Corrosion and Heat Treatment Study of Electroless NiP-Ti Nanocomposite Coatings Deposited on HSLA Steel

ZnO-Doped gC3N4 Nanocapsules for Enhancing the Performance of Electroless NiP Coating-Mechanical, Corrosion Protection, and Antibacterial Properties

A carbon nitride (C₃N₄) nanomaterial has superior mechanical, thermal, and tribological properties, which make them attractive for various applications, including corrosion-resistant coatings. In this research, newly synthesized C₃N₄ nanocapsules with different concentrations (0.5, 1.0, and 2.0 wt %) of ZnO as a dopant were incorporated into the NiP coating using an electroless deposition technique. The nanocomposite coatings either ZnO-doped (NiP-C₃N₄/ZnO) or undoped (NiP-C₃N₄) were heat-treated at 400 °C for 1 h. The as-plated and heat-treated (HT) nanocomposite coatings were characterized by their morphology, phases, roughness, wettability, hardness, corrosion protection, and antibacterial properties. The results indicated that the microhardness of as-plated and heat-treated nanocomposite coatings was significantly improved after the incorporation of 0.5 wt % ZnO-doped C₃N₄ nanocapsules. The outcomes of electrochemical studies revealed that the corrosion resistance of the HT coatings is higher than the corresponding as-plated ones. The highest corrosion resistance is achieved on the heat-treated NiP-C₃N₄/1.0 wt % ZnO coatings. Although the presence of ZnO in the C₃N₄ nanocapsules increased its surface area and porosity, the C₃N₄/ZnO nanocapsules prevented localized corrosion by filling the microdefects and pores of the NiP matrix. Furthermore, the colony-counting method used to evaluate the antibacterial behavior of the different coatings demonstrated superior antibacterial properties, namely, after heat treatment. Therefore, the novel perspective C₃N₄/ZnO nanocapsules can be utilized as a reinforcement nanomaterial in improving the mechanical and anticorrosion performance of NiP coatings in chloride media, together with providing superior antibacterial properties.

Electrochemical Processing and Thermal Properties of Functional Core/Multi-Shell ZnAl/Ni/NiP Microparticles

Electroless deposition on zinc and its alloys is challenging because of the negative standard potential of zinc, the formation of poor surface layers during oxidation in aqueous solutions, and extensive hydrogen evolution. Therefore, there are only few reports of electroless deposition on Zn and its alloys, neither of them on micro/nano powders. Here, we propose a two-step process that allows the formation of compact, uniform, and conformal Ni/NiP shell on Zn-based alloy microparticles without agglomeration. The process utilizes controlled galvanic displacement of Ni deposition in ethanol-based bath, followed by NiP autocatalytic deposition in an alkaline aqueous solution. The mechanism and effect of deposition conditions on the shell formation are discussed. Thermal stability and functional analysis of core-shell powder reveal a thermal storage capability of 98.5% with an encapsulation ratio of 66.5%. No significant morphological change of the core-shell powder and no apparent leakage of the ZnAl alloy through the Ni shell are evident following differential scanning calorimetry tests. Our two-step process paves the way to utilize electroless deposition for depositing metallic-based functional coatings on Zn-based bulk and powder materials.

Combined Experimental and Theoretical Insights into the Corrosion Inhibition Activity on Carbon Steel Iron of Phosphonic Acids

The inhibition effect of N,N'-phosphonomethylglycine (PMG) and vinyl phosphonic acid (VPA) on the 3% NaCl acidic solution corrosion of carbon steel iron was studied at different immersion times by potentiodynamic polarization, electrochemical impedance spectroscopy, attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy, and computational methods. It is found from the polarization studies that PMG and VPA behave as mixed-type inhibitors in NaCl. Values of charge transfer resistance (Rct) and double layer capacitance (Cdl) in the absence and presence of inhibitors are determined. The PMG and VPA inhibitors were capable of inhibiting the corrosion process up to ≈91% and ≈85%, respectively. In the presence of PMG, the synergic effect of chlorine ions was observed. Density functional theory (DFT) was engaged to establish the adsorption site of PMG, VPA, and their deprotonated states. For studied compounds, the resulted values of ELUMO, EHOMO, energy gap (∆E), dipole moment (μ), electronic hardness (η), global softness (σ), electrophilic index (ω), and the electronic potential map are in concordance with the experimental data results regarding their corrosion inhibition behavior and adsorption on the metal surface.