Characterization of the Welding Zone in Stainless Steels Used in CSP Plants Under Static Corrosion Conditions With Molten Salts

Mallco, Abdiel, Lague, Mauricio Teodoro, Vergara, Víctor, Viracochea, Grover

ISES Solar World Congress 2025 · Fortaleza, Brazil · 2025-11-03
Published by International Solar Energy Society (ISES)
DOI: 10.18086/swc.2025.01.04

Abstract

This study characterizes the corrosion of welded AISI 304 stainless steels, used in Concentrated Solar Power (CSP) plants, when exposed to molten solar salts (60% NaNO3, 40% KNO3). The research addresses the need to understand corrosion in welded areas, a critical area often overlooked compared to the base metal. Samples were subjected to static corrosion testing in the salt mixture at 550 °C for 1,350 hours. Gravimetric analysis revealed a multiphase corrosion process. Initially, a protective passive layer formed, but after approximately 650 hours, this layer began to degrade, initiating localized corrosion. In advanced stages (>1160 hours), the heat-affected zone (HAZ) was confirmed to be sensitized by the precipitation of chromium carbides (Cr23C6), leading to severe intergranular attack. This research clarifies the time-dependent degradation mechanisms in welded joints, highlighting the synergy between pitting and intergranular corrosion as the main failure mechanism.

Keywords

Static Corrosion, Gravimetric Analysis, Weld Zone, CSP, Sensitization, Intergranular Corrosion

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