Evaluation of the corrosion resistance of electroless Ni-P and Ni-P composite coatings by electrochemical impedance spectroscopy
TL;DR: In this paper, the same fundamental reaction is occurring on all the coatings of the present study but over a different effective area in each case, which can be attributed to the decrease in the effective metallic area prone to corrosion.
Abstract: Electroless Ni-P composite coatings have gained a good deal of popularity and acceptance in recent years as they provide considerable improvement of desirable qualities such as hardness, wear, abrasion resistance, etc. The disagreement among researchers on the corrosion behaviour of these coatings warrants a thorough investigation. Among the various techniques available for the determination of corrosion resistance, electrochemical impedance spectroscopy (EIS) is considered to be superior as it provides not only an assessment of the corrosion resistance of different deposits but also enables the mechanistic pathway by which the deposits become corroded to be determined. The present investigation focuses on the evaluation of the corrosion resistance of electroless Ni-P and Ni-P-Si3N4, Ni-P-CeO2 and Ni-P-TiO2 composite coatings produced using an acidic hypophosphite-reduced electroless nickel bath, using EIS. The study makes evident that the same fundamental reaction is occurring on all the coatings of the present study but over a different effective area in each case. The charge transfer resistance of electroless Ni-P and Ni-P composite deposits are in the range 32,253–90,700 Ω cm2, whereas the capacitances of these coatings are in the range 11–17 µF/cm2. The improved corrosion resistance obtained for electroless Ni-P and Ni-P composite coatings is due to the enrichment of phosphorus on the electrode surface, which enables the preferential hydrolysis of phosphorus over that of nickel. The better corrosion resistance obtained for electroless Ni-P composite coatings can be ascribed to the decrease in the effective metallic area prone to corrosion. Among the three electroless Ni-P composite coatings, the corrosion resistance is in the following order: Ni-P-CeO2=Ni-P-Si3N4>Ni-P-TiO2.
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TL;DR: The development of metal deposition processes based on electroless nickel, alloy and composite coatings on various surfaces has witnessed a surge in interest among researchers, with many recent applications made possible from many excellent properties as mentioned in this paper.
680 citations
Cites background from "Evaluation of the corrosion resista..."
...Among them, the combinations that have received considerable attention are SiC ([128]), CeO2, TiO2 ([150-151]), Al2O3, Zn3(PO4)2 ([155]), ZnSnO3, ZnSiO3 ([155]), single wall carbon nano tubes (SWCNTs) ([156]), and nanometer diamond (ND) ([135])....
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...In some cases, electroless Ni-P-Si3N4, Ni-P-CeO2 and Ni-P-TiO2 composite coatings, by electrochemical impedance spectroscopy, show better corrosion resistance than the plain electroless Ni-P deposits ([150-151])....
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TL;DR: In this paper, the authors outline the development of electroless Ni-P composite coatings and highlight the method of formation, mechanism of particle incorporation, factors influencing particle incorporation and the effect of incorporation on the structure, hardness, friction, wear and abrasion resistance, corrosion resistance, high temperature oxidation resistance, and their applications.
Abstract: This review outlines the development of electroless Ni–P composite coatings. It highlights the method of formation, mechanism of particle incorporation, factors influencing particle incorporation, effect of particle incorporation on the structure, hardness, friction, wear and abrasion resistance, corrosion resistance, high temperature oxidation resistance of electroless Ni–P composite coatings as well as their applications. The improvement in surface properties offered by such composite coatings will have a significant impact on numerous industrial applications and in the future they will secure a more prominent place in the surface engineering of metals and alloys.
359 citations
TL;DR: In this article, the formation of Ni-P/Ni-B duplex coatings by electroless plating process and evaluation of their hardness, wear resistance and corrosion resistance were dealt with.
160 citations
TL;DR: In this paper, 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, was studied.
Abstract: 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
157 citations
15 Jul 2007-Materials Science and Engineering A-structural Materials Properties Microstructure and Processing
TL;DR: In this article, the corrosion behavior of electrodeposited nanocrystalline Ni-W and Ni-Fe-W alloys was evaluated using polarization and electrochemical impedance spectroscopy techniques in 3.5% NaCl solution while their passivation behaviour was studied in 1N sulphuric acid solution.
Abstract: The present work deals with evaluation of corrosion behaviour of electrodeposited nanocrystalline Ni–W and Ni–Fe–W alloys. Corrosion behaviour of the coatings deposited on steel substrates was studied using polarization and electrochemical impedance spectroscopy techniques in 3.5% NaCl solution while their passivation behaviour was studied in 1N sulphuric acid solution. The corrosion resistance of Ni–W alloys increased with tungsten content up to 7.54 at.% and then decreased. In case of Ni–Fe–W alloys it increased with tungsten content up to 9.20 at.% and then decreased. The ternary alloy coatings exhibited poor corrosion resistance compared to binary alloy coatings due to preferential dissolution of iron from the matrix. Regardless of composition all the alloys exhibited passivation behaviour over a wide range of potentials due to the formation of tungsten rich film on the surface.
145 citations
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TL;DR: In this article, an amorphous Ni-19P alloy prepared by rapid quenching of white heat melt showed a higher anodic dissolution current density in 1 N HCl in comparison with the same amorphized alloy prepared with red heat melt, showing that the difference in anodic behavior between these two as-quenched specimens seems due to the differences in the amounts of quenched-in defects.
75 citations