Margherita Verrucchi

Palladium electrodeposition is widely employed in the electroplating industry due to its technical and aesthetic properties, serving as both a final coating and an intermediate barrier to enhance corrosion resistance and adhesion [1]. Beyond these applications, palladium’s ability to absorb hydrogen in atomic form enables the formation of two distinct hydride phases: the hydrogen-poor α-PdH _x (x ~0.02) and the hydrogen-rich β-PdH _x (~0.67). While the α-phase is preferred in electroplating to prevent microfracturing upon hydrogen release, the β-phase holds significant potential for hydrogen storage in the energy sector [2]. The incorporation and retention of hydrogen during electrodeposition depend on several factors, making process optimization crucial for tailoring the final application of the palladium deposit. This study investigates the impact of electrodeposition parameters (current densities and thickness of the coating) on hydrogen absorption and phase formation. Both direct and pulsed current deposition methods were explored to assess their influence on hydrogen uptake and desorption rates. X-ray diffraction (XRD) was employed to identify the α- and β-phases through their characteristic peaks at 40.1° and 38.34°, respectively. Results indicate that low current densities favor the formation of the β-phase, making these conditions suitable for hydrogen storage applications. Conversely, higher current densities promote the α-phase, which is desirable for electroplating due to its stability and lower hydrogen content. Additionally, we observed that the hydrogen desorption rate is influenced by the morphology of the deposit, with structured surfaces facilitating faster release. XRD analyses were performed at intervals of 10 minutes, 1.5 hours, 3 hours, and 24 hours post-deposition to evaluate desorption kinetics. Furthermore, a heat treatment process was identified to accelerate hydrogen release, promoting rapid α-phase stabilization. These findings provide valuable insights into optimizing palladium electrodeposition for distinct industrial applications, whether for corrosion-resistant coatings or hydrogen storage solutions. Project funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.3 - Call for tender No. 341 of 15 March 2023 of Italian Ministry of University and Research (MUR) funded by the European Union - NextGenerationEU - Project code PE_00000004, CUP B83C22004890007, Project title "3A-ITALY - Made-in-Italy circolare e sostenibile". References [1] W. Giurlani et al., Coatings, 2018, 8, 260 [2] Z. Zhao et al., J. Am. Chem. Soc. 2015, 137, 15672-15675 [3] J. D. Benck et al., Chem. Mater. 2019, 31, 4234-4235 Figure 1

The performance and longevity of metallic coatings produced in electroplating baths are heavily dependent on the presence of organic additives. However, these additives are susceptible to degradation and loss, necessitating regular monitoring to ensure consistent quality and aesthetic standards. Conventional chromatographic techniques are often unsuitable for industrial settings due to the intricate composition of the baths and the interplay between various additives. Electrochemical methods such as the Hull cell test and Cyclic Voltammetric Stripping (CVS) are widely employed to assess and maintain additive concentrations. While the Hull cell test provides qualitative results based on operator judgment, CVS relies on changes in copper deposition rates, limiting its effectiveness for baths with complex formulations. Electrochemical Impedance Spectroscopy (EIS) has previously been employed to qualitatively assess the aging of copper plating baths through impedance variations [1]. This study extends the approach by using EIS for quantitative evaluation of organic additives. Experimental data were analyzed through decomposition into resistive and capacitive elements, followed by the calculation of the distribution of relaxation times (DRT) using Lasso regression [2]. Multivariate statistical methods were then applied to interpret the data, enabling a deeper understanding of the electrochemical behavior of the bath. The results demonstrate the potential of this method to revolutionize additive analysis in both industrial and research environments. Its application to the galvanic field offers valuable insights into the roles and interactions of individual additives and the aging dynamics of plating baths [3]. Project funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.3 - Call for tender No. 341 of 15 March 2022 of Italian Ministry of University and Research (MUR) funded by the European Union - NextGenerationEU - Project code PE_00000004, CUP B83C22004890007, Project title "3A-ITALY - Made-in-Italy circolare e sostenibile". The authors also acknowledge Regione Toscana PR FESR 2021/2024-azione 1.1.4.1 “Ricerca e sviluppo per le imprese anche in raggruppamento con organismi di ricerca”-Bando 1 “Progetti Strategici di ricerca e sviluppo” project “FREEGALVAN” (CUP: 27716.29122023.042000059_2113) and Bando 2 project “PULSE” (CUP: 27717.29122023.043000271). References [1] C. Gabrielli et al., J. Appl. Electrochem. 2008, 38, 457–468. [2] A. Piccioni et al., J. Phys. Chem. C 2023, 127, 7957–7964. [3] M. Verrucchi et al., J. Electroanal. Chem. 2024, 954, 118045.

Organic additives play a crucial role in upholding the quality of metallic coatings within commercial electroplating baths. However, their effectiveness diminishes over time due to degradation and drag-out. Continuous monitoring and precise dosing are imperative to uphold optimal concentration levels, preserving both technical integrity and aesthetic appeal. Traditional chromatographic techniques are impractical for routine industrial analysis due to the complex formulation and synergistic effects of various additives. Electrochemical methods, such as the Hull cell test and Cyclic Voltammetric Stripping (CVS) measurements, are commonly employed to adjust additive concentrations based on their impact on the electrodeposition process. Although widely utilized, the Hull cell test relies on trial and error and operator experience, providing only qualitative assessments. CVS, which measures changes in the rate of copper deposition to reflect additive concentration, may not be universally suitable for all electroplating baths due to their varying complexities. Prior Electrochemical Impedance Spectroscopy (EIS) investigations on copper plating baths have qualitatively linked impedance changes with aging [1]. Our objective was to quantify additives using EIS. To achieve this, experimental data were analyzed in terms of resistive and capacitive components to calculate the distribution of relaxation times (DRT) via Lasso regression [2]. The resulting data were subjected to multivariate analysis to address this challenge. The promising outcomes [3] render this method highly appealing in both industrial and academic contexts. Its application in the galvanic field is particularly advantageous for gaining insights into the function of individual additives, their interactions, and the aging process of plating baths. Project funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.3 - Call for tender No. 341 of 15 March 2023 of Italian Ministry of University and Research (MUR) funded by the European Union - NextGenerationEU - Project code PE_00000004, CUP B83C22004890007, Project title "3A-ITALY - Made-in-Italy circolare e sostenibile". References [1] C. Gabrielli et al., J. Appl. Electrochem. 2008, 38, 457–468. [2] A. Piccioni et al., J. Phys. Chem. C 2023, 127, 7957–7964. [3] M. Verrucchi et al., J. Electroanal. Chem. 2024, 954, 118045.

The interest in scientific research in the metal-finishing sre is constantly growing. The market demand for durable metal coatings and adaptable manufacturing processes is increasing across a wide range of applications, from aerospace and automotive to machinery and jewelry. An essential step in the production line is the surface engineering of metal deposition, as this determines the final appearance and functionality of the final industrial/handcrafted product. Therein electroplating is recognized as a mature technology allowing for the low-cost fabrication of well-defined surfaces, with extensive property profiles. Galvanic electrodeposition accounts today for almost 40% of the global market value share of the metal-coating market, with North America and Western Europe leading the scenery. Although technological and processing advancements occurred in the past forty years, industrial firms are still struggling to provide solutions to corrosion protection as well as the reduction of toxic wastes. Specifically, large-scale industrialization of electroplating techniques will continue to be limited by strict environmental regulations. Environemental rules and regulations got more and more strict, and sustanability issues will further push for more restrictions concerning the industrial impact on the environment. Due to adverse ecological implications, the adoption of plating processes involving toxic metals such as lead or cadmium is prohibited. Moreover, price volatility of the highly demanding electroplated materials gold, copper, and nickel is expected to impact the market share by more than 60% by 2026. In that respect, alloy plating offers better answers in terms of economic growth and environmental sustainability, allowing for fine-tuning composition, morphology, and crystallinity [1]. In this paper, current trends in alloy electrodeposition research are reviewed highlighting open challenges and process innovations from an industrial perspective. The main categories of alloy compounds are presented, and the most important characteristics of the manufacturing process are critically discussed. With particular focus on advances in industrial quality-control and viable solutions for the reduction of precious metal content in electroplated accessories, as well as the replacement of cyanide and nickel baths with processes featuring non-toxic compounds. In particular, the use of pulsed currents, new alloy formulation acting as a barrier layer and the reduction of defective pieces are the novel strategies/solutions to increase the sustainability of production processes in the electroplating industries. References [1] W. Giurlani, M. Innocenti et all. , Electroplating for Decorative Applications: Recent Trends in Research and Development, Review, Coatings 2018, 8(8), 260.

Pulsed current has proven to be a promising alternative to direct current in electrochemical deposition, offering numerous advantages regarding deposit quality and properties. Concerning the electrodeposition of metal alloys, the role of pulsed current techniques may vary depending on the specific metals involved. We studied an innovative tin–ruthenium electroplating bath used as an anti-corrosive layer for decorative applications. The bath represents a more environmentally and economically viable alternative to nickel and palladium formulations. The samples obtained using both direct and pulsed currents were analyzed using various techniques to observe any differences in thickness, color, composition, and morphology of the deposits depending on the pulsed current waveform used for deposition.

The interest in scientific research within the metal finishing sector is growing. The demand for durable metals and adaptable manufacturing processes is increasing across a wide range of applications, from aerospace and automotive to machinery and jewelry. In that respect, alloy plating offers better answers in terms of economic growth and environmental sustainability due to fine-tuning composition, morphology, and crystallinity [1]. Here, current trends in alloy electrodeposition research are reviewed highlighting open challenges and process innovations from an industrial perspective. Combining basic electrochemical techniques with spectroscopic, microscopic, and structural techniques is crucial for characterizing the structure-activity relationship for many different technological devices. Particular attention is devoted to advances in industrial quality control and viable solutions for the reduction of precious metal content in electroplated accessories as well as the replacement of cyanide and nickel baths with non-toxic compounds. Project funded under the National Recovery and Resilience Plan (NRRP), Mission 4 Component 2 Investment 1.3 - Call for tender No. 341 of 15 March 2023 of Italian Ministry of University and Research (MUR) funded by the European Union - NextGenerationEU - Project code PE_00000004, CUP B83C22004890007, Project title "3A-ITALY - Made-in-Italy circolare e sostenibile". References [1] W. Giurlani, M. Innocenti et all. , Electroplating for Decorative Applications: Recent Trends in Research and Development, Review, Coatings 2018, 8(8), 260.

Commercial plating baths may contain a large number of organic additives that play an important role in ensuring good-quality deposits. During electrodeposition process these compounds tend to wear out and degrade, so they must be frequently monitored and dosed to keep constant their concentration. Plating baths are complex matrices in which organic additives are present in minimal quantities compared to the other components, electrochemical methods, therefore, represent a reliable alternative to conventional chromatographic techniques because they allow quantitative analyses to be carried out considering the effects of additives on the electrodeposition rate regardless of their chemical composition and provide, at the same time, useful information about the condition of the bath. Methods based on the Cyclic Voltammetric Stripping (CVS) technique can be employed to quantify additives generally used in commercial acid copper plating baths. However, such procedures tend to be time and reagents-consuming and do not always provide accurate results. Electrochemical Impedance Spectroscopy (EIS) can represent a reliable alternative because it allows to achieve a detailed knowledge of the function of each additive and the interactions between them and to study the aging of plating baths [1]. EIS measurements were performed to quantify the three main additives present in commercial acid copper plating baths. These baths are widespread in different industrial sectors, such as fashion and electronic. The experiments were performed in three-electrodes cell, at 30 °C, by using a 10⁵ – 10^-2 Hz frequency range. A large number of samples were investigated for a statistical treatment of the results that allowed us to find correlations between the concentration of each additive and some of the components of the equivalent circuit used to fit the data. The procedure applied to real samples provided promising results. The authors acknowledge MUR and EU-FSE for financial support of the PhD fellowship PON Research and Innovation 2014-2020 (D.M 1061/2021) XXXVII Cycle in Chemical Sciences. References [1] Gabrielli, C. et al. Journal of Applied Electrochemistry 2008, 38, 457-468, doi: 10.1007/s10800-007-9459-1

The interest in scientific research within the metal finishing sector is growing. The demand for durable metals and adaptable manufacturing processes is increasing across a wide range of applications, from aerospace and automotive to machinery and jewelry. An essential step in the production line is the surface engineering of metals, as this determines the final appearance and functionality of a product. Therein electroplating is recognized as a mature technology allowing the low-cost fabrication of defined surfaces with extensive property profiles. Galvanic electrodeposition accounts today for almost 40% of the global market value share with North America and Western Europe leading the scenery. Although technological and processing advancements occurred in the past forty years, industrial firms are still struggling to provide solutions to corrosion protection as well as the reduction of toxic wastes. Specifically, large-scale industrialization of electroplating techniques will continue to be limited by strict environmental regulations. Due to adverse ecological impacts, the adoption of plating processes involving toxic metals such as lead or cadmium is prohibited. Moreover, price volatility of the highly demanding electroplated materials gold, copper, and nickel is expected to impact the market share by more than 60% by 2026. In that respect, alloy plating offers better answers in terms of economic growth and environmental sustainability due to fine-tuning composition, morphology, and crystallinity [1]. Here, current trends in alloy electrodeposition research are reviewed highlighting open challenges and process innovations from an industrial perspective. The main categories of alloy compounds are presented and the most important properties of the manufacturing process are discussed. Particular attention is devoted to advances in industrial quality control and viable solutions for the reduction of precious metal content in electroplated accessories as well as the replacement of cyanide and nickel baths with non-toxic compounds. The authors acknowledge Regione Toscana POR CreO FESR 2014-2020 – azione 1.1.5 sub-azione A1 – Bando 1 “Progetti Strategici di ricerca e sviluppo” which made possible the project: “RAM-PVD” (CUP 3647.04032020.157000057_1225). References [1] W. Giurlani, M. Innocenti et all. , Electroplating for Decorative Applications: Recent Trends in Research and Development, Review, Coatings 2018, 8(8), 260.