Corrosion of Stainless Steel in Sodium Chloride Brine Solutions
- Sukanya Hggg Mameng (Outokumpu Stainless AB) | Arne Bergquist (Outokumpu Stainless AB) | Elisabeth Johansson (Elisabeth Johansson)
- Document ID
- NACE International
- CORROSION 2014, 9-13 March, San Antonio, Texas, USA
- Publication Date
- Document Type
- Conference Paper
- 2014. NACE International
- crevice corrosion, pitting corrosion, stainless steel, corrosion, sodium chloride, stress corrosion cracking., brine
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With increasing environmental awareness follows demands for handling of brines that remain after use in a variety of applications. For this reason, stainless steels are being used in increasingly corrosive brine environments. The risk for corrosion in brines is associated with the chloride content, temperature, pH and oxygen level. This paper aims to explore the corrosion resistance of some stainless steels in highly concentrated sodium chloride solutions.
The resistance to localized corrosion of stainless steels in 20,000,100,000 and 200,000 ppm Cl- sodium chloride solutions was investigated at 90°C. The effects of chloride content, oxygen content and solution pH were studied on test coupons with and without welds and on U-bend specimens. Evaluation was performed for pitting and crevice corrosion, as well as for stress corrosion cracking. Long-term exposures (>1300 hours) were combined with electrochemical measurements such as cyclic polarization curves and determination of the critical pitting temperature (CPT). Investigated materials included duplex, super duplex, as well as 6Mo and 7Mo super austenitic stainless steels, which were compared to a standard austenitic grade.
A ranking of the tested stainless steel grades according to their corrosion resistance in sodium chloride brine solutions was: UNS S31603 < UNS N08904, UNS S32205 < UNS S31254, UNS S32750 < UNS S34565 < UNS S32654. Oxygen content was found to be an important factor influencing the corrosiveness of the sodium chloride brine solutions, with aerated conditions being the most corrosive ones. Also increasing chloride content and decreasing pH increased the corrosiveness of sodium chloride brine solution.
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