London: ESA's Clean Space initiative, tasked with reducing the space industry's environmental impact on Earth and space, are planning to investigate new environmental-friendly methods like "lemon juice" for corrosion resistance and high strength stainless steel in order to make it an essential material for satellite and rocket designers.
Stainless steel has been commonly used in rockets and satellites for storage and handling of propellants and waste, components of thermal protection systems and fasteners such as high-strength bolts since centuries.
Before they are put to use, however, stainless steel parts must first be "passivated," stripping off their surface layer to remove any imperfections or contamination left over from the machining process, which might otherwise start to rust.
Traditionally this was done by bathing the parts in nitric acid, but this has environmental and safety disadvantages. It involves special handling and produces nitrogen oxides, which are greenhouse gases and potentially harmful to workers.
Citric acid, found in a dilute form in lemon juice, has been put forward as a greener passivation alternative, being adopted in a variety of sectors, including the medical, automotive and aerospace industries.
So the researchers aim to find whether this alternative option satisfies the unique requirements of the space industry.
The study would involve passivating stainless steel alloys and components typically used in the space sector, assessing their manufacturing process, then subjecting them to a gamut of environmental tests, including stress corrosion cracking, atmospheric and laboratory corrosion testing, adhesion testing and mechanical fatigue, along with a complete metallurgical analysis.