Corrosion Behavior of Selective Laser Melted AISi10Mg Alloy in NaCl Solution and Its Dependence on Heat Treatment

This work investigates the corrosion behavior of AlSilOMg alloy produced by selective laser melting(SLM) and the counterparts heat-treated at 450-550℃in 3.5 wt% NaCl solution.Electrochemical measurements and weight loss tests together with microstructural characterizations were conducted.The SLM-produced alloy displays a microstructure with a continuous network of Si particles,exhibiting superior corrosion behavior.After heat treatment,the Si particles are coarsened and isolated and A1 matrix dissolves into their surrounding area,thereby degrading the corrosion resistance properties.Therefore,the corrosion resistance of AlSilOMg alloy degrades with increasing the heat treatment temperature.

Influence of Direct Current Electric Field on the Formation,Composition and Microstructure of Corrosion Products Formed on the Steel in Simulated Marine Atmospheric Environment

X-ray diffraction, Raman spectroscopy and scanning electron microscopy were employed to investigate the effects of the DC electric field on the composition, formation and structure of corrosion products formed on the surface of the steel immersed in NaCl solution. The results show that goethite （α-FeOOH）, akaganeite （β-FeOOH）, lepidocrocite （γ- FeOOH） and magnetite （Fe3O4） are the major constituents among the corrosion products. The arrangement of different levels of the DC electric field intensity gives rise to the following results. The little higher DC electric field intensity （around 100-200 kV/m） promotes the crystallinity and growth of y-FeOOH; obviously, much higher DC electric field intensity （greater than 400 kV/m） prevents the growth of α-FeOOH and facilitates the generation of Fe3O4. Both the promotional growth of γ-FeOOH and suppression of α-FeOOH growth indicated the weakness of the protectiveness of the rust layer. Consequently, the suppression of the transformation of α-FeOOH from y-FeOOH favors the yield of the Fe3O4, which works as a large cathode area and would be about to quicken the subsequent steel corrosion.

Galvanic Corrosion Behavior of Copper-Drawn Steel for Grounding Grids in the Acidic Red Soil Simulated Solution

The influence of pH and metallographic structure on the corrosion behavior of copper-drawn steel is studied with the simulated system.The effect of pH on the corrosion behavior of copper-drawn steel has been investigated using open-circuit potential,potentiodynamic polarization,galvanic current measurement,scanning electron microscopy and scanning vibrating electrode technique techniques.The steel is corroded as anode,while the corrosion of copper plate is protected as cathode.All the results revealed that pH and metallographic structure had a significant influence on the corrosion behavior of copper-drawn steel.With the decrease in pH value from 6 to 2.4,the corrosion rate of copper-drawn steel galvanic couple(Cu-Fe GC)obviously increased in the simulated solution of acidic red soil.The electric field formed by the Cu-Fe GC changes the direction of ion migration between the copper and drawn steel electrodes,which impacts the composition and microstructure of corrosion products formed on the electrode surface.