Effect of Aluminum Powder Size on the Corrosion Resistance of Plasma Cladded Iron-Based Alloy Coatings

Abstract

Aluminum has a certain chemical activity， and easily forms a dense oxide film after the reaction with oxygen which can effectively prevent the sample from further deep oxidation， playing good oxygen-blocking protection， commonly used as cathodic protection material.By introducing aluminum into iron-based alloy coatings， the corrosion resistance of these coatings can be enhanced.In this research， different particle sizes of aluminum powder were incorporated into plasma cladded iron-based coatings to investigate the influence of particle size on the microstructure， morphology and corrosion resistance of the coatings.The underlying mechanisms affecting the corrosion resistance of the clad layers were also analyzed.Results showed that the iron-based clad layer had good metallurgical bonding with the substrate and the clad layer did not produce obvious cracks and pores.As the particle size of the aluminum powder (100～200 mesh， 200～300 mesh， 300～400 mesh， 400～500 mesh) decreased， the size of the black AlN phase within the overlay also reduced， resulting in a more uniform distribution.All overlays displayed pronounced passivation behavior in a 3.5%NaCl solution.The self-corrosion potentials were－0.665，－0.706，－0.752 and－0.822 V， which were higher than that of the substrate (－0.883 V)， and the self-corrosion current densities were 2.454×10－6， 6.313×10－6， 7.979×10－6 and 9.710×10－6 A/cm2， which were lower than that of the substrate 3.323×10－5 A/cm2.As the particle size of aluminum powder increased， the corrosion resistance of the clad layer gradually increased， and the best corrosion resistance of the clad layer was obtained when the particle size of aluminum powder was 100～200 mesh， and the corrosion resistance of the clad layer was better than the base material.

Keywords

• plasma cladding|compacted graphite cast iron|iron-based alloy coating|aluminum powder size|microstructure|electrochemical properties