Comparative study on the corrosion behavior of X52, 3Cr, and 13Cr steel in an O2–H2O–CO2 system: products, reaction kinetics, and pitting sensitivity

The corrosion behaviors of X52, 3Cr low-alloy steel, and 13Cr stainless steel were investigated in an O_2–H2O–CO_2 environment at various temperatures and O_2–CO_2 partial-pressure ratios. The results showed that the corrosion rates of X52, 3Cr, and 13Cr steels increased with increasing temperature. The corrosion rates slowly increased at temperatures less than 100°C and increased sharply when the temperature exceeded 100°C. In the absence of O_2, X52, 3Cr, and 13Cr exhibited uniform corrosion morphology and Fe CO3 was the main corrosion product. When O_2 was introduced into the system, various forms of Fe_2O_3 appeared on the surface of the samples. The Cr content strongly influenced the corrosion resistance. The 3Cr steel with a low Cr content was more sensitive to pitting than the X52 or 13Cr steel. Thus, pitting occurred on the surface of 3Cr when 1.25 MPa of O_2 was added; this phenomenon is related to the non-uniform distribution of Crin 3Cr.

Hydrogen embrittlement of X80 pipeline steel in H2S environment: Effect of hydrogen charging time, hydrogen-trapped state and hydrogen charging–releasing–recharging cycles

This study investigated the susceptibility of X80 pipeline steel to hydrogen embrittlement given different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles in H2S environment.The fracture strain of the steel samples decreased with increasing hydrogen pre-charging time;this steel degradation could almost be recovered after diffusible hydrogen was removed when the hydrogen pre-charging time was<8 d.However,unrecoverable degeneration occurred when the hydrogen pre-charging time extended to 16–30 d.Moreover,nanovoid formation meant that the hydrogen damage to the steel under intermittent hydrogen pre-charging–releasing–recharging conditions was more serious than that under continuous hydrogen pre-charging conditions.This study illustrated that the mechanical degradation of steel is inevitable in an H2S environment even if diffusible hydrogen is removed or visible hydrogen-induced cracking is neglected.Furthermore,the steel samples showed premature fractures and exhibited a hydrogen fatigue effect because the repeated entry and release of diffusible hydrogen promoted the formation of vacancies that aggregated into nanovoids.Our results provide valuable information on the mechanical degradation of steel in an H2S environment,regarding the change rules of steel mechanical properties under different hydrogen pre-charging times and hydrogen charging–releasing–recharging cycles.

Influence of S Contents on the Hydrogen Blistering and Hydrogen Induced Cracking of A350LF2 Steel

In the present work, the effects of chemical compositions on the hydrogen blistering and hydrogen induced cracking of A350LF2 steel with different S contents were studied. Four types of A350LF2 steels were evaluated by immersing samples in H2S-saturated NACE solution. The hydrogen blistering, crack length rate(CLR), crack thickness rate(CTR) and crack sensitivity rate(CSR) were evaluated. The results show that there are many hydrogen blisters on the sample surface with S content of 0.021%, a few on the sample surface with S content of 0.019% and 0.012% and no one on the surface with S content of 0.002%. There were 12, 2 and 1 strips of cracks of longer than 0.3 mm on the evaluated cross sections with S content of 0.021%, 0.019% and 0.012%, respectively. There was no any crack in the sample with 0.002% S. The corrosion rate was also evaluated. The S content has no obvious influence on the corrosion rate.