Aluminum coatings – limits of electroplating

Structured aluminum layer, deposited through electroplating.
© Fraunhofer IST, Falko Oldenburg
Structured aluminum layer, deposited through electroplating.

Challenge 

Within the scope of this project, the electrodeposition of a number of metals from ionic liquids was investigated. Metals such as titanium, tantalum or aluminum have good corrosion protection and are catalytically active, but cannot be electrodeposited from aqueous systems. The task of the IST was the up-scaling of aluminum deposition with the aim of technical implementation. 

Solution 

For the up-scaling of aluminum deposition, it was important to develop a system outside of a protective glove box. The processes with ionic liquids are extremely sensitive to moisture. Consequently, an open apparatus was constructed, which protected against the entry of moisture by means of a flow of dry inert gas. Special zeolites in the electrolyte were used to additionally trap incoming water molecules. The Fraunhofer IST was thereby a pioneer in the transfer of the electroplating process from the glove box to a semi-technical apparatus. 

Added value 

The result of the project was a greatly simplified process with a new class of (less expensive) ionic liquids for the deposition of aluminum. Further projects in the field of Li batteries as well as cadmium substitution with electroplated Al layers are planned. A DLR-funded project is currently being conducted which addresses metal extraction from lunar regolith based on ionic liquids (ELMORE).

Insights into the project

High-strength steel rivets were coated with aluminum for corrosion-protection reasons. This procedure avoids the critical hydrogen development.
© Fraunhofer IST, Falko Oldenburg
High-strength steel rivets were coated with aluminum for corrosion-protection reasons. This procedure avoids the critical hydrogen development.
Transverse section of an aluminum coating on copper in a scanning electron microscope.
© Fraunhofer IST
Transverse section of an aluminum coating on copper in a scanning electron microscope.

Further information

 

From research

Closed-loop electrochemical processes for the extraction of pure elements

Funding reference

 

 

Funded by the German Federal Ministry of Education and Research (BMBF) as part of the INNO-E-MAT program (Funding code 13XP5017C).