Citation: Miranda-Pérez, A.F.; Rodríguez-Vargas, B.R.; Calliari, I.; Pezzato, L. Corrosion Resistance of GMAW Duplex Stainless Steels Welds. Materials 2023, 16, 1847. https://doi.org/10.3390/ ma16051847 Academic Editors: Matthias Bönisch and Feng Qiu Received: 20 December 2022 Revised: 17 February 2023 Accepted: 22 February 2023 Published: 23 February 2023 Copyright: © 2023 by the authors. Licensee MDPI, Basel, Switzerland. This article is an open access article distributed under the terms and conditions of the Creative Commons Attribution (CC BY) license (https:// creativecommons.org/licenses/by/ 4.0/). materials Article Corrosion Resistance of GMAW Duplex Stainless Steels Welds Argelia Fabiola Miranda-Pérez 1, *, Bryan Ramiro Rodríguez-Vargas 2,3 , Irene Calliari 4 and Luca Pezzato 4, * 1 Department of Strategic Planning and Technology Management, Universidad Popular Autónoma del Estado de Puebla, 17 Sur, 901, Barrio de Santiago, Puebla 72410, Mexico 2 Corporación Mexicana de Investigación en Materiales S.A. de C.V., Ciencia y Tecnología No. 790, Saltillo 400, Saltillo 25290, Mexico 3 Department of Engineering, University of Perugia, Via G. Duranti 93, 06125 Perugia, Italy 4 Department of Industrial Engineering (DII), University of Padua, Via Marzolo 9, 35131 Padua, Italy * Correspondence: argeliafabiola.miranda@upaep.mx (A.F.M.-P.); luca.pezzato@unipd.it (L.P.); Tel.: +52-1-222-229-9400 (A.F.M.-P.); +39-0498275503 (L.P.) Abstract: The hydrocarbon industry constantly requires a better understanding of stainless-steel welding metallurgy. Despite the fact that gas metal arc welding (GMAW) is one of the most commonly employed welding processes in the petrochemical industry, the process is characterized by the presence of a high number of variables to control in order to obtain components that are dimensionally repeatable and satisfy the functional requirements. In particular, corrosion is still a phenomenon that highly affects the performance of the exposed materials, and special attention must be paid when welding is applied. In this study, the real operating conditions of petrochemical industry were reproduced through an accelerated test in a corrosion reactor at 70 ◦ C for 600 h, exposing robotic GMAW samples free of defects with suitable geometry. The results show that, even if duplex stainless steels are characterized for being more corrosion resistant than other stainless steels, under these conditions it was possible to identify microstructural damage. In detail was found that the corrosion properties were strongly related to the heat input during welding and that the best corrosion properties can be obtained with the higher heat input. Keywords: duplex stainless steels; robotic GMAW; corrosion; cracking; pitting 1. Introduction New oil reserves are one of the more hostile environments for metallic materials from the point of view of corrosion. Venezuela, Saudi Arabia, and Canada are the leading countries in this production field, with Mexico currently situated in the 17th position, mean- ing that all infrastructure must be renewed, maintained, and preserved since detrimental components in petroleum are present [1–4]. Considering that corrosion is one of the most important issues in the oil and gas industry, a high demand for corrosion-resistant steels is always required. Stainless steels are the most suitable for these applications, with the martensitic and duplex ones most commonly employed in the oil and gas industry, where hydrogen sulfide is the most dangerous compound on the exterior platform [4,5]. Duplex stainless steels (DSS) are not resistant to the presence of Cl ions. In the same way, under certain temperature conditions and concentrations of S, stainless steels decrease their anticorrosion response and initiate their mechanical failure [5,6]. The petrochemical industry has a growing interest in this type of material because it provides benefits and savings, not only in better performance of the components but also in hidden savings derived from maintenance reduction, thus increasing industrial efficiency. In a study performed by Hruska et al. for the biomass industry, stainless steels were coated, resulting in improved corrosion properties [7]. Stainless steels are a group of high-alloy steels based on the Fe-Cr, Fe-Cr-C, and Fe-Cr-Ni systems. To be considered stainless, they must have Materials 2023, 16, 1847. https://doi.org/10.3390/ma16051847 https://www.mdpi.com/journal/materials