Advanced Corrosion Resistance Treatment
For metallurgical applications where superior mechanical and corrosion resistance is desired, the University of Tartu offers a solution. Our team at the Laboratory of Thin Film Technology proposes a novel surface sealing layer that is resistant to both mechanical and chemical damage. The method is suitable for most metals and covers any surface geometry with a high-quality layer with uniform density.
Metals used in challenging environments from airplane or automotive parts to medical implants usually need surface passivation in order to make them resistant to the corrosive effects of the environments where they are used. The most common method for creating that passivation layer, besides painting, is via anodization.
Anodizing has the benefit of being able to treat both small and large surfaces with complex topographies, e.g. from intricate b
io-implants to whole car body frames. The downside is that due to the inherent properties of the process, the resulting layer is porous and some of these pores reach through the protective layer to the untreated metal surface. This, in time, will enable corrosion to set in, regardless of the passivation.
Chemical vapour deposition (CVD) and its related method, atomic layer deposition (ALD) also cover surfaces completely, including the inner sides of any open pores, sealing the surface with completely uniform, chemically very homogenous and durable layers. The method creates the surface film one atomic layer at a time, permitting a laminate of different nanolayers. The downside is that the process of laying down one atomic layer at a time is slow. Also, often these nanolayers have problems adhering to the substrate.
So far, a suitable method of combining the benefits of the two techniques has eluded practitioners. For example, the European Framework Programme 7 project "CORRAL" with partners from across the industrial spectrum, including the team from UT, was dedicated to this problem for over three years, with little success.
Continuing the work started in CORRAL, the team at UT's Laboratory of Thin Film Technology has developed a method that combines an advanced anodizing method with atomic layer deposition. The unique properties of the subsequent ALD step, ensure uniform growth of an oxide layer on top of the treated surface, sealing all pores left after anodizing.
The method includes preparation of the object surface, anodizing it in a novel tri-electrode bath and then sealing it using atomic layer deposition. The anodizing step gives the surface the thickness required for mechanical durability and the second layer fills the pores left, giving the surface exceptional durability in extreme environments. Also, the surface layer is thin and strong enough to move with the underlying material as it deforms under mechanical and thermal stresses, without cracking. The method is protected under an international patent application (publication number WO2014102758).
We offer a licence for the use of the developed method and to engage in co-operation to develop and adjust the method to suit the specific needs of your application.
The adaption process would take into account the composition and geometry of the object to be treated, along with any constraints set by the production process or client's requirements. This means after preliminary lab work, the method would be finalized on-site with the client, ensuring the highest possible quality and fit in the production process. All steps of the process shall be validated with top-of the range analysis methods, including electron and scanning probe microscopy, electron spectrometry, voltammetry etc.
The resulting method is capable of producing an object that has a surface much more resistant to chemical and mechanical damage than simple anodizing or ALD alone could achieve while at the same time having little to no impact on the size of the object. This low and predictable effect on the dimensions of the object allows the treatment to be performed as the last step in the production, helping to optimize the cost of production.
The principles of managing IP generated during such a cooperation is open for discussion. Usually, UT would retain publication rights for research results with a 30 day refusal period for the commercial partner for any sensitive material.
The team at the Laboratory of Thin Film Technology comprises leading scientists in the field of surface treatments, such as Professor Väino Sammelselg, as well as young and bright researchers like Maido Merisalu, PhD, and Lauri Aarik, PhD. This gives the team a good base of knowledge and experience with the flexibility to participate in applied research and development projects.
The University is looking to work with partners to come to attractive terms to develop new applications for this technology. In order to cover for licensing arrangements and working hours, as well as any necessary material and travel costs, it is envisaged that suitable financial contributions will be provided by industrial partners
surface treatment, passivation, corrosion, anodizing, atomic layer deposition, ALD