Salt Spray (fog) Corrosion Behavior of Cold-Sprayed Aluminum Amorphous/Nanocrystalline Alloy Coating
Journal of thermal spray technology(2022)
摘要
Aluminum amorphous alloys gained interest in aerospace, automobile and marine industry due to their high specific strength, better wear and corrosion resistances. In the present work, a gas-atomized aluminum amorphous/nanocrystalline alloy powder was deposited on Al-6061 alloy using cold spray technique. The as-sprayed coatings were heat treated at 573K (just below the glass transition temperature, 593K) to obtain a homogenized microstructure. The corrosion behavior of as-sprayed and heat-treated coatings was evaluated under potentiodynamic polarization (ASTM G59-97) and salt fog (ASTM B117) in NaCl medium. The potentiodynamic polarization study revealed a lowest corrosion rate of Al amorphous/nanocrystalline coating in the heat-treated condition than the as-sprayed condition due to reduction in coating defects like porosity and weaker inter-splat regions. The thickness of reaction layer formed during salt fog corrosion tests is 2 to 3 times lower in the case of cold-sprayed Al amorphous/ nanocrystalline coatings as compared to the Al-6061 substrate. The heat-treated coatings have demonstrated a further reduction in the reaction layer thickness. Pitting corrosion forming a porous oxide layer on the surface of bare substrate while a uniform, dense and thin corroded layer was noticed in as-sprayed and heat-treated coatings.
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关键词
aluminum amorphous alloy,cold spray,corrosion,focus ion beam milling,growth kinetics,salt spray (fog)
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