Characterization of localized corrosion pathways in 2195-T8 Al–Li alloys exposed to acidic solution

Abstract

The corrosion properties of aluminum-lithium (Al–Li) alloys, which are potential materials used to construct for tanks of liquid rockets or missiles, are essential for safe propellant storage and transport. In order to manifest the corrosion resistance of the 2195 Al–Li alloy in practical propellant tanks filled with N2O4, the alloy was soaked in 30% nitric acid solution, an accelerating corrosion environment, to test its corrosion behavior. Scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize microstructure and corrosion morphology of the alloy. Focused ion beam (FIB), combined with SEM, was used to demonstrate localized corrosion features and the propagation of corrosion pathways beneath the alloy surface. It was found that the corrosion network was formed with most intergranular corrosion and sparse intragranular corrosion. Additionally, the distribution and number of intermetallic particles influenced the localized corrosion degree and the direction of corrosion pathways. Aggregated particles made corrosion pathways continuously and caused more severe corrosion. The results from this work were valid and useful to corrosion prevention and protection for storage safety on propellant tanks in N2O4.

Keywords

• Al-Li alloy
• Corrosion behavior
• Corrosion features
• Immersion test
• Intermetallic particles