Volume 61 (2017): Edizione 2 (April 2017)

Mixed oxide-based pigments Mg–Zn–Fe with different particle morphologies were prepared by high-temperature solid phase reactions. The core shell pigments containing ferric oxide and non-isometric particles of layered silicates were also prepared. The pigments were tested in paints, the pigment volume concentrations in the modified alkyd resin based binder being 5%, 10%, and 15%. The paint properties were examined by accelerated corrosion tests and by physico-mechanical tests. The effect of the pigment particle morphology on the surface hardness of the paint films was also studied. The influence of pigment volume concentration on the coating properties, and the optimum concentrations providing the most efficient anticorrosive protection were processed. A higher anticorrosion efficiency was observed for the paints with pigments possessing the lamellar particle shape.

This work is focused on the initial realization of a multi-component coating deposition from the aqueous solution. The Coating composed of the elements Co-Cr-Fe-Mn-Ni was prepared by electroplating process. The chosen substrate was copper. The purpose of the work was to apply the high entropy alloy, which is defined as alloy with structure of a solid solution containing five or more elements in an approximately equal atomic ratio. The use of electrodeposition in this area is rare. The conditions of the plating process, the percentage of the metal ions and cohesion of the layers were studied. The morphology of the excluded coatings was monitored by scanning electron microscopy and their elemental composition was verified by the EDS analysis. The wear resistant features were examined approximately before and consequently also after the thermal resistance testing.

A number of damage functions or dose-response equation, which are compared to the atmospheric corrosion of metals with environmental parameters, have been determined in field programs ISOCORRAG, UN ECE ICP Materials Exposure Programme and Multi-Assess. The all of these dose-response equations are derived on field exposure results performed during period 1986-1995 where the SO₂ level was relative high at urban and very high at industrial test sites. Several exposure programmes, national and international, of structural metals’ atmospheric corrosion were conducted since the 1970s on Czech atmospheric test sites including on-site measurement of environmental data. All data from these exposure programs were compared with prediction models.

The paper summarizes the impact of produced hydrogen and calcium hydroxyzincate (Ca[Zn(OH)₃]₂·2H₂O) on the formation of the porous structure of cement paste in the vicinity of hot-dip galvanized steel. These substances result from cathodic (hydrogen) and anodic (zincates-formed by reaction with hydroxides) corrosion reactions of hot-dip galvanized steel (or pure zinc) in the cement paste.

The cement binder pore structure was studied by means of mercury porosimetry and analysis of scanning electron microscopy and confocal microscopy images. The porosity of the cement paste at the galvanized steel / cement interphase increased as a result of galvanized steel corrosion while hydrogen was formed. Such a porous structure was maintained throughout the maturation of cement paste. Kinetics of galvanized steel corrosion related primarily to water transport through the binder. The formation of calcium zincate did not result in transition of galvanized steel from active to passive state corrosion.

The surface treatment by a powder coating is one of the progressive technologies. Such coatings are resistant to corrosion and mechanical wearing. The quality of surface protection is affected primarily by a layer pre-treatment, the type of surface tretment, the system selection and the method and quality of application. Taking into account all the surface pre-tretment methods, the chemical pre-modification is a leading method. One of the methods is pre-treatment using a conversion coating which was developed on the nanotechnology basis - BONDRITE NT. That non-phosphate chemical pre-treatment is utilized at a surrounding temperature. It creates nano-ceramic protective layer on steel, zinc and aluminium surfaces, and as the result the coating has a significant adhesion. In the paper, the possibilities for the improvement of corrosion resistance of powder coatings using the subject conversion coating are presented at the current pasivation of respective surface.