EDP Sciences Journals List
Issue J. Phys. IV France
Volume 03, Number C9, Décembre 1993
Proceedings of the 3rd International Symposium on High Temperature Corrosion and Protection of Materials
Actes du 3ème Colloque International sur la Corrosion et la Protection des Matériaux à Haute Température
Page(s) C9-383 - C9-384
DOI http://dx.doi.org/10.1051/jp4:1993939

Proceedings of the 3rd International Symposium on High Temperature Corrosion and Protection of Materials
Actes du 3ème Colloque International sur la Corrosion et la Protection des Matériaux à Haute Température

J. Phys. IV France 03 (1993) C9-383-C9-384

DOI: 10.1051/jp4:1993939

Molten (Na, K)2SO4-NaCl salt corrosion of Ni3Al alloy

Caoliu Zen, Jianqing Zhang and Weitao Wu

Corrosion Science Laboratory, ICPM, 110015 Shenyang, China


Abstract
Two Ni3Al alloys namely Ni3AlB (Ni-18 3Al-0.2B (in at.%)) and Ni3AlBCrZr (Ni-18.0Al- 0.2 B-6.0Cr-0.5Zr (in at.%)) were tested. Specimens of 15 x 5 x 3 mm were cut from the extruded bars. A commercial nickel base superalloy IN 738 was used as a reference material. The corrosion tests were conducted at 750, 800 and 850 °C in (0.9 Na, 0.1 K)2SO4-25 NaCl (in mole %) melt in air. The measurements include free corrosion potential (Ecorr) and linear polarization resistance (Rp) . The test results show that during a test at 800 °C the Ecorr of IN 738 shifted gradually to a more noble direction and then stayed around -200 mV. With the same tendency, after 30 h its Rp reached about 100 ohm cm2 and become stable. The results proved that a protective oxide scale formed gradually on IN 738. In contrast, the corrosion behavior of Ni3Al-0.2 B was somewhat different. During test at 800 °C, its Ecorr dropped rapidly to -970 mV soon after immersion and Rp was only about 5.6 ohm cm2, e.g. one order of magnitude lower than that of IN 738. Obviously, the corrosion rate of Ni3Al-0.2 B was much higher, which can also be proved by the corrosion morphology that IN 738 was kept intact with a thin oxide scale on the surface after 100 h, whilst the whole specimen of Ni3Al-0.2 B was entirely corroded after only 6 h immersion.



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