Electroless Coating: Advances & Future Prospectives

Coatings have played a vital role in the history of materials science and engineering since the times of ancient Egypt and China. Either as a protective simple layer for artefacts and paintings or as a naturally formed one due to oxidation, coatings have been found in various samples that goes back to more than 2000 years ago. In our modern times, much more sophisticated coatings are produced to enhance the performance, durability, and sustainability of various materials and in a wide range of industries. Today we explore a coating technique that depends on electrochemical reactions but without the use of an external current. It is the electroless metal deposition, i.e. chemical deposition. Similarly to previous editions of this newsletter, we represent the discussion in simple materials science terms for an audience of early stage researchers, combined with some latest trends in the field to provide interesting insights for experienced and established researchers.

Electroless coating is a technique that involves depositing a metal layer (like nickel, boron, and/or phosphorus) on a substrate without the use of external electric current. It is also known as electroless plating or chemical deposition. This is done typically in an aqueous solution using a chemical reduction process, a chemically reducing agent, and a complex catalytic process. Electroless coating, therefore, depends on the thermodynamic and kinetic properties of the electrochemical reactions involved in the process and is driven by the potential energy difference between the two half-cell reactions. For further details of the fundamentals of electroless plating, we recommend the book: “Electroless Nickel Plating: Fundamentals to Applications”, edited by Prof. Véronique Vitry , Prof. Fabienne Delaunois , and Dr. Ing. Luiza Bonin [1].

For its uniform thickness and strong adhesion properties, electroless coating is used without the need of an external current. In the last three decades, the research in this field has tremendously advanced our understanding of electroless coatings, their process, and their various applications not only in the traditional fields of corrosion and wear resistance but also in more advanced prospective application.

This edition of ‘Materials Insights’ newsletter represents a summary of ongoing innovations within the field of electroless coating research, highlighting opportunities for further research and development. Aiming to foster engagement and knowledge sharing in the scientific community, this edition invites the readers to a discussion about various material innovations related to the development of electroless coatings and their possible applications in fields such as smart materials, capacitors, wearables, and hydrogen management systems.

Recent Developments and Trends

The development of electroless deposition, coatings compositions, and properties has tremendously increased in the last thirty years. In this edition of the ‘Materials Insights’ newsletter, we scan the recent new advancements and techniques within this field, exploring the role of materials science and engineering in developing new solutions, eying the transfer and scalability of these techniques from the lab-scale to the industrial-scale.

Ultrasound Assistance:

Although its mechanism is not yet fully understood, using low-frequency ultrasound can enhance the deposition rate and the properties of the deposited layer. Vitry et al have listed lately this trend among various other trends in the literature review of: “Recent advances in electroless nickel?boron coatings” [2]. See more here: https://www.sciencedirect.com/science/article/abs/pii/S0257897221011117

Advances in Coating Composition by Co-Deposition: (Composite, Multilayer, Polyalloys, and Graded Coatings):

Research by Mandal et al [3] has also been conducted on optimizing the composition of electroless composite coatings of Ni-W-P-nanoTiO2, aiming to enhance their performance for pipeline steel applications. The optimization focuses on the deposition rates and the integration of nanoparticles to improve the mechanical and electrochemical properties of the coatings. See more here: https://link.springer.com/article/10.1007/s13369-023-07928-0

Another example was reviewed by Chintada et al on the electroless Ni-P-SiC composite coatings, offering improved corrosion resistance and mechanical properties. These coatings are particularly relevant for applications requiring high durability and resistance to harsh environments. This review by Chintada et al has explored these advances among the state of the art of electroless Ni-bases electroless plating, focusing on Ni–P, Ni–B, and its composite coatings co-deposited with various micro and nano particles [4]. See more here: https://link.springer.com/article/10.1007/s40735-021-00568-7

Various other techniques of multilayer deposition, polyalloys, and composites have been reviewed recently by Vitry et al [2] showing the versatile advances provided by electroless deposition to improve surface properties by introducing outstanding mechanical and electrochemical properties. Combined with post-process heat treatments, these techniques increase the corrosion and wear resistance through grain refinement and other mechanisms. Further details can be seen in the book referred to at the beginning of this article [1], in addition to a summary in the review paper here [2]: https://www.sciencedirect.com/science/article/abs/pii/S0257897221011117

Electroless Deposition of Ni-W-P Films for Electrochemical Hydrogen Evolution:

Exploring the application in improving the hydrogen evolution reaction (HER), Asgari et al [5] investigated electroless Ni-W-P coatings, optimizing the electrocatalytic behavior by controlling the phosphorus and tungsten content, which demonstrates an improved performance of the deposited coating. See more here: https://www.sciencedirect.com/science/article/abs/pii/S0025540823001733

Electrocatalytic Properties for Hydrogen Evolution:

Electroless Ni-P coatings have been investigated by Chakarova and Monev [6] for their electrocatalytic activity towards the hydrogen evolution reaction in alkaline solutions. By varying the phosphorus content, the properties of these coatings and their catalytic performance were improved. This capability makes them promising candidates for hydrogen production by water electrolysis. See more here: https://link.springer.com/article/10.1007/s12678-022-00791-x

Application Challenges in Hydrogen Systems:

An in-depth examination of how hydrogen affects electroless nickel-plated materials was done by Shin and Kim [7]. In order to develop durable materials for hydrogen fuel cell electric vehicles (FCEVs), this research studies the electroless-plated hydrogen valves as a critical component of the hydrogen system. In addition, it investigates the accompanied hydrogen embrittlement, a phenomenon where hydrogen atoms diffuse into the metal, leading usually to cracking and eventually component failure. Therefore, despite the advantages of electroless nickel plating in enhancing mechanical characteristics, its performance under hydrogen-rich environments is still an ongoing dearea for development. See more here: https://journals.plos.org/plosone/article?id=10.1371/journal.pone.0302972

Co-Authorship Network Visualization of Some Publications in Electroless Coating:

There is a vast number of publications in the field of electroless plating since its discovery in 1946 [2]. The focus on this technique has increased recently due to its advantages and its industrial interest.

The following figures have been obtained using VOSviewer [8], a software tool for constructing and visualizing bibliometric networks. It allows users to create and explore maps based on the publication network data: including co-authorship, citation, co-occurrence, and bibliographic coupling. However, the results of the figures are highly dependant on the keywords used in the search for publications on bibliographic libraries. Therefore, extra care should be taken to filter irrelevant data from the search results. See more here: https://www.vosviewer.com/

Surface modification electroless deposition catalysis - co-authorship network visualization (year overlay) - weights by citation.

Electroless coating in relation to hydrogen - co-authorship network visualization (year overlay) - weights by citation.

Electroless coating in relation to smart applications - co-authorship network visualization (year overlay) - weights by citation.

Active Companies Worldwide for Electroless Plating:

These examples illustrate an active engagement of the industrial sector in enhancing and applying electroless deposition technologies across various high-quality industries.

UCT Coatings:

UCT Coatings INC is a leading provider of nickel-boron coating services, offering high-quality, wear-resistant, and low-friction coatings for metal parts with complex geometry. Their services and patented EXO nickel boron coating technology is regarded as a reliable industrial solution, which are applicable in several industrial fields such as: aerospace, automotive, oil & gas sector, saw blades, etc. See more here: https://www.uctcoatings.com/

PacTech:

A notable example in Europe is PacTech, a company that specializes in electroless plating services. It offers various solutions for electroless nickel plating to a wide range of industrial sectors, establishing itself as a competitive player in the field. See more here: https://pactech.com/wafer-level-packaging-services/electroless-plating-service/

Tompkins Metal Finishing

Located in New York, Tompkins Metal Finishing Inc is known for its various range of electroless nickel plating services. It offers nickel-phosphorus plating with a varying phosphorus content to adjust the properties of the deposited layer for various industrial applications. See more here: https://www.tompkinsmetalfinishing.com/

ENS Technology

Based in California, Ens Technology provides a broad variety of metal plating and finishing services, including electroless nickel plating. Backed by a fully equipped analytical lab and industry specifications, ENS provide coating services on different substrates, which are required by a wide range of industrial customers. See more here: https://www.enstechnology.com/

Opportunities for R&D:

The ongoing research of electroless coatings shows prospective solutions for various industrial applications. Nevertheless, to harness these advantage, it is vital to improve our understanding of its fundamentals as well as to expand its applications. On the other hand, it is essential to increase the scalability of electroless plating in order to facilitate and further increase the lab-to-industry transfer.

The following insights suggest some opportunities for R&D to further develop this technology:

1. Sustainable Approaches and Recyclability

While recent advances in layer composition and lab procedures are reshaping the future of electroless plating applications, the integration of eco-design principles can offer further advances of this field in particular and of material science methodologies in general. This integration is necessary to approach a sustainable reuse, refurbish, and/or up-cycling of produced materials as well as the chemical used in their production. Similarly to ecodesign, materials scientists can put into consideration all the steps of the material development into consideration from the choice of materials selection to the recycling of the end products. This can facilitates all possible sustainable practices, such as reducing consumption, reusing materials, refurbishing components, or recycling end-products.

In electroless coating, further research on bath replenishment and recycling is needed to develop sustainable procedures for the industry sector. A cooperation between industrial and research partners as well as sustainable supply chain networks is needed to accelerate the development of electroless plating sustainability as well as the standardization of best practices.

2. Long-Term Durability and Sustainability

While advancements in electroless coatings demonstrate an enhanced immediate performance, there is often a lack of long-term data under real-world environmental conditions. Future research could focus on the long-term studies and the performance of these materials under variable environmental factors.

3. Industrial Scalability and Cost-Effectiveness

While there is an intensive research on electroless coating, there is a need to further develop its scalability to the industry, cost-effectiveness, and new processing techniques.

4. Exploring New Applications

In the review paper by Vitry et al [2], one of the highlighted suggestions for further R&D was investigating of new fields of applications for electroless nickel-boron coatings. The paper highlighted that conductivity and catalytic activity of the technique present a possible thrilling features for the areas of water splitting and capacitors. Recent publications by Zhang et al [9], Czagany et al [10], Bhuiyan et al [11], and Hassan et al [12] validate this proposed application in the production of capacitors and wearables. See more here:

https://pubs.acs.org/doi/abs/10.1021/acssuschemeng.1c04613

https://www.mdpi.com/2075-4701/13/7/1233

https://pubs.acs.org/doi/abs/10.1021/acsami.1c01890

https://www.tandfonline.com/doi/abs/10.1080/00405000.2023.2225706

5. Detailed Performance Metrics

Studies often focus on specific attributes of materials, such as corrosion resistance or mechanical properties, without a holistic approach to evaluating performance across multiple metrics. Future research could develop more integrated performance evaluation frameworks that consider mechanical properties, cost, environmental impact, and functionality simultaneously.

6. Advanced Characterization Techniques

While current studies utilize advanced characterization techniques, combining both experimental and theoretical techniques can lead toward a multi-scale understanding of metallurgical processes at the macro, micro, and nano scales. This can advance not only our understanding of the materials and processes but also the development of novel materials and properties tailored to specific industrial applications.

7. Regulatory and Safety Standards

As new materials and coatings are developed, particularly for critical applications like hydrogen storage, there is a lag in developing corresponding regulatory and safety standards. Research into the implications of new materials on safety and the development of appropriate guidelines is needed.

Addressing these opportunities would enhance the functionality and applicability of new materials, in addition to ensuring their safety, sustainability, and integration into existing systems and global markets.

Thank you for reading our newsletter. Stay tuned to our next edition in September and visit our Linkedin page, Innovate Academy , and our Website: www.innovate.academy

Feel free to share this newsletter within your network and spark a conversation about electroless coatings and various innovations in materials science and engineering.

Bibliography:

[1] Delaunois, F., Vitry, V. and Bonin, L. eds., 2019. Electroless nickel plating: fundamentals to applications. CRC Press.

[2] Vitry, V., Hastir, J., Mégret, A., Yazdani, S., Yunacti, M. and Bonin, L., 2022. Recent advances in electroless nickel?boron coatings. Surface and Coatings Technology, 429, p.127937. https://doi.org/10.1016/j.surfcoat.2021.127937

[3] Mandal, B.B., Kumar, V. and Oraon, B., 2024. Optimization, Prediction, and Characterization of Electroless Ni-WP-nanoTiO2 Composite Coatings on Pipeline Steel. Arabian Journal for Science and Engineering, 49(2), pp.1643-1657. ? https://doi.org/10.1007/s13369-023-07928-0

[4] Chintada, V.B., Koona, R. and Raju Bahubalendruni, M.V.A., 2021. State of art review on nickel-based electroless coatings and materials. Journal of Bio-and Tribo-Corrosion, 7(4), p.134. https://doi.org/10.1007/s40735-021-00568-7

[5] Asgari, M., Abedi, B., Ashrafi, A., Darband, G.B. and Monirvaghefi, M., 2023. Electroless deposition of Ni-WP films as binder-free, efficient and durable electrode for electrochemical hydrogen evolution. Materials Research Bulletin, 166, p.112318. https://doi.org/10.1016/j.materresbull.2023.112318

[6] Chakarova, V. and Monev, M., 2023. Electrocatalytic properties of electroless Ni–P coatings towards hydrogen evolution reaction in alkaline solution: Ni–P coatings deposited on steel substrate at different concentrations of sodium hypophosphite. Electrocatalysis, 14(2), pp.259-266. https://doi.org/10.1007/s12678-022-00791-x

[7] Shin, D.-H., & Kim, S.-J. (2024). Effects of hydrogen permeation on the mechanical characteristics of electroless nickel-plated free-cutting steel for application to the hydrogen valves of hydrogen fuel cell electric vehicles. PLoS ONE, 19(5), e0302972. https://doi.org/10.1371/journal.pone.0302972

[8] Van Eck, N.J. and Waltman, L., 2011. Text mining and visualization using VOSviewer. arXiv preprint arXiv:1109.2058.? https://doi.org/10.48550/arXiv.1109.2058

[9] Zhang, Y., Zhang, T., Shi, H., Liu, Q., Shi, Y. and Wang, T., 2021. Electroless plating cycle process for high-conductivity flexible printed circuits. ACS Sustainable Chemistry & Engineering, 9(35), pp.11991-12004. https://doi.org/10.1021/acssuschemeng.1c04613

[10] Czagany, M., Hompoth, S., Windisch, M. and Baumli, P., 2023. Investigation of the supercapacitive behavior of electroless Ni-B coatings. Metals, 13(7), p.1233. https://doi.org/10.3390/met13071233

[11] Hossain Bhuiyan, M.E., Moreno, S., Wang, C. and Minary-Jolandan, M., 2021. Interconnect fabrication by electroless plating on 3D-printed electroplated patterns. ACS Applied Materials & Interfaces, 13(16), pp.19271-19281. https://doi.org/10.1021/acsami.1c01890

[12] Hassan, Z., Atalay, O., Kalaoglu, F., Ozat, F.A., Ozdemir, O. and Kesimci, M.O., 2024. Development and characterization of conductive textile (polyester fabric) for wearable electronics by using electroless metallization. The Journal of The Textile Institute, 115(8), pp.1312-1324. https://doi.org/10.1080/00405000.2023.2225706

Declaration of the use of generative AI:

This text has been produced partly using ChatGPT and partly by the author (about 50%). The figures were produced using Canva , OpenAI ’s ChatGPT and VOSviewer. The author has spent substantial efforts in authenticating and validating the information produced by the various AI tools, through revising, filtering, and comparing all publications mentioned in this article. If there is any piece of information that are inaccurate due to such a mix of both human and machine productivity, please feel free to contact us. We value the objectivity and reliability of our produced text and look forward to your feedback.

Acknowledgement:

Special thanks to Prof Véronique Vitry for providing the possibility to read the review paper on recent advances in electroless nickel?boron coatings, which was a guiding roadmap for the synthesis and validation of the explored advances and fundamentals of this technology.