Corrosion Resistance Of Ni-P Coatings Research Articles

Enhancing wear and corrosion resistance of electroless Ni-P coatings in CO2-saturated NaCl solution through polytetrafluoroethylene incorporation

In the realm of oil and natural gas, material durability is compromised by sand particle abrasion, corrosive media, and hydrogen-induced cracking. This study investigates the impact of PTFE on wear and corrosion resistance of Ni-P coatings in a CO2 environment. Hydrogen barrier properties of the substrate, Ni-P, and PTFE are evaluated using the Devanathan-Stachursky cell. Results show that incorporating PTFE enhances the coating's wear and corrosion resistance, and hydrogen barrier performance compared to substrate and Ni-P alone. The coating effectively hinders corrosive media transmission. A comprehensive analysis of the Ni-P-PTFE corrosion mechanism is provided, along with a robust corrosion model.

Influence of iron element on the structure and corrosion resistance of Ni-P coatings in different corrosive environments

Ni-P coatings and Ni-Fe-P coatings with the same thickness and the same phosphorus content were prepared by electroless deposition. The effects of iron on the structure, morphology and corrosion resistance of Ni-P coatings were studied. The results show that the iron can improve the flatness of the Ni-P coatings and increase its crystallite size to make it appear crystalline state. The corrosion behavior of the two coatings was investigated in 3.5 wt% NaCl solution, saturated CO2 solution and 0.1 mol·L−1 H2SO4 solution. During the corrosion process, iron can promote the conversion of Ni(OH)2 to NiO in the passive film. In 3.5 wt% NaCl solution, the Ni-Fe-P coatings exhibited better corrosion resistance, which was due to the fact that NiO can effectively inhibit the ion exchange during the corrosion process. In saturated CO2 solution, the corrosion resistance of Ni-P coatings was more excellent. This is because the corrosion reaction mainly occurs between the coating and the substrate, and the smaller crystallite size of the Ni-P coatings can effectively prevent the intrusion of corrosion ions. In 0.1 mol·L−1 H2SO4 solution, the Ni-Fe-P coatings was seriously damaged, which was not suitable for metal protection in strong acid environment.

The influence of phosphorus content on the microstructure and specific capacitance of etched electroless Ni-P coatings

Acidic and alkaline electroless bath Ni-P coatings with varying P contents (4.7–8.1 wt%) were deposited on Ti substrate. These as-deposited Ni-P coatings had no apparent difference in specific capacitance. The deposition rate of coating increased with the increase in NaH2PO2·H2O content regardless of the bath type, while the alkaline bath yielded a lower phosphorus content. After the Ni-P coatings were etched by a HNO3 solution, dealloying first occurred in the boundaries between the nodules and then, in the inside of the nodules. Finally, the nodules were etched into numerous nanoparticles with a size of 25–35 nm. An increased specific surface area, due to porous structures, is the major contribution for high specific capacitance. The phosphorus content significantly affects the corrosion resistance of Ni-P coatings and, thus, plays an important role in deciding the microstructure and specific capacitance of etched Ni-P coatings. The specific capacitance of etched Ni-P coatings is a function of phosphorus content and etching time at a fixed etching condition, and an optimum value exists. The highest value achieved is dependent on phosphorus content. The mechanism of the etched Ni-P coatings used as the electrode of the supercapacitor also was discussed further.

Ultrasonic-Assisted Electroless Ni-P Plating on Dual Phase Mg-Li Alloy

An ultrasonic-assisted method for electroless Ni-P plating on dual-phase Mg-Li alloy is proposed. Environmentally-friendly Ce(NO3)3-KMnO4 solution was successfully applied for the pre-treatment. Uniform and compact Ni-P coatings with fine structures have been successfully obtained. The Ni-P coatings are mixed with amorphous-crystalline features and well adhered to the substrates. The corrosion resistances were investigated by electrochemical impedance spectroscopy, open circuit potential, potentiodynamic polarization and hydrogen evolution tests. The results indicate that ultrasonic processing significantly improves the corrosion resistance of Ni-P coatings due to the formation of uniform, dense and fine structures, which strengthen the passive film.

Effect of KI on the Corrosion Resistance of Ni-P Electroless Plating Coating

To improve the corrosion resistance of Ni-P electroless coating, the KI was added in the electroless solution. The surface micrograph was observed using scanning electron microscopy (SEM), and the corrosion resistance of Ni-P coatings in 3.5%NaCl solution was examined by polarization curves and electrochemical impedance spectroscopy (EIS). The experimental results showed that KI reduced the amount of defects and the size of crystal grain of Ni-P coating, and the surface of Ni-P coating became more homogenous, smoother and compact by KI. In addition, the phosphorus content of Ni-P coating was increased by KI. These factors increased the ability to corrosion protection of Ni-P coating.

Effects on Corrosion Resistance of Ce-Sealed Ni-P Coatings with Ni-Low P and Ni-Medium P

The post-treatment with Ce-rich sealing of Ni-P coating (Ce-sealed Ni-P coating) was developed on Al surface. Effects of corrosion resistance with different phosphorus contents in the Ni-P coatings were investigated in this paper. The results of the polarization curves show that the Ce-sealed Ni-(10wt.%)P coatings have the higher corrosion potential (Ecorr) and the lower corrosion current (icorr), indicating that this coating iSubscript texts a better corrosion inhibitor than Ni-(3wt.%)P coating. These results demonstrate that the P content plays an obvious role on improving the corrosion resistance of Ni-P coatings. It is results of SEM analysis shows that the Ce-sealed Ni-(3wt.%)P coating has not obvious micro-cracks, the Ce-sealed Ni-(10wt.%)P surface with some micro-cracks are appeared on Ce-rich coating. But this micro-cracks phenomenon of Ce-rich coating can not effect on corrosion resistance. Otherwise, there are no peaks of Ce-riched coatings in both XRD patterns, because too less Ce elements and non-crystal tendency is more serious on these coatings.

Effect of surfactant on the fabrication and characterization of Ni-P-CNT composite coatings

In order to disperse carbon nano-tubes in electroless Ni-P coatings different surfactants (sodium dodecyl sulfate (SDS) as anionic surfactant and Hexadecyl Trimethylammonium Bromide (HTAB) as cationic surfactant) were added to the electroless bath and their respective dispersing power was monitored by using ultra violet visible (UV–vis) spectroscopy method. Then Ni-P-CNT coating deposited, using optimum surfactant-to-CNTs ratio of proper surfactant. The morphologies of composite coatings were analyzed using a scanning electron microscope (SEM). Moreover, hardness and corrosion resistance of the applied composite coatings were measured via microhardness, polarization and electrochemical impedance spectroscopy (EIS) methods. Results showed that an optimum ratio of SDS can uniformly disperse CNTs throughout the electroless Ni-P coating, which yields the highest hardness. Corrosion resistance studies showed that the incorporation of CNTs can increase the corrosion resistance of Ni-P coatings due to the filling of pores and micro-holes, while decreasing the metallic area that is prone to corrosion attack.