Made available in DSpace on 2014-06-11T19:28:35Z (GMT). No. of bitstreams: 0 Previous issue date: 2003Bitstream added on 2014-06-13T20:58:35Z : No. of bitstreams: 1 aguiar_fec_me_guara.pdf: 2530188 bytes, checksum: 16dfca08c4ceaff67e483005f4ffffa9 (MD5) / Fundação de Amparo à Pesquisa do Estado de São Paulo (FAPESP) / Neste trabalho estudou-se o comportamento eletroquímico e as características microestruturais de chapas de aço eletrozincado e zincado sem e com revestimentos de fosfatos, oriundos de diferentes banhos fosfatizantes, aplicados pelo processo industrial coil-coating utilizado pela TEKNO S.A. Este trabalho também traz contribuições referentes ao estudo da chapa revestida com Galvalumeâ que é um revestimento composto de uma liga constituída de 55% de alumínio, 43% de zinco e 2% de outros constituintes, entre eles o Silício. Com o estudo desse material pode-se comprovar e determinar qual revestimento com e/ou sem fosfatos tem maior resistência à corrosão. A análise metalográfica superficial das chapas e revestimentos foi realizada por Microscopia Óptica, Microscopia Eletrônica de Varredura e EDS. Ensaios normalizados de rugosidade e de dureza Vickers também foram realizados. A resistência à corrosão proporcionada pelos diferentes revestimentos de zinco e fosfatos foi avaliada por ensaios eletroquímicos como potencial vs tempo em circuito aberto e em corrente controlada, polarização potenciodinâmica, voltametria cíclica e espectroscopia de impedância eletroquímica em solução de cloreto de sódio 3,5% e pH ~ 8,1, equivalente à água marinha. Todo este trabalho teve como objetivo principal, comparar quanto à resistência a corrosão, três diferentes banhos fosfatizantes aplicados nas chapas zincadas, com o intuito de propor ajustes no processo vigente da TEKNO que forneceu todo suporte necessário para realização deste estudo. / In this work it was studied the electrochemical behavior and the microstructure characteristics of zinc coated steel plates with and without phosphate coatings originating from different baths applied for the coil-coating industrial process used by TEKNO S.A. This work also brings referring contributions to the study of Galvalumeâ coating, that is a coating composed of 55% of aluminum, 43% of zinc and 2% of other constituent league, among them the silicon. With this material study it was possible to estimate and determinate which coating has larger resistance to the corrosion. The surface metallographic analysis of all the coatings were accomplished by Optical Microscopy, Scanning Electron Microscopy and Energy Dispersive Spectrography techniques. Normalized methods of rugosity and hardness Vickers were also accomplished. The corrosion resistance for the different coatings was evaluated by electrochemical techniques as potential x time in open circuit , potenciodynamic polarization curves, cyclic voltammetric curves, galvanostatic curves and Electrochemical Impedance Spectroscopy in sodium chloride solution of 3,5% to the pH ~ 8,1 equivalent to the sea water. The main objective, in this work, was to compare the corrosion resistance of three different phosphates baths applied in the galvanized steel sheets, in order improve the effective process of TEKNO that supplied every necessary support for accomplishment of this study.

Orientador : Roberto Zenhei Nakazato / Banca: Tomaz Manabu Hashimoto / Banca: Maria Auxiliadora Silva de Oliveira / Resumo: Neste trabalho estudou-se o comportamento eletroquímico e as características microestruturais de chapas de aço eletrozincado e zincado sem e com revestimentos de fosfatos, oriundos de diferentes banhos fosfatizantes, aplicados pelo processo industrial coil-coating utilizado pela TEKNO S.A. Este trabalho também traz contribuições referentes ao estudo da chapa revestida com Galvalumeâ que é um revestimento composto de uma liga constituída de 55% de alumínio, 43% de zinco e 2% de outros constituintes, entre eles o Silício. Com o estudo desse material pode-se comprovar e determinar qual revestimento com e/ou sem fosfatos tem maior resistência à corrosão. A análise metalográfica superficial das chapas e revestimentos foi realizada por Microscopia Óptica, Microscopia Eletrônica de Varredura e EDS. Ensaios normalizados de rugosidade e de dureza Vickers também foram realizados. A resistência à corrosão proporcionada pelos diferentes revestimentos de zinco e fosfatos foi avaliada por ensaios eletroquímicos como potencial vs tempo em circuito aberto e em corrente controlada, polarização potenciodinâmica, voltametria cíclica e espectroscopia de impedância eletroquímica em solução de cloreto de sódio 3,5% e pH ~ 8,1, equivalente à água marinha. Todo este trabalho teve como objetivo principal, comparar quanto à resistência a corrosão, três diferentes banhos fosfatizantes aplicados nas chapas zincadas, com o intuito de propor ajustes no processo vigente da TEKNO que forneceu todo suporte necessário para realização deste estudo. / Abstract: In this work it was studied the electrochemical behavior and the microstructure characteristics of zinc coated steel plates with and without phosphate coatings originating from different baths applied for the coil-coating industrial process used by TEKNO S.A. This work also brings referring contributions to the study of Galvalumeâ coating, that is a coating composed of 55% of aluminum, 43% of zinc and 2% of other constituent league, among them the silicon. With this material study it was possible to estimate and determinate which coating has larger resistance to the corrosion. The surface metallographic analysis of all the coatings were accomplished by Optical Microscopy, Scanning Electron Microscopy and Energy Dispersive Spectrography techniques. Normalized methods of rugosity and hardness Vickers were also accomplished. The corrosion resistance for the different coatings was evaluated by electrochemical techniques as potential x time in open circuit , potenciodynamic polarization curves, cyclic voltammetric curves, galvanostatic curves and Electrochemical Impedance Spectroscopy in sodium chloride solution of 3,5% to the pH ~ 8,1 equivalent to the sea water. The main objective, in this work, was to compare the corrosion resistance of three different phosphates baths applied in the galvanized steel sheets, in order improve the effective process of TEKNO that supplied every necessary support for accomplishment of this study. / Mestre

A proteção contra a corrosão do aço galvanizado com um tratamento via cromatização, apesar de apresentar desempenho superior à outras alternativas, gera efluentes tóxicos ao meio ambiente e em especial aos seres humanos. Dentre as alternativas apresentadas até o presente momento, que incluem diversos tipos de tratamentos para esse substrato, um deles é o revestimento com silanos. Apesar desse revestimento ter um satisfatório desempenho, vem se utilizando incorporações em seu preparo, para se potencializar seu desempenho. A incorporação escolhida nesse trabalho foi a do tanino, um inibidor de corrosão natural, extraído de vegetais. O objetivo desse trabalho é avaliar um revestimento do silano Ortossilicato de tetraetila (TEOS) junto de um tanino para o aço galvanizado destinado a aplicações onde não há pintura. Essa sinergia deve proteger a superfície até que o zinco consiga de forma natural desenvolver sua pátina protetora, formando uma barreira entre substrato e eletrólito. Foram revestidas chapas de aço galvanizado com períodos de imersão que variaram entre 2 e 10 minutos, com soluções na concentração de tanino de 2g/L e 10g/L com diferentes valores de pH, em uma solução previamente preparada de TEOS em concentração de 2%, água 49% e etanol 49%. Realizou-se análise comparativa entre os diferentes parâmetros de tratamento proposto neste trabalho com aço galvanizado somente desengraxado e aço galvanizado cromatizado nas seguintes técnicas: espectroscopia de impedância eletroquímica, polarização potenciodinâmica, microscopia eletrônica de varredura acoplada a espectroscopia de energia dispersiva, e ensaios de corrosão acelerada em câmara úmida e névoa salina. Os resultados apresentados indicam que diferentes concentrações de tanino e tempos de imersão não são significativos para causar diferenças relevantes entre os desempenhos e que os substratos tratados demonstraram um desempenho superior comparado às amostras que não tinham nenhum tipo de tratamento e inferiores às amostras cromatizadas. / The corrosion protection of galvanized steel with a chromatized treatment, despite superior performance to other alternatives, generates effluents toxic to the environment and especially to humans. Among the alternatives presented to date, which include several types of treatments for this substrate, one of them is the coating with silanes. Although this coating has a satisfactory performance, it has been using incorporations in its preparation, to enhance its performance. The incorporation chosen in this work was that of tannin, a natural corrosion inhibitor, extracted from plants. The objective of this work is to evaluate a coating of silane tetraethyl orthosilicate (TEOS) with tannin for galvanized steel, for applications where there is no paint. This synergy should protect the surface until zinc can naturally develop its protective patina, forming a barrier between substrate and electrolyte. Galvanized steel plates were coated with immersion times ranging from 2 to 10 minutes, with solutions at tannin concentration of 2 g/L and 10 g/L with different pH values, in a previously prepared solution of TEOS at a concentration of 2% , 49% of water and 49% of ethanol. A comparative analysis was performed between the different treatment parameters proposed in this work with galvanized steel only degreased and galvanized steel chromatized in the following techniques: electrochemical impedance spectroscopy (EIE), potentiodynamic polarization, scanning electron microscopy coupled to dispersive energy spectroscopy, and corrosion tests accelerated in humid chamber and saline mist. The results indicated that different concentrations of tannin and immersion times are not significant to cause relevant differences between the performances and that the substrates demonstrated superior performance compared to the samples that had no type of treatment, and inferior to the samples chromatized.

The major concern regarding the use of hot-dip galvanized (HDG) steel as reinforcement in concrete has been the high rate of corrosion experienced by the zinc during the first hours in the fresh, wet, and highly alkaline concrete. The present work was aimed at clarifying three issues associated with these concerns. The first involves the metallurgical phases at the surface of the zinc coating. The concentration of zinc at the surface is a function of processing procedures, surface treatment, and exposure to weathering. Differences in the coating surface composition influence the corrosion behaviour of HDG steel reinforcing bars when they are embedded in concrete. The second issue involves the increasing use of supplementary cementing materials in concrete, which change the chemistry of the concrete pore fluid, and also influence the corrosion. The third issue is that the initial corrosion is accompanied by hydrogen evolution, which could increase the pore volume of adjacent cement and thereby, decrease the bond stress between the concrete and the steel. In order to limit the hydrogen evolution, a chromate layer is applied after galvanizing. The results of the project have demonstrated that, during zinc corrosion in ordinary Portland cement (OPC) concrete, calcium hydroxyzincate formed on untreated HDG steel provided sufficient protection against corrosion. Therefore, it is concluded that treating HDG rebar with dilute chromic acid is unnecessary as a method of passivating zinc. A layer of zinc oxide and zinc carbonate formed through weathering on HDG bars slightly increased the initial corrosion rate and passivation time compared with the non-weathered rebars. HDG steel with an alloyed coating, i.e. consisting of Fe-Zn intermetallic phases, required a longer time to passivate than those with a pure zinc surface layer. The lower zinc content of the surface limited the rate of CHZ formation and, hence, delayed passivation. However, regardless of the surface condition, the coating depth loss after two days of embedment in OPC concrete was insignificant. In concretes containing 8% cement replacement with silica fume, or 25% cement replacement with slag, the initial corrosion rates were higher than those in OPC due to higher pH and lower calcium contents of the concrete pore solution. The higher corrosion rates lead to initial depth losses which are considered significant. However, in these concretes, chromate treatment was also shown to be unnecessary. Through porosity assessment of cements adjacent to HDG bars, it was found that hydrogen evolution accompanying zinc corrosion did not have an impact on the pore volume of cements: any additional pores created by hydrogen gas are filled by the zinc corrosion products. The negligible difference in pore volume between cements adjacent to chromated and non-chromated bars further confirmed that chromated treatment was unnecessary.

The major concern regarding the use of hot-dip galvanized (HDG) steel as reinforcement in concrete has been the high rate of corrosion experienced by the zinc during the first hours in the fresh, wet, and highly alkaline concrete. The present work was aimed at clarifying three issues associated with these concerns. The first involves the metallurgical phases at the surface of the zinc coating. The concentration of zinc at the surface is a function of processing procedures, surface treatment, and exposure to weathering. Differences in the coating surface composition influence the corrosion behaviour of HDG steel reinforcing bars when they are embedded in concrete. The second issue involves the increasing use of supplementary cementing materials in concrete, which change the chemistry of the concrete pore fluid, and also influence the corrosion. The third issue is that the initial corrosion is accompanied by hydrogen evolution, which could increase the pore volume of adjacent cement and thereby, decrease the bond stress between the concrete and the steel. In order to limit the hydrogen evolution, a chromate layer is applied after galvanizing. The results of the project have demonstrated that, during zinc corrosion in ordinary Portland cement (OPC) concrete, calcium hydroxyzincate formed on untreated HDG steel provided sufficient protection against corrosion. Therefore, it is concluded that treating HDG rebar with dilute chromic acid is unnecessary as a method of passivating zinc. A layer of zinc oxide and zinc carbonate formed through weathering on HDG bars slightly increased the initial corrosion rate and passivation time compared with the non-weathered rebars. HDG steel with an alloyed coating, i.e. consisting of Fe-Zn intermetallic phases, required a longer time to passivate than those with a pure zinc surface layer. The lower zinc content of the surface limited the rate of CHZ formation and, hence, delayed passivation. However, regardless of the surface condition, the coating depth loss after two days of embedment in OPC concrete was insignificant. In concretes containing 8% cement replacement with silica fume, or 25% cement replacement with slag, the initial corrosion rates were higher than those in OPC due to higher pH and lower calcium contents of the concrete pore solution. The higher corrosion rates lead to initial depth losses which are considered significant. However, in these concretes, chromate treatment was also shown to be unnecessary. Through porosity assessment of cements adjacent to HDG bars, it was found that hydrogen evolution accompanying zinc corrosion did not have an impact on the pore volume of cements: any additional pores created by hydrogen gas are filled by the zinc corrosion products. The negligible difference in pore volume between cements adjacent to chromated and non-chromated bars further confirmed that chromated treatment was unnecessary.

Along with science and technology gradually make progress, there is no distance between country. WTO world commerce cloggy eliminate, have no frontier's confine to make product and service that almost be obvious everywhere in the world. Under economic liberalization and internationalize affection, make enterprise management no longer confine to one area or single country. Economic globalization impact everywhere in the world. Iron and steel industry can¡¦t also avoid meeting severely impact and change. In 2002, because global economies gradually change better, lead to international steel market demand to grow up quickly. It is fourth season to reach the best. Price appears take on upspring, too. Due to every important manufacturer rob to buy materical each other in the world, appear steel materical demand to exceed supply. At the end of the year 2003, America, European union, mainland China cancel import restriction successively. At the beginning of the year 2004, price of freight, iron ore, coalmine, scrap steel (Steel ingredient) increases largely at the same time. Many countries ensure steel requirement materials at home, so steel importation tariff transfer fall successively. It makes strict confine measure gradually change to loose. Hot Rolled Galvanized Steel Sheet requires mean consumption to grows up 4.4% near five years in the world. Price also rise along with the price of Hot-Rolled Steel Coil is on raise at the same time. Steel market changes quickly like electronic product¡¦s life. Steel industry face structure change and reform management. In the world, all steel industry is toward competition and cooperative style. Industry internationalize brings manufacture and sales mode's changed. Industry protection policy already do not exist. With environment changed quickly, enterprise do the best increase management performance. It just be able to abidingly run and develop. The study chiefly use questionaire as interview style to get information and organize theoretical document to review and research. Let us know Hot Rolled Galvanized Steel Sheet and Prepainted Hot-Dip Zinc Coated Steel Sheet company how to develop in the world now. It is as Yiehphui company for example, explore Hot Rolled Galvanized Steel Sheet and Prepainted Hot-Dip Zinc Coated Steel Sheet industry how to take advantage of limited source and face industry environmental change to upgrade management technique. By industry internationalization working principles, make enterprise management risk asunders and create industry competition advantage. It becomes industry developmental reference. The study shows some conclusions as follows: 1. Materials source need stability and multiplication. It avoid confining provider but have no method to acquire advantaged negotiate. 2. International steel area integrated tendency have already formed. Major company become bigger and bigger can not avoid. Individual company should cooperation or tactic federation at home with same industry company, form area economy magnitude and debases competition pressure. 3. Push and import TPM management system and TSM work safe management system to healthy company operate constitution and attract elitist. 4. Global market runs for springboard as strengthen developmental technology, develop high affixation value product and new product use domain. It aggravates brand impression and difference product to used for seize more market area and market benefit.

A proteção contra a corrosão do aço galvanizado com um tratamento via cromatização, apesar de apresentar desempenho superior à outras alternativas, gera efluentes tóxicos ao meio ambiente e em especial aos seres humanos. Dentre as alternativas apresentadas até o presente momento, que incluem diversos tipos de tratamentos para esse substrato, um deles é o revestimento com silanos. Apesar desse revestimento ter um satisfatório desempenho, vem se utilizando incorporações em seu preparo, para se potencializar seu desempenho. A incorporação escolhida nesse trabalho foi a do tanino, um inibidor de corrosão natural, extraído de vegetais. O objetivo desse trabalho é avaliar um revestimento do silano Ortossilicato de tetraetila (TEOS) junto de um tanino para o aço galvanizado destinado a aplicações onde não há pintura. Essa sinergia deve proteger a superfície até que o zinco consiga de forma natural desenvolver sua pátina protetora, formando uma barreira entre substrato e eletrólito. Foram revestidas chapas de aço galvanizado com períodos de imersão que variaram entre 2 e 10 minutos, com soluções na concentração de tanino de 2g/L e 10g/L com diferentes valores de pH, em uma solução previamente preparada de TEOS em concentração de 2%, água 49% e etanol 49%. Realizou-se análise comparativa entre os diferentes parâmetros de tratamento proposto neste trabalho com aço galvanizado somente desengraxado e aço galvanizado cromatizado nas seguintes técnicas: espectroscopia de impedância eletroquímica, polarização potenciodinâmica, microscopia eletrônica de varredura acoplada a espectroscopia de energia dispersiva, e ensaios de corrosão acelerada em câmara úmida e névoa salina. Os resultados apresentados indicam que diferentes concentrações de tanino e tempos de imersão não são significativos para causar diferenças relevantes entre os desempenhos e que os substratos tratados demonstraram um desempenho superior comparado às amostras que não tinham nenhum tipo de tratamento e inferiores às amostras cromatizadas. / The corrosion protection of galvanized steel with a chromatized treatment, despite superior performance to other alternatives, generates effluents toxic to the environment and especially to humans. Among the alternatives presented to date, which include several types of treatments for this substrate, one of them is the coating with silanes. Although this coating has a satisfactory performance, it has been using incorporations in its preparation, to enhance its performance. The incorporation chosen in this work was that of tannin, a natural corrosion inhibitor, extracted from plants. The objective of this work is to evaluate a coating of silane tetraethyl orthosilicate (TEOS) with tannin for galvanized steel, for applications where there is no paint. This synergy should protect the surface until zinc can naturally develop its protective patina, forming a barrier between substrate and electrolyte. Galvanized steel plates were coated with immersion times ranging from 2 to 10 minutes, with solutions at tannin concentration of 2 g/L and 10 g/L with different pH values, in a previously prepared solution of TEOS at a concentration of 2% , 49% of water and 49% of ethanol. A comparative analysis was performed between the different treatment parameters proposed in this work with galvanized steel only degreased and galvanized steel chromatized in the following techniques: electrochemical impedance spectroscopy (EIE), potentiodynamic polarization, scanning electron microscopy coupled to dispersive energy spectroscopy, and corrosion tests accelerated in humid chamber and saline mist. The results indicated that different concentrations of tannin and immersion times are not significant to cause relevant differences between the performances and that the substrates demonstrated superior performance compared to the samples that had no type of treatment, and inferior to the samples chromatized.

A proteção contra a corrosão do aço galvanizado com um tratamento via cromatização, apesar de apresentar desempenho superior à outras alternativas, gera efluentes tóxicos ao meio ambiente e em especial aos seres humanos. Dentre as alternativas apresentadas até o presente momento, que incluem diversos tipos de tratamentos para esse substrato, um deles é o revestimento com silanos. Apesar desse revestimento ter um satisfatório desempenho, vem se utilizando incorporações em seu preparo, para se potencializar seu desempenho. A incorporação escolhida nesse trabalho foi a do tanino, um inibidor de corrosão natural, extraído de vegetais. O objetivo desse trabalho é avaliar um revestimento do silano Ortossilicato de tetraetila (TEOS) junto de um tanino para o aço galvanizado destinado a aplicações onde não há pintura. Essa sinergia deve proteger a superfície até que o zinco consiga de forma natural desenvolver sua pátina protetora, formando uma barreira entre substrato e eletrólito. Foram revestidas chapas de aço galvanizado com períodos de imersão que variaram entre 2 e 10 minutos, com soluções na concentração de tanino de 2g/L e 10g/L com diferentes valores de pH, em uma solução previamente preparada de TEOS em concentração de 2%, água 49% e etanol 49%. Realizou-se análise comparativa entre os diferentes parâmetros de tratamento proposto neste trabalho com aço galvanizado somente desengraxado e aço galvanizado cromatizado nas seguintes técnicas: espectroscopia de impedância eletroquímica, polarização potenciodinâmica, microscopia eletrônica de varredura acoplada a espectroscopia de energia dispersiva, e ensaios de corrosão acelerada em câmara úmida e névoa salina. Os resultados apresentados indicam que diferentes concentrações de tanino e tempos de imersão não são significativos para causar diferenças relevantes entre os desempenhos e que os substratos tratados demonstraram um desempenho superior comparado às amostras que não tinham nenhum tipo de tratamento e inferiores às amostras cromatizadas. / The corrosion protection of galvanized steel with a chromatized treatment, despite superior performance to other alternatives, generates effluents toxic to the environment and especially to humans. Among the alternatives presented to date, which include several types of treatments for this substrate, one of them is the coating with silanes. Although this coating has a satisfactory performance, it has been using incorporations in its preparation, to enhance its performance. The incorporation chosen in this work was that of tannin, a natural corrosion inhibitor, extracted from plants. The objective of this work is to evaluate a coating of silane tetraethyl orthosilicate (TEOS) with tannin for galvanized steel, for applications where there is no paint. This synergy should protect the surface until zinc can naturally develop its protective patina, forming a barrier between substrate and electrolyte. Galvanized steel plates were coated with immersion times ranging from 2 to 10 minutes, with solutions at tannin concentration of 2 g/L and 10 g/L with different pH values, in a previously prepared solution of TEOS at a concentration of 2% , 49% of water and 49% of ethanol. A comparative analysis was performed between the different treatment parameters proposed in this work with galvanized steel only degreased and galvanized steel chromatized in the following techniques: electrochemical impedance spectroscopy (EIE), potentiodynamic polarization, scanning electron microscopy coupled to dispersive energy spectroscopy, and corrosion tests accelerated in humid chamber and saline mist. The results indicated that different concentrations of tannin and immersion times are not significant to cause relevant differences between the performances and that the substrates demonstrated superior performance compared to the samples that had no type of treatment, and inferior to the samples chromatized.

O comportamento eletroquímico do aço-carbono 1005, do aço galvanizado e do zinco foi estudado em meios aerados de ácido sulfúrico 0,5 mol.L-1 (aço-carbono) e cloreto de sódio 0,01 mol.L-1 na ausência e presença do inibidor de corrosão benzotriazol (BTAH), a 25 ºC. Foram empregadas como técnicas ensaios gravimétricos, medidas de transitórios de potencial de circuito aberto, voltametria linear, espectroscopia de impedância eletroquímica (EIE), varredura com eletrodo vibratório (SVET), microscopia eletrônica de varredura (MEV), espectroscopia por dispersão de energia (EDS), espectroscopia eletrônica de raio X (XPS), espectroscopia Raman. O BTAH se mostrou inibidor para os três materiais metálicos nos meios estudados, comportando-se como inibidor misto. A sua ação inibidora decresce na ordem Zn>aço carbono>aço galvanizado em meio de cloreto de sódio. Para o aço-carbono em meio de ácido sulfúrico a adição de íons Cu(II) eleva a eficiência do BTAH, mas em tempos mais elevados de imersão há formação de cobre metálico que promove corrosão galvânica. Em meio de cloreto de sódio os filmes formados sobre aço e sobre zinco correspondem aos respectivos complexos Fe(III) e Fe(II) e de Zn(II) com BTAH. A ação sobre o zinco do BTAH, no caso do aço galvanizado reduz a eficiência na proteção catódica conferida pelo zinco ao aço. A eficiência inibidora sobre aço-carbono depende da composição da liga e da natureza das inclusões presentes no material. Estudos sobre a secção transversal do aço galvanizado em meio de cloreto de sódio mostraram que o BTAH inibe a oxidação do zinco, com formação do complexo, e a redução do oxigênio sobre o aço, com adsorção da molécula de BTAH. O filme formado sobre zinco, ensaiado separadamente, obedece à isoterma de Langmuir, com valores de energia livre padrão de adsorção que evidenciam a natureza química da adsorção, apontando para um complexo com BTAH. / The electrochemical behavior of carbon steel, galvanized steel and zinc has been studied in aerated 0.5 mol.L-1 sulfuric acid and 0.01 mol.L-1 sodium chloride solutions in the absence and presence of benzotriazole (BTAH) at 25ºC. Weight loss experiments, open circuit potential, transient measurements, linear voltammetry, electrochemical impedance spectroscopy (EIS), scanning electronic microscopy (SEM), energy dispersive spectroscopy (EDS), canning vibrating electrode technique (SVET), X-ray photoelectron spectroscopy and Raman spectroscopy used as techniques. BTAH has shown inhibition for the three materials in the media studied and acted as a mixed inhibitor. Its inhibitive effect decreases in the sequence Zn>carbon steel>galvanized steel in chloride medium. In sulfuric medium the BTAH efficiency is improved with the presence of Cu(II) ions but this effect is suppressed at long times immersion when metallic copper is formed promoting galvanic corrosion. The films formed on zinc and carbon steel in chloride medium correspond, respectively to a Fe(II), Fe(III) mixed complex and to Zn(II) complex with BTAH. Studies on the cross section of galvanized steel (cut edge) have shown that the high effect of BTAH as inhibitor for zinc tends to decrease the efficiency of cathodic protection of this metal on carbon steel. For carbon steel in sulfuric medium the composition and the nature of inclusions have an important role on the inhibitor efficiency. On the cut edge the inhibitor promotes the formation of a zinc complex on this metal and it is adsorbed on carbon steel as a molecule inhibiting the oxygen reduction. The film formed on zinc when separately studied obeys to a Langmuir isotherm with standard adsorption free energy values denoting the presence of chemical adsorption as an indicative of the presence of a complex

O uso de chapas finas de aço, revestidas ou não, tem sido crescente nos últimos anos, principalmente aquelas que tem revestimento à base de zinco. Isto ocorre tanto na indústria automobilística e mecânica como na construção civil, que geralmente fabricam suas peças e estruturas utilizando um procedimento de soldagem. O objetivo deste trabalho é estabelecer procedimentos de soldagem à arco elétrico com proteção gasosa - GMAW - com transferência por curto circuito, para elementos de chapa fina de aço carbono não revestido e aço zincado, de modo a se obter junções de qualidade aceitável e diminuição das distorções decorrentes dos ciclos térmicos presentes durante a soldagem e, consequentemente a redução das tensões residuais. Em termos de qualidade da solda, propões-se uma combinação de consumíveis disponíveis no mercado, de modo a reduzir os defeitos como: porosidade, respingos, trincas e perda de revestimento. No caso das chapas finas de aço zincado, a melhor combinação de consumíveis encontrada foi: arame com baixo teor de desoxidantes, ER70S-3, e como gás de proteção a mistura 8% CO2 + 92% Ar. Quanto à redução e controle das distorções, três técnicas são utilizadas. A técnica que utiliza em escoadouro dinâmico de calor, formado por um jato de gás refrigerador aplicado logo após o arco de solda durante a soldagem, apresentou maior eficiência na redução das distorções, provenientes do ciclo térmico. / The thin sheet steels, coated or not, has been widely used nowadays, mainly the hot dip galvanized steel sheets. It\'s observed as in the mechanic and automobilist industry as in the civil construction that in manufacturing of pieces and structures employ welding procedures. The aim of this work is to establish procedures to gas metal are welding with short circuit transfer of thin sheet steel elements, not coated and zinc-coated steel, in order to get junctions of acceptance quality and reduction of welding stress and distortion. This distortion arise of the thermal cycles that occur during the welding. In terms of the weld quality is defined the best consumables combination available in the market, in such a way to reduce the weld defects like porosities, spatters, cracks and loss of covering. To galvanized steel sheets, the combination: wire ER70S-3 and mixture 8%CO2 + 92% Ar showed the best performance. Three techniques were employed for control and reduce the welding distortion. One that using a spot heat sink following the arc, in this case the cooling jet, was more efficient that others techniques.