Mechanical Investigation of Carbon Steel under Strong Corrosion Effected by Corrosion Pits

This study investigated the effect of corrosion pits on the mechanical degradation of steel Q345 under strong acid corrosion. The experiment on a total of 27 steel Q345 specimens corroded by 36% industrial hydrochloric acid for 0 h, 1 h, 2 h, 4 h, 8 h, 12 h, 24 h, 48 h, and 72 h, respectively, is conducted to study failure mode and stress-strain curves. After that, a noncontact topography scanner (DSX500) scanned geometric parameters of corrosion pits in steel Q345 to establish its mechanical degradation. The surface morphology and the corresponding degradation law of corroded steel are also revealed. In addition, the steel plastic fracture criterion taking into account equivalent plastic fracture strain and average stress triaxiality T is adopted to propose the uniform pit model. The analysis results show that the failure mode gradually changes from ductile to brittle. It is noted that the depth and relative size of the corrosion pit are the main factors affecting the increase of the maximum pit coefficient. Further, FEM based on uniform corrosion pits is found by the flexible damage evolution criterion. Its calculation results are entirely consistent with experimental results, indicating that this model can mirror the surface morphology of steel suffering strong corrosion, and simulated accurately stress flow law and necking failure of strong corrosion steel. The proposed criterion is validated with verification results and can provide good references for the design of steel bridges under strong corrosion.