Browsing by Author "Frankel, Gerald S."

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    Cyclic polarization study of thick welded joints of lean duplex stainless steel for application in biodiesel industry.
    (2017) Sicupira, Dalila Chaves; Cardoso Junior, Ronaldo; Bracarense, Alexandre Queiroz; Frankel, Gerald S.; Lins, Vanessa de Freitas Cunha
    Thick welded joints of UNS S32304 lean duplex stainless steel (LDSS) has been studied in acidified glycerin, a byproduct of biodiesel plants, using cyclic polarization technique. LDSS S32304 thick plates were welded by different processes commonly employed in the fabrication process: shielded metal arc welding, gas metal arc welding and flux cored arc welding. The electrochemical behavior of different weldment zones was characterized. Transmission electron microscopy and scanning electron microscopy (SEM) were used for sample characterization. SEM images showed that the heat affected zone was the most critical zone for pitting corrosion for all samples. The results were associated to the microstructural features of the materials. Generally, the breakdown potential of the top regions of welds was higher in acidified glycerin than the weld root for welds fabricated with two different filler metals. Basically, all the welded samples exhibited similar or higher corrosion resistance, compared with the corresponding base metal.
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    Electrochemical study of passive films formed on welded lean duplex stainless steel.
    (2016) Sicupira, Dalila Chaves; Cardoso Junior, Ronaldo; Bracarense, Alexandre Queiroz; Frankel, Gerald S.; Lins, Vanessa de Freitas Cunha
    Duplex stainless steel (DSS) has been considered as an excellent material of construction for applications where high corrosion resistance and high mechanical strength are required. The use of this material can minimize costs related to corrosion in different industries, for example, in the biodiesel industry. The objective of this study is to evaluate the electrochemical and electronic properties of passive films of thick welded joints of UNS S32304 lean duplex stainless steel (LDSS) fabricated by different welding processes, in acidified glycerin, a byproduct of the biodiesel industry. The electrochemical and electronic behavior of the passive films formed on UNS S32304 LDSS was evaluated using electrochemical impedance spectroscopy and Mott–Schottky measurements. The capacitance study shows that the passive films formed on welded DSS behave as n- and p-type semiconductors above and below the flat band potential, respectively. Furthermore, the samples welded by the gas metal arc welding process exhibited better corrosion resistance than other welding process using the same filler metal.