Corrosion of Stainless Steels S31603, S31655, and S32101 in Sulfuric Acid Solutions: Effects of Concentration, Chlorides, and Temperature

E. Huttunen-Saarivirta*, E. Isotahdon, M. Lindgren, A. Mardoukhi, P. Mocnik, T. Kosec, J. B. Jorcin, S. Hägg Mameng, Y. El Ouazari, L. Wegrelius

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

7 Citations (Scopus)

Abstract

This study investigates the corrosion behavior of three stainless steel grades at two H2SO4 concentrations, namely 1 wt% and 10 wt%, with varying NaCl concentrations in the range from 500 mg/L to 10,000 mg/L. Dissociation of sulfuric acid yields the hydrogen (H+) and sulfate (SO24-) ions, the former of which lowers the pH value of a solution while the latter increases the concentration of sulfate ions that act as a corrosion inhibitor. The equilibrium chemistry of the solutions was defined at the test temperatures of 22°C, 50°C, 90°C, and 130°C, and correlated with the observations on the electrochemical and microstructural examination of the materials. The results showed clear differences in the main corrosion form between the two H2SO4 concentrations. In 1 wt% H2SO4, pitting was the major form of corrosion attack in the presence of chlorides, whereas uniform corrosion dominated in 10 wt% H2SO4. The pitting corrosion tendency for the three stainless steel grades under various test conditions was consistent, but there were differences in their resistance to uniform corrosion. The chloride-to-sulfate activity ratio, a(Cl-)=a(SO24-), was found to be the key parameter in defining the occurrence of pitting corrosion for all three alloys. In H2SO4-NaCl systems, no pitting occurred at the activity ratio a(Cl-)=a(SO24-) below 10, with higher values inducing pitting attack, particularly in 1 wt% H2SO4. The described novel results are presented and discussed in this paper.

Original languageEnglish
Pages (from-to)943-962
Number of pages20
JournalCorrosion
Volume78
Issue number10
DOIs
Publication statusPublished - Oct 2022
MoE publication typeA1 Journal article-refereed

Funding

The financial support by EIT Raw Materials and the partner organizations: VTT Technical Research Centre of Finland Ltd., Metso Outotec Finland Oy, ZAG Slovenian National Building, and Civil Engineering Institute, Tecnalia, Outokumpu Stainless AB, Boliden Harjavalta Oy, Ferritico AB, and Data Measuring Systems DMS, for the CORTOOLS project under the acceleration program (Project No. 18158) is gratefully acknowledged.

Keywords

  • chloride
  • pitting
  • stainless steel
  • sulfate
  • sulfuric acid
  • uniform corrosion

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