Influence of liquid surface segregation on the pitting corrosion behavior of semi-solid metal high pressure die cast alloy F357

Abstract

Semi-solid metal processing results in liquid segregation at the surface of the components. The pitting behaviour of this surface layer of semi-solid metal processed alloy F357 was compared with the centre (or bulk) of cast plates in 3.5% NaCl aqueous solution. It is shown that pitting attack occurs preferentially in the eutectic regions at the interface between silicon particles and the alpha phase in the eutectic. Since the surface liquid segregation layer consists of mainly eutectic, this makes semi-solid metal processed components especially susceptible to pitting corrosion attack.