The pitting corrosion of welded joints of lean duplex stainless steel (LDSS) UNS S32304 was studied. LDSS S32304 thick plates were welded by different processes commonly employed in the manufacture of equipment and piping: shielded metal arc welding, gas metal arc welding, and flux cored arc welding. The electrochemical behavior of different weldment zones (fusion zone, base metal, and heat affected zone (HAZ)) was characterized both independently, using an electrochemical microcell, and together by testing the whole welded area. The electrochemical testing was performed in acidified glycerin, a process fluid of the biodiesel industry.The HAZ was the most susceptible zone for pitting corrosion for all samples. The results were correlated to the microstructural features of the materials. Finally, the results from the microcell and whole weld approaches were compared. According to the results, the gas metal arc welding process with 2209 as filler metal was found to be the optimum for application of 2304 duplex stainless steels in the acidified glycerin environment. Figure 3. Optical microstructure of base metal (a) and top samples welded by different processes showing HAZ and FZ, 2209 as filler metal: (b) SMAW, (c) GMAW, (d) FCAW.

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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.