The influences of alloying elements on the corrosion properties of as-cast Al-Si alloy

The corrosion behaviour of Al-7%Si alloys in 3.5%NaC1 solution has been studied by electrochemical and immersion corrosion tests,at the same time,the effect of Cu,Mg,Mn and Sn on corrosion potentials,corrosion current densities and corrosion behaviour of Al-7%Si alloys have been researched in this paper. The morphology of alloys before and after immersion corrosion were analyzed by SEM(scanning electron microscopy).The results of electrochemistry tests indicate that all the tested alloys may be passivated rapidly.The free corrosion potentials shifted to negative and the corrosion current densities of the alloys grew with increasing alloy elements.The results of immersion corrosion tests show that corrosion resistance of Al-7%Si alloy is decreased when it content the testing alloying elements.The most influence element is Cu.The mode of corrosion changed from pitting corrosion to inter-granular corrosion due to the addition of Cu into the alloy.