Corrosion behavior of high-pressure die-cast secondary AlSi9Cu3(Fe) alloy

This research investigated the corrosion behavior and susceptibility to stress corrosion cracking (SCC) of a high-pressure die-cast secondary AlSi9Cu3(Fe) alloy in 3.5 % NaCl solution. Microstructural observations by scanning electron microscope, coupled to energy dispersion spectroscopy, polarization curve recording, electrochemical impedance spectroscopy tests and slow strain rate tests evidenced the presence of critical surface segregation zones, where strong corrosion attack occurs due to composition differences and peculiar morphology of noble Al2Cu phases. No SCC susceptibility was detected, but very strong localized corrosion attack and abundant hydrogen gas bubbling evolved from noble phase/alpha-Al matrix interphases, determining positive going potential transients.