By Christopher Brown of OCDCarCare.com
Ceramic coating hydrophobics and hydrophobicity, the topics and terms appear nearly everywhere automotive ceramic coatings are marketed, advertised, or discussed.
But what do the terms “hydrophobics” and “hydrophobicity” actually mean for vehicle owners, car enthusiasts, and professional detailers?
Frankly, its often difficult to crawl past the marketing speak of products to understand how their benefits work.
This article was written because little to no practical information, explaining the science of hydrophobic properties (water behavior), exists to educate vehicle owners, consumers, or auto detailers.
This article’s concepts primarily focus toward the performance and characteristics of ceramic coating hydrophobics.
However, MOST of this information is applicable to understanding the surface characteristics for all last stage products. This includes ceramic nano coatings, waxes, and sealants.
Understanding how ceramic coating hydrophobics work will directly lead to greater long-term performance and satisfaction both for vehicle owners and professional detailers.
Ever Wonder HOW Automotive Ceramic Coating Hydrophobics (water behavior) work to:
- Cause water to quickly slide off a surface?
- Make vehicle car washing so fast and easy?
- Keep vehicles looking cleaner for longer?
. . . The Answer lies in a scientific concept: Surface Free Energy.
If any of these ^^^ explain why you’re reading this article– then know you’re in the right place!
Ceramic Coating Hydrophobics a.k.a. Water Behavior a.k.a. Surface Energy: What on Earth is that?
In auto detailing the concept of a ceramic coating’s hydrophobics, or water behavior, refers to how water (and sometimes light contaminants) interact with a vehicle’s surface. Specifically, the difficulty of water to rest and/or stick (adhere) to a ceramic coated automotive surface.
Low surface energy (short for ‘surface free energy‘) is the scientific concept responsible for the level of hydrophobic properties (water behavior) a ceramic coated surface displays.
Within general vehicle cleaning, low surface energy containts on a surface is good because it creates a hydrophobic surface, causing water beading and water sheeting.
Water beading is the surface condition where water quickly forms tight individual water droplets on a surface. The droplets must fall merge into one another to gain enough mass for gravity to pull them off a surface. Water sheeting is the surface condition where water tends to form into pools and the pooled water falls off a surface together like a sheet.
A ceramic coating’s water beading and water sheeting properties help automotive surfaces to remain cleaner for longer periods of time and make surfaces easier and faster to clean.
Understanding how a ceramic coating’s water behavior is achieved, and how it’s properly maintained, is important to modern high quality professional auto detailing.
In terms of ceramic nano coatings, the scientific concept of low surface energy explains the positive behavior of a hydrophobic surface on automotive surfaces.
This is important because hydrophobics (water behavior) is marketed, to detailers and vehicle owners, as a main selling point and key benefit to ceramic coated surfaces, saving owners time and frustration with quick and easy vehicle washing. Therefore, in-depth knowledge of conditions that promote low surface energy (hydrophobics) allows professional detailers a better understanding to maintain and troubleshoot potential ceramic coating surface issues.
For instance, frequently vehicle owners and even detailers are quick to claim some ceramic coatings “fail” when a coating’s hydrophobic properties have diminished or stopped.
Quite often, this is not a case of a “failure” at all. A ceramic coating’s hydrophobic (water behavior) characteristics are only one small aspect of overall coating protection. Furthermore, the sustained water behavior of a surface is dependent on many factors, not just the coating formulation alone.
Read on to explore the fickle nature of a ceramic coatings hydrophobic properties.
Learn how water behavior is only one aspect of a ceramic coating’s many protective characteristics.
How is Surface Energy Relevant and Important in Auto Detailing?
The level of free surface energy contained within automotive surface protection is rarely discussed, yet carries great significance in modern auto detailing. In fact, it is vital to the hydrophobics (water behavior) of any ceramic coated surface.
Since ceramic nano coatings are a standardized surface protection option within auto detailing, understanding surface energy (a.k.a. hydrophobic properties or ‘water behavior’) is more relevant today than ever.
Therefore, modern auto detailers should understand of the characteristics of how ceramic coatings work. This knowledge will prove invaluable for relevant issues that may arise around ceramic coating upkeep and maintenance.
Ceramic Coating Hydrophobic Properties: Scientific Terms & Concepts Defined
The following scientific terms are used to measure, test, define many characteristics about a ceramic coating’s hydrophobics (water behavior).
Surface Energy of a Ceramic Coating
Surface energy measures the surface tension of a solid piece of matter. Simply explained, surface tension measures the ability of water (liquid) to rest on a surface in a tight or loose formation. In regards to auto detailing and car care surface tension refers to how a liquid reacts to a vehicle’s surface.
High Surface Energy means a liquid will have great success adhering to and “wetting” that surface. Think of a pool of water on a sidewalk.
Low Surface Energy means a liquid has difficulty adhering or sticking to a surface, causing it to fall off the surface with relative ease. Think of droplets of water, quickly falling off the surface of an umbrella.
Contact Angle of a Ceramic Coating
Contact Angle measures how a liquid interacts with the surface energy of a vehicle’s surface. The higher the contact angle measurement, the more difficulty a liquid has adhering to a solid surface.
Contact angle analyzes how well a single droplet of water touches, or ‘wets’, a surface.
At a very high contact angle, say 145 degrees, water almost appears as three quarters of sphere sitting on top of a surface. With high contact angles, a small portion of the spherical droplet is touching (wetting) the surface.
At a low contact angle, say 30 degrees, a water droplet appears as a small wide pool. A droplet with a contact angle of 30 degrees mostly touches, or wets, the surface.
Most simply: contact angle quantifies the ‘wettability’ of a solid surface by a liquid.
Sliding Angle of a Ceramic Coating
Sliding Angle measures how easily water releases (slides) off of a surface in response to gravity. Specifically it measures the angle (and therefore the amount of gravitational force) at which a drop of water begins to fall down an incline on a surface. The lower the sliding angle the easier it is for water, and any topical contamination, to release, slide, or fall off of a surface.
Sliding angle is arguably more important than contact angle for measuring the effectiveness of a ceramic nano coating’s hydrophobic characteristics. This is because a low sliding angle typically indicates that water and contamination is easily removed from vehicle surfaces when cleaned.
A low sliding angle aids in many aspects of protection and automotive surface care. Low slide angles help ceramic coatings to avoid the creation of hard water spots left by the minerals deposits contained within evaporated water.
A low sliding angle greatly aids in the ‘self cleaning’ ability of ceramic coating formulations. This is because water sliding down a surface has the chance to pick up and embed surface contamination within itself, potentially removing the contamination entirely from the surface.
Note: It’s important to understand that when measuring slide angle, water sources should include those which average vehicles owners typically encounter. This includes garden hoses (with varying nozzles), pressure washers, spray bottles, or rain. This is noteworthy because many of these sources tend to apply water to surfaces in small drops which quickly combine into larger droplets. However, slide angle testing could be easily manipulated by using machinery to create excessively large drops, or pool of water that will naturally tend to fall off most surfaces, due to the gravitational pull from a large body of water.
Hydrophobics of a Ceramic Coating
In auto detailing and car care the term “Hydrophobics”, or “Hydrophobicity” refers to the tendency (and measure) of water to either rest on or ‘wet’ a surface. Generally the discussion of hydrophobics references how easily water is shed from a surface– a.k.a. its water behavior.
Hydrophobic literally translates to “fear of water.” A surface is Hydrophobic when liquid contacting it demonstrates a contact angle of 90 degrees or greater. This indicates low surface energy levels.
Hydrophobic surfaces are hard to wet; they reject water.
Think of a new umbrella; pouring rain water quickly beads up, falling off the surface. It is very difficult to wet an umbrella because its surface contains a low surface energy which creates very a high contact angle of any water contacting the surface.
Note: The concepts of Hydrophobic and Hydrophilic both utilize the concept of contact angle to define how a solid surface interacts with liquid.
In contrast, the word Hydrophilic means “friend of water.” Hydrophilic surfaces have water contact angles below 90 degrees. These surfaces demonstrate high surface energy levels.
Hydrophilic surfaces are easy to wet; they accept water.
A perfect example of a hydrophilic surface is hose water contacting a sidewalk. The water easily rests onto the concrete sidewalk. There is almost no discernible difference between the water and the concrete. The water seems to fuse with and darken the concrete, almost fully wetting it.
Beading | Water Beading | Water Beads of a Ceramic Coating
The terms “Beading,” “Water beading,” and “Water beads” refer to the tight, individual, mostly spherical shaped water droplets forming on an automotive surface.
Surfaces which display water beads on their surface are hydrophobic in nature. The more a water bead resembles a complete sphere, sitting on top of a surface, the higher the droplet’s contact angle on that surface.
Typically water beads sit or rest on horizontal automotive surfaces which are immune from the forces of gravity. However, when a vehicle moves the airflow easily pushes the liquid beads on horizontal surfaces to slide off the surface.
Sheeting | Water Sheeting of a Ceramic Coating
The terms “Sheeting” or “Water Sheeting” or “Release Properties” refer to a surface with a tendency to quickly release liquids from the surface. A surface with a strong tendency to ‘sheet’ liquid off itself will hold less liquid on its surface.
The easier a surface ‘sheets’ liquid off itself is directly related to its sliding angle. Surfaces with extremely low sliding angles do not need much gravitational force for liquid to fall off. This is important because sheeting automotive horizontal panels, which are immune to or have a greatly reduced ability for liquids to fall off the surface, will contain less liquid resting on their surfaces over time.
In terms of ceramic coatings, surfaces that display sheeting are still hydrophobic in nature. The less water that sits on a surface, directly correlates to a lower sliding angle.
Sheeting is arguably the best and/or most important attribute of a ceramic coating’s water behavior. This is because it greatly aids in the ‘self cleaning’ effect and the avoidance of water spots. Due to a low slide angle, liquid cannot sit on a surface and quickly evacuated the surface. As this liquid slides down the panel it potentially picks up and removes much or all the contamination it contacts from the surface.
Some may argue that a hydrophilic surface is the best way to obtain the best sheeting surface. However, a baseline of hydrophobiticy is necessary to more quickly move the water in order to fully vacate liquid from a surface.
How Topical Contamination Changes a Vehicle’s Hydrophobic Surface Behavior
ALL vehicle protection options including ceramic coatings, waxes, and sealants are partially engineered to protect vehicles by keeping surfaces clean.
The level of surface energy an automotive protection product provides accounts for its ability to repel contaminants and liquid off of automotive surfaces.
Surface energy scientifically explains how ceramic coatings and waxes ‘bead’ and some ceramic coatings ‘sheet’ water off a surface.
When any form of contamination, such as dust, sap, pollen, overspray, fine chemicals, etc. falls onto a vehicle panel and stick, the hydrophobic (water behavior) properties of that surface may begin to diminish. Hydrophobic properties may also diminish when layering another type of protection on top an already existing layer of protection.
The only way to preserve optimal water behavior of a ceramic coating, sealant, or wax is by keeping a regular vehicle wash schedule. Regular vehicle washing keeps vehicle surfaces clear of contaminants that may land and bond to the surface. This is the only way to ensure automotive surface protection retains its hydrophobic properties for extended periods of time.
When vehicle surfaces are NOT cleaned regularly, topical contamination layers form on the surface. They layer on top of one another like a brick wall over time. The dust and contamination from the day are the bricks. Dew or light precipitation is the mortar that locks in the contamination from the previous day.
Without a regular vehicle wash routine, topical contamination layers stack up enough to completely cover and overtake the ceramic coating’s surface. When this occurs the hydrophobic properties of the vehicle surface display the water behavior of the contamination. This results because the surface contamination is now directly reacting with the environment.
This is why the understanding how surface energy affects hydrophobic characteristics, and how to maintain them through proper washing intervals, is critical to ceramic coating surface performance and longevity.
Speaking of ceramic coatings specifically; often the public, or even some detailers, quickly proclaim a coating has failed when it stops displaying positive hydrophobic properties. This is not entirely the case when investigating the matter at a surface level.
Most times, a proclaimed coating “failure” is due to topical contamination resting or bonding on top of the coating. This contamination may drastically alter the surface energy characteristics of the surface, masking most or all of the coating’s water behavior.
High Surface Energy. This surface accepts liquid and is therefore ‘wettable’ meaning liquid has the ability to dwell on the surface.
Proper Products for “Layering” or “Toping” Ceramic Nano Coatings
As a wax, Swissvax Concourso is a stunning choice for automotive finishing. Its high carnauba content causes vehicles to glow with a sexy cinematic halo around them.
However, if a vehicle has a ceramic nano coating applied to its surface, then wax is NOT the correct product to maintain it with. Even if the intent is to add an additional sacrificial barrier of protection.
The ONLY thing to ‘layer’ or ‘top’ a coating with is a long term silica sealant or another semi permanent coating product.
It is highly recommended, that any topper product should remain in the same chemical family as the ceramic coating. Remaining within a chemical family helps ensure the topper product applied to a ceramic coating maintains the continuity of the coating’s original water behavior. Additionally, products from the same chemical family ensures optimal adhesion of the topical product to the ceramic coating.
Putting anything else over a ceramic paint coating, other than these types of topper products, alters the surface energy for the worse.
As stated previously, some protection characteristics of an automotive ceramic coating depend on the ability to remain hydrophobic. This ability is maintained through low surface energy. Applying the wrong product on top of a coating can change the water behavior for the worse and negate some of the protection benefits a ceramic coating provides.
The Fickle Nature of a Ceramic Coating’s Hydrophobics (Water Behavior)
The hydrophobic properties (water behavior) of an automotive ceramic coating are the easiest performance characteristics to verify. However, they are extremely fickle if not maintained properly or are neglected for long periods of time.
It is quite simple to negatively alter the water behavior of a coating. This is the exact reason why most coatings companies insist on or stress regular wash intervals for coated vehicle surfaces.
With a regular vehicle washing routine, surfaces stay clean and smooth by avoiding topical bonded contamination build up. A regularly cleaned surface allows a coating’s water behavior to function at peak levels. This occurs because the coating’s hydrophobic properties directly interact with the environment. This allows vehicle owners and auto detailers to easily identify the coating’s significant hydrophobic properties.
Ease of maintenance, and the ability to keep vehicle surfaces clean, are prime benefits and selling points of ceramic nano coating technology. These traits only occur when the coating maintains its original hydrophobic properties of low surface energy.
In short, vehicles must be washed regularly to maintain an automotive ceramic coating’s optimal water behavior characteristics and longevity.
For a more in-depth look into vehicle washing benefits and a method to determine how often you should wash your vehicle, read our article “Detailing DIY How To: How Often Should I Wash my Car?“
Auto Detailing and Misinterpretations of Ceramic Coating Water Behavior
A change in a vehicles hydrophobics, or water behavior, alone is never a reliable indication of a coating failure.
Hydrophobic ‘failure’ could easily happen by smearing olive oil or grease over a coated section. Whatever residue remained after wiping off the oil or grease would negatively alter the water behavior of that coated section. The coating’s hydrophobics would appear very weak or possible completely gone in the areas with oil and grease residue.
This example clearly indicates that surface energy of these areas has shifted away from the ideal characteristics of the coating to the properties of the left over oil or grease. This does not automatically mean coating failure, but rather the hydrophobic properties are masked by whatever rests on top of the coating.
Often, vehicle owners or detailers form snap judgements or conclusions about ceramic coating effectiveness or durability based on hydrophobic properties.
Frequently these opinions are without a true or full understanding of the principals behind vehicle surface energy. This type of uninformed dialogue floods literally hundreds of online forums and social media groups, many times marketing related.
Let’s set the record straight:
Hydrophobics, or Water Behavior, alone do not provide an accurate picture of an automotive ceramic nano coating’s overall protection characteristics.
Hydrophobics are only one, highly specific aspect of the overall protection offered by ceramic coatings.
When a coating ‘fails’ to produce water beading or sheeting, most times topical surface contamination is the culprit. Surface contamination generally builds up from neglecting to execute regular cleanings or from a heavy and durable contaminant.
Final Words on Ceramic Coating Hydrophobics in Auto Detailing
Vehicle surfaces require regular maintenance (washing) to keep them free of topical contamination. Clean surfaces optimize the hydrophic properties (water behavior) of all surface protection, including ceramic nano coatings, sealants, and waxes.
If surface contamination builds up enough it becomes the vehicle’s surface. Eventually, contaminated vehicle panels adopt the surface energy (hydrophobic) properties of this outermost contamination layer. A surface completely covered by topical contamination no longer beads or sheets water.
Lack of water beading or sheeting is not a clear indication that a ceramic coating has automatically failed. Most likely, the surface contamination is masking the ceramic coating’s hydrophobic properties.
If a coating exhibits poor hydrophobics or water behavior, its other protective qualities are not automatically gone. A ceramic nano coating’s benefits and protective capabilities of: UV protection, chemical resistance, enhanced ‘hardness’, gloss, and measurable thickness; do not vanish if the surface does not bead or sheet liquid.
The myth exists within the detailing world that a coating’s overall quality and durability relate directly to water behavior. Unfortunately, some individuals boldly proclaim complete coating failures within 6 months, due to a lack of hydrophobic water behavior on vehicle surfaces. This is definitely not always the case.
**Warning: Next time you think a ceramic nano coating or wax is ‘bad’ or has ‘failed’, first consider the vehicle panel’s hydrophobic properties realted to surface energy. Surface energy plays a critical role in surface care within automotive detailing. Understanding of the science of, and properties associated with, surface energy will arm detailers with knowledge to better troublehoot potential ceramic coating surface issues.
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