Desenvolvimento de recobrimentos orgânicos contendo Solidago chilenisis como inibidor natural de corrosão para aplicação em embalagens de alimentos

Abstract

A corrosion process in metallic food packing can be started during the manufacturing of these, as well as throughout the period in which the food is in contact with it. The use of plant extracts as green inhibitors in protective coatings for aluminum can help reduce corrosion, and reduce concern about the risk of toxicity caused by synthetic inhibitors used industrially. Extracts of the species Solidago chilensis, known as arnica-Brazilian, abundant in Brazil and in greater concentration in the southern region of the country, have not yet been reported in the literature used as natural corrosion inhibitors, however, have properties and compounds that have been presented indicating corrosion efficiency. This study aims to develop a coating containing solidated chilensis as green corrosion inhibitor for use in packaging of aluminum alloys for food. To evaluate these coatings were conducted Potentiostatic Polarization tests (PP), Electrochemical Impedance Spectroscopy (EIS), Atomic Force Microscopy (AFM), Infrared Spectroscopy in the region Fourier Transform (FT-IR) and X-Ray Diffraction (XRD). Considering the possibility of change in resistance to corrosion due to some mechanical damage was assessed the adhesion of coating by mechanical strength tests for Dynamic-Mechanical Analysis (DMA). For the development of the surface were carried out anodizing, in order to corrosion protection and adhesion inhibitor and coating; and applied the natural inhibitor (Solidago chilensis) and the varnish coating, in order to protect against corrosion. The anodizing was performed in three different times 15, 20 and 30 minutes after the samples were immersed in inhibitor solution containing three different inhibitor concentrations (2.5, 5 and 15 g/L methanol) and finally were coated with varnish. The corrosion resistance and the efficiency of the inhibitor were evaluated by electrochemical tests. The modulus of elasticity of the samples were evaluated by DMA. The morphology of the samples were determined by AFM. The inhibitor composition and interaction between the chemical bonding inhibitor compounds, varnish, and anodization of aluminum are determined by FT-IR. The crystal structure of the samples were determined by XRD. The results showed that the best time of anodization as the corrosion resistance and the mechanical strength of the system was 15 min. The anodized samples at this time were chosen to be immersed in a solution containing the natural inhibitor. The electrochemical results indicated that the highest concentration of corrosion inhibitor (15 g of Solidago chilensis extract per L of solvent) had higher efficiency corrosion, 92.5%. The use of natural corrosion inhibitor with anodization and varnish coating reduced the degradation of the sample over time, potential increased corrosion resistance and polarization. The system stiffness decreased with the application of varnish but was not significantly influenced by p≤0,05 anodizing. These results indicated that the anodized Al containing Solidago chilensis extract as a corrosion inhibitor coated with varnish can be an interesting alternative in the food industry in use in metal packaging.