One of the main ingredients in Transhield’s anti-corrosion protective covers are vapor corrosion inhibitors, or as we like to call them, VCIs. Transhield’s patented VCI technology is a key component for reducing corrosion by up to 85 – 95% as compared to a standard tarp made out of vinyl or canvas. But what exactly are VCIs and how do they work? The short answer is that it’s a combination of physics and chemistry.
What is VCI?
Vapor corrosion inhibitor technology was first invented by the Shell Oil Company in 1949 for the purpose of protecting and preserving military equipment. The earliest VCI technology wasn’t the safest chemistry because it contained nitrates and nitrites and other harmful chemicals. But we’ve come a long way since 1949. Transhield’s VCI technology does not contain any amine nitrites, nitrosamines, chromates, phosphate or heavy metals. In fact, Transhield uses 100% “green” technology in all of it’s protective covers. Bottom line, Transhield protective covers are safe to handle and safe for the environment.
Now that we gotten the safety disclaimer out of the way, let’s talk about what VCIs are and how they work to reduce corrosion. VCIs are organic chemistries extracted from natural gas. They actually have many of the same chemical properties as fish oil, which is why some of the earliest Transhield covers smelled like fish when they were brand new off the production line (we’re happy to report that we’ve since changed the smell to something more like vanilla).
VCI’s are actually molecules that travel through space from the carrier (in this case the inside of the cover) to the metal the cover is protecting. VCI molecules contain an ion that gives off a charge that causes these molecules to be attracted to metal like a magnet. Once a Transhield cover is properly installed on equipment, VCIs begin to form a protective layer, usually no more than 5 to 7 molecules thick. This forms a protective barrier on the metal, which prevents moisture, salts, dirt and other airborne particles from reacting with the metal. VCIs essentially render the metal non-polar by disrupting the formation of anode and cathode regions.
Amount of VCI in a Cover
Customers often ask if there is a correlation between the effectiveness of an anti-corrosion cover and total amount of VCI it contains. First of all, there is enough VCI contained in a cover to outlast the normal lifespan of the cover, which is 2 – 4 years for XT and 3 – 5 years for ArmorDillo. But the truth is, effective corrosion reduction isn’t so much based on the amount of VCI contained in the cover but has more to do with the delivery rate to the metal being protected. Transhield protective covers have the most efficient and effective delivery rate of VCI to a metal surface than any other cover on the market today, bar none. Without getting too much further into the weeds, the delivery rate of VCI is governed by a very small pressure differential that builds up on the inside of the cover and can be explained by Fick’s laws of diffusion.
VCIs are most effective when they have the ability to volatilize and will typically travel up to 35 inches from the carrier unimpeded. In other words, bare metal within this 35-inch environment on the inside of a protective cover will be less susceptible to corrosion than metal that is in direct contact with the inside fabric of the cover. Testing has proven this every time.
The Value of VCI
So that leads us to answer the overall question of what compelling value does VCI technology bring to the corrosion fight?
When it comes to protecting metal, the first line of defense is a good coat of paint. It’s no secret that the U.S. military, as well as industrial manufacturers, spend a lot of money on expensive coatings, such as polysiloxane paints and powder coatings. Transhield’s VCI custom cover technology provides a valuable enhancement to these coatings based on several realities. First, all painted surfaces break down over time due to exposure to UV light from the sun – the #1 culprit of corrosion. But another major factor to consider – and often overlooked – is that all painted surfaces contain micro-cracks, usually unseen to the naked eye. Painted surfaces also have other microscopic imperfections, especially around corners and along curved surfaces, which expose bare metal to the outside environment. And this is where corrosion begins – at the microscopic level – and continues at a rate governed by oxygen concentration, temperature, relative humidity and the presence of soluble particles in the air.
This is precisely why an anti-corrosion protective cover that emits VCI provides a valuable enhancement to paint – because it can protect bare metal where paint does not, and protect it in a way that other fabrics like canvas or vinyl cannot.
If you have any questions about the technology, let us know!