Avaliação do efeito protetivo de revestimentos de silano aplicados sobre sensores magnetoelásticos METGLAS 2826MB3

Abstract

Magnetoelastic alloys can be used as sensors because they do not require direct electrical connections, which facilitates their use in different media. However, the ease of alloys to undergo oxidation due to the high concentration of iron in their alloy, imposes the study of coatings that protect the alloy from corrosion. Considering that the sensitivity of magnetoelastic sensors are directly influenced by their mass, it is important that the protective film is thin and effectively protects the sensor substrate. Films with silicio alkoxides offer a non-toxic physical protection of the alloy and can be used in different media. Aiming at the use of this sensor as a possible functionalized sensor for use in the detection of bacteria in milk, the research aimed to evaluate the corrosion protection offered by some combinations of silane films, also evaluating their behavior in different types of milk through the analyzer network. Therefore, this study evaluated some important corrosion protection characteristics through two formulations. We used a mixture of 10% silicio alkoxide, 15% alkoxy crosslinker, 15% deionized water and 60% ethyl alcohol PA. The solutions were applied after 24 hours of silanization, with the immersion time of 1min in sol-gel solution, dip-coating emersion and cure of 1h in an oven at 120ºC. The research was divided in two steps, in the first the samples were of 4x20 mm and were evaluated only with the silane films, in the second stage the samples were 1x5 mm and also samples with a second layer of gold were evaluated. The evaluations were: optical microscopy, field emission scanning microscopy (SEM-FEG), atomic force microscopy (AFM), contact angle, electrochemical impedance spectroscopy (EIS) and frequency analysis. The films formed did not show cracking, provided layer leveling and corrosion resistance compatible with the sensor application. The protective behavior of the films are similar in all types of milk evaluated. The research also pointed out that even with the addition of a gold layer, the corrosion protection generated by the films presents potential for use in a future functionalized sensor.