Hot Corrosion of Nickel-Chromium and Nickel-Chromium-Aluminum Thermal-Spray Coatings by Sodium Sulfate-Sodium Metavanadate Salt
- 1 September 1996
- journal article
- Published by Association for Materials Protection and Performance (AMPP) in Corrosion
- Vol. 52 (9) , 680-689
- https://doi.org/10.5006/1.3292158
Abstract
The hot corrosion behavior of low-pressure plasma-sprayed (LPPS) 80 wt% Ni-20 wt% Cr and flame-sprayed (FS) 75 wt% Ni-20 wt% Cr-4.0 wt% Al coatings on type 304 (UNS S30400) stainless steel (SS) by thin fused films of sodium sulfate (Na2SO4) and 0.7 mol fraction Na2SO4-0.3 mol fraction sodium metavanadate (NaVO3) at 900°C in a 1% sulfur dioxide (SO2)-oxygen (O2) atmosphere was studied using an electrochemical method. The 80% Ni-20% Cr coatings were tested in the as-sprayed condition. 75% Ni-20% Cr-4% Al coatings were tested under as-sprayed and laser-glazed conditions. Evolution of the fused salt film chemistry, in terms of the thermodynamic activities of O2 and sodium oxide (Na2O), was monitored using a zirconia O2 probe and a fused-silica Na sensor. Results permitted qualitative evaluation of the corrosion resistance of the coatings and could be interpreted in terms of previously proposed hot corrosion mechanisms.Keywords
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