Abstract: As human social activities continue to expand towards coastlines, the impact of chloride ion erosion on the structural durability of coastal buildings has become a non-negligible issue. One of the main reasons is the exposure and subsequent erosion of reinforcement in the post-cast strip of basement floor slabs due to immersion in groundwater. Therefore, it is necessary to conduct research on the causes of chloride ion erosion in post-cast strips of basements in offshore environments and explore protective technologies. Currently, systematic research on the erosion and protection caused by long-term exposure and immersion of reinforcement in post-cast strips of basements due to process interruptions during construction is still insufficient. To this end, this paper analyzes the causes of corrosion of reinforcement in the post-cast strip of floor slabs by measuring and analyzing the chloride ion concentration in groundwater from the post-cast strip. It also compares different rust removal schemes and selects an appropriate one for rust removal experiments. The experimental results indicate that manual rust removal alone fails to meet the requirements, and there are signs of re-rusting without regular rust removal. The combined regular rust removal method using manual mechanical rust removal and rust removers demonstrates good rust removal and anti-re-rusting effects on metal structures exposed due to construction. The research findings provide valuable insights for analyzing the mechanism of chloride ion erosion on exposed reinforcement in post-cast strips of basement floor slabs in offshore environments and for long-term erosion protection construction in practical engineering projects.