Analysis of the causes of pitting corrosion in the 304 stainless steel gate slot of a hydropower station

• Published in: Engineering failure analysis 2025-03, Vol.170, p.109268, Article 109268
• Main Authors: Zhu, Yesen, Dong, Yipei, Teng, Kai, Xu, Yunze, Wang, Huakun, Zhang, Qiliang
• Format: Article
• Language: English
• Subjects: 304 stainless steel; Cavitation; Gate slot; Hydropower station; Pits
• ISSN: 1350-6307
• DOI: 10.1016/j.engfailanal.2025.109268

•The cause of pitting corrosion in the 304 stainless steel gate slot of a giant hydropower station was investigated.•The pitting mechanism was examined through a combination of numerical simulations and experimental tests.•The gate slot is subjected to high-velocity fluid (range 29.5–47.3 m/s) scour and sever cavitation impacts.•The combined effects of high flow velocities and cavitation are critical to severe pitting damage in gate slot. The causes of pitting corrosion damage of 304 stainless steel gate slot in a giant hydropower station were investigated. The study began with an on-site examination of water quality composition, the operational conditions of the hydropower station, and the corrosion damage observed in the steel structure of the gate slot. Following this, numerical simulations were conducted to analyse the hydraulic distribution characteristics of the gate slot section. Based on the simulation results, the corrosion behaviour of 304 stainless steel under corresponding operating conditions was experimentally investigated through a combination of electrochemical measurements and microscopic morphological characterization. The results indicate that within the normal operational head range, the water flow velocity at the gate slot varies between 29.5 m/s and 47.3 m/s, accompanied by significant cavitation. The film resistance of 304 stainless steel under high flow rate and cavitation conditions is considerably lower than that observed under still water conditions, with both scenarios exhibiting notable pitting potential. However, the film resistance during cavitation is less than that at high flow rates, and the pitting potential is also reduced. The synergistic effect of high flow rate and cavitation is a critical factor contributing to severe pitting damage to the steel structure of the gate slot. Specifically, various strategies have been proposed to prevent pitting corrosion of 304 stainless steel gate slot in hydropower stations.