A coating is a covering that is applied to the surface of an object. The purpose of applying the coating may be decorative, functional, or both. Coatings are ubiquitous and can be found on walls, furniture, on all sorts of wires and printed circuits, the outside of houses and cars, and much more. In addition, the decorative duties of coatings span quite a broad spectrum.
Decorative coatings are mainly used for their color, texture or other visual property. Functional coatings are applied to change the surface properties of the substrate, such as adhesion, wettability, corrosion resistance, wear resistance and more. In some cases, the coating adds an entirely new property such as a magnetic response or electrical conductivity and forms an essential part of the finished product.
Coatings may be used in various processes, that are roughly divided into: vapor deposition, spraying, chemical and electrochemical techniques, roll-to-roll coating processes and other, less prominent techniques.
Graphene is a two dimensional layer of carbon atoms, arranged in the form of a honeycomb lattice. It is touted as a “miracle material” because it is endowed with an abundance of astonishing traits - this thin, one atom thick substance is the lightest, strongest, thinnest material known to man, as well as the best heat and electricity conductor ever discovered - and the list does not end there. Graphene is the subject of relentless research and is thought to be able to revolutionize whole industries, as researchers work on many different kinds of graphene-based materials - each one with unique qualities and purpose.
The vast selection of extraordinary properties that graphene possesses can open the door to many interesting types of coatings, paints, inks and more. Graphene's high resistivity can make for durable coatings that do not crack and are resistant to water and oil; its excellent electrical and thermal conductivity can be used to make various conductive paints, and a strong barrier effect can contribute to extraordinary anti-oxidant, scratch-resistant and anti-UVA coatings.
Graphene enables a wide array of functional coatings and paints, for many possible applications. Among these can be high performance adhesives enabled by graphene's high adhesion property, anti-bacterial coatings, solar paints (capable of absorbing solar energy and transmitting it), paints that provide isolation for houses, anti-rust coatings, anti-fog paints and UV ray blockers, non-stick coatings for various domestic applications (like frying pans and countertops) and even a much-hyped possibility (currently under scientific examination) of a coating that turns a regular wall into a screen.
Graphene-enhanced products are yet to reach widespread commercialization. Nonetheless, given graphene’s impressive array of properties and the vigorous R&D that is taking place, graphene-enhanced coatings should not be too far away.
The Sixth Element Materials, a Chinese company that focuses on R&D, mass production and sales of graphene and related materials, showcased its graphene-zinc anti-corrosion primer used for offshore wind power tower, that can come at a competitive price compared with zinc rich epoxy primer.
Garmor, the University of Central Florida spin-off formed to develop a new graphene oxide flakes production process, has developed graphene oxide-based coatings useful for limiting UV radiation damage to sensors and polymers. Garmor's transparent GO-films are reportedly derived from a commercially-viable and scalable process that can be readily implemented with minimal constraints.
Four layers of GO coating on polycarbonate
The Spain-based Graphenano announced the launch of a graphene-based series of paints and coatings called Graphenstone in 2014. These are said to be very strong and also acts as a protective layer against environmental damage. Graphenstone is made from a graphene powder and limestone powder.
The British Electro Conductive Products released a sprayable transparent conductive coating based on a CNT and graphene platelets (GNP) hybrid material. TBA are targeting the food, electronics, pharmaceuticals and petrochemicals markets.The new ATEX-compliant product is available as a clear, anti-static aerosol, and it should also be available as bulk paint. Its application will safeguard electronic equipment used in explosive environments and bring it up to European standards.
Latest Graphene coating news
Versarien recently announced it will be collaborating with fire retardant coatings supplier Advanced Insulation to work on a graphene project.
The collaboration will focus on incorporating Versarien's Nanene few layer graphene nano-platelets into sub-sea insulation materials to improve tear resistance and reducing water absorption of these materials.
Greece-based industrial paint producer Hydroton has launched a new graphene-enhanced zinc epoxy paint - the 23303 ZINCTON GNC. This is a two-component epoxy based coating that offers improved cathodic protection due to the addition of the graphene, compared to epoxy zinc rich primers.
The new primer also offers improved adhesion to metal and as the zinc content is low, it is still cost effective. It is recommended for applications in highly corrosive environments.
Haydale has been jointly awarded a contract by the English Institute for Sport (‘EIS’) for the development of advanced wearable technology for elite athletes in training for the 2020 Olympic and Paralympic Games.
The EIS will use Haydale and its long-term partner the Welsh Centre for Printing and Coating at Swansea University to incorporate graphene coatings into a range of clothing for elite performers.
Earlier in 2018 Applied Graphene Materials (AGM) launched their Genable 3000 dispersion range - graphene based, active non-metallic, anti-corrosion additives. AGM has now reported results from further testing, which not only underlines the potential for significant anti-corrosion performance gains but also the products commercial attractiveness – particularly under harsher C4/C5 corrosive environments.
Incorporated into the formulation of an industry standard C3 epoxy primer system, and tested under representative cyclical salt spray testing (ASTM G-85-94 Prohesion), Genable 3000 series materials have been shown to deliver a 5-fold extension in coating lifetime, based on a single 60 micron dry film thickness. These results are supported by a detailed mechanical dataset and studies incorporating combination with a PU topcoat exploring intercoat adhesion and overcoating intervals. All results confirm the products attractiveness for development into commercial anti-corrosion systems.
Gilding is the process of coating intricate artifacts with precious metals. Ancient Egyptians and Chinese coated their sculptures with thin metal films using gilding—and these golden sculptures have resisted corrosion, wear, and environmental degradation for thousands of years.
Microscope image of a graphene crystal on a palladium leaf
In a new study at the University of Illinois at Urbana-Champaign, Sameh Tawfick was inspired by this ancient process and used it with a twist - he added a layer of graphene on top of palladium metal leaves—doubling the protective quality of gilding against wear and tear.