Abstract: The Floating Production Storage and Offloading （FPSO） unit is a key facility for offshore oil development. Its ballast tanks suffer severe corrosion in the long-term wet-dry alternating environment,posing significant hidden dangers to offshore oil production. Through on-site investigation and sampling analysis of the corrosion conditions of ballast tanks,this paper explores the corrosion mechanism of tank walls and the working status of in-service anodes on site. The results show that the in-service anodes on site are in a passivated state and have failed. Factors such as ambient temperature,metal stress,and wet-dry alternating conditions will accelerate the formation of coating cracks,which in turn leads to deep corrosion of the tank walls.

Key words: FPSO unit, dry-wet alternation, anode failure, corrosion