Corrosion behavior of coated low-alloy steels in a coal gasifier environment under thermal-cycling conditions

Technical Report · Mon Sep 01 04:00:00 EDT 1986

OSTI ID:7007023

Baxter, D J

Corrosion tests were conducted on coated 2-1/4Cr-1Mo and 0.3% carbon steels under thermal-cycling conditions in a gaseous atmosphere typical of that expected in a downstream waste heat recovery system of a coal gasifier. The corrosion tests were run in a rig designed to expose specimens under simulated heat-exchanger conditions. Under these conditions, the uncoated steels exhibited breakaway corrosion behavior. The corrosion behavior of coatings, which contained the stable oxide-forming elements Al and/or Cr and were applied by pack-diffusion processes by several commercial vendors, was dependent upon both chemical composition and the presence of physical defects. Results indicate that a minimum Cr concentration of approximately 20 to 22 wt % is required to suppress rapid corrosive degradation under thermal-cycling conditions, although even at the high Cr levels, intergranular corrosion of coatings was observed. Sulfide scale growth could not be suppressed even with Al concentrations in excess of 20 wt %. While the rate of scale growth on Al-rich coatings was relatively low, internal attack via preexisting cracks caused localized breakdown of the coatings. The two Ni-base weld metals that were used to simulate joining or repair of prior aluminized steels, IN 625 and IN 72, exhibited breakaway corrosion behavior. The corrosion behavior of all coated and coated/welded materials is described. The results were used to formulate a provisional specification for the procurement of coatings for eventual commercial application. 28 refs., 13 figs., 4 tabs.

• Research Organization: Argonne National Lab., IL (USA)
• DOE Contract Number: W-31109-ENG-38
• OSTI ID: 7007023
• Report Number(s): ANL/FE-86-6; ON: DE87002351
• Country of Publication: United States
• Language: English

Related Subjects

01 COAL, LIGNITE, AND PEAT
010404* -- Coal
Lignite
& Peat-- Gasification
36 MATERIALS SCIENCE
360105 -- Metals & Alloys-- Corrosion & Erosion
ALLOYS
ALUMINIUM
CARBON STEELS
CHEMICAL COMPOSITION
CHEMICAL REACTIONS
CHROMIUM
CHROMIUM ALLOYS
CHROMIUM STEELS
CHROMIUM-MOLYBDENUM STEELS
COAL GASIFICATION PLANTS
CORROSION
DATA
DEPOSITION
ELEMENTS
EXPERIMENTAL DATA
FABRICATION
HEAT EXCHANGERS
INDUSTRIAL PLANTS
INFORMATION
IRON ALLOYS
IRON BASE ALLOYS
JOINING
MATERIALS TESTING
METALS
NUMERICAL DATA
SIMULATION
STEELS
SURFACE COATING
TESTING
TRANSITION ELEMENTS
WELDING