The corrosion behavior of Ni-Cr-Mo ternary alloys in hot concentrated sulfuric acids with active carbon (part 2)

Katsuo Sugahara, Yoshio Takizawa, Eiji Akiyama, Koji Hashimoto

Research output: Contribution to journalArticlepeer-review

1 Citation (Scopus)

Abstract

The detrimental effect of active carbon on dew point corrosion by carbon-containing sulfuric acids was investigated using Ni-Cr-Mo alloys in 60 and 80% H2SO4 with and without active carbon at 120° C. The addition of active carbon leads to an increase in the dissolution rate of the alloys over a wide potential rage from -900 to 1200 mV vs. SCE, along with an increase in current densities of both anodic and cathodic reactions. Active carbon decomposes adsorbed molecular Sulfuric acid into active oxygen and sulfur dioxide, the latter of which is identified by gas chromatography. The reaction of active carbon with sulfuric acid also forms sulfonic acids. These reactions lead to a decrease in the intrinsic concentration of sulfuric acid and an increase in the corrosiveness in addition to acceleration of cathodic reaction. Spontaneous passivation in carbon-containing 80% H2SO4 occurs by the formation of a remarkably chromium-enriched passive film containing about 20 cationic % of molybdenum.

Original languageEnglish
Pages (from-to)702-708
Number of pages7
JournalZairyo to Kankyo/ Corrosion Engineering
Volume46
Issue number11
DOIs
Publication statusPublished - 1997

Keywords

  • Active carbon
  • Dew point corrosion
  • Hot sulfuric acid
  • Ni-Cr-Mo alloy
  • XPS

ASJC Scopus subject areas

  • Surfaces, Coatings and Films
  • Metals and Alloys
  • Electrochemistry
  • Materials Chemistry

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