High temperature corrosion by deposits of alkali salts

Book · Sun Dec 01 04:00:00 EST 1996

OSTI ID:397811

Kloewer, J ^[1]

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1. Krupp VDM GmbH, Werdohl (Germany)

In order to understand and predict how corrosion behavior of metallic high temperature materials is affected by deposits of alkali salts, eight commercial high temperature alloys (AISI 314, alloy 800H, alloy 31, AC66, alloy 45-TM, alloy 625, alloy 59 and alloy C-4) coated with alkali sulfates and chlorides (Na{sub 2}SO{sub 4}/KCl) were investigated in both air and in HCl/SO{sub 2}-containing waste incineration environments. The corrosion rates were found to depend sensitively on the alloy composition, especially on the concentration of molybdenum and silicon. Both stainless steels and nickel base alloys without molybdenum were resistant to dissolution by sulfates in air. Molybdenum-containing steels and nickel base alloys, on the other hand, were extremely susceptible to acidic dissolution in sodium sulfate. These high corrosion rates can be attributed to an increase in salt acidity caused by dissolution of MoO{sub 3}. The effect of HCI in the gas atmosphere was contradictory. All alloys without molybdenum suffered severe internal oxidation, when chlorine was present in the gas atmosphere. The corrosion rates of the nickel-molybdenum alloys, however, were decreased when chlorine was added to the gas phase. The highest corrosion resistance to synthetic waste incineration gas in combination with deposits of alkali sulfates and chlorides was found in the nickel base alloys 45 TM and alloy 625.

• OSTI ID: 397811
• Report Number(s): CONF-960389--
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
32 ENERGY CONSERVATION, CONSUMPTION, AND UTILIZATION
36 MATERIALS SCIENCE
42 ENGINEERING
AIR
BOILERS
CHEMICAL COMPOSITION
CHLORIDES
COAL GASIFICATION PLANTS
CORROSION
DISSOLUTION
EXPERIMENTAL DATA
FLUIDIZED-BED COMBUSTORS
HEAT RESISTING ALLOYS
HYDROCHLORIC ACID
INCINERATORS
MATERIALS
OPTICAL MICROSCOPY
SCALING
SCANNING ELECTRON MICROSCOPY
SULFATES
SULFUR DIOXIDE
WEIGHT MEASUREMENT
X-RAY SPECTRA