RESISTÊNCIA A CORROSÃO EM DIFERENTES TRATAMENTOS DE SUPERFÍCIE SOBRE LIGAS DE ZINCO UTILIZADOS EM METAIS SANITÁRIOS

Entre as ligas não ferrosas, as ligas de zamac são as mais utilizadas para a fundição e vêm sendo aplicadas na substituição de peças de latão, utilizadas industrialmente em metais sanitários. O zamac apresenta propriedades mecânicas semelhantes às do latão, porém com custo inferior. Entretanto, a alta porosidade destas ligas, impede que tratamentos superficiais garantam bom acabamento e resistência à corrosão. Visando melhorar o desempenho, frente à corrosão de peças de zamac, o objetivo do presente trabalho é avaliar o processo de diferentes tratamentos de superfície dos metais sanitários produzidos em zamac. As amostras foram injetadas sobre pressão e submetidas a diferentes tratamentos superficiais (tratamento mecânico, tratamento químico, cobre alcalino, cobre ácido, níquel, cromo). Os corpos de prova foram expostos a um meio agressivo, por meio de nevoa salina a fim de analisar a resistência à corrosão das peças, além de análises de polarização, metalografia e microdureza. Observou-se que a maior incidência de corrosão ocorreu nas partes de injeção e solda da peça, as amostras tratadas com níquel e cromo demonstraram o melhor desemprenho frente a resistência a corrosão.Palavras-chave: Zamac. Metais sanitários. Corrosão.ABSTRACTAmong the non ferrous alloys, zamak are the most used for casting and have been applied to substitute brass parts, industrially utilized in sanitary metals. The zamak presents mechanical properties similar to brass, however with lower cost. Meanwhile, the high porosity of these alloys hinders the superficial treatments ensure good finishing and corrosion resistance. Aiming to improve the performance against corrosion of zamak parts, this work evaluates the process of different superficial treatments of sanitary metals produced with zamak. The samples were injected under pressure and submitted to different superficial treatments (mechanical, chemical, alkaline copper, acid copper, nickel and chromium). The specimens were exposed to an aggressive medium through salt spray test to evaluate the corrosion resistance, and the following analysis: polarization, metallography and microhardness. It was observed that the higher corrosion incidence occurred on the injection and weld regions. The samples treated with nickel and chromium demonstrated better performance of corrosion resistance. Keywords: Zamak. Sanitary materials. Corrosion

ANÁLISE DE SOLDA EM ESTRUTURA METÁLICA

O processo de soldagem em estruturas metálicas possui destaque dentro da indústria metalúrgica, pois é a melhor maneira de unir materiais com baixo custo, quando comparado a outros métodos. Diversos são os segmentos de mercado onde se faz necessário o uso de estruturas metálicas soldadas. Estruturas metálicas possuem algumas vantagens sobre os sistemas construtivos convencionais, tais como precisão, devido ao fato de os elementos serem produzidos em fábrica, possibilidade de seções menores, construções com maiores vãos e rapidez na execução da obra. A soldagem de estruturas metálicas pelo processo MIG/MAG tem se mostrado muito eficiente, sendo o método mais utilizado nas soldas de emendas dessas estruturas. O presente trabalho relata uma análise laboratorial através de metalografia da solda em questão, avaliando o seu comportamento microestrutural e sua composição química em diferentes zonas. Portanto, este trabalho tem como objetivo geral analisar a microestrutura formada em determinada parte de uma estrutura metálica soldada. Para tanto, inicialmente foi realizado o acompanhamento termográfico da estrutura durante o processo de soldagem, seguido da retirada dos corpos de prova. O processo metalográfico possibilitou análises de microscopia ótica, microscopia eletrônica de varredura e análises de EDS. Os resultados mostraram um crescimento já esperado dos grãos na região da solda e apresentaram variações em relação à composição química ao longo da área soldada.Palavras-chave: Estruturas metálicas. Soldagem. Corrosão.ABSTRACTThe welding process in metal structures is prominent within the metallurgical industry, as it is the best way to join materials with low cost when compared to other methods. Several are the market segments where it is necessary to use welded metal structures. Metal structures have some advantages over conventional constructional systems, such as accuracy due to the fact, that the elements are produced in the factory, smaller sections are possible, constructions with bigger spans besides the speed in the execution of the work. The welding of metallic structures by the MIG / MAG process has been proved very efficient and is the most used method for this purpose in the welds of joints of these structures. The present work reports a laboratory analysis through metallography of the weld in question, evaluating its microstructural behavior and its chemical composition in different zones. Therefore, this work has as general objective to analyze the microstructure formed in certain part of a welded metal structure. To do this, the thermographic monitoring of the structure was carried out during the welding process, followed by the removal of the samples. The metallographic process allowed the analysis of optical microscopy, scanning electron microscopy and EDS analysis. The results showed an expected growth of the grains in the region of the weld and showed variations in relation to the chemical composition along the welded area. Keywords: Metal structures. Welding. Corrosion

Superficial treatment by anodization in order to obtain titanium oxide nanotubes applicable in implantology

Titanium and its alloys are the most popular metals applied on end osseous implants manufacturing. Commercially pure titanium (Ti c.p.) has been successfully used as a biomaterial because of its mechanical and chemical properties, excellent corrosion resistance and biocompatibility. In order to improve and accelerate the osseointegration process after implantation, superficial treatments are performed aiming properties that stimulate the growth of the newly-formed bone. In this work, self organized titanium dioxide (TiO2) nanotubes were obtained by anodic oxidation on Ti c.p. (grade 2). Also, it has been shown that the process is industrially reproducible for this purpose. As parameters for the anodizing process, it was concluded that the optimal electrolyte was H3PO4 solution + 0.15% HF under potentiostatic mode for 30 minutes. Potentials of 1, 5, 10, 15 and 20 V were tested in order to verify the best conditions to obtain nanotubes. In this case, potential was set at 10V. The morphology of the samples was characterized by Scanning Electron Microscopy (SEM), Scanning Electron Microscopy with Field Emission (SEM-FEG) and Atomic Force Microscopy (AFM). The results showed the nanotubes formation throughout the titanium samples surface. In accordance to the obtained roughness, it was observed that the formed nanotubes film is thin, however, the literature indicates that the film thickness is not relevant on the performance of nanostructures as optimizers of the osseointegration process, unlike the nanotubes morphology and diameter. In the wettability analysis, the nanotubes behaved as hydrophilic. Therefore, it is possible to obtain TiO2 nanotubes for using in implants by a superficial treatment, allowing a better osseointegration quality.Keywords: Titanium, Nanotubes, Anodization, Implants, Osseointegration.

Colored anodizing of titanium with pyroligneous solutions of black wattle

In many places, charcoal production, using Australian Blackwood, is still a rudimentary process, generating huge environmental impact, due to the release of pyrolysis smoke into the atmosphere. Both the society and governmental agencies is pushing the factories to condense the smoke, generating byproduct known as pyroligneous liquor. Although it's largely used for agricultural purpose, as a fertilizer and phytosanitizer, its chemical composition presents hydrogen and oxygen rich compounds, making it a potential electrolyte in the surface treatment industry, especially for anodization. Organic alternatives are being used to replace these electrolytes to make the anodizing process cleaner. Then, for the first time, Australian Blackwood pyroligneous liquor was used as an anodizing electrolyte for titanium TICP-G2, to obtain oxides for protection and coloring of the metal. For such, suitable parameters to execute the process were determined (dilution, current density, temperature, agitation, pH, conductivity) and an analysis of the transient potential over time was made. The anodized surfaces were characterized using top view Scan Electronic Microscopy (SEM) and Grazing Incidence X-ray Diffraction (GIXRD).  Based on the results presented, it can be concluded that the best parameters to anodize the titanium were obtained with 50% pyroligneous liquor diluted in water, obtaining colored surfaces and promoting the formation of oxide crystallites clusters mainly in longer  process times (3600s).  Keywords: Pyroligneous liquor, Titanium, Anodizing