Degradation Behavior of High Chromium Sodium-Modified A356.0-Type Al-Si-Mg Alloy in Simulated Seawater Environment

M. Abdulwahab, I.A. Madugu, S.A. Yaro, A.P.I. Popoola

Department of Chemical and Metallurgical Engineering, Tshwane University of Technology,Pretoria, Republic of South Africa.
Department of Metallurgical and Materials Engineering, Ahmadu Bello University, Zaria,Nigeria.

DOI: 10.4236/jmmce.2011.106041                

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.

Keywords

pits diameter, MSTAT, degradation behavior, corrosion rate.

Conflicts of Interest

The authors declare no conflicts of interest.

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