Solid State Phenomena Vol. 227

Abstract: The aim of this paper is to evaluate the efficiency of hybrid sol-gel coatings reinforced with electrospinning nanofibers doped with cerium nitrate and ceria particles to increase the corrosion properties of the coating. Poly(vinyl alcohol) solutions doped with cerium nitrate and ceria were electrospun onto clean commercial aluminum alloy AA2024-T3 plates and then coated with a hybrid sol-gel system using the dip-coating procedure. The hybrid materials synthesized via sol-gel chemistry were prepared from inorganic-organic precursors: zirconium (IV) propoxide and 3-glycidoxypropyltrimetoxysilane. The electrochemical impedance spectroscopy technique was applied to evaluate the electrochemical properties of the film whereas scanning electron microscopy and atomic force microscopy were employed to characterize the surface characteristics. The incorporation of nanofibers into the sol-gel system provides good barrier properties that increase the corrosion resistance of the aluminum at longer exposure times in saline media. This protection depends of the type of inhibitor loaded within the electrospun nanofibers.

Abstract: In this paper substantiated the possibility of creating on the basis of epoxy-polyelectrolyte composites of anticorrosive coatings sensitive to corrosive environment and its application for protection from underfilm corrosion cathode-polarized structures, which include, for example, underground steel pipelines.

Abstract: Properties of commercially available epoxy coating were modified using multi-walled carbon nanoparticles (MWCNT) to obtain functional coating with improved abrasion resistance. Simultaneously, corrosion resistance of the epoxy resin could not be negatively affected by the particles addition. Composite coatings with various MWCNT content were prepared and evaluated with regard to their function by abrasion and corrosion tests. We found out that the abrasion resistance of the coatings increased with increasing amount of CNT particles in the matrix. Corrosion protection properties of pure epoxy coating as well as its adhesion were slightly improved by adding 0.5 and 1 wt% MWCNT.

Abstract: Sol-gel SiO₂ and hybrid films were deposited on 316L stainless steel by the dip process. Epoxy bisglycidyl hydroquinone (EBH) was used as an organic component in hybrid films. Both coatings were uniform and homogeneous and displayed good adhesion to the substrates. The thickness of hybrid coatings was greater than that of SiO₂ coatings. Thermal condition preparation has significant influence on spectroscopic properties of samples. These features are due to changes of morphology of epoxy-silica hybrid compared to unmodified silica-gels and are related to decomposition at higher temperature. The corrosion behaviour of 316L stainless steel samples coated with SiO₂ and hybrid films was studied in Ringer’s solution by electrochemical impedance spectroscopy. SiO₂ and silica-based hybrid coatings produced by the sol-gel method offers a good protection against corrosion of stainless steel in Ringer’s solution. In contrast to the SiO₂-coated samples and the hybrid coating heated to 200°C, the behaviour of the hybrid coating heated to 300°C changed from resistive to a barrier-like one during exposure to the solution. This change was found to be a transient effect only. During 1-month exposure to Ringer’s solution the coating lost its barrier properties.

Abstract: Hot Dip Galvanized (HDG) coating protects steel from corrosion by providing a thick, tough metallic zinc envelope, which completely covers the steel surface and seals it from the corrosive action of its environment. The anti-corrosion ability of this sacrificial anode cathodic protection can be improved upon through the protective nature of passivation films on zinc like potassium dichromate.This study investigated the anti-corrosion effect of potassium dichromate (K₂Cr₂O₇) film on freshly galvanized coating in distilled water (pH=7.92). The K₂Cr₂O₇ film passivity on the hot-dip zinc coated steel sheets (taken as treated in the context of this study) was used in direct comparison with their untreated counterparts. The test was run for 30 days at 120 hours interval during which the corresponding weight losses, corrosion rates, inhibitor efficiencies, and pH of the final solutions were obtained of the coupons. Analysis of results was made using Microsoft office applications. The surface morphology of the samples was obtained using Optical microscope. The results obtained revealed the greater influence of the action of the K₂Cr₂O₇ film on selected and examined HDG steel sheets corrosion performance. Weight losses increased with increase in immersion time. Inhibitor efficiency of 4.1% was achieved. The photomicrographs confirmed the occurrence of corrosion on untreated coating more than the treated ones. Conclusively, potassium dichromate was effective in passivating galvanized coating from white rust.

Abstract: The investigations on anodic oxidation of galvanic Zn-Ni alloy coating in the baths containing sodium hydroxide, sodium silicate and ammonium pentaborate was described in this paper. The surface morphology studies (SEM) and corrosion characterization was the main part of the work. It was found that the anodic treatment of the Zn-Ni alloy coating in the alkali solutions basis on NaOH permit to the obtaining the oxide layer with cracks formation. Application of the baths containing also sodium silicate and ammonium pentaborate cause the cracks decay. The corrosion studies may indicate that the cracks are shallow.

Abstract: The electrochemical deposition of zinc coatings from 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) baths on steel substrate was described in this paper. The influence of [ZnCl₂]/[BMIMCl] ratio, current density as well as temperature have been investigated. It was found that electrodeposition in all of tested baths and parameters allowed to obtain zinc coatings. The surface of coatings were matte and in the most of cases the coating morphology was not homogenous. On the basis of corrosion investigation it was pointed out that application of the baths of higher ZnCl₂ content are more beneficial for zinc coatings electrodeposition that the one of [ZnCl₂]/[BMIMCl]= 2:3.

Abstract: Zn-Ni and Zn-Co monolayer and Zn-Ni/Zn-Co multilayer (from 2 to 128 layers) alloy coatings were formed on steel substrate by electrodeposition from acidic Zn-Ni bath and neutral Zn-Co bath. Samples were tested in salt chamber for corrosion resistance in neutral salt spray. Open circuit potential measurement and gravimetric study of corrosion were carried for samples immersed in the 5% NaCl solution.It was found that coatings of Zn-Ni surface layer occurred higher corrosion resistance then the coatings of Zn-Co surface layer. Sixteen-layer coating with Zn-Ni surface layer proved to be most effective in protecting the steel substrate. Zn-Ni monolayer showed the lowest corrosion potential, which affects the corrosion properties. Sample weight changes during exposure to a corrosive environment are related to digestion of the coating and the formation of corrosion products.

Abstract: In this work the results of investigations on thickness distribution of conversion coatings on magnesium alloy AZ91D obtained by plasma electrolytic oxidation (PEO) in sodium silicate solution are presented. The morphology and chemical composition as well as thickness distribution of obtained coatings, with special respect to hard to reach points are shown. Also the corrosion resistance of obtained alloy samples is determined.

Abstract: In the paper, there are presented XPS results of surface layer formed after electrochemical polishing of AISI 316L (EN 1.4404) stainless steel at high current density of 2000 A/dm². For the investigation, electrolyte based on orthophosphoric (H₃PO₄) and sulfuric (H₂SO₄) acids in proportions 3:2, was used. The obtained results have shown, that high current density has considerably influences the composition of passive layer formed after electrochemical treatment. The study was focused mainly on the amount of carcinogenic nickel, sensitization chromium compounds on the sixth degree of oxidation as well as the [(Cr+3.3∙Mo)/Fe] coefficient.