Abstract: In order to obtain the influence laws of hydraulic testing on the corrosion in the pipeline, take good measures for corrosion protection and improve the safety of hydraulic testing, scanning electron microscope and XRD analysis methods are adopted to analyze the tube that has failed in the hydraulic testing. The microstructure, corrosion products and local corrosion cross sections of the pipe surface near the leakage point of hydraulic testing are analyzed and studied. The results show that the existence of more serious local corrosion on the surface of the pipe and axial cracks in the pipeline are the two causes for the failure of pressure stabilizing during the hydraulic testing; the corrosion products of the inner wall of the hydraulic test pipe are mainly stable γ-Fe₂O₃, α-Fe(OH)₂, and there is also a small amount of unstable corrosion intermediate product γ-Fe(OH)₂ with poor protection, causing the bottom of the pipeline to be still in active corrosion phase; the inner wall of the hydraulic testing pipeline corrodes the material film in the inner, middle, and outer layers; the outer layer is loose, unstable, and poorly protected; the middle layer is mostly a relatively stable α-Fe(OH)₂, and the inner layer has a higher oxygen content; the binding between the metal matrix is relatively close, and it is mostly very stable γ-Fe₂O₃; there's a gap between the outer layer, the middle layer and the inner layer, which is prone to crevice corrosion and leads to severe local corrosion.

Key words: hydraulic testing, local corrosion, axial crack, corrosion production film, three layer structure