Effect of Si/Mg ratio on the corrosion behaviour of Al-Mg-Si alloys for automotive applications

Wrought Al-Mg-Si alloys find extensive use in the form of sheets, plates, etc. for various automotive parts. This 6000 series of Al-Mg-Si alloys with different Si/Mg ratio are selected for automotives because of excellent performance in the area of transportation i.e. components of cars, trucks and buses. Observation of corrosion behaviour of some wrought Al-Mg-Si alloys (Si Mg in the range of 3.2 to 4.2) as studied through complete immersion tests in decinormal solutions of common inorganic and organic acids are reported. It has been observed that Si/Mg ratio of 3.2 (in inorganic acids) and 3.6 (in organic acids) gives optimum corrosion resistance of these alloys under identical conditions of exposure. Further, dissolution tendency of common inorganic acids are found to decrease in the following order HC>HNO3>H2SO4 whereas aggressiveness of anions acids follow the order.