A long-term field study investigated the corrosion of steel pipe piles (SPPs) used for industrial buildings near Phu My port, Vietnam. This environment is particularly aggressive due to brackish water and pollution from the Thi Vai River. Researchers monitored STK400 steel pipe piles (165 mm diameter, 12 m length) placed in various zones (atmospheric, tidal, submerged, and mud) to assess the impact on corrosion rate and rust formation. The distribution of organisms, particularly barnacles, oysters, and seaweeds, influenced the layering of rust in the tidal and submerged zones. The highest corrosion rates and pitting occurred at the highest water level (HWL) and submerged zones due to constant renewal of corrosive agents at HWL and the influence of organisms at the lowest water level (LWL) and below. Conversely, the tidal and mud zones experienced lower corrosion rates due to cathodic protection from the corroding HWL and submerged zones. This study highlights the complex interplay of environmental factors affecting steel pile corrosion. The findings provide valuable insights for designing and implementing effective anti-corrosion strategies for steel structures in Phu My port’s challenging environment.