Comparative laboratory testing of molten salt attack of superheater tube materials

Maria Oksa, Martti Mäkipää

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

Abstract

In some practical superheater corrosion failure cases one finds that the corrosion environment has actually been a low-melting salt film spreading on the tube surface. In this study a modified crucible test method is introduced that simulates this corrosion condition. Metallic specimens exposed in air atmosphere as half-immersed into a molten alkali chloride - alkali sulphate salt mixture of eutectic composition in 520-530°C. Materials evaluation is based on the post-experiment examination of the specimens and their cross-sections. Low-alloy steels and various austenitic steels and nickel alloys were tested using this method. For low-alloy steels and austenitic stainless steels the characteristic corrosion attack mode was intergranular attack and growth of oxide scales. More corrosion resistant steels and alloys suffered from pitting attack. Corrosion morphologies observed had a close resemblance to practical corrosion morphologies in cases involving alkali sulphate - alkali chloride melt attack.
Original languageEnglish
Title of host publication10th International Symposium on Corrosion in the Pulp and Paper Industry- ISCPPI. Vol. 2
Place of PublicationEspoo
PublisherVTT Technical Research Centre of Finland
Pages523-538
ISBN (Electronic)951-38-5724-7
ISBN (Print)951-38-5721-2
Publication statusPublished - 2001
MoE publication typeA4 Article in a conference publication
Event10th International Symposium On corrosion in the Pulp and Paper Industry, ISCPPI - Helsinki, Finland
Duration: 21 Aug 200124 Aug 2001

Publication series

NameVTT Symposium
PublisherVTT
Number215
ISSN (Print)0357-9387
ISSN (Electronic)1455-0873

Conference

Conference10th International Symposium On corrosion in the Pulp and Paper Industry, ISCPPI
Abbreviated title10th ISCPPI
CountryFinland
CityHelsinki
Period21/08/0124/08/01

Fingerprint

Superheater tubes
Molten materials
Salts
Corrosion
Testing
High strength steel
Superheaters
Austenitic steel
Crucibles
Nickel alloys
Alloy steel
Austenitic stainless steel
Pitting
Eutectics
Melting
Oxides
Steel

Cite this

Oksa, M., & Mäkipää, M. (2001). Comparative laboratory testing of molten salt attack of superheater tube materials. In 10th International Symposium on Corrosion in the Pulp and Paper Industry- ISCPPI. Vol. 2 (pp. 523-538). Espoo: VTT Technical Research Centre of Finland. VTT Symposium, No. 215
Oksa, Maria ; Mäkipää, Martti. / Comparative laboratory testing of molten salt attack of superheater tube materials. 10th International Symposium on Corrosion in the Pulp and Paper Industry- ISCPPI. Vol. 2. Espoo : VTT Technical Research Centre of Finland, 2001. pp. 523-538 (VTT Symposium; No. 215).
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Oksa, M & Mäkipää, M 2001, Comparative laboratory testing of molten salt attack of superheater tube materials. in 10th International Symposium on Corrosion in the Pulp and Paper Industry- ISCPPI. Vol. 2. VTT Technical Research Centre of Finland, Espoo, VTT Symposium, no. 215, pp. 523-538, 10th International Symposium On corrosion in the Pulp and Paper Industry, ISCPPI , Helsinki, Finland, 21/08/01.

Comparative laboratory testing of molten salt attack of superheater tube materials. / Oksa, Maria; Mäkipää, Martti.

10th International Symposium on Corrosion in the Pulp and Paper Industry- ISCPPI. Vol. 2. Espoo : VTT Technical Research Centre of Finland, 2001. p. 523-538 (VTT Symposium; No. 215).

Research output: Chapter in Book/Report/Conference proceedingConference article in proceedingsScientificpeer-review

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AB - In some practical superheater corrosion failure cases one finds that the corrosion environment has actually been a low-melting salt film spreading on the tube surface. In this study a modified crucible test method is introduced that simulates this corrosion condition. Metallic specimens exposed in air atmosphere as half-immersed into a molten alkali chloride - alkali sulphate salt mixture of eutectic composition in 520-530°C. Materials evaluation is based on the post-experiment examination of the specimens and their cross-sections. Low-alloy steels and various austenitic steels and nickel alloys were tested using this method. For low-alloy steels and austenitic stainless steels the characteristic corrosion attack mode was intergranular attack and growth of oxide scales. More corrosion resistant steels and alloys suffered from pitting attack. Corrosion morphologies observed had a close resemblance to practical corrosion morphologies in cases involving alkali sulphate - alkali chloride melt attack.

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Oksa M, Mäkipää M. Comparative laboratory testing of molten salt attack of superheater tube materials. In 10th International Symposium on Corrosion in the Pulp and Paper Industry- ISCPPI. Vol. 2. Espoo: VTT Technical Research Centre of Finland. 2001. p. 523-538. (VTT Symposium; No. 215).