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

Abstract

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).

Novel Approach for Improving Papaya Fruit Storage with Carnauba Wax Nanoemulsion in Combination with Syzigium aromaticum and Mentha spicata Essential Oils

“…This result is consistent with the findings for the CWN coating, which showed the lowest weight loss (Figure 1) and the highest inhibition of ethylene biosynthesis and gas exchange (CO2 and O2) (Figure 2) in papayas, followed by the CWN-MEO:β-CD coating. The greater the chemical homogeneity of the nanometric coatings, the greater the uniformity and adhesion to the fruit [76]. CWN presents a regular structure due to the stability of the nanoemulsion (with the diameter size parameters of 44, 1 nm, PDI 0.28, and zeta potential of −43.8 mV) [38].…”

“…The antifungal action of the oils delayed fruit rot. The greater the chemical homogeneity of the nanometric coatings, the greater the uniformity and adhesion to the fruit [76]. CWN presents a regular structure due to the stability of the nanoemulsion (with the diameter size parameters of 44, 1 nm, PDI 0.28, and zeta potential of −43.8 mV) [38].…”

Electron-beam synthesis of ceramic- and boron-based coatings

“…One of the most promising directions in the development of modern mechanical engineering is the use of wearresistant parts with ceramic coatings [1,2] in friction units, which can maintain their operational performance under heavy duty conditions (high temperatures and aggressive environments), under which metal coatings lose their properties [3]. Much attention is being paid to studying the characteristics of dielectric, in particular ceramic, materials [4,5].…”