Influence of Calcium Phosphates on the Morphology and Properties of Polylactide Composites

Materials Science - We developed polylactide composite materials with calcium-containing fillers; in particular, calcium orthophosphate and calcium hydroorthophosphate. It is shown that the degree...     

Inhibitor protection of the steel reinforcement of armored concrete damaged by cracks

For corrosion-electrochemical investigations, we have developed and manufactured original model concrete specimens-cells to identify testing conditions for six reinforcement specimens. We have studied the polarization characteristics of model specimens held in an environment of weak-acid rain, as well as the kinetics and frequency dependences of impedance characteristics. It has been established that, for the rust protection of steel reinforcement, an inhibiting mixture containing equal quantities of sodium molybdate and calcium nitrate is the most efficient. Its inhibiting efficiency is 10 to 12 times as high as the efficiencies of its components separately, which demonstrates the synergetic effect. The mechanism of the synergetic protective action of these inhibitors lies in passing two processes, which mutually strengthen each other, on the metal surface. The addition of inhibitor to the polyurethane injection composition, applied for the repair of armored concrete structures, increases the strength of adherence of reinforcement with concrete, subjected to the long-term action of a corrosive environment, as compared with noninhibited. Using the synergetic effect in developing inorganic inhibiting mixtures, one can reduce significantly the consumption of materials and improve substantially the manufacturability of injection polymeric compositions for the repair of armored concrete structures of long-term operation.     

Influence of Surface-Modified Conducting Fillers on the Properties of Epoxy Coatings

We have developed a new epoxy composition for antistatic coatings on metallic surfaces, filled with technical carbon and talc, which had been surface-modified by paranitroaniline and phosphoric acid. It has been shown that, with the introduction of modified fillers, the content of gel fraction in an epoxy coating increases by 5–6%, its adhesion becomes 2.5–2.7 times higher, and the amount of organic solvents decreases. We have also established that the electric resistance of the coating is more stable in time as compared with the commercial antistatic ground-coat enamel, and the frequency dependence of the resistance is more clearly pronounced after exposure to a chloride-containing medium, which corroborates the better protective properties of antistatic coatings with modified current conductive fillers. __________ Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 41, No. 4, pp. 53–58, July–August, 2005.     

Surface Films on Zinc-Plated Steel Formed on Holding in Aqueous Extracts of Anticorrosion Pigments

The methods of X-ray photoelectron spectroscopy and Auger spectroscopy are used to study surface films formed on zinc and zinc-plated steel in the process of holding in aqueous extracts of mixtures of phosphate and calcium-containing pigments. It is shown that protective films formed mainly of zinc and calcium phosphates of different chemical structure are deposited in inhibited solutions on specimens of pure zinc and zinc-plated steel. The protective properties of these films are much better than the protective properties of the surface layers formed on the metal in the extracts of a single phosphate (or calcium-containing) pigment. The mixture of these pigments may serve as a promising substitution of chromate inhibitors in anticorrosive organic coatings.     

Specific features of the corrosion inhibition of an aluminum alloy by a nonchromate pigment mixture

The combination of zinc phosphate/molybdate and calcium-containing ion-exchange pigment enables one to inhibit efficiently the local corrosion of an aluminum-copper alloy in a slightly acid medium. Here, the charge-transfer resistance of the metal under the action of extract of this mixture of nonchromate pigments is at the same level as in a medium with the extract of strontium chromate. Using the methods of surface analysis, we have established that this protective effect is caused by the deposition of a protective film on the aluminum matrix (anode) and intermetallic phase (cathode). Under the corrosion potential, a protective film, consisting of a mixture of zinc and calcium phosphates with admixture of zinc hydroxide, is formed on a specimen of the alloy in a medium inhibited by a nonchromate mixture. Mainly zinc phosphate and zinc hydroxide with admixture of calcium phosphate deposit on the cathode polarized surface of the alloy under study. Under anodic potentials, the film consists of zinc and aluminum phosphates. Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 44, No. 5, pp. 45–52, September–October, 2008.     

Method of Equivalent Electrode for the Evaluation of Electrochemical Currents in Corrosion Pits

We deduce a new condition for the electric potential of an electrolyte in a circular pit formed in a body with plane boundary in the case where the potential and current density in the pit depend only on the axial coordinate. This condition enables one to study corrosion processes inside the pit without analyzing the processes running outside the corresponding region.