What are 'ceramic' (or 'SiO2') coatings?
Updated: Oct 11
What is in a bottle of ceramic coating and how does it work? What is SiO2? Why do some products need applying professionally? And what about graphene?
Our chemical experts are going to answer all these questions and more within this article in the typical Black Diamond fashion - Straight to the point without any marketing rubbish. Keep reading for the real truths behind ceramic coatings. - We’re going to ruffle a few feathers with this one!
Ceramic coatings have become the gold standard in car paint protection, offering durability that traditional waxes simply can’t match. To any complete novices reading this who are wondering what these coatings are used for, it's actually very simple - they provide non stick protective finishes on automotive exteriors, much like a wax. A ceramic coating provides a water and dirt repellent finish which protects bodywork from the elements, reduces the likelihood of scratches and keeps the vehicle cleaner for longer. Unlike a wax though, they do not need regularly reapplying - some products even promise a set number of years of protection, although we’ve always found these claims hard to prove as in the real world durability hugely depends on a long list of external factors such as where the vehicle is stored and how it is cleaned.
However, not all ceramic coatings are the same. In fact, there are two main types, and they work in slightly different ways. Both coating types use reactive materials and so called ‘ceramic’ chemistry, which is where their name originates. However, almost all readers will probably be surprised to learn that despite common misconceptions and misleading labelling, neither type uses ‘SiO2’ as an active raw material. SiO2 is actually the chemical formula for quartz which is sometimes used in car care for surface polishing as an abrasive powder or as a thickening agent, but is virtually useless in its raw state for surface coating. Therefore ‘SiO2 infused’ on product labels carries little meaning and is often used simply for marketing. In reality it doesn’t tell you anything about how the product is really working. Here’s a breakdown of the two main coating types and the real chemistry behind them:
Type 1:
Polysilazane Based Coatings.
These are usually professionally applied and they use a special group of ingredients called polysilazanes - highly reactive materials which turn into a glass-like network when exposed to moisture.
What happens when you apply it?
Polysilazanes are made up of chains with Si–NH–Si (silazane) bonds.
When exposed to air and humidity, they react with water and oxygen to form Si–O–Si (siloxane) bonds.
This reaction also gives off ammonia (NH₃) as a byproduct - you might notice quite a strong ammonia odour from the product or during application.
The end result is a hard, microscopic shell made from silicon and oxygen atoms, similar to glass.
How is this useful?
These Si–O–Si bonds are extremely stable - they resist UV, heat, cleaning chemicals and can even protect against mild abrasions, vastly reducing the likelihood of swirl marks from washing.
The resulting coating is therefore extremely hardwearing and typically lasts between 1 to 5 years depending on the specific formula and subsequent maintenance.
The coating formulation is typically supported by hydrophobic additives which orientate themselves at the surface and provide fantastic water beading.
Future washing and drying on coated vehicles is therefore much faster and easier.
So what are the disadvantages?
They need very clean, dry paint to bond properly - prep is essential.
The polysilazane itself usually creates a slightly rough, grabby feel to paint surface, unlike the slick finish from waxing.
Curing typically takes 12 hours or longer and may even require heat. For best results the coating must be protected from rain and environmental contamination until fully cured.
The polysilazane itself is extremely sensitive to moisture which severely limits the types of products available. Polysilazane products must be solvent based and completely dry of water.
The products are pretty much single use - once opened the product comes in to contact with the air and begins to react with moisture, starting the curing process inside the bottle and severely reducing shelf life. This is why these types of professionally applied products almost always come in small, single use bottles.
They take practice to apply evenly and are even harder to remove if applied too thick. Once the product has set it is almost impossible to remove without sustained machine polishing, which is why they are usually applied by professionals and are generally not suitable for DIY or untrained users - application must be done correctly first time around or permanent streaks and blemishes may occur.
Type 2:
Siloxane Based Coatings And Other Sol-Gel Silanes
These are the more common of the two coating types and are often found in shampoos, snowfoams, polishes, sealants and spray on products. These are the ceramic products you’ll typically see on the shelf at your local automotive stores. They’re designed for easy DIY use and they typically use modified silicone resins called aminosiloxanes to provide impressive protection with minimal effort.
What happens when you apply it?
The main ingredients are usually aminoalkoxy siloxanes — these are silicone molecules with reactive –OCH₃ (methoxy) groups and amino groups (–NH₂).
When applied to the paint and exposed to air humidity, the methoxy groups react with water to form Si–OH (silanol) groups
The amino groups help to anchor the molecules to the surface and help catalyze this reaction, making it happen faster and more completely - even at room temperature.
The result is a thin, flexible protective layer of crosslinked silicone (Si–O–Si bonds), which is effectively bonded to your paint.
What does that mean in practice?
The result is a coherent film, like a resin, which bonds itself to the surface and repels water.
It creates a durable barrier which makes cleaning much easier and resists weathering and cleaning chemicals, typically lasting 4-12 months depending on the specific product, the degree of paint prep and subsequent weather exposure.
They give off much less ammonia odour in use.
They typically provide a high gloss and a slick finish similar to a more traditional wax.
These coatings usually have some degree of self-levelling, are easier to remove and have longer, more forgiving working times meaning they’re easy to apply evenly without streaks.
Aminoalkoxy siloxanes are less sensitive to water than polysilazanes - they can be emulsified and used in water based products such as detailers, rinse aids, snowfoams and shampoos.
The resulting coating compliments any existing coating on the vehicle,
including polysilazane - they are great for maintaining or 'topping up' polysilazane coatings. They are often added to shampoos specifically designed to prolong the life of professionally applied coatings.
They are ideal for home users or for regular use throughout the year.
What are graphene coatings?
So what is the difference between a ceramic coating and a 'graphene' coating? Graphene is a man made material which is made up of a single layer of carbon atoms which has many unique and useful properties. Scientists are still discovering areas where graphene can be extremely useful. From what we’ve seen, car care is not one of them… it is often added to sealant formulas which are then sold as graphene coatings. In truth these are usually just one of the coating types we've already covered but now with additional small graphene particles suspended in solution. However, it is common knowledge within the industry and in independent testing that in practice there is virtually no measurable improvement to the coating with these particles present, as they are mostly removed during buffing and those that do remain in the cured coating are unable to coat the surface in any meaningful way. Our own in house testing has never proven otherwise. Graphene is typically added only for marketing purposes as many consumers believe coatings containing graphene are a step up from the ceramic coatings we've already covered. This is why we do not add it to any of our own Black Diamond branded products and are always completely upfront with our white label and rebranding customers, only adding it when asked to.
When using a graphene coating, we recommend doing some research or using the points above to find out which of the two coating types already mentioned is doing the work. And then use it accordingly.
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