Carbon dioxide can be used to alter zinc surface for cleaner industrial processes

In his doctoral dissertation, MSc Aaretti Kaleva presents a synthesis method using pressurized carbon dioxide (CO2) that could reduce harmful chemical use in industrial zinc processes. “The artificial patina method” mimics natural zinc patination that occurs spontaneously in the outside atmosphere but produces more definite and controllable patina structures as well as reducing patina formation time from years to hours.

Aaretti Kaleva’s dissertation focuses on presenting a CO2-based synthesis method for producing different nano- and micron-sized carbonate structures on zinc surfaces called collectively artificial patina. CO2 utilization is widely researched in applications such as fuel production, polymer synthesis and mineralization, but Kaleva’s dissertation brings another perspective on using CO2 as a raw material. The artificial patina can be formed using only CO2 and water making it an environmentally friendly process for functionalizing zinc surfaces. In the dissertation, Kaleva presents two case example uses for the artificial patina: a pre-treatment for galvanized surfaces before painting and synthesis of zinc oxide (ZnO) nanowires.

The artificial patina method as a pre-treatment for galvanized surfaces enhances the corrosion protection and paint adhesion of the zinc surface. Currently in the galvanizing industry, chemical pre-treatment is applied on zinc before painting due to the zinc surface’s poor adhesion properties. In the past, and in some cases today, a common adhesion promoting technique has been to let a natural patina to form on the surface for over a year before painting. The artificial patina method uses mainly CO2 and water without harmful chemicals providing a cleaner alternative to current pre-treatment methods while being vastly quicker compared to natural patination. In addition to promoting paint adhesion, the artificial patina provides a barrier layer on zinc reducing corrosion in the outside atmosphere.

The second case example presented by Kaleva uses the artificial patina method to form ZnO nanowires in a simple process. ZnO nanowires can be used in various semiconductor applications like antibacterial surfaces, gas sensors and solar cells. The artificial patina method produces zinc carbonate nanowires on the surface, which can be later converted to zinc oxide by heat-treatment. Compared to current methods used for ZnO nanowire formation, producing ZnO nanowires with the artificial patina method is a fast and facile method using only pressurized CO2 and water.

The research was part of the Doctoral School of Industrial Innovations and funded by SSAB Europe Oy and Tampere University. Other collaboration partners included Top Analytica Ab and the University of Bordeaux. Kaleva’s dissertation topic was also awarded an encouragement grant from Hämeen Ammatillisen Korkeakoulutuksen ja Tutkimuksen Säätiö.

Aaretti Kaleva is originally from Tampere and graduated as Master of Science from Tampere University of Technology. He currently works full-time at ColloidTek Oy that makes liquid analyzers. The research has also lead to a continuation research project to explore additional applications for the artificial patina method where Kaleva serves in a part-time consulting role.

The doctoral dissertation of MSc (Tech) Aaretti Kaleva in the field of Materials Science and Engineering titled Zinc Surface Functionalization: Artificial Patination with CO2 will be publicly examined in the Faculty of Engineering and Natural Sciences at Tampere University at 12.00 on Friday 12.3.2021 in the Festia Pieni Sali in Festia building. The Opponent will be Dr Michael Rohwerder from Max Planck Institut für Eisenforschung, Düsseldorf, Germany and Dr Ralph Bäβler from Federal Institute for Materials Research and Testing, Berlin, Germany. The Custos will be Professor Erkki Levänen from the Faculty of Engineering and Natural Sciences, Tampere University, Finland.

The audience can follow the event via a remote connection at Zoom.

The dissertation is available online at

Photo by Thanida Dharmajiva