Comparison of Atmospheric Corrosion of Additively Manufactured and Cast Al-10Si-Mg Over a Range of Heat Treatments

Abstract

Additive manufacturing (AM) of metals has gained attention as a technology to rapidly produce complex components while reducing waste generated by traditional manufacturing methods. The corrosion properties of AM alloys are not well understood and merit further exploration. The goal of this study is to compare the atmospheric corrosion susceptibility of printed Al-10Si-Mg alloy to its cast counterpart over a range of heat treatments, including as-produced, T5, and T6 tempers. Atmospheric corrosion testing was performed in a salt-fog chamber using a modified G85-A2 cycle for 31 d. Additionally, potentiodynamic testing was used to assess the kinetics of each sample type in dilute Harrison’s solution. Comparison of corrosion damage revealed that cast and AM samples of similar temper had similar damage frequency and average damage depth, but AM samples had greater maximum depths. In as-built and T5 tempers, the AM samples showed preferential attack of the melt pool boundaries. The corrosion was dominated by a dissolution of Al that appeared to favor a path of least resistance through coarser or more discontinuous regions of the Si network at the melt pool boundary. The heat treatment protocol for the T6 temper removed the melt pool structure and resulted in a more general, and more severe, attack because the Si network was no longer present to impede dissolution. Heat treatments after printing were found to be deleterious to the atmospheric corrosion resistance of AM Al-10Si-Mg alloy.