceramic nanoparticles (TiO2, SiC and diamond) on the erosion-corrosion resistance of the composite coatings was also investigated. The composite coatings were obtained by an electroless process and were characterized using scanning electron microscopy, Raman spectroscopy and X-ray diffraction. The erosion-corrosion behavior of fabricated composite coatings was elucidated using in situ techniques of potentiodynamic polarization and electrochemical impedance spectroscopy (EIS). It was found that the simultaneous formation of Ni-P and β-Ni(OH)2 phases in the coating and the improvement in the micro hardness of the coating were due to the incorporation of nanoparticles. According to the polarization curves and EIS spectra, the β-Ni(OH)2 compound behaves like a pre-passive film which is responsible for substantial improvement in the anticorrosion properties of the coating. Better erosion-corrosion resistance was obtained for the composite coatings than the neat Ni-P coating. This was a consequence of the β-Ni(OH)2 co-deposition. The formation of the β-Ni(OH)2 compound in the coating does not depend on the nature and concentration of the nanoparticles.

Pub.: 30 Apr '16, Pinned: 19 Apr '17

Effects of SiC particles size on electrochemical properties of electroless Ni-P-SiC nanocomposite coatings

Abstract: Abstract Silicon carbide (SiC) nanoparticles were co-deposited by electroless deposition in nickel-phosphorous (Ni–P) acidic bath. In order to understand the size effect of SiC nanoparticles on the electrochemical properties of the coatings, SiC nano particles with different size (20, 50 and 200 nm) in 2 g/L concentration was added to the bath. All samples was heat treated in 400°C in order to obtain crystalline structure. Potentiodynamic polarization and electrochemical impedance spectroscopy was employed to examine of corrosion performance of the coatings. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) were used for phase and morphological studies, respectively. Experimental results show that SiC particles size in the coating bath affected both composition and morphology of the coating. Presence of SiC nanoparticles in the Ni–P coating with 50 nm increased the corrosion resistance of the coating more than the other sizes.AbstractSilicon carbide (SiC) nanoparticles were co-deposited by electroless deposition in nickel-phosphorous (Ni–P) acidic bath. In order to understand the size effect of SiC nanoparticles on the electrochemical properties of the coatings, SiC nano particles with different size (20, 50 and 200 nm) in 2 g/L concentration was added to the bath. All samples was heat treated in 400°C in order to obtain crystalline structure. Potentiodynamic polarization and electrochemical impedance spectroscopy was employed to examine of corrosion performance of the coatings. X-ray diffraction (XRD) and Scanning Electron Microscopy (SEM) were used for phase and morphological studies, respectively. Experimental results show that SiC particles size in the coating bath affected both composition and morphology of the coating. Presence of SiC nanoparticles in the Ni–P coating with 50 nm increased the corrosion resistance of the coating more than the other sizes.

Pub.: 01 Jul '16, Pinned: 19 Apr '17

The Effect of Adding Corrosion Inhibitors into an Electroless Nickel Plating Bath for Magnesium Alloys

Abstract: Abstract In this work, corrosion inhibitors were added into an electroless nickel plating bath to realize nickel-phosphorus (Ni-P) coating deposition on magnesium alloy directly. The performance of five corrosion inhibitors was evaluated by inhibition efficiency. The results showed that only ammonium hydrogen fluoride (NH4HF2) and ammonium molybdate ((NH4)2MoO4) could be used as corrosion inhibitors for magnesium alloy in the bath. Moreover, compounding NH4HF2 and (NH4)2MoO4, the optimal concentrations were both at 1.5 ~ 2%. The deposition process of Ni-P coating was observed by using a scanning electron microscope (SEM). It showed corrosion inhibitors inhibited undesired dissolution of magnesium substrate during the electroless plating process. In addition, SEM observation indicated that the corrosion inhibition reaction and the Ni2+ replacement reaction were competitive at the initial deposition time. Both electrochemical analysis and thermal shock test revealed that the Ni-P coating exhibited excellent corrosion resistance and adhesion properties in protecting the magnesium alloy.AbstractIn this work, corrosion inhibitors were added into an electroless nickel plating bath to realize nickel-phosphorus (Ni-P) coating deposition on magnesium alloy directly. The performance of five corrosion inhibitors was evaluated by inhibition efficiency. The results showed that only ammonium hydrogen fluoride (NH4HF2) and ammonium molybdate ((NH4)2MoO4) could be used as corrosion inhibitors for magnesium alloy in the bath. Moreover, compounding NH4HF2 and (NH4)2MoO4, the optimal concentrations were both at 1.5 ~ 2%. The deposition process of Ni-P coating was observed by using a scanning electron microscope (SEM). It showed corrosion inhibitors inhibited undesired dissolution of magnesium substrate during the electroless plating process. In addition, SEM observation indicated that the corrosion inhibition reaction and the Ni2+ replacement reaction were competitive at the initial deposition time. Both electrochemical analysis and thermal shock test revealed that the Ni-P coating exhibited excellent corrosion resistance and adhesion properties in protecting the magnesium alloy.42424424242+

Pub.: 03 Aug '16, Pinned: 19 Apr '17