Effect of zirconia in the corrosion behavior of intermetallic Mo₃Si alloy in molten salts mixture of NaNO₃ and KNO₃

Abstract

The corrosion effect of zirconia addition, 1, 2, and 5 atomic percent (at.%), on the hot corrosion behavior of Mo3Si intermetallic alloy in 60 wt.% NaNO3 + 40 wt.% KNO3 at 600°C, has been evaluated by using electrochemical methods. Electrochemical techniques included electrochemical noise analyses (ENA), polarization curves (PC), and linear polarization resistance (LPR). The average grain size decreased when the specimen was alloyed with Zr from 90 μm for as‐cast Mo3Si, down to 25 and 10 μm for alloys containing 1, 2, and 5 at.% Zr, respectively. All specimens showed a passive behavior, with the corrosion current density values decreasing for adding either 1 or 2 at.% Zr but increasing for specimens containing 5 at.% Zr. The corrosion process was under charge transfer control for the as‐cast alloy or when 1 or 2 at.% Zr was added, but it was diffusion controlled when 5 at.% Zr was added. The noise resistance value (Rn) increased for specimens containing 1 or 2 at.% Zr but decreased when 5 at.% Zr was added. X‐ray diffraction showed the presence of SiO2, MoO4, Mo4O11, and ZrO2 in the passive layer.

Overview of corrosion behaviour of ceramic materials in molten salt environments

“…Cracks and gaps in materials can act as entrance routes for corrosive species, hastening the deterioration process. Electrochemical techniques have been used to assess the corrosion effect of zirconia addition at 1, 2, and 5 atomic percents (at.%) on the hot corrosion behaviour of Mo3Si intermetallic alloy in 60 weight per cent NaNO3 and 40 weight per cent KNO3 at 600°C [37]. For the as-cast alloy or when 1 or 2 wt.% Zr was added, and the corrosion process was controlled by charge transfer, but when 5 wt.% Zr was added, and it was controlled by diffusion [37].…”