Corrosion Behavior of Ti60 Alloy under a Solid NaCl Deposit in Wet Oxygen Flow at 600 °C.

Lei Fan,Li Liu,Zhongfen Yu,Fuhui Wang,Min Cao,Ying Li

doi:10.1038/srep29019

Lei Fan, Li Liu + Show 4 more

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https://doi.org/10.1038/srep29019

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Abstract

The corrosion behavior of Ti60 alloy covered with a solid NaCl deposit in wet oxygen flow at 600 °C has been studied further by SEM, EDX, XPS, XRD, TEM and EPMA analysis. The results show that solid NaCl and H2O react with Ti oxides, which destroyed the Ti oxide scale to yield the non-protective Na4Ti5O12 and other volatile species. The resulting corrosion product scale was multilayered and contained abundant rapid diffusion channels leading to the fast diffusion which improved the corrosion rate. A possible mechanism has been proposed for the NaCl-covered Ti60 alloy, based on the experimental results.

Highlights

The results revealed that the corrosion of Ti60 alloy was severe and a non-protective, thick and complex corrosion product layer was formed in the presence of solid NaCl
It is evident that the weight of samples in the pure O2 environment (O600) and wet O2 (WO600) changed little during the testing time, which suggests that the corrosion of Ti60 alloy in these environments was not very significant in the absence of the NaCl deposit
The mass gain is about two orders of magnitude larger in NaCl+O2 (NO600) and NaCl+H2O+O2 (NWO600) than in O600 and WO600, due to the presence of the solid NaCl deposit. This means that Ti60 alloy suffered severe corrosion due to the presence of the NaCl deposit at 600 °C. It appears that the corrosion in NWO600 was more serious than in NO600, especially at the earlier stages (0–20 hr), which indicates that water vapor further accelerated the corrosion process under these conditions

Summary

Methods

As follows; 5.62 Al; 3.85 Sn; 2.98 Zr; 0.9 Mo; 0.4 Nb; 1.05 Ta; 0.35 Si and balance Ti. The metallographic and the backscattered electron images presented in Fig. 3a,b, respectively show a bimodal microstructure, obtained by Environment NWO600 NO600 WO600 O600. Flow rate of O2 (mL/min) near - βforging at about 1035 °C29. The specimens were cut into pieces of 10 mm × 15 mm × 2 mm and ground to 800 grits using silicon carbide papers. The specimens were ultrasonically degreased in alcohol for about 20 min and dried in air. The preheated specimen surfaces were covered with NaCl deposit by repeatedly brushing and drying with saturated NaCl solution[1,2,3,4,5,6,7,17], until about 4 ± 0.2 mg/cm[2] of NaCl was deposited on the surface

Results

Discussion

Conclusion