Hybrid Zinc Coating with CuO Nanocontainers Containing Corrosion Inhibitor for Combined Protection of Mild Steel from Corrosion and Biofouling

In this study, a multifunctional hybrid coating is designed for the combined protection of mild steel from corrosion and biofouling in aggressive salt water. This involves preparation of a pH-responsive-release system based on copper oxide (CuO) as a biocide, and the corrosion inhibitor Safranin loaded in polymeric nanocontainers by alternate adsorption of poly(acrylic acid) and poly(ethylenimine) on CuO nanoparticles in water solutions. By optimizing the conditions, i.e., pH and concentration, good stability of the suspensions and the loading amount of Safranin is achieved. The nanocontainers are electrodeposited as an intermediate layer in an ordinary zinc coating on steel (“sandwich-like” structure) from the water solution in order to minimize the effect of CuO dissolution. To highlight the role of Safranin in reducing steel corrosion, a second zinc coating containing CuO nanoparticles without a corrosion inhibitor is also examined. The surface morphology and corrosion behavior of the hybrid coatings are evaluated in a model corrosion medium (5% NaCl solution). Both coatings are found to improve the anticorrosion behavior of steel for a time interval of 55 days and at conditions of external polarization. It can be expected that the newly developed hybrid coatings would also demonstrate potential for marine applications due to the main characteristics of their components

Hybrid Zinc-Based Multilayer Systems with Improved Protective Ability against Localized Corrosion Incorporating Polymer-Modified ZnO or CuO Particles

Localized corrosion and biofouling cause very serious problems in the marine industries, often related to financial losses and environmental accidents. Aiming to minimize the abovementioned, two types of hybrid Zn-based protective coatings have been composed. They consist of a very thin underlayer of polymer-modified ZnO or CuO nanoparticles and toplayer of galvanic zinc with a thickness of ~14 µm. In order to stabilize the suspensions of CuO or ZnO, respectively, a cationic polyelectrolyte polyethylenimine (PEI) is used. The polymer-modified nanoparticles are electrodeposited on the steel (cathode) surface at very low cathodic current density and following pH values: 1/CuO at pH 9.0, aiming to minimize the effect of aggregation in the suspension and dissolution of the CuO nanoparticles; 2/ZnO at pH 7.5 due to the dissolution of ZnO. Thereafter, ordinary zinc coating is electrodeposited on the CuO or ZnO coated low-carbon steel substrate from a zinc electrolyte at pH 4.5–5.0. The two-step approach described herein can be used for the preparation of hybrid coatings where preservation of particles functionality is required. The distribution of the nanoparticles on the steel surface and morphology of the hybrid coatings are studied by scanning electron microscopy. The thickness of the coatings is evaluated by a straight optical microscope and cross-sections. The protective properties of both systems are investigated in a model corrosive medium of 5% NaCl solution by application of potentiodynamic polarization (PDP) curves, open circuit potential (OCP), cyclic voltammetry (CVA), and polarization resistance (Rp) measurements. The results obtained allow us to conclude that both hybrid coatings with embedded polymer-modified CuO or ZnO nanoparticles ensure enhanced corrosion resistance and protective ability compared to the ordinary zinc

Obtaining and Corrosion Performance of Composite Zinc Coatings with Incorporated Carbon Spheres

The present work describes one possible way to prepare a stable aqueous suspension of carbon sphere particles with a positive charge that is suitable for simultaneous electrodeposition with zinc on steel substrate. In order to stabilize the suspension against aggregation, tri-block amphiphilic copolymer Pluronic F127, which is commercially available, was adsorbed on the surface of carbon sphere particles. This polymer contained poly (ethylene oxide) blocks as hydrophilic segments and poly (propylene oxide) blocks as the hydrophobic part. Scanning electron microscopy and visual observations confirmed the stability of the obtained suspension. The carbon sphere particles were embedded into the zinc coating by the co-electrodeposition process. The surface morphology of the composite coating was investigated using scanning electron microscopy. The influence of the carbon spheres on the cathodic and anodic processes was evaluated with cyclic voltammetry studies. The electrochemical investigations were realized in a model corrosion medium (5% NaCl solution with pH 6.7) by application of selected methods such as polarization resistance, potentiodynamic polarization, and electrochemical impedance spectroscopy, which revealed higher protective ability of the composite coating against corrosion in an aggressive environment

Comparative Corrosion Characterization of Hybrid Zinc Coatings in Cl−-Containing Medium and Artificial Sea Water

The presented investigations demonstrate the corrosion behavior and protective ability of hybrid zinc coatings specially designed for combined protection of low-carbon steel from localized corrosion and biofouling. Polymer-modified copper oxide (CuO) nanoparticles as widely used classic biocide are applied for this purpose, being simultaneously electrodeposited with zinc from electrolytic bath. The corrosion behavior of the hybrid coatings is evaluated in a model corrosive medium of 5% NaCl solution and in artificial sea water (ASW). Scanning electron microscopy (SEM) and atomic force microscopy (AFM) are used to characterize the surface morphology of pure and hybrid zinc coatings. Contact angle measurements are realized with an aim to determine the hydrophobicity of the surface. X-ray photoelectron spectroscopy (XPS) is applied for evaluation of the chemical composition of the surface products appearing as a result of the corrosion treatment. Potentiodynamic polarization (PDP) curves and polarization resistance (Rp) measurements are used to estimate the protective characteristics in both model corrosive media. The results obtained for the hybrid coatings are compared with the corrosion characteristics of ordinary zinc coating with the same thickness. It was found that the hybrid coating improves the anticorrosion behavior of low-carbon steel during the time interval of 35 days and at conditions of external polarization. The tests demonstrate much larger corrosion resistance of the hybrid coating in ASW compared to 5% NaCl solution. The obtained results indicated that the proposed hybrid zinc coating has a potential for antifouling application in marine environment

Protective Characteristics of TiO₂ Sol-Gel Layer Deposited on Zn-Ni or Zn-Co Substrates

This study aimed to present the differences in the corrosion properties and protective ability of two bi-layer systems obtained on low-carbon steel in a model corrosive medium of 5% NaCl solution. These newly developed systems consist of Zn-Co (3 wt.%) or Zn-Ni (10 wt.%) alloy coatings as under-layers and a very thin TiO2 sol-gel film as a top-layer. Scanning electron microscopy (SEM) is used for characterization of the surface morphology of the samples indicating that some quantitative differences appear as a result of the different composition of both zinc alloys. Surface topography is investigated by means of atomic force microscopy (AFM), and the hydrophobic properties are studied by contact angle (CA) measurements. These investigations demonstrate that both sample types possess grain nanometric surface morphology and that the contact angle decreases very slightly. X-ray diffraction (XRD) and X-ray photoelectron spectroscopy (XPS) are used for characterization of the chemical composition and electronic structure of the samples. The roughness Rq of the Zn-Ni/TiO2 is 49.5 nm, while for Zn-Co/TiO2, the Rq value is 53.4 nm. The water contact angels are 93.2 and 95.5 for the Zn-Ni/TiO2 and Zn-Co/TiO2 systems, respectively. These investigations also show that the co-deposition of Zn and Ni forms a coating consisting entirely of Ni2Zn11, while the other alloy contains Zn, Co and the intermetallic compound CoZn13. The corrosion resistance and protective ability are estimated by potentiodynamic polarization (PDP) curves, as well as polarization resistance (Rp) measurements for a prolonged test period (35 days). The results obtained are compared with the corrosion characteristics of ordinary zinc coating with an equal thickness. The experimental data presents the positive influence of the newly developed systems on the enhanced protective properties of low-carbon steel in a test environment causing a localized corrosion—lower corrosion current density of about one magnitude of order (~10−6 A.cm−2 for both systems and ~10−5 A.cm−2 for Zn) and an enhanced protective ability after 35 days (~10,000–17,000 ohms for the systems and ~900 ohms for Zn)

Modified Approach Using Mentha arvensis in the Synthesis of ZnO Nanoparticles—Textural, Structural, and Photocatalytic Properties

Zinc oxide arouses considerable interest since it has many applications—in microelectronics, environmental decontaminations, biomedicine, photocatalysis, corrosion, etc. The present investigation describes the green synthesis of nanosized ZnO particles using a low-cost, ecologically friendly approach compared to the classical methods, which are aimed at limiting their harmful effects on the environment. In this study, ZnO nanoparticles were prepared using an extract of Mentha arvensis (MA) leaves as a stabilizing/reducing agent, followed by hydrothermal treatment at 180 °C. The resulting powder samples were characterized by X-ray diffraction (XRD) phase analysis, infrared spectroscopy (IRS), scanning electron microscopy (SEM), and electron paramagnetic resonance (EPR). The specific surface area and pore size distribution were measured by the Brunauer–Emmett–Taylor (BET) method. Electronic paramagnetic resonance spectra were recorded at room temperature and at 123 K by a JEOL JES-FA 100 EPR spectrometer. The intensity of the bands within the range of 400–1700 cm−1 for biosynthesized ZnO (BS-Zn) powders decreased with the increase in the Mentha arvensis extract concentration. Upon increasing the plant extract concentration, the relative proportion of mesopores in the BS-Zn samples also increased. It was established that the photocatalytic performance of the biosynthesized powders was dependent on the MA concentration in the precursor solution. According to EPR and PL analyses, it was proved that there was a presence of singly ionized oxygen vacancies (V0+) and zinc interstitials (Zni). The use of the plant extract led to changes in the morphology, phase composition, and structure of the ZnO particles, which were responsible for the increased photocatalytic rate of discoloration of Malachite Green dye