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- Gelman1,2*, E. Grishina3 , S. Belopukhov3, D. Starosvetsky4, A. Groysman2,5 and Y. Ein-Eli 2,4
- Department of Chemical Engineering, Technion- Israel Institute of Technology, Haifa Israel 3200003
- 2. The Nancy and Stephen Grand Technion Energy Program, Technion- Israel Institute of Technology, Haifa Israel 3200003
- 3. Department of Physical and Organic Chemistry, Russian State Agrarian University Moscow, Russia
- Department of Materials Science and Engineering, Technion- Israel Institute of Technology, Haifa Israel 3200003
- 5. Israeli Association of Chemical Engineers and Chemists
*gelmand@campus.technion.ac.il
Aluminum is the most abundant metal in the earth crust and as such, it is the most inexpensive available metal for industrial applications. Physical and chemical properties of Al hold the greatest promise as an alternative energy source. However, a very strong Al corrosion occurring in alkaline solutions accompanied with hydrogen depolarization is the main obstacle for Al implementation as an efficient anode in alkaline batteries. The high dissolution rate of Al along with a massive hydrogen evolution significantly reduce the battery's capacity, shelf life and may even result in an electrolyte leakage. Thus, it is clear that an efficient alkaline battery would be developed only by a drastic suppressing the of Al corrosion rate in the alkaline solutions.
One of the possible approaches to overcome this challenge is to mitigate Al corrosion via the addition of inhibitors to the alkaline media. However, unlike inhibition protection of technological equipment (pipeline, heat exchanger and tubes) there are additional and unique requirements from anodes corrosion inhibitors in batteries. In the case of Al anode, it is beneficial to achieve a corrosion protection by only suppressing the cathodic process (hydrogen evolution reaction). The anodic process should remain intact, similarly to the one occurring in the inhibitor-free solution, since the suppression of the anodic process by the inhibitors may negatively affect the performances of the entire battery. Although significant progress in Al corrosion inhibition in alkaline solutions was
achieved, no sufficient inhibitors have been found yet to allow commercialization of Al based alkaline batteries.
In the last decade, increased interest has been focused on the development of environmentally friendly corrosion inhibitors, which must possess low toxicity (better of course, to be a non-toxic). In addition, such inhibitors should be biodegradable, having low bioaccumulation, and should not contain harmful elements and substances[27]. Saccharides, saccharides fructose, mannose, barbiturates, natural honey, caffeic acid, black radish juice, tryptophan, tryptamine, pectin and other nature made materials were examined as inhibitors for various metals and alloys.
In this work, The effect of a flax straw extract on aluminum corrosion inhibition in a strong alkaline solution was studied using electrochemical measurements, weight loss analysis, scanning electron microscopy (SEM) and Fourier Transform Infra-Red (FTIR) spectroscopy. Flax straw extract added (3 vol. %) to the 5 M KOH solution acts as a mixed type Al corrosion inhibitor. The electrochemistry of Al in the presence of a flax straw extract added to the alkaline solution, as well as the effect of the extract on the Al morphology and surface films formed and the corrosion inhibition mechanism are discussed in this report. Finally, Al-air battery discharge capacity recorded from a cell utilizing the flax straw extract in the alkaline electrolyte is substantially higher, compared with Al-air battery discharge capacity utilizing only a pure alkaline electrolyte. This improved sustainability of the Al anode is attributed to Al corrosion inhibition and consequently, to hydrogen evolution suppression.
Key Words: Aluminum, Batteries, Inhibitor, Alkaline, Green.
