METHOD OF DEFINING INTERCRYSTALLINE CORROSION AND SURFACE DAMAGES OF UNDERGROUND AND UNDERWATER PIPELINES CAUSED BY CORROSION Russian patent published in 2012 - IPC G01N17/02 

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=40000·E_emf(corr)ΔL, where E_emf(corr)=E_pa-E_pc [B]; E_pa is anode potential; E_pc is cathode potential; ΔL is half the cathode length [m]. Then, damages are identified, their depth δ(corr) being defined by the formula: δ(corr)=2[E_emf(corr)/ΔL]·(T_p-5)·[I_max/I_a(av)]; where T_p is pipeline life in years; I_max is maximum possible (nameplate) current of cathodic protection station [A]; I_a(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.

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