Hot Corrosion Mechanism of Steels Exposed to Heavy Metal Chlorides and Sulphates in SO2 Environment

Hanna Viitala*, Pekka Taskinen

*Corresponding author for this work

Research output: Contribution to journalArticleScientificpeer-review

3 Citations (Scopus)

Abstract

Copper flash smelting produces flue dust containing SO2-rich exhaust gas, causing corrosion problems in the heat recovery boiler of the gas train. In order to understand the corrosion behaviour of boiler steels, conditions of the boiler were simulated in the laboratory. Corrosion damage occurred as chlorine reacted with steel surfaces forming chlorides which deplete the steels from their alloying metals. At the scale/dust deposit interface, where the highest sulphur partial pressures prevail, a sulphate layer covered the mixed oxide and chloride scale. Molten sulphate deposit reduced the metal loss of AISI 304 steel by preventing chromium chloride diffusion away from the steel surface. The Cr2O3 scales were quite stable under molten sulphates. The dust deposit melted partially due to the presence of ZnCl2 in the deposit which initiated corrosion damage by producing a molten salt layer on the steel surfaces bringing it in contact with aggressive compounds in the copper smelter flue dust.

Original languageEnglish
Pages (from-to)239–262
Number of pages24
JournalOXIDATION OF METALS
Volume86
Issue number3
DOIs
Publication statusPublished - Oct 2016
MoE publication typeA1 Journal article-refereed

Keywords

  • Arsenic oxide
  • Copper smelter flue dust
  • Laboratory-scale corrosion research equipment
  • Molten salts
  • Zinc chloride

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