Abstract
In order to prevent dew point corrosion by sulfuric acid, the roles of chromium and molybdenum in enhancing the corrosion resistance in 60 and 80% H2SO4, at 120°C were investigated. Particular attention was paid to the addition of active carbon to H2SO4. The chromium contents of alloys were 16 and 20% and the molybdenum contents were 17, 20, 24 and 25%. In carbon-free H2SO4 increasing molybdenum content gives rise to a decrease in corrosion rate and Ni-20Cr-24Mo alloy shows high corrosion resistance by spontaneous passivation forming a remarkably molybdenum-enriched passive film. In carbon-containing H2SO4 increasing chromium content is effective in decreasing the corrosion rate. Three Ni-20Cr-Mo alloys are spontaneously passive in 80% H2SO4 with carbon. Because the carbon addition increases the open circuit potential exceeding the stability limit of tetravalent molybdenum as a result of enhancement of the cathodic activity, the spontaneously passivated film consists of remarkably concentrated chromium ions along with some molybdenum ions.
Original language | English |
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Pages (from-to) | 643-650 |
Number of pages | 8 |
Journal | Zairyo to Kankyo/ Corrosion Engineering |
Volume | 46 |
Issue number | 10 |
DOIs | |
Publication status | Published - 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