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This study is aiming at controlling the
microstructure of plasma sprayed Al2O3-TiO2 composite coatings using freeze granulated powders. As sprayed and sintered Al2O3 + 3wt%TiO2 powders were air plasma
sprayed with industry process parameters and compared with a commercial powder.
The resulting coatings were investigated with respect to powder flowability,
porosity and microstructure of the granules. The results showed that
microstructure and melting fraction in the coatings could be tailored with the freeze granulation
process and heat treatment conditions.
The weathering steel (Corten B) was exposed to out-door atmosphere of Hanoi (urban site) and Donghoi (marine site). The results showed the protective ability of corrosion product layer formed on weathering steel in the initial stage. The SEM-EDX analysis detected the presence of chromium and copper in the inner layers of corrosion product formed on weathering steel. These elements improved corrosion resistance of corrosion product layers. In addition, the dense α-FeOOH phase were appeared early in corrosion product which is detected by X-ray diffraction and Micro Raman investigations. The results of polarization and EIS measurements also demonstrated the protectiveness of the corrosion product of weathering steel.