In the quest for greener and more efficient propulsion systems, researchers have turned their attention to hydroxylammonium nitrate (HAN)-based propellants. These eco-friendly alternatives promise to revolutionize the aerospace industry, but their compatibility with traditional materials remains a critical area of study. A recent breakthrough by a team led by TANG Zhanmei from the Aerospace Liquid Propellant Research Center at the Beijing Institute of Aerospace Testing Technology sheds new light on how these propellants interact with titanium alloys, a cornerstone of aerospace engineering.
Titanium alloys, particularly TC4, are renowned for their strength-to-weight ratio and corrosion resistance, making them ideal for aerospace applications. However, their behavior in the presence of HAN-based propellants has been less understood until now. TANG Zhanmei and her team, in collaboration with Beihang University, have conducted an in-depth study using electrochemical noise (EN) technology to monitor the corrosion behavior of TC4 titanium alloy over extended periods.
The study, published in ‘Cailiao Baohu’ (translated to ‘Materials Protection’), reveals that as TC4 titanium alloy is immersed in HAN-based propellant, it undergoes a dynamic process of active corrosion, oxide film formation, and corrosion equilibrium. “The electrochemical noise data showed distinct patterns that reflected these stages,” explained TANG Zhanmei. “The standard deviation of potential noise reached its peak on the first day of immersion, indicating the highest corrosion activity during this period.”
One of the most intriguing findings was the difference in corrosion behavior between the base material and welded material. The welded material exhibited slightly higher corrosion activity, as evidenced by a marginally higher standard deviation of potential noise. This insight is crucial for the aerospace industry, where welded joints are common and understanding their behavior in new propellant environments is essential.
The research also delved into the chemical reactions occurring on the surface of the TC4 alloy. The alloy element aluminum (Al) formed compounds like Al2O3 and Al(OH)3, while the titanium (Ti) oxide reacted with the alkaline HAN medium to form soluble salts. This reaction prevented the formation of a stable and dense passivation film, which is typically responsible for the corrosion resistance of titanium alloys. “The power spectral density (PSD) curve in the high-frequency region remained at approximately -1 dB/dec, indicating strong localized corrosion behavior,” noted TANG Zhanmei.
The implications of this research are far-reaching. As the energy sector increasingly adopts green technologies, understanding the compatibility of materials with new propellants becomes paramount. The findings by TANG Zhanmei and her team provide valuable insights that could shape the development of future aerospace materials and propulsion systems. Engineers and researchers can now approach the design and implementation of HAN-based propellants with a clearer understanding of how they interact with titanium alloys, potentially leading to more efficient and durable aerospace components.
Moreover, the use of electrochemical noise technology in this study highlights its potential as a powerful tool for monitoring corrosion in real-time. This method could be instrumental in the ongoing development and testing of new materials and propellants, ensuring that the aerospace industry continues to push the boundaries of innovation while maintaining safety and reliability.
As the industry moves towards greener technologies, the work of TANG Zhanmei and her colleagues serves as a beacon, guiding the way forward. Their research not only advances our understanding of material behavior in new propellant environments but also paves the way for future innovations that could redefine the aerospace and energy sectors.
