Step-by-Step Tuning of Tribological and Anticorrosion Performance of Zinc Phosphate Conversion Coatings through Effective Integration of Spherical P-Doped MoS2 Nanoparticles

Surface coatings with enhanced mechanical stability, improved tribological performance, and superior anticorrosion performance find immense application in various industrial sectors. Herein, we report the development of multifunctional composite zinc phosphate coatings by the effective integration of a structurally and morphologically tuned P-doped MoS2 nanoparticle additive (3P-MoS2) into the zinc phosphate matrix to offer attractive characteristics suitable for industrial applications. The integration of spherical nanoparticles as additive leads to the formation of homogeneous and compact coatings with a densely packed crystalline microstructure having enhanced microhardness, distinctive leaf-like morphology, and comparatively smooth topographical features. The attractive lubricity of the additive (3P-MoS2), coupled with its spherical morphology, facilitates a transition from sliding to rolling friction and contributes significantly toward the performance enhancement of the tuned composition of the composite zinc phosphate coating (0.3-PMS). Thus, the tuned 0.3-PMS coating delivers the lowest specific wear rate (1.334 × 10-5 mm3/Nm) and coefficient of friction (0.114) that significantly outperform bare-zinc phosphate coating. Further, the electrochemical corrosion study results indicate the improvement in corrosion resistance behavior of the composite zinc phosphate coatings with reduced corrosion current density (icorr) and charge transfer resistance (Rct) values, as compared to the bare-zinc phosphate coating. The effect of passivation in conjunction with the barrier protection characteristics of the composite coatings induced by the optimal composition of the integrated additive nanoparticles (3P-MoS2) can efficiently prevent the infiltration of corrosive ions and thereby significantly reduce the rate of corrosion.

Preparation and Modification of Polydopamine Boron Nitride-Titanium Dioxide Nanohybrid Particles Incorporated into Zinc Phosphating Bath to Enhance Corrosion Performance of Zinc Phosphate-Silane Coated Q235 Steel

In this work, PDA@BN-TiO₂ nanohybrid particles were incorporated chemically into a zinc-phosphating solution to form a robust, low-temperature phosphate-silane coating on Q235 steel specimens. The morphology and surface modification of the coating was characterized by X-Ray Diffraction (XRD), X-ray Spectroscopy (XPS), Fourier-transform infrared spectroscopy (FT-IR), and Scanning electron microscopy (SEM). Results demonstrate that the incorporation of PDA@BN-TiO₂ nanohybrids produced a higher number of nucleation sites and reduced grain size with a denser, more robust, and more corrosion-resistant phosphate coating compared to pure coating. The coating weight results showed that the PBT-0.3 sample achieved the densest and most uniform coating (38.2 g/m²). The potentiodynamic polarization results showed that the PDA@BN-TiO₂ nanohybrid particles increased phosphate-silane films' homogeneity and anti-corrosive capabilities. The 0.3 g/L sample exhibits the best performance with an electric current density of 1.95 × 10^-5 A/cm², an order of magnitude lower than that of the pure coatings. Electrochemical impedance spectroscopy revealed that PDA@BN-TiO₂ nanohybrids provided the greatest corrosion resistance compared to pure coatings. The corrosion time for copper sulfate in samples containing PDA@BN/TiO₂ prolonged to 285 s, a significantly higher amount of time than the corrosion time found in pure samples.

Effect of Graphene Oxide Addition on the Anticorrosion Properties of the Phosphate Coatings in Neutral and Acidic Aqueous Media

Graphene oxide (GO) is an advanced additive improving the properties of various types of coatings and intensifying the deposition process. In this work, GO is used as an additive to the traditional phosphating solution of the widely used Russian low-carbon steel 08YU (DC04). The anticorrosion properties of the obtained phosphate coatings were investigated in neutral (0.5 M NaCl) and acidified (0.1 M Na₂SO₄ + 0.02 M H₂SO₄) aqueous solutions. Increasing the GO concentration in the phosphating solution to 0.3 g/L was found to improve the anticorrosion properties of the phosphate coatings in neutral NaCl solutions. At the same time, in acidified Na₂SO₄ solutions, the corrosion rate of 08YU steel with phosphate coatings increased as a function of the GO concentration. It is assumed that a possible reason for various corrosive behavior is the influence of the GO plates distributed in the coating on the rate of the oxygen or hydrogen reduction reactions.

The effect of riboflavin on the microbiologically influenced corrosion of pure iron by Shewanella oneidensis MR-1

The microbiologically influenced corrosion of pure iron was investigated in the presence of Shewanella oneidensis MR-1 with various levels of exogenous riboflavin (RF) serving as electron shuttles for extracellular electron transfer (EET). With more RF available, a larger and denser phosphate layer was formed on the surface of pure iron by the bacteria. The results of electrochemical impedance spectroscopy, linear polarization resistance and potentiodynamic polarization tests showed that the product layer provided good corrosion protection to the pure iron. Using electrochemical noise, we observed that the addition of RF accelerated the corrosion at the initial stage of immersion, thereby accelerating the deposition of products to form a protective layer subsequently.

R, T. S. N. SN. Cathodic electrodeposition of zinc–zinc phosphate–calcium phosphate composite coatings on pure iron for biodegradable implant applications

Faster degradation of iron based degradable implants in physiological media, particularly during the initial stages of implantation, poses difficulties in directly using them for clinical applications.

Microstructural characterization and film-forming mechanism of a phosphate chemical conversion ceramic coating prepared on the surface of 2A12 aluminum alloy

Phosphate chemical conversion (PCC) ceramic coatings on the surface of 2A12 aluminum alloy substrate have been fabricated by a simple and inexpensive chemical conversion process in CrO₃–NaF–H₃PO₄ solution. Microstructure characterization showed that the average diameter of micro-pores and the thickness of the PCC ceramic coating were about 50 nm and 4 μm, respectively, and the ceramic coating was compact and uniform when the conversion time was 60 min. Meanwhile, we found that the PCC ceramic coating mainly consisted of AlPO₄, AlOOH, AlF₃, and a few amorphous phases (CrPO₄ and CrOOH) via EDS, XRD, XPS analyses. TG-DSC results indicated that the PCC ceramic coatings had excellent thermal stability. Significantly, the adhesion strength (178.55 N) between the PCC ceramic coatings and 2A12 Al substrate was remarkably improved owing to the strong chemical bond between the PCC ceramic coating and 2A12 Al substrate and the increase of surface roughness. Furthermore, a lower corrosion current density (1.382 × 10⁻⁷ A cm⁻²) and a higher corrosion inhibition efficiency (99.91%) confirmed that PCC ceramic coatings had fantastic corrosion resistance because of the presence of crystalline AlPO₄/AlF₃/AlOOH and amorphous CrPO₄/CrOOH as a barrier layer. Additionally, a possible film-forming mechanism of the PCC ceramic coating was proposed during the chemical conversion process, which could be divided into four stages: dissolution of 2A12 aluminum substrate and hydrogen evolution; crystallization of insoluble phosphates and formation of an amorphous phase; growth of insoluble phosphates and dissolution of PCC ceramic coatings; growth and dissolution of PCC coatings to dynamic equilibrium.

Phosphate chemical conversion (PCC) ceramic coatings on the surface of 2A12 aluminum alloy substrate have been fabricated by a simple and inexpensive chemical conversion process in CrO₃–NaF–H₃PO₄ solution.

Anti-corrosion performance of chemically bonded phosphate ceramic coatings reinforced by nano-TiO2

To promote anti-corrosion property of chemically bonded phosphate ceramic coatings (CBPCs), the nano-TiO₂ is selected as the reinforcement. Differential scanning calorimetry (DSC), X-ray diffraction (XRD), Scanning electron microscope (SEM), Energy Dispersive Spectrometer (EDS) and the electrochemical analysis are carried out to clarify the role of nano-TiO₂ on the improvement of anti-corrosion performance. The experiments show that with the addition of nano-TiO₂, the curing temperature and the activation energy of the curing process increase, which allows longest reaction and positively drives curing reactions at elevated conversions. The enhancement of anti-corrosion performance of CBPCs reinforced by nano-TiO₂ particles is based on three main mechanisms. Firstly, more bonded phase (AlPO₄) can be formed with the addition of nano-TiO₂, which can help CBPCs to get more compact microstructure. Additionally, AlPO₄ particles possess the low density and good corrosion resistance, which leads to the increase in the corrosion resistance of CBPCs. Secondly, increasing content of nano-TiO₂ can also strengthen the compactness of CBPCs to protect the substrates from the penetration of aggressive electrolyte and prolong electrolyte diffusion path. Thirdly, through the analysis of microstructure of CBPCs, it is found that most of the hydrophobic nano-TiO₂ particles homogeneously distribute on the surface of CBPCs. Therefore, CBPCs show well hydrophobic performance, which can further improve the anti-corrosion property of themselves.

Structural effect of different carbon nanomaterials on the corrosion protection of Ni–W alloy coatings in saline media

The equivalent circuit models used for the fitting of the EIS data of the Ni–W alloy and Ni–W carbon nanomaterial nanocomposite coatings in a corrosive solution of 3.5% NaCl.

R, T. S. N. SN. Protecting electrochemical degradation of pure iron using zinc phosphate coating for biodegradable implant applications

The surface of pure iron was modified with the formation of a zinc phosphate coatingviaa chemical conversion method for biomedical applications.