Federico Bertasi

Sulfuric acid anodizing is a widely adopted surface treatment for aluminium alloys, primarily aimed at producing a protective oxide film with thicknesses typically in the range of tens of micrometres. This process is extensively utilized in sectors such as automotive and aeronautics, where stringent durability and corrosion resistance requirements must be met. However, the anodic alumina layer formed during sulfuric acid anodizing exhibits an inherently porous morphology, which significantly limits its corrosion resistance. This structural characteristic allows aggressive species, such as chlorides, to penetrate the oxide layer, thereby compromising the long-term integrity of the underlying substrate. To overcome these limitations, a sealing step is commonly introduced as a post-treatment to enhance the protective performance of the anodic coating. Sealing processes aim to either precipitate salts within the pores or induce hydration and expansion of pore walls, effectively reducing porosity and hindering the access of corrosive agents. Among the various sealing agents, hot water and heavy metal salt solutions (e.g. Cr, Ni) are widely used, depending on the desired functional properties of the final coating.

The work investigates the effect of eutectic silicon morphology and distribution on the anodizability and corrosion resistance of a recycled cast EN AC‐43 200 (AlSi10 Mg) alloy. A family of specimens combining different eutectic Si morphologies (platelet‐like and spheroidal) with variable secondary dendrite arm spacings (17 µm ≤ SDAS ≤ 38 µm) is produced by tuning the EN AC‐43 200 casting conditions. The samples are then anodized and characterized with several imaging and electrochemical techniques (i.e., optical and electron microscopy, electrochemical noise measurements, and scanning electrochemical microscopy), demonstrating an intriguing correlation between microstructure and corrosion resistance. In particular, it is shown that the corrosion protection capability of anodic layers is higher in those samples possessing reduced SDAS (<26 µm) and small, well‐spheroidized Si particles. The shape and distribution of Si particles are found to play a key role in achieving an anodic layer with good thickness homogeneity and an excellent degree of Si‐particle embedding, leading to high corrosion resistance.

The manuscript investigates the synthesis and characterization of Aluminum alloys, comprising Si, Ti and B as alloying elements, as anodes for Al-ion batteries. Deposition/stripping measurements, impedance spectroscopy, metallographic, energy dispersive X-ray spectroscopy (EDXS) and X-ray diffraction (XRD) techniques unveil the complex interplay existing between the microstructures of the alloys and the obtained electrochemical performance. Prototype cycling and post-mortem battery failure analysis are performed as well. It is demonstrated that a remarkable improvement in the: a) oxidation/reduction currents and overvoltages; and b) interfacial stability with the electrolyte; can be obtained, with respect to a conventional Al anode.

The development of batteries based on metals alternative to Lithium (e.g. Na, Mg, Zn, Al) requires the investigation of new electrodes and electrolytes. [1,2]. This is particularly true in the case of non-aqueous Aluminum batteries which typically include a pure (>99.8%) Aluminum anode which: a) suffer of poor cycling stability and low coulombic efficiency; b) is particularly subjected to dendrite growth; c) can undergo to corrosion phenomena upon cycling; and d) show a poor compatibility toward chloroaluminated electrolytes [3]. In this regard, the development of Aluminum alloys, alternative to pure Al anodes, is a challenging task which is barely investigated in the field of Aluminum ion batteries and requires experience in both battery electrochemistry and Aluminum metallurgy and casting. In this scenario, the proposed work investigates the synthesis and characterization of ternary Aluminum, alloys comprising Si, Ti and B as alloying elements, as anodes for Al-ion batteries [4]. Deposition/stripping measurements, impedance spectroscopy, metallographic analysis, EDXS and XRD techniques unveil the complex interplay existing between the microstructures of the alloys and the obtained electrochemical performance. It is demonstrated that a remarkable improvement in the: a) oxidation/reduction currents and overvoltages; and b) interfacial stability with the electrolyte; can be obtained, with respect to a conventional Al anode. Results allow to demonstrate that the investigation of Aluminum alloys can be crucial for the development of future Aluminum batteries. [1] F Bertasi, C Hettige, F Sepehr, X Bogle, G Pagot, K Vezzù, E Negro, S J Paddison, S G Greenbaum, M Vittadello, V Di Noto, ChemSusChem, 2015, 8 (18), 3069-3076 [2] F Bertasi, F Sepehr, G Pagot, SJ Paddison, V Di Noto, Advanced Functional Materials 2016, 26 (27), 4860-4865 [3] Y Zhang, S Liu, Y Ji, J Ma, H Yu, Advanced Materials 2018, 30 (38), 1706310 [4] Italian Patent Application n° 102022000024522

Aluminum alloys are widely used in the automotive, aerospace and construction fields due to their excellent physico-mechanical properties. Nevertheless, the corrosion resistance of bare Al alloys is often insufficient to meet the requirements of several industrial applications and protection strategies are needed. Among these, anodizing is particularly effective since it can lead to the formation of a compact and thick dielectric oxide layer with barrier and corrosion protection capabilities. However, anodizing of highly alloyed Aluminum alloys (e.g. those with an alloy element concentration higher than 5%_wt) can be particularly challenging due to the presence of intermetallic precipitates within the Al matrix which generates micro-galvanic coupling events with an associated thickness inhomogeneity of the obtained anodic layer [1]. In this context, the work investigates ten new current waveforms for anodizing of Aluminum Silicon alloys (AlSix). Particular attention is devoted to the interplay among waveform parameters (e.g. duty cycle, peak and rest step intensities), oxide layer morphology and corrosion resistance. In particular, metallography, voltammetry and contact angle methods are used in order to correlate different figures of merit with the anodic layer morphological features. It is concluded that a careful optimization of the current waveform parameters can modulate the: a) corrosion current; b) corrosion potential; c) breakdown potential; and d) polarization resistance; of coated specimens. In conclusion, the most effective waveforms are identified and coated Aluminum alloy specimens with a remarkable corrosion resistance are obtained. [1] M Bandiera, A Bonfanti, M Bestetti, F Bertasi, SAE International Journal of Advances and Current Practices in Mobility 3 (2), 973-979.