TITLE:
Degradation Behavior of High Chromium Sodium-Modified A356.0-Type Al-Si-Mg Alloy in Simulated Seawater Environment
AUTHORS:
M. Abdulwahab, I.A. Madugu, S.A. Yaro, A.P.I. Popoola
KEYWORDS:
pits diameter, MSTAT, degradation behavior, corrosion rate.
JOURNAL NAME:
Journal of Minerals and Materials Characterization and Engineering,
Vol.10 No.6,
May
10,
2011
ABSTRACT: The effect of multiple-step thermal ageing treatment (MSTAT) on the corrosion characteristics of
A356.0-type Al-Si-Mg alloy in simulated seawater has been studied. The MSTAT treatment also
consists of Double Thermal Ageing (DTAT- T7), Single Thermal Ageing (STAT- T6), Step-
Quenching and Ageing (SQA). The corrosion of the thermal treated samples was characterized
by electrochemical Potentiodynamics polarization techniques consisting of linear polarization
and chronopotentiometric method using the fit Tafel plot. Generally, from the linear
polarization, the corrosion rate decreases at all temperatures with the ageing time. The
corrosion behavior of the DTAT and SQA Al-Si-Mg alloy in the simulated seawater showed
better resistance than the STAT Al-Si-Mg alloy. Samples in the SQA-STAT have improved
corrosion resistance than the SQA-DTAT one. The chronopotentiometric corrosion study of some
selected samples indicates a decrease in the corrosion resistance with open circuit potential
exposure time. Consequently, the form of corrosion in the studied Al-Si-Mg alloy are slightly
uniform and predominantly pitting corrosion as obtained from the SEM study. The pits diameter
were found to range from 30-50μm.