Stress Corrosion Cracking of 13Cr Steels in CO2-H2S-Cl− Environments

CORROSION ◽  
1985 ◽  
Vol 41 (4) ◽  
pp. 211-219 ◽  
Author(s):  
H. Kurahashi ◽  
T. Kurisu ◽  
Y. Sone ◽  
K. Wada ◽  
Y. Nakai

Abstract Stress corrosion cracking (SCC) behavior of two 13Cr steels was investigated in aqueous CO2-H2S environments. U-bend tests, constant load tensile tests, and corrosion tests were performed in CO2 environments containing different amounts of H2S. In addition, the slow strain rate tensile (SSRT) tests and hydrogen absorption measurements were done under cathodic hydrogen charging conditions to determine why 13Cr steels are more susceptible to SCC in H2S environments than low alloy steels are. The 13Cr steels were less resistant to SCC in the CO2-H2S environments than low alloy steels were, but some 13Cr steels were not subject to SCC even at a hydrogen sulfide partial pressure of 0.3 atm. Furthermore, it was found that SCC in a CO2-H2S environment was caused by hydrogen embrittlement and that the SCC susceptibility of 13Cr steels was affected by their intergranular cracking behavior. Thus, their microstructures and carbide dispersions are important factors in defining SCC susceptibility of 13Cr steels.

An important contributory role of grain boundary segregation of residual impurities in the intergranular stress-corrosion cracking of carbon and low alloy steels is proposed. Experimental results are presented of the stress corrosion susceptibility of mild steel in nitrate solution, and in relation to varying grain boundary composition as monitored by Auger electron spectroscopy. The harmfulness of a particular impurity element depends on three factors: its bulk level; its segregation thermodynamics and kinetics resulting in an equilibrium enrichment at the grain boundaries; and its ability to promote electrochemical dissolution of the grain boundary. A hierarchy of impurity elements that exacerbate stress corrosion cracking is presented and correlated with equilibrium oxidation potentials. The results and simple model allow the prediction of the relative harmfulness of impurity elements with respect to intergranular stress corrosion in commercial carbon and low alloy steels from a knowledge of the bulk concentration only. This enables significant improvements in performance to be designed in the alloy by respecifying lower levels of only the one or two highly detrimental impurities.


CORROSION ◽  
1981 ◽  
Vol 37 (6) ◽  
pp. 320-327 ◽  
Author(s):  
Wu-Yang Chu ◽  
Tian-Hua Liu ◽  
Chi-Mei Hsiao ◽  
Shi-Qun Li

Abstract For four low alloy steels with a wide range of tensile strengths, the dynamical processes of the nucleation and propagation of stress corrosion cracking (SCC) in water with various polarization conditions and in a inhibitor solution were traced with an optical microscope. The results show that if the tensile strength of the steel is higher than a critical value, which is different in the different polarization conditions, and KI>KISCC, the plastic zone in front of a loaded crack tip is enlarged with time, i.e., the delayed plastic deformation occurs in all the environments used. The nucleation and propagation of SCC will follow when this delayed plastic deformation develops to a critical condition. Neither anodic and cathodic polarization nor the inhibitor can change the feature of the delayed plasticity and the nucleation and propagation of SCC in water. In all the environments used, the KISCC is increased and da/dt is decreased with decreasing strength of the steel. Anodic polarization and the addition of the inhibitor make KISCC increase and da/dt decrease. But cathodic polarization is just opposite.


CORROSION ◽  
1976 ◽  
Vol 32 (10) ◽  
pp. 395-401 ◽  
Author(s):  
MASAMICHI KOWAKA ◽  
SABURO NAGATA

Abstract This paper is related to the new stress corrosion cracking phenomenon of mild and low alloy steels in a CO/CO2 environment. The incidents of cracking are described and these were reproduced by laboratory tests. The results obtained are as follows: (1) No stress corrosion cracking of mild steel was found to occur in water containing just CO or CO2. (2) The transgranular stress corrosion cracking occurred only in CO/CO2 environment with water. (3) Stress corrosion cracking occurred in a wide range of CO/CO2 ratios in water. (4) The susceptibility to stress corrosion cracking of mild steel decreases with increasing temperature. (5) No stress corrosion cracking was found to occur on 18Cr-10Ni stainless steel. (6) From the study of electrochemical measurements, the mechanism has been proposed that this form of cracking is stress corrosion cracking rather than hydrogen embrittlement. (7) Prevention of stress corrosion cracking in these environments is discussed.


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