I am a postgraduate researcher at the University of Leeds. I have completed my master's degree in the Erasmus Tribos program at the University of Leeds, University of Ljubljana, and University of Coimbra and my bachelor's degree in Mechanical Engineering from VTU in NMIT, India. I am an editor and social networking manager at TriboNet. I have a YouTube channel called Tribo Geek where I upload videos on travel, research life, and topics for master's and PhD students.
Nanocomposite Coatings
Table of Contents
Introduction
In industrial systems, corrosion and tribological issues such as friction and wear significantly impact components performance and operational longevity. This results in substantial energy and material losses and economic setbacks. Consequently, there is a growing focus on developing strategies for anticorrosion and antifriction/wear surface protection. Coatings have emerged as an efficient and proven solution in this regard. However, designing and developing coatings tailored to specific substrates, applications, and operating environments presents challenges due to various influencing parameters like thickness, grain size, and adhesion. Understanding the physical and chemical phenomena of coating-substrate systems requires interdisciplinary knowledge encompassing materials science, solid mechanics, and electrochemistry. Moreover, coatings in real-world applications endure a wide range of temperatures, affecting component service life and potentially exposing underlying substrates to corrosive environments or increasing friction and wear under tribological conditions.
Types of Nanocomposite coatings
The field of nanotechnology has seen a rapid expansion in the development of nanocomposite coatings. These coatings are increasingly finding applications across various sectors, including aerospace, marine, automotive, sensors, dental implants, and electronics. The functionality of nanocomposite coatings is influenced by several factors, such as the properties of matrices and fillers, the spatial dispersion of fillers, surface morphology, and deposition techniques.
Polymer matrix nanocomposite coating
Polymer nanocomposite coatings utilizing polymers as matrices have gained significant attention for their anticorrosion applications. By incorporating nanomaterial fillers into polymer matrices helps in enhancing various properties, such as stiffness, strength, corrosion resistance, and wear resistance. For instance, nanostructured chitosan/ZnO coatings have demonstrated the ability to mitigate corrosion on mild steel, with corrosion resistance improving with an increasing number of layers. Additionally, a nanocomposite coating comprising oleic acid-modified chitosan/graphene oxide on carbon steel exhibited a significant enhancement in corrosion resistance, attributed to reduced hydrophilicity, oxygen permeability, and ion transport within the coating.
Figure-1 Polymer based nanocoating [3]
Waterborne Polymer Nanocomposite Coatings
Volatile organic compounds (VOCs) are commonly employed as plasticizers in paints to aid polymer dispersion and enhance flexibility. However, their use poses severe environmental risks. In response, waterborne polymer coatings have been developed, utilizing water as a solvent instead of VOCs. Compared to VOCs, waterborne coatings offer numerous advantages, including eco-friendliness, low viscosity, ease of cleaning, and non-toxicity. Researchers have explored the corrosion behavior of polymer-based waterborne coatings integrated with nanoparticles like Fe3O4, Fe2O3, and ZnO, seeking to enhance their protective properties.
Figure-2 Film formation of waterborne coatings [4]
Metallic Matrix Nanocomposite Coatings
To enhance corrosion resistance, reinforcements such as ceramic nanoparticles and carbon nanotubes are integrated into metallic matrices to create nanocomposite coatings. Several examples illustrate this approach. Incorporating SiC nanoparticles into Ni and Ni alloys have been shown to improve the corrosion resistance of the resulting nanocomposite coatings. Similarly, Ni-P electroless coatings infused with SiC, Al2O3, and CeO2 nanoparticles demonstrated enhanced anticorrosion properties in NaCl and H2SO4 solutions. Furthermore, the addition of nanoparticles of SiO2, Al2O3, and CeO2 to Ni-P electroless coatings led to improved corrosion resistance in similar environments.
Figure-3 Photos of the applied powder Stellite Grade 12 HMSP 2541, Osprey [5]
Tribological Challenges
The development and synthesis of nanostructured coatings for achieving both anticorrosion and desired tribological performance face several practical challenges. These challenges include selecting the appropriate nanocoating material that is compatible with the substrate and operating environment. Factors such as ease of deposition, particularly for substrates with complex geometry or varying sizes, and adhesion to the substrate must be considered. Additionally, choosing the right reinforcement or filler for the coating material and application is crucial. Factors such as mechanical compatibility and thermal expansion mismatch with the matrix material need to be addressed. Dealing with the chemical complexity involved in synthesizing nanocoating can also pose challenges in achieving desired properties. Ensuring cost and time effectiveness in the development and deployment of nanocoating is essential, considering factors such as material cost, synthesis methods, and application processes. Moreover, having the capability to apply nanocoating over large surface areas efficiently and effectively is vital. Finally, ensuring long-term performance and maintenance of the nanocoating, including considerations for durability, degradation mechanisms, and repairability over time, is crucial for their practical application.
Reference
[2] https://www.paryleneconformalcoating.com/conformal-coating-education-center/nano-coatings/
