Critical flow intensities expressed in terms of critical wall shear stresses for initiation of flow induced localized corrosion (FILC) at carbon steel under CO2 corrosion conditions (1 M NaCl, 5 bar CO2, 80°C) were evaluated using the submerged jet impingement method. Flow
independent pitting facilitates FILC initiation in uninhibited systems already at wall shear stresses below 0.2 Pa. If pitting is prevented by corrosion inhibitors critical wall shear stresses can be clearly identified. They depend on the type and concentration of the inhibitor. In the presence of an aromatic quat critical wall shear stresses were found at 250 Pa. The effect of flow intensity on the carbonate scale properties (crystal size, scale thickness, cracking tendency) was studied in detail. The experimental results support the authors’ hypothesis on flow induced fatigue cracking of carbonate scales as important FILC initiation
step. Keywords: carbon steel, carbon dioxide, brine, corrosion, iron carbonates, erosion corrosion, flow, jet impingement, wall shear stress, scale morphology, corrosion inhibitor, quaternary ammonium compound.