How Carbon Nanotubes Contribute to High Strength
When used in protective coatings for steel, carbon nanotubes (CNTs) offer a wide host of benefits. Above all else, CNTs are best known for their incredible strength despite their nanoscopic size. They also offer unrivaled electrical conductivity and unique chemical and physical bonds, which makes them a prime choice for an offshore coating additive. To understand the magnitude of the improvements that CNTs can make in a coating, we must first understand the performance issues that fault traditional coatings.
The CNT Matrix in Coatings
A major issue with traditional protective coatings is that they rely solely on the strength of the film itself. While these coatings may demonstrate effective protection against creep in controlled weathering tests, real world applications often demonstrate drastically different results, namely expedited failure. The severity of conditions that these coatings are subjected to can decimate their lifespan from an anticipated cycle of 10~ years to an actual cycle of around only 2-5 years.
Here at Tesla, we integrate carbon nanotubes into many of our coatings. One of the most significant benefits of the addition of CNTs to our coatings is unrivaled strength and durability. TESLAN coatings have been shown to have a coating life of 2-5 times that of traditional coatings, depending on the environmental conditions that it is subjected to on a daily basis. This is how it works:
Consider the physical dimensions of a protective coating. While it may be relatively thin, there is an element of height to the coating- typically several microns thick. Within that coating film, the CNTs are inextricably bound to the epoxy polymer matrix at the atomic level, as the CNTs are almost incomprehensibly small. Most other additives- take glass flake, for example- inhibit the strength of the coating by effectively acting as voids which disturb the polymer matrix. Additives like this also have a tendency to disperse unevenly throughout the film so any desired physical properties such as permeation resistance will not be evenly distributed throughout the entire coating.
CNTs operate differently. Without the need for any external interference, the carbon nanotubes will arrange themselves in a way that forms something of a matrix or a network throughout the entire coating. They will not simply sink to the bottom, but they will occupy all three dimensions of the coating film which ensures that its properties will be equally effective between its outer surface and its core. The pattern that they follow is what gives TESLAN coatings their incredible strength. The CNTs act like rebar to physically reinforce the coating rather than inhibit its strength as other additives are prone to do.
CNTs Unique Bond with Polymers
Their unique structural pattern is not the only way that CNTs increase strength in TESLAN coatings. Another special property they possess is the ability to form a very stable and robust wet film that allows wet-on-wet application between our primers and topcoats without fear of runs, sags or solvent entrapment. This is thanks to the network that the CNTs form along with the unique way they bond to the polymer film in the coating. Unlike the glass flake additive that simply displaces the polymer, CNTs are inextricably bound with the epoxy polymer, further elevating the already incredible strength of the coating.
The Conductivity of Carbon Nanotubes
Zinc is an additive used in protective coatings, primarily to aid in cathodic protection. However, the epoxy polymers used in these coatings act as insulators and typically surround and isolate the zinc from contact with the steel. In order for zinc to be an effective anode, it must have direct electrical connection to the steel. To overcome the isolating effect of the epoxy polymer, zinc-filled coatings must be so heavily formulated with zinc that the coating film itself becomes fragile and weak. Said another way, there simply isn’t enough glue (epoxy) to hold the zinc powder together. The presence of these zinc particles reduces the overall impact resistance of the coating, leading to an increase in mechanical failures and more corrosion overall.
Thanks to their rebar-like structure and monolithic bonding properties, CNTs exponentially boost the conductivity of TESLAN coatings. This allows for our coatings to not only offer extreme physical protection, but also cathodic protection.
When steel comes into contact with an electrolyte like salt water, it will readily give up its valence electrons which is what causes oxidation to form. CNTs facilitate cathodic protection by connecting the zinc to the steel and allowing the zinc to give up its valence electrons which maintains the integrity of the steel asset. Since CNTs form a cohesive network throughout the entire film, they can transfer zinc electrons from any other part of the coating regardless of distance to the damage site. This allows for unmatched longevity of steel assets when they are protected with TESLAN.
Carbon Nanotube Coatings in Industry
The biggest problem with CNT coatings is that in theory, they just sound too good to be true. However, the reality is that they deliver on the promised benefits of increased strength, cathodic protection, and so much more.
A few of the main industries we serve here at Tesla include offshore, midstream, and marine industries. In all of these, maintenance work is often performed offshore. Offshore labor never comes cheap, so any chance to cut down on labor time is one worth taking.
TESLAN coatings don’t just cut labor time- they slash it. Where a traditional coating takes up to 5 days to apply, TESLAN only takes 1. This means that application of our coatings can be completed in just a single visit. The resultant time savings of the wet-on-wet application process gives TESLAN the lowest overall install cost when compared to similar coatings on the market. Best of all, the reduction of downtime offers yet another facet of financial savings. Gone are the days of applying coatings one small area at a time, closing the area off while the coating dries, then repeating the process in perpetual maintenance limbo. With TESLAN coatings, application can be completed in a fraction of the time, potentially saving millions in reduced downtime.
To learn more about Tesla NanoCoatings technologies, visit our About Page. If you’re interested in utilizing our coatings in your marine, offshore, or midstream operations, contact us today.
