Evaluation in Real Conditions of New Anticorrosive Formulations Based on Polyphenols from Natural Sources and Encapsulated Nanoparticles

Abstract

The objective of this study was to examine the combined protection effect of a two-layer system consisting of organic corrosion inhibitors (tannins derived from the bark of radiata pine) and anodic protection by means of the incorporation of zinc oxide nanoparticles modified superficially by chemical methods to improve the protection of metallic structures against corrosion. Film evaluations are performed in accordance with ISO and ASTM standards. This study also took into account the evaluation of the performance of two commercial coatings according to the scheme suggested by the supplier, in addition to the electrochemical impedance spectroscopy (EIS) characterizations at 0 h, 720 h of accelerated exposure, and 4 months of atmospheric exposure in a corrosive environment of classification C3. The results obtained indicated that the combination of tannins derived from pine bark and encapsulated zinc oxide nanoparticles is a viable alternative to commercial coatings with a higher concentration of synthetic compounds. Although the film properties decrease slightly, performance tests at different exposure times show that they can still be classified as high-performance coatings.

Natural Polyphenols and the Corrosion Protection of Steel: Recent Advances and Future Perspectives for Green and Promising Strategies

“…Pine tannins (condensed) have been extensively studied as active compounds in primer formulations [82,83,93]. The second most employed tannins for this purpose are the tara ones [75,76,80], which are hydrolysable.…”

“…As discussed in the following and summarized in Table 2, tannins are rarely used alone as primers or adhesion promoters [84]. The preparation of a primer or adhesion promoter layer often foresees the combination of tannins with phosphoric acid [77,78] or a polymer such as polyvinyl butyral [75,76,82,83], epoxy [93], or acrylic [77,78] resins and their application on the substrates by brushing [75][76][77][78]82,84], spraying [80], or bar coating [79].…”

“…The introduction of metal oxide nanoparticles, such as ZnO, Fe 2 O 3 , and TiO 2 , in epoxy resin-based coatings provides a more uniform distribution and thus, a better protection performance against corrosion [94]. In this framework, Ramírez et al successfully incorporated tannins from Pinus radiata barks into an epoxy-based primer enriched by zinc oxide nanoparticles to improve the functionality of the coating system, such as the resistance against aggressive agents, mechanical response, and film adhesion [93].…”