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Corrosion protection with perfect atomic layers

Periodic Report Summary - CORRAL (Corrosion protection with perfect atomic layers)

The aim of this project is to develop high-density defect-free ultra-thin sealing coatings with excellent barrier properties and improved corrosion resistance. The study has quickly been focused on the development nanoscale multilayers. These impermeable sealing layers are able to block the ion exchange between the substrate material and an aggressive environment, thus offering an efficient protection against corrosion. Coatings were deposited with four alternative vapour deposition techniques, Filtered cathodic arc deposition (FCAD), High power impulse magnetron sputtering (HIPIMS) and Atomic layer deposition (ALD), Plasma enhanced atomic layer deposition (PEALD). The technological objective of the project is to demonstrate the feasibility of corrosion protection by ultrathin sealing layers.

15 nm of Al2O3 deposited on a ground surface of a flat manufactured from Al2024 illustrating best the problems and achievements: The poor quality of the grinding has produced a large burr (a) that was folded onto the surface creating a deep narrow gap (b) (~ 40 nm). The burr has been work hardened (c) by the plastic deformation. An abrasive grinding particle (d) has also been incorporated by the bur. The 15 nm amorphous Al2O3 coating (e) deposited by PEALD covers completely all features even the walls of the narrow gaps providing perfect sealing.

The project has made progress on all three challenges:
- Preparing, observing and controlling engineering surfaces @ nanoscale.
- Developing technologies for coatings that are perfect @ nanoscale and can handle the residual defects.
- Studying corrosion initiation and development @ nanoscale.

So far only three 'model' applications involving 100Cr6, Al2024 and 34CrMo4 have been followed. One of them has shown such promising results, that its industrial implementation is scheduled before the conclusion of the project. For the second half term participation in application demonstration will be opened to a larger audience in the form of user pools.