Solid State Phenomena Vol. 227

Abstract: Ti-containing coatings as chromate replacement were prepared on electrogalvanized steel. Zinc coatings were deposited from a weak acid chloride bath. Cr-free conversion coatings were deposited from bath composed of: TiCl₃, H₂SiF₆, H₂O₂ and oxalic acid. XPS was used to evaluate chemical composition of the coatings as a function of deposition time. Deposited coating were of conversion type. Regardless of the achieved conversion coating thickness, Zn from the substrate was always present. In the coatings were identified: Zn₂SiO₄ / Zn₄Si₂O₇(OH)₂, ZnTiO₃, ZnO, Zn (OH)₂, Zn⁰, SiOx and Ti-O-Si in varying proportions. The chemical composition of the outer surface of the coating depended on deposition time, e.g. in a time interval 0-300 s 30 fold increase of the Si:Ti ratio and 20 fold of the Si:Zn ratio were observed. Estimated thickness of conversion coating was 3, 14, 35, and 100 nm for the time deposition of 1, 40, 80 and 300 s respectively. It is the proposed model for distinguishing Zn (0) phase from Zn (2+) quantitatively, based on the Zn L₃M₄₅M₄₅ spectrum. The composition of the ZnTiSi conversion coating determined its mechanical properties and corrosion resistance. Standard tests carried out showed that the coatings obtained at the time of 20-40 s had the best corrosion performance and mechanical resistance

Abstract: In the present work we analyzed the anti-corrosive properties, on AA6061, of sol-gel silane-zeolite hybrid coatings doped with cerium nitrate ions as inhibitor. Three different types of composite coatings were prepared by using cerium doped zeolite and/or silane matrix. For each type, four formulations, varying the zeolite amount (in the range 60-90% wt), were tested. All composite coating evidenced a high homogeneity and good adhesion performances. Cerium addiction in the coating formulation did not compromise the hydrophobic properties of the coating. Furthermore the addition of the cerium ions improved the anti-corrosion properties of the composite films inducing a significant stability of the electrochemical behavior.

Abstract: This study concerns laser cleaning technology and its impact on copper corrosion resistances. The results of the treatment process were analyzed after irradiation at various laser powers and scanning velocities of the laser beam. The corrosion resistance of copper sheets, before and after laser irradiation, was examined in an NaCl solution at room temperature. Investigations included surface topography observations using a scanning electron microscope (SEM) together with chemical and phase composition determined by energy dispersive X-ray spectrometry (EDS) and Raman spectroscopy.

Abstract: The use of technical construction parts in corrosive environments frequently leads to costly damage and sometimes to a loss of the functionality of the component parts. Particularly to be noted in this regard are steel structures exposed to industrial and maritime weather conditions (e.g. steel towers, tower flanges for the wind energy industry, primarily in coastal and offshore regions, supports and arch parts used in bridge construction, etc.). These require an especially high corrosion resistance.

Abstract: The paper presents the comparison of the structures of the zirconium modified aluminide coatings deposited on pure nickel by the CVD and method for different conditions, that is the gas flow and the time of deposition. The time of the aluminizing processes varied from 1.5 to 10 hours and the gas (HCl) flow varied from 0.4 to 1.4 l/min. Aluminum was deposited from the AlCl₃ and zirconium from the ZrCl₃ gas phases at 1040 oC. The obtained coatings were examined using an optical microscope (microstructure and coating thickness) a scanning electron microscope (chemical composition on the cross-section of the modified aluminide coating) and an XRD phase analyzer. Microstructures and phase compositions of coatings obtained at different process parameters do not differ significantly. In all cases, it is a triple zone structure. Chemical compositions of zones correspond to β-NiAl, γ’-Ni₃Al and γ-Ni (Al) phases. The elongation of the time of zirconium-aluminizing process from 1.5 to 10 hours leads to the increase of the coating thickness from 30 to about 60 μm. The EDS analysis and concentration profiles of the cross-section of the coating showed the nickel outward diffusion from the substrate and the aluminum inward diffusion from the surface to the nickel substrate. In coatings deposited at a slow gas flow porosity was observed on the border between β-NiAl and γ’-Ni₃Al layers. In coatings deposited at fast gas flow, zirconium does not form any inclusions but dissolves in the matrix. The Kirkendall porosity was not observed.

Abstract: In the presented experiments, the influence of a liquid magnesium alloy with Zr and RE reinforced on glassy carbon particles (GCp) in composites obtained by the mechanical mixing of a suspension, its pressureless solidification and by pressure die casting was examined. The microstructure of the as-received GCp and after their isolation from the composite was characterized by SEM and EDS methods. The presence of a thin oxide type layer with a high RE content was found, independent of the applied composite technology.

Abstract: Corrosion inhibition of concrete steel-reinforcement in 3.5% NaCl, simulating saline/marine environment, by the leaf extract of Rhizophora mangle L. was studied in this paper. For this, duplicated specimens of steel-reinforced concrete slabs, admixed with different concentrations of the leaf extract, were immersed in the corrosive test-medium. Analyses, as per ASTM G16-95 R04, of the electrochemical test-results identified 0.0833% Rhizophora mangle L., per weight of cement, with optimal inhibition efficiency η = 95.73±0.15%. The study established a decrease in inhibition effectiveness as concentration of Rhizophora mangle L. increases.

Abstract: The paper is aimed at comparative study of resistance of Portland cement composites with addition of silica fume as durability increasing factor in various aggressive environments (sulphuric acid with pH 4, the medium of activated bacteria and the cultivating medium without bacteria) during 150 days under model laboratory conditions. Experimental studies confirmed: the leaching of silicon ions calculated to 1 g of concrete sample affected with bacteria Acidithiobacillus thiooxidans was 2.5 times lower (31.78 mg/g of sample) for concrete sample with silica fume addition comparing to concrete sample of ordinary CEM I Portland cement without any additives (82.98 mg/g of sample). The highest concentration of calcium ions released (60.808 mg/g of sample) was observed for reference sample without silica fume addition placed in the cultivating medium. Silica fume based concrete samples were found to have better performance in terms of calcium ions leaching for all environments and silicon ions leaching.

Abstract: Degradation of building materials is an important phenomena influencing its design and utilization. Corrosion of concrete, due to common use of this material is especially important. Chemical corrosion of cementitous materials may be mitigated using various methods. Among them introduction of properly chosen active supplementary cementitous materials to the mix is one of most commonly used. One of possible additives possessing pozzolanic properties is ground waste expanded perlite. No data on the influence of such perlite on chemical durability of cementitous materials can be found in literature. Present paper presents results of investigation on the influence of ground waste expanded perlite on chemical durability of cement mortars. Results obtained showed that there is an improvement of durability of mortars modified with ground waste expanded perlite in sodium sulfate enviroment.

Abstract: This work compares the anticorrosion features of polysiloxane hybrid films deposited on carbon steel substrates by dip-coating. To assess the influence of the components, sol-gel coatings were prepared from condensation and polymerization of TEOS and MPTS, TEOS and MTES, TMOS and MPTS or TMOS and MTES in three molar ratios. The corrosion resistance of the coatings was evaluated by means of polarization curves and the coatings’ thicknesses and compositions were analyzed by a field emission-scanning electron microscopy.