Resumo em Inglês:

Research on eco-friendly methods led to the investigation of natural inhibitors and silane films modified with nanostructured mesoporous silica (SBA-15), a molecular sieve that can carry molecules with inhibitory properties. Combining natural extracts such as cocoa husk with SBA-15 aims to develop an enhanced silane-based pretreatment. This involves obtaining an alcoholic extract, and then mixing it with SBA-15 to modify the silane film. Different concentrations (1%, 2%, and 3%) of SBA-15 loaded with extract were prepared. Electrochemical tests, especially electrochemical impedance spectroscopy (EIS), in a 0.1 mol/L NaCl solution, revealed improved corrosion resistance with the tetraethylorthosilane (TEOS) film modified using 3% SBA-15 loaded with extract. Scanning electron microscopy showed the film and SBA-15 on the steel surface, while Fourier transform infrared spectroscopy identified functional groups characteristic of SBA-15, pure or loaded, and silane film. Therefore, it was possible to enhance the TEOS silane film by adding SBA-15 loaded with plant residue extract.

Resumo em Inglês:

This study aims to provide clarity on the potential of graphene in real-life coatings applications and can be viewed as guidelines for graphene end users. To illustrate this, examples of different industrial applications are presented, where graphene-based additives demonstrate a significant impact on corrosion resistance. Furthermore, the underlying mechanisms behind these new products are elucidated.

Resumo em Inglês:

Duplex stainless steels are widely used due to their good mechanical properties and corrosion resistance. However, they are susceptible to microstructural fragility related to harmful transformations taking place in intermetallic phases, such as the sigma phase. These transformations reduce mechanical properties like toughness and corrosion resistance. The current study aims to analyze the effect of different thermodynamic- and electrochemical-reactive phases based on using both linear sweep voltammetry tests as non-destructive tests, as well as the concept of microelectrodes. This technique is capable of detecting small amounts of intermetallic phases at the UNS-S31803 duplex stainless steel surface. Results have evidenced the influence of reduced electrode-solution exposure area on improving sensitivity for deleterious phase analyses. Peak potential and current peak recorded direct correlation to sigma phase concentration and it enabled detecting very low sigma-phase surface concentration, at the order of 0.04%. The study has shown improved sensitivity of linear sweep voltammetry tests used to detect harmful phases in duplex stainless steels.

Resumo em Inglês:

The industry's principal objective is to comprehend the optimal application of each metal alloy in terms of corrosion resistance. A key focus lies in exploring alternative approaches to address this corrosive process in a manner that is both sustainable and economically feasible. The major strategy to mitigate this contest involves the utilization of inhibitors. However, it is imperative to note that certain inhibitors pose environmental risks. This study explores the effect of the addition of protic ionic liquids (PILs) on the corrosion of carbon steel (A36) in a saline solution (3.5 wt% NaCl), considering variations in pH and temperature. It focuses on understanding the effects of pH and temperature on the PILs' ability to protect the steel surface. Notably, changes in pH do not affect the protective capacity of the inhibitors. Efficiency values exceeding 72% were achieved under both acidic conditions tested. The study reveals two scenarios: At 40 °C, the PILs effectively protect the steel, with an efficiency of approximately 74% at concentrations of 500 and 1000 ppm. However, at 60 °C, efficiency decreases notably, reaching a maximum of 51% at a concentration of 500 ppm. Afterward, to evaluate the protective effectiveness of these compounds, gravimetric and electrochemical impedance spectroscopy (EIS) serve as the main methods, accompanied by optical and atomic force microscopy (AFM) for evaluating the surface. In electrochemical tests, PILs 1 and 2 exhibit superior efficiency, with film formation, while PILs 3 to 6 demonstrate comparatively lower values.

Resumo em Inglês:

This work aims to determine the best substrate preparation and conversion coatings that may enhance the anti-corrosive performance of alumina film/stainless steel substrate systems in Ringer’s solution. Boehmite, silica, silica/boehmite, and boehmite/silica conversion coatings were deposited on sanded or sandblasted 304L stainless steel samples, and the best results were further covered with alumina film for a long-time exposure evaluation. The best anti-corrosive performances for each substrate preparation were observed for the sandblasted sample covered with silica/boehmite conversion coating (JSB500) and the sanded sample covered with silica (LS500), which showed the highest global resistance (Rg) values (828 Ω.cm2 and 1837 Ω.cm2, respectively) and the smallest values of global capacitance, Cg (2.19 X 10-6 F.cm-2 and 3.37 X 10-9 F.cm-2, respectively). After covering with the alumina film and evaluating for 216 h in the corrosive medium, it was noted an increase in the Rg values for both systems (JSBA500 and LSBA500), likely due to the presence of a corrosion products layer. The presence of iron oxides in these conversion coatings led to a more stable alumina film. Comparing the selected coating systems, the LSBA500 exhibited an improved performance, reaching an increase of 85% in Rg and a decrease of 94% in Cg.

Resumo em Inglês:

The use of fluorescent nanomaterials in various fields of study has become increasingly common. In this work, the use of carbon quantum dots as a corrosion marker in carbon steel is proposed. To produce the sensor, carbon quantum dots based on ethylenediamine and citric acid were used, dissolved in a polymeric matrix. The quantum dot used showed a quantum yield of 42.34%. The nanomodified coatings emitted blue light under ultraviolet radiation lamp. However, it was observed that there is a loss of photoluminescence in the coating on the carbon steel substrate compared to the coating on the polymeric substrate, which maintained photoluminescence activity after natural exposure. Thus, it is inferred that the loss of photoluminescence may be associated with the corrosion process.