METHOD OF DEFINING INTERCRYSTALLINE CORROSION AND SURFACE DAMAGES OF UNDERGROUND AND UNDERWATER PIPELINES CAUSED BY CORROSION

摘要

FIELD: machine building. ^ SUBSTANCE: proposed method comprises pipeline cathodic polarisation, measurement of its potential in 5 to 10 s after polarisation elimination and detection of defect location and size from change of potential. Note here that polarisation curve valley crests and edges are used to define area S [mm2] of damage in waterproof coat by the formula: S=40000Eemf(corr)öL, where Eemf(corr)=Epa-Epc [B]; Epa is anode potential; Epc is cathode potential; öL is half the cathode length [m]. Then, damages are identified, their depth (corr) being defined by the formula: (corr)=2[Eemf(corr)/öL](Tp-5)[Imax/Ia(av)]; where Tp is pipeline life in years; Imax is maximum possible (nameplate) current of cathodic protection station [A]; Ia(av) is average actual current of said station [A]. Note here that intercrystalline corrosion is identified by peaks of polarisation potential at peak amplitude exceeding 150 mV and amplitude peak potential gradient exceeding 50 mV/m. ^ EFFECT: higher efficiency and reliability. ^ 4 dwg