The European Space Agency (ESA) is planning to investigate an alternative, environmental-friendly method of readying stainless steel, that will be able to be used all over the world wherever the metal is used in aerospace applications.
For the aerospace industry, stainless steel is often used in the storage and handling of propellants and waste, components of thermal protection systems and fasteners including high-strength bolts. However, before any of the stainless steel parts are used, they must first be passivated. This is the process were the surface layer is stripped off to remove any imperfections or contamination left over from the machining process. If this isnt done, then those imperfections might start to rust. Usually, the passivation process involves 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 that could potentially harm workers.
Citric acid is found in a dilute form of lemon juice and has been recommended as a greener passivation alternative, being adopted in a variety of sectors, including the medical, automotive and aerospace industries. A new study by ESA’s Clean Space initiative, tasked with reducing the space industry’s environmental impact on Earth and space, will aim to find out if this new method is effective enough to use to in the Aerospace Industry.
The study will involve passivating stainless steel alloys and components typically used in the space sector, assessing their manufacturing process, then subjecting them to environmental tests such as stress corrosion cracking, atmospheric and laboratory corrosion testing, adhesion testing and mechanical fatigue.