Avaliação de novas tecnologias de tintas ricas em zinco aplicadas em pintura anticorrosiva de manutenção do setor elétrico

Abstract

The Brazilian electricity sector has several structures and metallic equipment distributed throughout the national territory. Such assets as, for example, transmission lines, are often exposed to intense corrosive processes, mainly at the interface of the soil with the atmosphere, due to the corrosion mechanism by differential aeration. Companies operating in the sector demand knowledge of new zinc-rich paint technologies to be used in anti-corrosive paints for maintenance of the assets, especially in conditions where the structure is aged and corroded. For these cases, the surface treatment is usually carried out using mechanical and manual tools, and it is impossible to remove the corrosion product completely, thus impairing the cathodic protection offered by zinc-rich paints. Based on that, this master's dissertation evaluates the anticorrosive performance of different zinc-rich paint technologies, available on the market, for use in equipment maintenance paintings and underground structures in the electrical sector. Seven zinc-rich paint technologies and a reference barrier paint, usually used to in maintenance services, were evaluated for two distinct surface treatments: white metal abrasive blasting (Sa 3) and use of hand and power tools cleaning (St 3). To evaluate the barrier and cathodic protection properties, carbon steel sheets coated with the different ink technologies were submitted to open circuit potential monitoring, potentiodynamic polarization and electrochemical impedance spectroscopy tests. The paints that showed the most promising cathodic protection were selected to be submitted to anticorrosive performance tests in painting schemes, using humidity condensation chambers, cyclic tests, natural exposure tests in soil and complementary tests of adhesion (pull-off). Electrochemical tests revealed that paints containing galvanic particles (Zgalv) and aluminum (Zal) had better barrier properties, but low or no cathodic protection. The paints with and without graphene (Zcgrf and Zsgrf, respectively), showed a mixed behavior, initially having satisfactory barrier properties and a subsequent action of zinc in the cathodic protection of steel. The paint containing carbon nanotubes (Zntc) showed short-term galvanic protection in the Sa 3 surface treatment and was not able to provide protection in the St 3 treatment. Finally, the traditional epoxy paints (Zn) and those containing ceramic particles (Zcer) showed the best cathodic protection properties. In performance tests, these same zinc-rich paints showed superior anti-corrosive performances, or at least similar to the reference aluminum epoxy mastic barrier paint (EMA). It is concluded that both Zn and Zcer paint can efficiently replace EMA paint under the aforementioned maintenance conditions.