ISSN:
1573-4889
Keywords:
nickel
;
cobalt
;
alloys
;
hot corrosion
;
sulfates
;
sulfides
Source:
Springer Online Journal Archives 1860-2000
Topics:
Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
Notes:
Abstract The corrosion of Ni, Co, Ni-10Cr, Co-21Cr, and IN738 was studied at 750°C in the presence of molten sulfate mixtures (Na2SO4-Li2SO4 and Na2SO4-CoSO4) and in an atmosphere consisting of O2+0.12% SO2-SO3. The corrosion was observed to be similar for both Na2SO4-Li2SO4 and Na2SO4-CoSO4 melts. The corrosion of Ni and Co tookplace by the formation of a mixed oxide plus sulfide scale, very similar to the corrosion in SO2 or SO3 alone. The initial stage for the corrosion of Ni-10Cr involved the formation of a thick NiO+Ni3S2 duplex scale, and Cr sulfide was formed during the later stages. A pitting type of morphology was observed for both Co-21 Cr and IN738. The pit was Cr sulfide at the beginning, and subsequently the sulfides oxidized to Cr2O3. A base-metal oxide layer was present above the pit, and this was observed to be formed very early in the corrosion process. A mechanism is proposed to explain this. In general, the formation of sulfides appears to be the primary mode of degradation in mixed sulfate melts.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1007/BF01072916
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