Group of the agents Pragokor Seal Cu, Fe and Zn comprises water-borne varnishes convenient predominantly for the finish coating, sealing and preservation of the metallic surfaces or conversion coatings. In particular cases, they may be used as an irremovable inter-machinery operations protection against corrosion. They create thin polymeric colourless and transparent layers bearing both versatile and specific corrosion inhibitors, hydrophobic and preservation additives and other modifying substances. The polymeric layer, together with corrosion inhibitors, will create both mechanical as well as chemisorption barrier against the adverse activity of corrosion stimulators. The Pragokor Seal agents should be applied by dipping technique only as the last technological operation just before drying, after the last rinsing step. They may be alternatively applied for the clean and dry surfaces, the surface must be, anyway, wettable with water.
Pragokor Seal Cu should be predominantly used for the protection of copper, brass, bronze and other metallic substrates or copper-based metallic coatings and, further, for sealing and impregnation of passivated or patinized copper and its alloys. It offers, furthermore, the protection of the surfaces against darkening and will seal the pores in copper plated coatings. The varnish layer will create the decorative finish on copper and its alloys to ensure the long-term appearance stability of the surface treated. By the Pragokor Seal Cu agent, the same appearance stability is also imparted to both silver and aluminium substrates and metallic coatings made of them.
Pragokor Seal Fe is of a more versatile use. It should be particularly used for sealing and impregnation of the phosphate coatings on steel and blackening coatings on steel or cast iron, for the protection of nickel plated coatings against darkening and for pores sealing in Ni-Cr and Cu-Ni-Cr plated coatings. Besides, it will create an irremovable inter-machinery operations protection of the steel parts previously alkaline degreased or degreased and consequently acid pickled. Due to its versatility, the agent is suitable for the anticorrosion protection of the machinery parts made of more metals.
Pragokor Seal Zn should be predominantly used for the protection of chromate and phosphate conversion coatings on zinc, zinc alloys or cadmium plated coatings and will impart the enhanced anticorrosion protection to the substrates like that. The corrosion durability of the chromate coatings on zinc, topcoated with Pragokor Seal Zn, in the neutral salt spray test, until the first spots of white rust, was proved to be increased by 200 – 600 hours as compared with the unprotected chromate. Furthermore, the coating of the agent is able to make the appearance of the chromate more uniform, the undesirable iridescence being avoided. The Pragokor Seal Zn varnish coating creates the decorative finish on chromates and will impart the long-term stability of the appearance to the surface treated.
Pragokor Seal Si is suitable for the sealing of the conversion both chromate and non-chromate-based passivating layers on zinc and zinc alloys coatings, aluminium and its alloys, passivated zinc casts etc. The agent will boost the anticorrosion performance of the conversion coatings substantially and, hence, impede the onset of the first corrosion marks on the substrate. It should be especially used after the chromating processes without six-valence chromium components and will enhance the entire corrosion durability of the parts treated in the neutral salt spray test by 200 – 400 hours. The agent may be alternatively used in the cases when sealing with more common water-based organic lacquers is not allowed as a loosened piece of such a paint might cause the clogging and failure of hydraulic braking or cooling circuits. The agent is water-based colloid solution of a slightly milk-like appearance containing nanoparticles of the silica sol which, at the application from the water solution, will deposit on the surface of the conversion coating forming a very thin colourless and transparent silica gel-based layer. After drying out and dehydration of the gel, the network of siloxane bonds will be created which will add to the overall anticorrosion performance of the coating the thickness of which varies within 0,3 – 3 µm. The gel-based coating will improve the adhesion of the subsequent paints to the substrate and, for the water-borne paints, their spreadability as well if applied by spraying. The agent must be stored within the temperatures +5 - 30 °C, freezing must be avoided!