Effects of seasonal Ciona macrofouling on corrosion and hydrogen permeation behavior of a low-alloy high-strength steel in marine environments

As a common macrofouling organism with seasonal adhesion patterns, Ciona poses a significant threat to steel materials in marine environments. Field studies conducted in natural seawater revealed that the metabolic activity of Ciona could reduce the overall corrosion rate and hydrogen permeation in low-alloy high-strength steel but might increase local hydrogen concentration. Meanwhile, severe localized corrosion occurred at the edge of the adhesion area. This phenomenon was attributed to the intense metabolic activity of Ciona, which created favorable conditions for the formation of chloride ion enrichment and self-catalyzed corrosion pits. The seasonal nature of Ciona adhesion disrupted the uniform corrosion pattern on steel surfaces, leading to more aggressive localized corrosion and hydrogen permeation.