Journal of Surface Science and Engineering (한국표면공학회지)

The Korean Institute of Surface Engineering (한국표면공학회)
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Corrosion of Fe-Cr Steels at 600-800℃ in NaCl Salts

  • Lee, Dong Bok (School of Advanced Materials Science and Engineering, Sungkyunkwan University) ;
  • Kim, Min Jung (School of Advanced Materials Science and Engineering, Sungkyunkwan University) ;
  • Yadav, Poonam (School of Advanced Materials Science and Engineering, Sungkyunkwan University) ;
  • Xiao, Xiao (School of Advanced Materials Science and Engineering, Sungkyunkwan University)
  • Received : 2018.11.02
  • Accepted : 2018.11.20
  • Published : 2018.12.31
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Abstract

NaCl-induced hot corrosion behavior of ASTM T22 (Fe-2.25Cr-1Mo), T91 (Fe-9Cr-1Mo), T92 (Fe-9Cr-1.8W-0.5Mo), 347HFG (Fe-18-Cr-11Ni), and 310H (Fe-25Cr-19Ni) steels was studied after spraying NaCl on the surface. During corrosion at $600-800^{\circ}C$ for 50-100 h, thick, non-adherent, fragile, somewhat porous oxide scales formed. All the alloys corroded fast with large weight gains owing to fast scaling and destruction of protective oxide scales. Corrosion rates increased progressively as the corrosion temperature and time increased. Corrosion resistance increased in the order of T22, T91, T92, 347HFG, and 310H, suggesting that the alloying elements of Cr, Ni, and W beneficially improved the corrosion resistance of steels. Basically, Fe oxidized to $Fe_2O_3$, and Cr oxidized to $Cr_2O_3$, some of which further reacted with FeO to form $FeCr_2O_4$ or with NiO to form $NiCr_2O_4$.

Keywords

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Fig. 1. Weight gain versus corrosion time curves of steels after corrosion in NaCl. (a) 600℃, (b) 700℃, (c) 800℃.

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Fig. 2. X-ray diffraction patterns after corrosion at 700℃ for 100 h. (a) T22 (Fe-2.25Cr-1Mo), (b) T91 (Fe-9Cr-1Mo), (c) T92 (Fe-9Cr-1.8W-0.5Mo), (d) 347HFG (Fe-18Cr-11Ni), (e) 310H (Fe-25Cr-19Ni).

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Fig. 3. T22 (Fe-2.25Cr-1Mo) steel after corrosion at 700℃ for 100 h. (a) SEM cross-sectional image, (b) EDS line profiles along A-B.

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Fig. 4. SEM cross-sectional images after corrosion. (a) T91 (Fe-9Cr-1Mo) at 600℃ for 100 h, (b) T92 (Fe-9Cr-1.8W-0.5Mo) at 600℃ for 100 h, (c) T91 (Fe-9Cr-1Mo) at 800℃ for 50 h, (d) T92 (Fe-9Cr-1.8W-0.5Mo) at 800℃ for 50 h.

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Fig. 5. T92 (Fe-9Cr-1.8W-0.5Mo) steel after corrosion at 700℃ for 100 h. (a) SEM cross-sectional image, (b) EDS line profiles along A-B.

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Fig. 6. 347HFG (Fe-18Cr-11Ni) steel after corrosion at 700℃ for 100 h. (a) SEM cross-sectional image, (b) EDS line profiles along A-B.

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Fig. 7. 310H (Fe-25Cr-19Ni) steel after corrosion at 700℃ for 100 h. (a) SEM cross-sectional image, (b) EDS line profiles along A-B.

Table 1. Nominal compositions of chromium steels (wt.%)

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