Vanessa de Freitas Cunha Lins

The influence of chemical composition and microstructure of API linepipe steels on hydrogen induced cracking and sulfide stress corrosion cracking

The chemical composition and microstructure are known to have a significant effect on the resistance to hydrogen induced cracking (HIC) and sulfide stress corrosion cracking (SSCC) of structural steels in wet H2S environments. In this paper, the influence of microstructure on HIC and SSCC behavior of two low C–Mn–Nb–Mo API linepipe steels has been investigated. Subjecting the steel to different thermomechanical processes modified the microstructure. The results showed that refined and homogeneous quenched and tempered bainite/martensite microstructures had the best performance with respect to both HIC and SSCC susceptibility.

Aspectos do coprocessamento de resíduos em fornos de clínquer

The practice of co-processing of residues has increased due to the requirement of environmental and social friendly disposal of dangerous wastes from several industrial processes. The aim of this work was to perform a revision of co-processing of residues in Brazil and in the world, aiming at process optimization and also to identify the aspects already studied as well as those which still request research efforts. Social, environmental, and technological aspects of co-processing were discussed in the present work as well as the life cycle analysis (LCA) in the cement production and the technical and scientific literature about co-processing.

SCALE MORPHOLOGIES AND COMPOSITIONS OF AN IRON- MANGANESE-ALUMINUM-SILICON ALLOY OXIDATED AT HIGH TEMPERATURES

Abstract An Fe-34Mn-7.3Al-1.4Si alloy was prepared by vacuum induction melting. The cylindrical-shaped ingots were first homogenized at 1200 °C, forged at 1000 °C, cut and cold-rolled, followed by a homogenization heat treatment at 1000 °C, for 1 hour. The samples were submitted to oxidation tests in air at temperatures ranging from 600 to 1200 °C, for times between 1 and 45 hours. The morphologies of the oxide scales were studied by X-ray diffraction, optical and scanning electron microscopy with EDS facilities. The results showed a good oxidation resistance between 600 and 900 °C and poor oxidation resistance at temperatures above 1000 °C. The presence of a second phase after oxidation was responsible for the poor oxidation resistance. Three classes of oxides of aluminum, manganese and iron were identified and established according to the oxidation conditions. The levels of aluminum required to form protective scales as a function of the oxidation temperature and time were discussed.

Corrosion Resistance of API X52 Carbon Steel in Soil Environment

The aim of this work is to evaluate the corrosion resistance of the API SL X52 steel in soil from the Serra do Ouro Branco, Minas Gerais, Brazil. The electrolytes studied were an aqueous extract of the soil and a synthetic solution of the soil medium. The electrochemical techniques used were Tafel analysis and electrochemical impedance spectroscopy. The semi-quantitative chemical analysis of the soil was performed using X-ray fluorescence spectroscopy. The steel samples, after Tafel analysis, were analyzed using the scanning electron microscopy coupled with the energy dispersive spectrometry. The API steel showed a higher corrosion potential and polarization resistance and a lower current density in aqueous extract of soil. The Nyquist diagrams show two capacitive arcs, with two time constants.

Avaliação da soldagem multipasse de chapas espessas de aços inoxidáveis lean duplex UNS S32304 soldadas pelos processos SMAW, GMAW e FCAW: parte 1: propriedades mecânicas

The duplex stainless steels (DSS ́s) have been placed as an excellent alternative for applications where high corrosion resistance and high mechanical strength are required. However, DSS ́s, including the lean duplex, present lower weldability than the austenitic stainless steels. Thus, this study aims to evaluate the multipass welding of 22 mm plates of lean duplex stainless steel alloy UNS S32304, using the process SMAW, GMAW and FCAW with consumables with two types of chemical composition, 22%Cr9%Ni3%Mo and 23%Cr7%Ni giving a total of six experiments. V-grooves with 60° and ceramic backing for welding the root pass were used and the heat input was maintained constant at 1.6 kJ.mm-1. It was determined the time and sequence of welding passes, aiming an analysis of productivity. The welded joints were subjected to x-ray END and specimens for tensile, bending, Charpy at -30°C and microhardness were extracted. The productivity of the semi-automatic processes proved to be at least 63% greater than the SMAW process while the process FCAW showed 6-18% faster than the GMAW. It was found discontinuities (porosity) acceptable according to ASME B31.3 in some experiments that did not affect negatively the mechanical results, which stayed above the parent material requirement and meet fabrication standards. Key-words: Duplex, Lean Duplex, Weldability, Multipass Welding, Mechanical Properties.The duplex stainless steels (DSSs) have been placed as an excellent alternative for applications where high corrosion resistance and high mechanical strength are required. However, DSSs, including the lean duplex, present lower weldability than the austenitic stainless steels. Thus, this study aims to evaluate the multipass welding of 22 mm plates of lean duplex stainless steel alloy UNS S32304, using the process SMAW, GMAW and FCAW with consumables with two types of chemical composition, 22%Cr9%Ni3%Mo and 23%Cr7%Ni giving a total of six experiments. V-grooves with 60o and ceramic backing for welding the root pass were used and the heat input was maintained constant at 1.6 kJ.mm-1. It was determined the time and sequence of welding passes, aiming an analysis of productivity. The welded joints were subjected to x-ray END and specimens for tensile, bending, Charpy at -30oC and microhardness were extracted. The productivity of the semi-automatic processes proved to be at least 63% greater than the SMAW process while the process FCAW showed 6-18% faster than the GMAW. It was found discontinuities (porosity) acceptable according to ASME B31.3 in some experiments that did not affect negatively the mechanical results, which stayed above the parent material requirement and meet fabrication standards.

Infrared-spectroscopy analysis of zinc phosphate and nickel and manganese modified zinc phosphate coatings on electrogalvanized steel

Hopeite-type phosphate coatings in which zinc is partially replaced by other metals like manganese and nickel are of great interest for the automotive and home appliance industries. Such industries use phosphate conversion coatings on galvanized steels in association with cataphoretic electropainting. Zinc phosphates modified with manganese and nickel are isomorphic with the hopeite, and the phase identification using X-ray diffraction is difficult. In this paper, the phosphate coatings are identified using the Fourier transform infrared spectroscopy (FTIR).

Effect of nickel and magnesium on zinc electrowinning using sulfate solutions

Zinc electrowinning is performed with the application of a current through insoluble electrodes (Pb - Ag), causing the electrolysis of zinc sulfate, with or without impurities, and zinc deposition on the cathode of aluminum. The impurities can reduce the current efficiency and increase the energy consumption in zinc electrolysis. In this work, the effect of nickel and magnesium on zinc electrodeposition was studied using the electrochemical techniques of galvanostatic deposition and cyclic voltammetry. Additions of nickel, magnesium or both cations in zinc sulfate electrolyte resulted in a marginal increase in current efficiency. Addition of nickel or magnesium polarizes the cathode; however, the extent of polarization in the presence of magnesium is more than that of nickel. Addition of magnesium to the zinc electrolyte caused zinc reduction at a more negative potential. The addition of nickel to the zinc electrolyte increased the current density of the anodic peaks, thus increasing the dissolution of zinc and hydrogenated phases. The addition of nickel to the zinc and magnesium solutions decreased the nucleation loop, facilitating zinc deposition.

Ethanol extract of propolis as a protective coating for mild steel in chloride media

The anticorrosion performance of commercial extract of ethanolic propolis (EP)-coated mild steel samples immersed in a 3.5% w/v NaCl in neutral and near neutral media was evaluated by classical electrochemical and electrochemical probe beam deflection techniques. The functional groups and major components of the extract were identified by Fourier transform infrared spectroscopy and high-performance liquid chromatography, respectively. The extract and the major constituent identified in the extract, 3,5-diprenyl-4-hydroxycinnamic acid (DHCA), are poorly hydro-soluble in a neutral medium. The bare and coated carbon steel surfaces were characterized by scanning electron microscopy and atomic force microscopy before and after a saline immersion. The electrochemical response of the coated electrodes was compared with bare mild steel electrodes and all qualitative and quantitative data obtained supported the hypothesis that EP is a potential mild steel corrosion inhibitor. Although several flavonoids are known to have remarkable antioxidant properties and be effective metal corrosion inhibitors, this work is pioneering in its evaluation of the inhibitory capacity of a natural product whose main constituent is DHCA.

Avaliação da soldagem multipasse de chapas espessas de aços inoxidáveis lean duplex UNS S32304 soldadas pelos processos SMAW, GMAW e FCAW -: resistência à corrosão

Duplex stainless steels (DSSs) have been placed as an excellent alternative for applications where high corrosion resistance and high mechanical strength are required. However, the DSSs, including the lean duplex stainless steels, present lower weldability than the austenitic stainless steels. This study aims to evaluate the corrosion resistance of welded joints using multipass welding of lean duplex stainless alloy UNS S32304 plates 22 mm thick, using the SMAW, GMAW and FCAW consumables with two types of chemical composition, 22%Cr9%Ni3%Mo and 23%Cr7%Ni, giving a total of six experiments. The welded joints were evaluated using the anodic potentiodynamic polarization technique to determine the pitting potential of the material. The electrolyte studied was 3.5% w/v sodium chloride aqueous solution. The lean duplex steel welded by GMAW process with consumable with 22%Cr9%Ni3%Mo showed the best behavior against corrosion in saline solution. The root of the weld region had the highest pitting potential compared to the top of the welded joints. The lean duplex steel joints welded using FCAW process showed a behavior characteristic of general corrosion in the medium of saline solution, unlike the other samples.

Recobrimentos de poli (tereftalato de etileno) depositados em aço por aspersão térmica a partir de pós obtidos em diferentes condições de moagem

Resumo: Neste trabalho foram analisados recobrimentos de poli(tereftalato de etileno), PET, depositados em aco carbo- no atraves da tecnica de aspersao termica a combustao, e produzidos a partir de pos oriundos de processos de moagem, em moinho de bolas e de facas, de garrafas de PET pos-consumo. Algumas condicoes de moagem foram testadas, tendo- se obtido pos com diferentes caracteristicas morfologicas. As caracteristicas morfologicas dos pos e dos recobrimentos foram avaliadas por microscopia optica e eletronica, tendo-se observado que o recobrimento apresentava bolhas, prova- velmente devido a degradacao do polimero. Alem disto, os recobrimentos produzidos, bem como as amostras de po, foram caracterizados por espectroscopia na regiao do infravermelho, por calorimetria exploratoria diferencial e atraves da determinacao de viscosidade intrinseca em solucao. Os resultados obtidos mostraram que e possivel a producao de aco carbono recoberto com PET atraves da tecnica de aspersao termica, sendo que o grau de degradacao, a morfologia e a distribuicao granulometrica dos pos utilizados influenciaram significativamente as caracteristicas e propriedades dos recobrimentos formados. Palavras-chave: Poli(tereftalato de etileno), aspersao termica, analise termica, viscosidade intrinseca. Thermally Sprayed-Coated Carbon Steel Produced Using PET Powder Obtained under Different Grinding Conditions Abstract: The main purpose of this work was to study the production of a thermal spray coated poly(ethyleneterephthalate) (PET) steel. PET coatings were made of a thin grinding waste produced by a PET recycling company, and of a PET powder, which was obtained by grinding post-consumer beverage bottles. Some grinding conditions, using a ceramic ball mill, were studied. Scanning Electronic Microscopy (SEM) and optical microscopy (OM) were used in the study of powder and coating morphologies, and this analysis showed that PET coating presents bubbles due to polymer degrada- tion. PET powder and coating characteristics were investigated using Differential Scanning Calorimetry (DSC) and measurements of intrinsic viscosity. It was observed that the powder morphology and the degradation and size distribu- tion of the PET powder affect significantly the characteristics and properties of coatings.