Continuous improvement of surface engineering processes with respect to occupational safety, sustainability, and resource efficiency is critical for maintaining industrial competitiveness and meeting increasingly stringent technical and regulatory requirements worldwide. In automotive and sanitary applications, chromium coatings are commonly applied as multilayer systems with copper and nickel. Hard chromium layers enhance component lifetime through favorable tribological behavior and high resistance to wear and corrosion, with typical hardness values of 600–1,200 HV [1-2], making them suitable for press moulds and rollers. However, the use of hexavalent chromium is now highly restricted due to its carcinogenic properties [3], prompting the search for environmentally friendly alternatives. Boriding, a thermochemical surface hardening process, produces hard, wear-resistant layers on steels [4] and nickel-based alloys, such as Inconel [5]. The process forms FeB and Fe 2 B layers up to 250 µm deep, with hardness values reported between 1,200–1,600 HV on steel and 1,700–2,300 HV on Inconel. Typical treatment temperatures range from 750–950 °C for 2–6 hours, however, result in high energy consumption. This study investigates the incorporation of boron particles into NiP coatings combined with heat treatment to improve functional properties. A key advantage of this approach is the significantly shorter annealing time required to activate boron diffusion, enabling substantial energy savings compared with conventional boriding while maintaining high hardness and wear resistance. Hardness, wear resistance, and residual stress are evaluated for applications including industrial knives, bending tools, and injection moulding tools. The ability to form hard, boride-enriched NiP layers through shorter, lower-energy heat treatments provides the potential to replace high-alloy steels traditionally used for tempering, nitriding, or boronizing with more economical substrates such as 100Cr6, thereby improving both performance and process sustainability. [1] C. Schade and H. Käszmann, “Galvanisch abgeschiedenes Chrom - Ein Blick auf die mechanischen Eigenschaften,” Werkstoffe , Mar. 2013. doi: DOI:10.7395/2013/Schade2. [2] Z. Zeng, L. Wang, L. Chen, and J. Zhang, “The correlation between the hardness and tribological behaviour of electroplated chromium coatings sliding against ceramic and steel counterparts,” Surf Coat Technol , vol. 201, no. 6, pp. 2282–2288, Dec. 2006, doi: 10.1016/j.surfcoat.2006.03.038. [3] “European Chemicals Agency (ECHA) Authorisation List.” Accessed: May 27, 2025. [Online]. Available: https://www.echa.europa.eu/web/guest/authorisation-list?p_p_id=disslists_WAR_disslistsportlet&p_p_lifecycle=1&p_p_state=normal&p_p_mode=view&_disslists_WAR_disslistsportlet_javax.portlet.action=searchDissLists [4] W. Muhammad, “Boriding of high carbon high chromium cold work tool steel,” IOP Conf Ser Mater Sci Eng , vol. 60, p. 012062, Jun. 2014, doi: 10.1088/1757-899X/60/1/012062. [5] I. Campos-Silva, A. D. Contla-Pacheco, U. Figueroa-López, J. Martínez-Trinidad, A. Garduño-Alva, and M. Ortega-Avilés, “Sliding wear resistance of nickel boride layers on an Inconel 718 superalloy,” Surf Coat Technol , vol. 378, p. 124862, Nov. 2019, doi: 10.1016/j.surfcoat.2019.06.099.

Thermal spraying is an established technology in the coating industry offering high deposition rates and a broad range of processable materials. In addressing the scale-up of proton exchange membrane water electrolyzers, thermal spraying presents a promising solution for cell component production, despite several challenges that need to be overcome: Firstly, the substrate material is typically characterized by a relatively thin thickness and complex geometries. Secondly, the coatings often exhibit process-related roughness. This study demonstrates that this rough coating can be beneficial in enhancing the connection between the bipolar plate (BPP) and the porous transport layer (PTL). The developed coldgas sprayed BPP-PTL coating system was tested in an electrochemical accelerated stress test (AST) as well as in an intermittent long-term single-cell test. The results indicate that the BPP-PTL coating system is electrochemically stable during the AST, and subsequent measurements of electrical resistance confirm that the interface is preserved from severe oxidation. In the long-term test, it was demonstrated that a single cell could be operated with a cell voltage of U cell = 1.9 V at a current density of i = 2 A/cm2 over 3 months. For the first time, a fully cold gas sprayed BPP-PTL coating system has been tested in a single-cell test for proton exchange membrane water electrolysis applications.

Next-generation semiconductor technologies increasingly demand massively parallel assembly methods that can integrate discrete microscopic chiplets with high throughput, precision, and scalability 1,2 . Fluidic self-assembly (FSA) 3 has emerged as a powerful candidate for parallel integration 4 , yet its application has remained limited to chiplets larger than several tens of micrometers. Here, we present the FSA of microscopic light-emitting diodes (microLEDs) onto molten solder-based receptor arrays, where the chiplets attach, self-align, and form electrical connections autonomously until all receptors are occupied. MicroLEDs with dimensions of 18 × 18 × 2 µm 3 are assembled with a 99.77% yield and at rates exceeding 12,000 chiplets per minute. These metrics push the FSA into the deep microscale by achieving dimensions five and twelve times smaller in area and volume, respectively, than previous records 5 . Three mutually necessary criteria define the operational window for high-yield assembly, each addressing a distinct challenge inherent to this scale. First, a mobile slurry of chiplets maximizes efficient chiplet-receptor interaction across the solder bumps. Second, precisely tuned acid concentration in the fluidic transfer medium enables reliable solder wetting and attachment. Third, a 20-fold suppression of oxidation is essential, as oxide growth kinetics increasingly outcompete solder wetting at the microscale. Device functionality is validated through a self-assembled microLED display with a transparent top electrode. Ultimately, these results demonstrate massively parallel assembly of truly microscopic chiplets at scales previously inaccessible, opening new pathways for emerging photonic and semiconductor integration technologies.

Ni-P layers demonstrate various favorable functional characteristics, where the P content is the most important property-controlling factor. Therefore, the development of prompt and cost-effective methods for determination of the P quantity in the layer is important. In response to this challenge the current work proposes a simple and low-cost microgravimetric approach for rapid in-situ evaluation of the P content in galvanostatically deposited Ni-P layers. The method is based on the application of electrochemical quartz crystal microbalance (EQCM) for electrogravimetric analysis of Ni-P anodic dissolution in acidic electrolyte environment. Important factors, including deposition potential, current density and temperature are considered for understanding of the reaction mechanism corresponding to Ni-P redox behavior and its gravimetric response. The approach can be realized in a sequential galvanostatic mode, enabling straightforward analysis of the current density impact on the layer composition. The analytical results obtained by means of EQCM are verified by EDX and XPS spectroscopy methods.

This study aims to employ a machine learning (ML)-based regression model that accurately captures nonlinear relationships between electroplating process parameters and chromium thickness, while enabling the interpretation and visualization of these nonlinear effects. For this purpose, two statistically distinct datasets from laboratory-scale (1L) and pilot-scale (14L) experiments were analyzed. Hyperparameter tuning and fivefold cross-validation are used for training to make the results robust and transparent for different data constellations. Several models were evaluated and achieved coefficients of determination () of up to 75%, often outperforming linear regression (LR) due to nonlinear parameter interactions. Model performance varied depending on the dataset, with no single ML approach proving universally superior. For the entire dataset, the CatBoost model achieved the best result with an average of 70.5%. A deeper analysis of the data was performed using SHAP, permutation importance, and global feature importance. To visualize potential nonlinear relationships, a partial dependence analysis was conducted to assess the influence of individual process parameters. This analysis confirmed the presence of specific nonlinear dependencies for several parameters in relation to chromium thickness. The correlations among the process parameters identified in this study are highly relevant for industrial bath management and process optimization.

Additively processed materials are increasingly used to manufacture customized parts, e.g. medical implants. Implant surfaces often require a smooth finish, which can be achieved by post-processing and well-defined process parameters. In this study, the effects of electropolishing of metal parts produced by laser powder bed fusion are investigated using Hull cell experiments and a three-electrode setup. Current density voltage curves were measured with the three-electrode setup to identify the regimes for electropolishing. Subsequently different constant-currents were applied and Hull cell experiments were conducted. The surface roughness (Sz, Sa) and the mass removal were analysed. Surface morphologies were assessed using laser scanning and scanning electron microscopy. A reduction of the initial surface roughness of more than 90% to Sa < 0.3 μm has been achieved. Considering the passed electrical charge during electropolishing, results from Hull cell experiments are systematically correlated with current-controlled electropolishing. This approach enables the precise tailoring of polishing parameters to achieve surfaces with defined roughness. Furthermore, the study demonstrates the suitability of Hull cells in determining electropolishing parameters for additive materials and highlights their contribution to post-processing in additive manufacturing.

The maximum deposition rate of an electroplating process (limiting current density) is determined by the transport of metal ions to the cathode. This transport depends on the type, velocity, and direction of the electrolyte flow. In the case of laminar flow, the limiting current density is proportional to the square root of the flow velocity. In turbulent flow, the limiting current density increases more strongly with flow velocity. To investigate these effects, electrochemical deposition from an acidic copper sulfate bath was investigated in a Taylor-Couette reactor (TCR). This reactor consists of a rotating inner cylinder and a stationary outer cylinder with two opposing electrodes. Limiting current densities were determined from cyclic voltammograms (CVs) at various rotational speeds. Taylor vortices theoretically form at low speeds due to axial electrolyte movement, becoming more pronounced with increasing rotation rate. At approximately 60 rpm, the vortices begin to move, and at around 500 rpm, a transition to a fully turbulent flow occurs. A similar transition is observed for the limiting current densities, measured both in a rotating disk electrode (RDE) setup and in the TCR. The RDE exhibits laminar flow, where the limiting current density is proportional to the square root of the rotation speed. In the TCR, a similar relationship holds up to around 500 rpm, beyond which turbulence causes a sharp increase in the limiting current density (Fig. 1). The experimental investigations were supplemented by numerical simulations using COMSOL, which show similar results and improve the understanding of the hydrodynamic conditions. Applying turbulent flow in industrial electroplating processes could improve efficiency by increasing deposition rates, reducing process times, and optimizing layer properties. Fig. 1: Levich plot of the measured cathodic limiting current densities in the RDE and TCR in a 0.01 mol/L copper sulfate electrolyte Figure 1

Gas-phase electrodeposition is presented as a nanoparticle-based route toward the fabrication of Pt/Al bimetallic stacks (self-propagating reactive system). This approach enables localized self-assembly of spark discharge-synthesized sub-10-nm Pt and Al nanoparticles on patterned substrates. Precise control over Pt film morphology (porosity) through modulation of spark power and carrier gas flow rate is demonstrated. Porous Pt layers lead to diffused Pt/Al interfaces, which become sharper for densely packed Pt layers. On ignition, the self-sustained high-temperature alloy formation reaction wavefronts are recorded. The bimetallic interface strongly influences the Pt/Al reaction kinetics, with three orders of magnitude faster reaction speeds for sharper interfaces. Porous morphologies and hence diffused interfaces are hindered by excessive air gaps and premixed regions, intermediate porosities achieved speeds of 0.012 m s-1, and dense morphologies have sharp interfaces with minimal air pockets reaching speeds up to 6 m s-1. Selected area (electron) diffraction (SAED) and X-Ray diffraction (XRD) studies reveal Al2Pt and Al3Pt2 as the dominant alloy phases amongst other intermediate PtAl phases. Furthermore, XRD demonstrates temperature-dependent facet growth of Pt-Al alloys. These results prove the critical influence of film morphology on reaction kinetics and emphasize the potential of tuneable Pt/Al bimetallic systems for future energy-related applications.

Metal-semiconductor compounds are widely used in microelectronics and are constantly being developed further. Platinum-silicon semiconductor contacts are frequently used in sensors and detectors, especially infrared detectors and cameras. More recent developments enable applications in medical technology, especially for pressure sensors as implants in the human body. Currently, platinum coating on silicon-based semiconductor components is realized using sputtering techniques or platinum-containing printing pastes with subsequent heat treatment. This presentation will discuss an approach for platinum electrodeposition. Special attention is paid to the pre-treatment of the silicon for the subsequent platinum deposition by varying the current density, electrolyte composition and illumination of the substrate (light induced plating). The challenges include achieving a homogeneous platinum coating with low contact resistance and high adhesive strength. The layer characterization with SEM, EDX, laser scanning microscopy, etc. will also be a central part of the contribution.

CO2 2 electrocatalytic reduction (CO2RR) 2 RR) to CO in organic electrolytes has received considerable attention due to its potential industrial application prospect. However, the reaction mechanism is not fully understood. In this study, we employed experimental observation, in-situ ATR-IRAS and Raman spectroscopy to elucidate the reaction mechanism of CO2 2 electro-reduction to CO in an organic medium. The reaction intermediates *CO2 center dot-, 2 center dot- , * (CO 2 ) 2 center dot- and *CO has been identified during CO2RR. 2 RR. Based on these results, the reaction mechanism has been discussed extensively. Density Functional Theory (DFT) analysis further indicates that the electrolytic CO2 2 reduction to CO in organic electrolyte is relatively more difficult than that in aqueous solutions.

This work explores the effect of in situ electrochemical pretreatment of copper current collectors (CuCC), acting as anodes in anode‐free lithium‐metal battery (AFLMB) with sulfolane‐based localized high‐concentration electrolyte. Two electrochemical pretreatment methods, not involving lithium overpotential deposition are in focus. These strategies are investigated in terms of passive layer growth, surface morphology evolution, composition of the formed interphases, and electrochemical performance for AFLMBs. The passive layers formed on CuCC (Cu–solid‐electrolyte interphase [SEI]) are in situ characterized by means of electrochemical quartz crystal microbalance with damping monitoring, which indicates that the Cu–SEIs exhibit detectable viscoelastic properties. The morphological characterization of the modified CuCCs shows highly homogeneous Cu–SEI structure with low surface roughness. The composition and physical properties of the Cu–SEI layers are correlated with the electrochemical performance of the anodes. The observed positive effect of the procedures for SEI preformation is associated with the synergistic influence of balanced inorganic–organic composition, enhanced viscoelastic properties, and homogeneous morphology of the layer. The study demonstrates the positive impact of the designed pretreatments and provides an appropriate comparison between the proposed in situ approach and the state of the art.

A new strategy has been proposed for phosgene (COCl2) production from CO2 and waste HCl. In an H-type electrolysis cell, CO2 is reduced to CO in the catholyte, while HCl is oxidized to Cl₂ in the anolyte. The generated CO and Cl2 can be used as feedstock for phosgene synthesis. While CO2RR in aqueous electrolytes has been extensively studied, it remains limited to the laboratory scale due to issues such as cathode deactivation. In this work, we introduce an organic electrolyte system using tetrabutylammonium perchlorate (Bu4NClO4) in propylene carbonate (PC), which exhibits improved stability and high CO selectivity. Notably, making a direct comparison of catalyst stability between aqueous and organic systems is inherently challenging due to their distinct electrochemical environments. In this work, we have extensively discussed this issue. Therefore, the direct comparison of catalyst stability between these two electrolyte systems represents a key novelty of this study. This approach not only enables efficient and stable CO production but also provides a sustainable route for CO2 utilization and waste HCl treatment.

Artificial leaves could be the breakthrough technology to overcome the limitations of storage and mobility through the synthesis of chemical fuels from sunlight, which will be an essential component of a sustainable future energy system. However, the realization of efficient solar‐driven artificial leaf structures requires integrated specialized materials such as semiconductor absorbers, catalysts, interfacial passivation, and contact layers. To date, no competitive system has emerged due to a lack of scientific understanding, knowledge‐based design rules, and scalable engineering strategies. Herein, competitive artificial leaf devices for water splitting, focusing on multiabsorber structures to achieve solar‐to‐hydrogen conversion efficiencies exceeding 15%, are discussed. A key challenge is integrating photovoltaic and electrochemical functionalities in a single device. Additionally, optimal electrocatalysts for intermittent operation at photocurrent densities of 10–20 mA cm −2 must be immobilized on the absorbers with specifically designed interfacial passivation and contact layers, so‐called buried junctions. This minimizes voltage and current losses and prevents corrosive side reactions. Key challenges include understanding elementary steps, identifying suitable materials, and developing synthesis and processing techniques for all integrated components. This is crucial for efficient, robust, and scalable devices. Herein, corresponding research efforts to produce green hydrogen with unassisted solar‐driven (photo‐)electrochemical devices are discussed and reported.

Hydrogen production by electrolysis offers significant advantages over established and more common processes such as steam reforming with regard to carbon dioxide emissions, in particular through the use of electrical energy from renewable sources and the establishment of a decentralized supply structure. The advantages of PEM (proton exchange membrane) electrolysis include high power density, scalability, and the high purity of the produced hydrogen. However, so far the manufacturing of PEM electrolyzers is time consuming, which makes their widespread use difficult and is a significant cost driver for this technology. A promising strategy for the cost-effective production of the cell components is functionalization of low-cost materials with protective coatings. In the framework of the publically funded flagship project H2Giga, coating systems for the bipolar plates (BPP) and porous transport layers (PTL) are developed and tested under real conditions in an electrolyzer stack. The anode PTL is facing very low pH and high anodic potentials as it is in close proximity to the anode catalyst layer. Therefore, the PTL is made of titanium which is proven to be long term stable under these conditions. However, titanium forms a passive layer under anodic polarization leading to an increase of contact resistance and ohmic drop in the cell. The passivation can be suppressed by electrodeposition of platinum at the interface to the catalyst layer. To ensure a good adhesion of the platinum and low material loss during electrolyzer operation, a pretreatment of the titanium surface is crucial. A state-of-the-art fluoride-containing etching solution was compared to fluoride-free processes in terms of stability of the subsequent platinum coating. Investigations on the morphology by SEM and FIB show a good correlation to polarization experiments. The results are further validated by operando testing in a five cell test stack. The fluoride-free solutions are very promising for industrial applications, but so far only provide limited activation of the titanium surface and need to be further optimized to ensure a reliable coating adhesion.

In lithium-ion batteries, the solid electrolyte interphase (SEI) passivates the anode against reductive decomposition of the electrolyte but allows for electron transfer reactions between anode and redox shuttle molecules, which are added to the electrolyte as an internal overcharge protection. In order to elucidate the origin of these poorly understood passivation properties of the SEI with regard to different molecules, we used a four-electrode-based generator-collector setup to distinguish between electrolyte reduction current and the redox molecule (ferrocenium ion Fc+) reduction current at an SEI-covered glassy carbon electrode. The experiments were carried out in situ during potentiostatic SEI formation close to battery operation potentials. The measured generator and collector currents were used to calculate passivation factors of the SEI with regard to electrolyte reduction and with regard to Fc+ reduction. These passivation factors show huge differences in their absolute values and in their temporal evolution. By making simple assumptions about molecule transport, electron transport, and charge transfer reaction rates in the SEI, distinct passivation mechanisms are identified, strong indication is found for a transition during SEI growth from redox molecule reduction at the electrode | SEI interface to reduction at the SEI | electrolyte interface, and good estimates for the transport coefficients of both electrons and redox molecules are derived. The approach presented here is applicable to any type of electrochemical interphase and should thus also be of interest for interphase characterization in the fields of electrocatalysis and corrosion.

In this study, a possible alternative to hard chromium coatings is investigated. Amorphous boron particles have been incorporated in electroless nickel-phosphorus (NiP) deposits, yielding a dispersion coating. The distribution of the particles is homogenous and the maximum mass fraction of particles embedded in the coating is 6.2 +/- 0.2 wt%. Measurements of the zeta potential and particle size of amorphous boron particles in a diluted electrolyte showed that the particles withstood agglomeration until 120 days. Primary and secondary hardness maxima are observed after thermal annealing at 400 degrees C and 860 degrees C due to the formation of nickel phosphide, nickel boride and nickel boride phosphide phases. X-ray diffractometry shows an increase in nickel and nickel phosphide crystal size at 400 degrees C before levelling off at 600 degrees C. The annealing duration should be kept between 30 and 60 min for optimal hardness. The wear resistance increases when the coating is annealed at 400 degrees C. DSC mea-surements on nickel phosphorus incorporated with boron particles, Ni-P-B, bulk material with P-content (9.6 +/- 0,6 wt%) and B-content (4.5 +/- 0.8 wt%) showed that the solidus line lies at 926 degrees C, which is why a maximum annealing temperature of 860 degrees C was chosen to avoid melting of the material. The relative texture and phase coefficients, RTC and RPC, showed that the nickel phase is preferred in the Ni-P system at 400 degrees C and 600 degrees C while the Ni3P phase is preferred in the Ni-P-B system at the same annealing temperature. REM and EDX area analyses are used to show the areal distribution of nickel, phosphorus, and boron before and after the annealing process along the thickness of the coating. A diffusion layer between substrate and coating that contains iron nickel boride and iron nickel phosphide lamellar structure is observed.

Cobalt-iron alloys are interesting soft magnetic materials which are used for example in magnetic sensors and transducers. They can be obtained by different techniques such as PVD, magnetron sputtering, or casting. One easy and not very expensive way to produce these alloys is the electrochemical deposition technique, which was also chosen in this study. This contribution will describe the electrodeposition of Co, Fe and Fe-Co alloys (Fe 70 Co 30 ) from an aqueous sulphate-based electrolyte containing boric acid as a buffer and sodium citrate and citric acid besides the metal sulphates. Potentiostatic step experiments and cyclic voltammetry were performed in parallel to electrochemical quartz crystal microbalance. Thus, we could identify the potential at which the deposition of the metals sets in, the mass of the deposited species as well as the current efficiency. We could also extract the partial current due to hydrogen evolution reaction and the partial current due to individual metal or their alloys from the total current density. The morphology and structure of the deposited films were investigated by means of SEM and XRD, respectively. The grain size of the deposits was calculated from the XRD data using Scherrer equation. Addition of citric acid to the electrolyte results in the smaller grain size of the deposited Fe-Co films.

Results of an investigation of the action of various pyridinic and acetylenic brighteners during the electrodeposition of nickel are reported here. The focus was on the qualitative and quantitative analysis of the individual compounds 1-(3-sulphopropyl)-pyridinium betaine (PPS) and sulphopropylated 2-butyne-1,4-diol (HBOPS) and their reaction products. High performance liquid chromatography (HPLC) with a mass spectrometric detector (HPLC-MS) and a diode array detector in the UV range (HPLC-UV) were used to examine the various additives and the cathodic reaction products. PPS is almost completely hydrogenated to the piperidine compound (3-piperidin-1-yl-propane-1-sulphonate, PIPS) at the catalytically active nickel electrode; as intermediate products, only tetrahydrogenated pyridine (THPPS) compounds occur in the solution, in low concentrations. The entire hydrogenation chain takes place on the surface; partially hydrogenated products are either not desorbed at all or only desorbed in small quantities. Further by-products are dimers and after ring cleavage a pentylamine derivative 3-(pentylamino)-1-propanesulphonic acid, PAPS. Via the olefinic intermediate stage, the butynediol compound (HBOPS) reacts to become sulphopropylated butanediol. After elimination of water, this forms butanoxy-propanesulphonate in a further hydrogenation step.

Al/Ni reactive coatings are fabricated via electrochemical deposition (ECD) at different applied voltages for reactive bonding application. AlCl3:1-Eethyl-3:1-ethyl-3-methylimidazolium chloride ([EMIm]Cl) (1.5:1) ionic liquid electrolyte is used as source of Al, whereas Ni is in the bath and incorporated into final coatings as nanoparticles (NPs). Scanning electron microscopy and Auger electron spectroscopy reveal a homogeneous Ni particle dispersion, as well as a high amount of particle incorporation into the Al matrix. A maximum of 37 wt% (22 at%) of Ni is detected via atomic absorption spectroscopy in the Al/Ni coating deposited at -0.1 V from an electrolyte containing 20 g L(-1 )of Ni NPs. Previous literature show that for bonding application an ideal concentration is around 50 at% of Ni and 50 at% Al. However, this is achieved using high vacuum, time-consuming processes, and costly techniques like evaporation and magnetron sputtering. The ECD used in this work represents a more cost-efficient approach which is not reported up to date for the aforementioned application. The reactivity of the coatings is confirmed by Differential scanning calorimetry. Herein, an exothermic reaction is detected upon the mixing of Al and Ni occurring at high temperatures.

The suitability of various nitrogen, sulfur, oxygen, and phosphorus compounds as complexing agents in a silver electrolyte was examined by using potentiometric titration under practical conditions. The setup consisted of three electrodes to measure the pH and the activity of the silver ions simultaneously. Different ratios of silver to complexing agent from 1:10 to 1:1 at a constant ionic strength of 0.2 mol/L were investigated. The type of the complexes and their corresponding critical stability constants were evaluated by fitting the measured data using a self-developed algorithm. The pH and Nernst potential curve were calculated for the assumed complexes based on the law of mass action to find the best approximation. The correct definition of the occurring species is challenging and can lead to significant changes in the calculation of stability constants. For this reason, the measured silver potential curves were primarily used for the rating of the complexing agents. An evaluation of the measurements shows that the donor atom of the complexing agent and its ligand field strongly affected the stability and type of the complexes. Only a few complexing agents were found to be suitable for use in the cyanide-free silver electrolyte.