Gustavo Alberto Ludwig

Hybrid films with (trimethoxysilylpropyl) methacrylate (TMSM), poly (methyl methacrylate) PMMA and tetraethoxysilane (TEOS) applied on tinplate

The tetraethoxysilane (TEOS) influences morphological and electrochemical properties of hybrid films by function of concentration. Moreover, the use of acetic acid as a catalyst in the sol enables a more complete hydrolysis of the silane precursors due to the fact that the acetic acid goes through a more complete ionization when in aqueous solution. The aim of this paper is to study the effect of the concentration of tetraethoxysilane (TEOS) on the protective properties of the film on tinplate substrate. The tinplate was coated with a hybrid film obtained from a sol-gel method constituted of the following alkoxide precursors: 3 - (trimetoxisililpropil) methacrylate (TMSM) and poly(methyl methacrylate) PMMA. The effect of tetraethoxysilane (TEOS) concentration has also been evaluated. The films hydrolysis was performed at a pH value of 3.0 using acetic acid as a catalyst. The films were obtained by dip-coating process, cured for 3 hours at 160 °C. The film morphology was evaluated by SEM and profilometry. The electrochemical behavior of the films was evaluated by open circuit potential monitoring, potentiodynamic polarization and electrochemical impedance spectroscopy. The film hydrophobicity was determined by contact angle measurements. The studied films have shown good performance as to corrosion resistance on tinplate. The hybrid film which was obtained through the addition of an excessive amount of TEOS (T3A3) showed increased thickness. Nevertheless, due to an intense densification of the film, promoted by the addition of TEOS, a formation of cracks was registered, thereby compromising the corrosion resistance.

Effect of Application of the Shot Peening Process in the Corrosion Resistance of the AISI 430 Ferritic Stainless Steel

Stainless steels are materials used in specific applications where a good corrosion resistance property combined with high material mechanical resistance are required. The shot peening process has been used in order to improve the mechanical properties of metallic surfaces. Besides, it might has influence on the material electrochemical behavior, depending of the used parameters in the operational process. The purpose of this study is to evaluate the effect of the shot peening process in the corrosion resistance of AISI 430 ferritic stainless steel. Wettability test, atomic force microscopy (AFM), open circuit potential (OCP) and potentiodynamic polarization curves have been used in order to evaluate the behavior of AISI 430 ferritic stainless steel after the shot peening process. The aim of this study was to demonstrate the influence of shot peening on the surface properties of ferritic stainless steel AISI 430 and correlate them with the reactivity of the surface. The results showed that the shot peening process, contributes to avoid the localized corrosion resistance of the AISI 430 ferritic stainless steel.

Effects of Mould Temperature in Squeeze Casting of Zamak 5

Squeeze casting process of Zamac 5 for obtain faucets enables higher productivity associated with better dimensional characteristics. In this process, the die cooling system can influence the solidification of the alloy and its properties. This study evaluates the influence of die temperature on solidification under pressure from Zamac 5. Pieces were removed from the die at several temperatures. Samples were evaluated by neutral salt spray corrosion, optical microscopy and microhardness. The results show that the corrosion is related to the porosity defects, which was most intense in part regions which solidified lastly. These regions also showed different results of microhardness. However, the behavior of the samples was similar in the range of die temperatures studied.

Formation of Spinel from Fe-Ni Coating Electrodeposited on AISI 430 Ferritic Stainless Steel

Ferritic stainless steels exhibit properties, such as good electrical conductivity, good corrosion resistance and low cost, that are beneficial for their application as interconnects in intermediate temperature solid oxide fuel cells (ITSOFC) that function at temperatures between 600°C and 800°C. However, the stainless steel corrosion resistance is attributed to the amount of Cr, which is an element that forms a chromium oxide (Cr2O3) layer, acts as an oxidation protective barrier at high temperatures, and reduces the interconnector performance due to its low electrical conductivity. In this context, the objective of this work was to obtain spinel coatings from the Fe and Ni metallic alloy thermal conversion on AISI stainless steel 430 substrate produced by electrodeposition. The morphology and microstructure of the spinel films deposited on stainless steel were characterized by SEM, EDS, XRD and adherence analysis. The results obtained showed that the films were adherent, dense and continuous along the AISI stainless steel 430 substrate surface. In addition, the heat treatment procedure effectively produced crystalline spinels ((NiFe)3O4).

La, Sr and Co Based Coatings Obtained on Ferritic Stainless Steel by Dip-Coating Technique

The ferritic stainless steels have been used in applications where suitable properties are required at high temperatures. These metallic materials are applied, for example, as interconnects in ITSOFC fuel cells (600-800 °C).The aim of this work is to produce a La, Sr and Co based coatings using the dip-coating and spray pyrolysis techniques, on an AISI 430 ferritic stainless steel. These coatings are known for acting as barriers, increasing the oxidation resistance when applied on stainless steel at high temperatures. The obtained coatings were heat treated at 800 °C for 120 min, seeking the formation of La0,6Sr0,4Co,and, then characterized regarding their morphology and microstructure using scanning electron microscopy (SEM) and X-ray diffraction. The results showed that the coatings obtained by spray pyrolysis covered regularly the surface while the ones obtained by dip-coating exhibited some crack formation.

Corrosion Resistance of Hybrid Films Applied on TiN Plate: Precursor Solution Acidified with Hydrochloric Acid

The aim of this work is to coat tin plate with a hybrid film obtained from a sol consisting of alkoxide precursors: 3 - (trimethoxysilylpropyl) methacrylate (TMSM), poly (methyl methacrylate) PMMA with and without tetraethoxysilane (TEOS) addition. The pH = 3 was adjusted with hydrochloric acid. The films were obtained by dip-coating process, cured for 3 hours at 160 ° C, and characterized for their electrochemical behavior. The hydrophobicity of the film was determined by the contact angle measurements and its morphology was evaluated by SEM. Results showed that the hybrid films studied presented good performance concerning their corrosion resistance in tin plate. Besides the addition of TEOS, it has contributed to the increase of the film thickness, however at the same time promoting the crack formation, which compromises the corrosion resistance of the coated tin plate.

Phases Obtained from Heat Treatment of Mn-Co-Based Coatings Deposited by Dip Coating

Studies have been performed to improve the oxidation resistance of ferritic stainless steels at high temperatures because these materials have been proposed for the manufacture of interconnectors for solid oxide fuel cell (SOFCs) and solid oxide electrolysis cells (SOECs) operating at intermediate temperatures (IT-SOFCs). Among the coatings employed, ceramic spinel-type oxides have been the most frequently applied. In this context, Mn-Co-based coatings were deposited on ferritic stainless steel (AISI 430) in this study using a dip-coating technique. The obtained coatings were characterized with respect to their morphology by SEM, their elementary composition by EDS and their structure by XRD. It was possible to produce continuous and adherent Mn-Co-based coatings on the surface of the metallic substrates.