管线钢土壤应力腐蚀开裂研究进展及展望

余德远, 刘智勇, 杜翠薇, 黄辉, 林楠

Research Progress and Prospect of Stress Corrosion Cracking of Pipeline Steel in Soil Environments

YU Deyuan, LIU Zhiyong, DU Cuiwei, HUANG Hui, LIN Nan

表1 管线钢两类典型pH SCC特征比较[7]

Table 1 Comparison of two typical pH SCC characteristics of pipeline steel[7]

Factor High pH SCC (Classical) Near-neutral pH SCC (Non-classical) Location The typical occurrence is within 20 km from the compression station, and the number of failures decreases with increasing distance from the compression station and decreasing temperature 65 per cent occurred between the compressor station, 12 per cent occurred between the 1st and 2nd valves, 5 per cent occurred between the 2nd and 3rd valves, 18 per cent occurred downstream of the third valve Electrolyte Concentrated carbonate-bicarbonate solution with an alkaline pH greater than 9.3 Dilute bicarbonate solution with a neutral pH in the range of 5.5 to 7.5 Electrochemicalpotential -600 to -750 mV (Cu/CuSO4) at room temperature, and as the temperature of the solution increases, the SCC susceptible potential range becomes wider At free corrosion potential: -760 to -790 mV (Cu/CuSO4), where cathodic protection does not reach pipe surface at SCC sites Temperature Growth rate decreases exponentially with temperature decrease No apparent correlation with temperature of pipe but appear to occur in the colder climates where CO2 concentration in groundwater is higher Crack path and morphology Primarily intergranular, narrow, tight cracks with no evidence of secondary corrosion of the crack wall Primarily transgranular (across the steel grains), wide cracks with evidence of substantial corrosion of crack side wall