Abstract: The boiler fan coil pipe in about three years after the use of multiple water leakage, this batch of fan coil pipe Q215 hot-dip galvanized steel pipe. In order to find out the cause, some of the steel pipes cut on site were respectively subjected to macroscopic testing, chemical composition analysis, inner wall adhesion detection, microstructure inspection, mechanical property detection, hole topography analysis and energy spectrum analysis. The results show that the chemical composition and mechanical properties of the pipe meet the standard requirements, the oxygen content of circulating water exceeds the standard, and there are more attachments on the inner wall of the pipe, which makes the pipe oxygen corrosion ineffective.