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Investigation of Halide Free Ionic Liquids for the Electrodeposition of Zinc and Zinc Alloys

Periodic Reporting for period 1 - INHALE (Investigation of Halide Free Ionic Liquids for the Electrodeposition of Zinc and Zinc Alloys)

Reporting period: 2020-10-26 to 2022-10-25

Metallic zinc coatings play a crucial role in various industries, particularly in transportation. Electroplated zinc and zinc-alloy coatings are widely used for corrosion resistance in mechanical components, such as fasteners and brake calipers. Traditional aqueous solutions for zinc electrodeposition are toxic, corrosive, and induce hydrogen embrittlement. The INHALE project addresses these challenges, aiming to develop environmentally responsible halide-free ionic liquids (ILs), deep eutectic solvents (DESs), and organic solutions as electrolytes for corrosion-resistant coatings. The project's objectives encompass screening protic ionic liquids and metal precursors, investigating deposition conditions, characterizing electrodeposited coatings, understanding deposition mechanisms, and validating electrolyte and plating performance. By systematically evaluating candidate solvent systems, including Chloride–DES and HF-based non-aqueous electrolytes, the project successfully developed more environmentally responsible halide-free electrolytes. Coatings prepared with these solvents exhibit functionality comparable to conventional approaches. The project demonstrates scale-up potential and includes a preliminary techno-economic assessment. Overall, INHALE significantly contributes to the advancement of non-aqueous electrodeposition for zinc and zinc-alloy coatings, addressing environmental concerns and advancing coating application methods using environmentally responsible non-aqueous electrolytes.
The project initiated with the comprehensive screening of 193 halide-free non-aqueous systems using MCDA tools, ultimately downselecting 6 optimal systems (protic ILs, DESs, organic solutions). Versatility was demonstrated through the successful development of zinc and zinc-alloy coatings, employing various combinations of acetate and propionate-based solutions, metal precursors, and conducting buffers on two different substrates. The research compared electrolytes, highlighting the eco-friendly nature of non-aqueous solutions, showcasing efficiency (~75% vs ~60% for conventional aqueous systems), enhanced crystalline growth, and promising corrosion resistance. Extending to zinc-alloy coatings with 48 electrolyte combinations, the study provided insights into optimal conditions. Scaling up was successfully validated in a 5L in-house plating line, emphasizing practical applicability and economic feasibility with a projected cost reduction of at least 60%. Dissemination efforts included 8 scientific publications, a book chapter, and participation in international conferences. Outreach activities targeted diverse audiences, from academic events like the Doctoral College Summer Showcase to unconventional platforms like the Chocolate Welding Shop, engaging with school students. Multimedia releases on platforms like the TWI Innovation Network and LinkedIn enhanced project visibility, aligning with the project's broader goal of promoting scientific knowledge and making research accessible to the public.
The project's contribution extends beyond conventional studies by offering a comprehensive evaluation of the impact of different electrolytes on zinc and zinc-alloy electrodeposition. Considerations for environmental impact (through MCDA approach), corrosion resistance, and scalability provide a holistic perspective on the suitability of developed systems, contributing valuable insights. The study provides valuable insights into the use of halide-free non-aqueous systems for electrodeposition, addressing their environmental impact, safety, and scalability. Comparative assessments between conventional aqueous electrolytes and chloride-based DES contribute to the understanding of alternative electrolytes for electroplating applications. The inclusion of a cost analysis for the developed systems adds a practical dimension to the research. Considering the economic feasibility of these systems on an industrial scale, the study contributes to decision-making processes for adopting environmentally friendly alternatives in electroplating industries. Recycling the drag out solution (process solution transferring into subsequent rinse tanks) shall enhance the life of the halide free non aqueous-based plating solution, saving cost while eliminating the environmental impact of the process due to the drag out (reducing the source of pollutants). The plating solution and the rinse can be recycled many times without affecting the quality of the coatings formed, as long as the contamination level is closely monitored. This demonstrates that the process could be easily adopted to the current set up without increasing the capital expenditure.
This innovative low toxic environmentally responsible technology has been instrumental in expanding the realm of corrosion protection, and it has undergone a series of key developmental and testing phases.
The technology developed in this project has undergone rigorous testing and validation. Real-time parts were used in plating experiments conducted in a 5-liter plating line. The aim was to assess the plating performance of the novel halide-free non-aqueous plating electrolytes on industrially relevant test parts, specifically Norton panels. This testing included the deposition of zinc on mild steel and copper-based Norton panels under various conditions, such as temperature, plating times, and applied currents. The research not only confirmed the technology's preliminary techno economic viability but also provided valuable insights into the behavior of the plating bath and the coating process.
The setup and tests carried out in this study on halide free non-aqueous systems stand out unique and are pioneering, , marking a significant milestone in the development of corrosion-resistant coatings obtained via electroplating using low toxic halide free non-aqueous electrolytes. In the next phase of the project, further trials are planned on other industrial test parts like fasteners and brake calipers, demonstrating the versatility and applicability of the technology. These test parts will be plated with zinc and zinc-based alloys using the novel halide-free non-aqueous plating electrolytes, showcasing the environmentally friendly aspects of the technology.
The innovation activities in this project have encompassed the selection of halide-free ILs, organic solutions and DESs, the development of coatings employing these electrolytes, and the rigorous testing and validation of the technology on real industrial test parts. The results of this work hold great promise for advancing corrosion protection and opening up new avenues for the use of halide-free non-aqueous plating electrolytes in various applications, with plans to showcase these innovations at exhibitions in the near future.
Project Achievements at a Glance: Illustrated Figure