Near-Neutral pH Stress Corrosion Cracking in Steel Pipelines

摘要

An introduction to the phenomenon is given with reference to two summary reports. The important contributing factors to failure are briefly reviewed. Since stress variation is required, the process can be viewed as corrosion fatigue and many corrosion fatigue experiments have been done to guide our understanding of the problem. The typical stress cycles in a liquid and gas pipeline are compared. Research needs to be done to determine the effect of delays between cycles, since stress cycles are stochastic. The effects of millscale, cathodic current and calcium precipitation on the cracking processes are reviewed. Research has shown that variations in electrolyte composition can have a strong effect on the cracking and more study is recommended. The effects of variations in microstructure, residual stress, and room temperature creep are discussed. The important unresolved problem of growing cracks from the colony stage to the point where they are sufficiently deep to grow by corrosion fatigue is introduced and some of the progress in understanding initiation is reviewed. More research is required on the effects of seasonal variations in environment. Finally a corrosion fatigue model for liquid pipelines and a superposition model for gas pipelines are briefly discussed and some missing information is noted.