Layer | Fill | Outline |
---|
Map layers
Theme | Visible | Selectable | Appearance | Zoom Range (now: 0) |
---|
Fill | Stroke |
---|---|
Collaborating Authors
Results
Effect of Alloy Composition On Stress Corrosion Cracking Susceptibility of Duplex Stainless Steels In Hot Alkaline Sulfide Solution
Leinonen, Heikki (VTT Technical Research Centre of Finland) | Pohjanne, Pekka (VTT Technical Research Centre of Finland) | Chasse, Kevin R. (Georgia Institute of Technology) | Singh, Preet M. (Georgia Institute of Technology) | Romu, Jyrki (Aalto University) | Saukkonen, Tapio (Aalto University) | Hänninen, Hannu (Aalto University)
ABSTRACT ABSTRACT Stress corrosion cracking (SCC) susceptibility of the duplex stainless steels EN1.4162 (UNS S32101) and EN1.4462 (UNS S32205) was evaluated with U-bend specimens in the alkaline sulfide solution containing 100 g/l NaOH and 55 g/l Na2S. Complementary potentiodynamic measurements were used to evaluate the effect of alloy composition on corrosion and on passivation behavior of the duplex stainless steels. The reference material in the study was the austenitic stainless steel EN1.4301 (UNS S30400). Based on separate potentiodynamic curves and the free corrosion potential measurements of the alloys during the SCC tests, it is evident that Cr and Ni as the main alloying elements in duplex stainless steels raised the corrosion potential and lowered the critical current density of the steel, thus improving SCC resistance. Based on the potentiodynamic curves the alloying elements Mo and Mn were highly active in the hot caustic solution. SCC in the austenitic reference stainless steel was severe penetrating in the unaffected material but in the duplex stainless steels cracking was observed only inside the affected surface layer. Selective dissolution of Fe, Cr, Mn and Mo and/or enrichment of Ni and Cr as well as Na, S and O took place in the affected surface layers of the duplex stainless steels depending on the steel grade. INTRODUCTION Austenitic-ferritic stainless steels, i.e., duplex stainless steels, are widely used in chemical processing industries that utilize sulfide-containing, caustic environments. The most common of these processes include procedures used in alumina ore, heavy water production, and various kraft pulping processes in pulp mills. However, field and laboratory experience has shown that duplex stainless steels may experience environmental assisted cracking and general corrosion under certain conditions. Structural reliability of high-performance recovery boilers and evaporation plants can be enhanced by using advanced stainless steels that have higher stress corrosion cracking (SCC) resistance than the current solutions.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)
Selective Dissolution And Stress Corrosion Cracking Susceptibility of Austenitic And Duplex Stainless Steels In Sodium Sulfide Containing Alkaline Solutions
Leinonen, Heikki (VTT Technical Research Centre of Finland Materials for Power Engineering) | Pohjanne, Pekka (VTT Technical Research Centre of Finland Materials for Power Engineering) | Romu, Jyrki (Aalto University, School of Engineering) | Saukkonen, Tapio (Aalto University, School of Engineering) | Schildt, Tanja (Aalto University, School of Engineering) | Hänninen, Hannu (Aalto University, School of Engineering)
ABSTRACT: The role of de-alloying in stress corrosion cracking (SCC) of the austenitic EN1.4301 (UNS S30400) and duplex stainless steels EN 1.4362 (UNS S32304) and EN 1.4462 (UNS S32205) was evaluated in simulated hot liquor environments. The samples were tested at 190ºC using U-bend specimens in 100 g NaOH + 55 g Na2S and 15 g NaOH + 150 g Na2S caustic environments simulating hot white (HWL) and hot black (HBL) liquors, respectively. SCC and general corrosion was detected in the steel surface layers. In austenitic stainless steels, severe cracking was observed throughout the samples in both solutions. In duplex stainless steels, cracking was observed only in the affected surface layer in both solutions. In EN 1.4301 steel, selective dissolution of Fe and Cr and enrichment of Cr, Ni, S, O and Na was observed in the affected surface layer and on the wakes of the large SCC cracks depending on the solution. In HWL, Na was clearly enriched and Cr was both selectively dissolved and enriched at different parts of the affected surface layers. In HBL, Na enrichment was lower and Cr was selectively dissolved in the affected surface layers. In the duplex stainless steels EN 1.4362 and EN 1.4462, dissolution of Fe, Cr and Mo and/or enrichment of Ni, Cr, Mo, Na, S and O took place depending on the steel and test solution. Cr content of both steels remained unaffected in HBL. In HWL, Cr was enriched in the surface layer in the Mo-alloyed steel (EN1.4462) and remained unaffected in the non-Mo-alloyed steel (EN 1.4362). In HWL, Mo dissolved selectively from the affected surface layer, whereas in HBL Mo enriched in the surface layer in the Mo-alloyed steel. Na was enriched in the affected surface layer of both duplex stainless steels immersed in HWL.
- Well Completion > Well Integrity > Subsurface corrosion (tubing, casing, completion equipment, conductor) (1.00)
- Production and Well Operations > Production Chemistry, Metallurgy and Biology > Corrosion inhibition and management (including H2S and CO2) (1.00)
- Facilities Design, Construction and Operation > Pipelines, Flowlines and Risers > Materials and corrosion (1.00)