Environmental Factors that Influence the Susceptibility of Line Pipe Steels to External Stress Corrosion Cracking
1983 Volume 69 Issue 11 Pages 1463-1470
Details
1983 Volume 69 Issue 11 Pages 1463-1470
Stress corrosion cracking (SCC) susceptibility of X60 line pipe steel was evaluated by means of the slow strain rate technique (SSRT) as well as the static load technique (SLT) in four environments, i.e., NaOH, Na2CO3-NaHCO3, Ca(NO3)2 and SO2, that were found potentially to cause SCC by the potentiodynamic polarization screening tests on 25 chemical species present in the soil. The results obtained are summarized as follows :
1) SCC in NaOH could be produced at temperatures above 40°C, at stresses above 30 kg/mm2 and at potentials between -880 and -1230 mV vs. Cu-CuSO4.
2) SCC in Na2CO3-NaHCO3could be produced above 15°C, above 42 kg/mm2 and between -650 and -875 mV.
3) SCC in Ca(NO3)2 could be produced above 30°C, above 5 kg/mm2 and between +1 120 and -480 mV.
4) The minimum concentration required to produce SCC was 5% for NaOH and 0.5 N for Na2CO3-NaHCO3.
5) A saturated SO2 solution was found to promote transgranular stress corrosion cracking in X60 line pipe steel at ambient temperature.
6) The SCC potential region indicated by SSRT in terms of reduction in area was in good agreement with that by SLT in terms of time to failure.
