Monday, 21 September 2015

Automotive Paint Systems Part I

There is a plethora of information available on the various abrasive compounds, chemical cleaning fluids and paint protection products that can be applied,  but understanding the paint itself seems critical to detailing excellence.

The Basics
All paints are made up of three ingredients: binder, pigment, and a carrier agent. Pigment, or tint, is self-explanatory-it's the colour you see. Binder is often referred to as resin, and it can be helpful to think of it like tree sap, that thick, sticky hydrocarbon liquid that hardens when exposed to air. And carrier agent refers to the solution (water or solvent) that the resin is suspended in. It keeps the binder in liquid form until it is applied, at which time it either evaporates or chemically bonds to the surface of the car.

In general, urethane and enamel refer to the chemistry of the hydrocarbon polymers that form the resin (binder) of the paint. And that chemistry affects the look and durability of the finish, how it is sprayed on the car. Most new cars are painted with a type of urethane, and most collision repair shops use urethane to repair damage.

OEM Finishes
Consistent quality and the most durable paint finish coatings available to consumers are produced at the OEM level. These coatings comply with the vehicle manufacturer’s specifications and quality controls and are applied in a controlled environment, using quality materials and highly specialized application equipment. Also, the prefabricated metal used for body panels will never be cleaner and in better condition than when it’s used to manufacture new products. The longer the original factory coating lasts, the higher its value to the owner.

Most popular vehicle colours
1. White-22%
2. Silver-20%
3. Black-19%
4. Red-9%
5. Blue-7%
6. Green-2%

Automotive Coating

[: any liquid, liquefiable, or mastic composition which after application to a substrate in a thin layer is converted to an opaque solid film]

Paint is a liquid, usually comprising 30 to 40% solids and 60 to 70% liquid. As it dries it becomes a solid and a gas (the solvent) that evaporates, leaving behind the solid. The three primary type of ingredients found in most paint type coatings are –
1.      Binder (film former)
2.      Carrier (solvent)
3.      Solutes (pigment)

The binder is the film-forming component of paint, it imparts properties such as gloss, durability, flexibility, and toughness.  Many binders are too thick to be applied and must be thinned. The thinner is also called the carrier, because it makes it possible to transfer the binder to the surface. The pigment provides the paint with colour. All paints consist of a solids portion, essentially comprised of the pigments and binder, and a liquid portion. After the liquid portion evaporates and a coating dries, it is the solids that remain on the surface. Some paints form by solvent evaporation only, but most rely on cross-linking processes

Surfactants are added to stabilize the paint so that it will not separate, settle or become too thick to use. They also keep pigments dispersed for maximum gloss and hiding; and they help “wet” the surface being painted so the paint won’t “crawl” when it is applied. Surfactants also provide compatibility between tinting colorants and bases so that the correct colour will be obtained.
Urethane paint was first created in the mid-1960s, utilizing the newly-developed plastics technology of that era, to be superior to enamel paint in terms of durability. It also has the advantage of being a surface that can be applied over enamel if the enamel-painted surface is prepared first. A urethane painted surfaces is minimally affected by ultraviolet rays, making the paint a good choice for outdoor surfaces.

It is widely used in the automotive industry because of its durability. Inexpensive urethane paint might contain less than 10 percent polyurethane. High-quality polyurethane paint has a higher percentage of the expensive polyurethane ingredient. A urethane-painted surface can be expected to contract and shrink over time.

Polyurethane (PUR and PU) is polymer composed of a chain of organic units joined by carbamate (urethane) links. Polyurethane polymers are formed by combining two bi- or higher functional monomers. One contains two or more Isocyanate functional groups and the other contains two or more hydroxyl groups.

Approximately 30% of OEM body panels are coated with a scratch resistant clear coat and 70% are coated with traditional clear coats. When scratch-resistant clear coat systems were developed, conventional polishes were unable to eliminate the sanding defect. Menzerna took the lead in designing an innovative new polishing system that was successful on scratch-resistant clear coats while achieving even higher levels of surface quality and gloss.

The highest quality, longest lasting surface coatings available to consumers are the finishes produced at the factory. Factory coatings are applied in a controlled environment, using quality materials and highly specialized application equipment. Also, the prefabricated metal will never be cleaner and in better condition than when it’s used to manufacture new products. The longer the original factory coating lasts, the higher its value to the asset and the owner.

Finish quality is the primary attraction for new customers, but durability is also important. For this reason, many manufacturers go to great lengths to prevent the conditions that cause new coatings to fail prematurely. This involves critical surface preparation, rust inhibitive pre-treatment, and state-of-the art base coat/clear coat paint systems. The integrity of the original application allows responsible owners to provide a significant increase in service life through proactive maintenance.

Among the inorganic pigments, TiO2TiO2 white is, by far, the most important one. The photo catalytic activity of TiO2TiO2 leads to a rapid degradation of the organic binder matrix, so the surface of the TiO2 particles has to be covered by an inorganic coating to prevent the matrix from being photo oxidized. This is done by applying layers of SiOand Al2O3

Automotive Paint Systems

Paint, a common polymer coating, is used to change the colour, change the reflectance (gloss), as well as forming a protective coating. The structure of paint consists of pigments in a matrix of resin; colour is determined by light-reflecting chemical particles (pigments) in the paint.

The paint on every vehicle is different; dense (hard) less dense (soft) etc. even if they are the same colour, year, make and model, so take that into consideration when you are detailing.

Worldwide, approximately 80% of all passenger cars are coated with 1K clear coats and the remainder with 2K clear coats. The 1K clear coats are subdivided into solvent-based (solvent borne) acrylic melamine systems; clear coats with enhanced surface etch resistance, high solid-systems, water-based (waterborne) systems and powder versions.   The 2K clear coats include solvent-based, super high-solids and water-based versions.

A paint resin system comprises a binder, which as its name implies holds the paint molecules and various other components (additives} together and a film former, which creates a dense surface. Various solvents are used, one as a carrier system, one holds the paint together and the final solvent that evens out the paint to create a smooth, glossy surface (this solvent has the most bearing on the ripple effect (orange peel). These solvents are responsible for the paints density (hard or soft) the paint becomes

Basecoat / Colour Coat Formula
·         Petroleum –Based Solvents - 40-60%
·         Resins and Binders - 30-50%
·         Pigments & Colorants - 5-10%
·         Silicone Polymers & Other Additives (Catalysts, etc.) - 1-2% 

A clear coat / colour coat system consists of one or more primer layers, a flat colour layer and a glossy, clear top layer.  The primer is a corrosion inhibitor and a bonding agent for the bare metal and the colour layer.  It prevents corrosion and provides a stable substrate for the colour and clear coats.  The colour layer is applied to the primer and is typically very thin.  Its only purpose is to provide colour.  The clear coat is two to three times the thickness of the colour layer, adding to the appearance of paint depth and offering additional protection.  Many luxury car manufacturers also use ultraviolet-light-blocking technology in their clear coat systems for protection against sun fading.

Clear coat 2K Formula
·        Petroleum –Based Solvents - 20-40%
·         Resins and Binders - 50-70%
·         UV Absorbers - 1-2%
·         Silicone Polymers & Other Additives (Catalysts, etc.) - 1-2%
·         Isocyanate hardener and catalyst: 0 -2%

E-Coat (Electro coat)

In order to achieve maximum coverage and therefore maximum corrosion resistance, this first coating layer is applied in a process known as electro deposition.  The metal body is electrically charged, then immersed in a bath containing oppositely charged paint particles.  These particles are attracted to the metal surface, neutralized, and can then be baked into a coherent, tough film.  E-Coat is very sensitive to ultra violet (UV) exposure and if allowed, will exhibit a "powdery" surface as it breaks down, and is no longer able to protect the metal surface from corrosion.

Current practice favours making the vehicle body the cathode in this process (this minimizes corrosion for steel). These products are called cathode electro coats. A new environmental requirement requires that the electro coats must function without the addition of heavy metals such as lead and in some areas in Europe also without tin.


The primer layer is the coating layer that joins a corrosion-protected substrate to the topcoat.  It functions to smooth out surface irregularities, improve stone-chip performance, and helps to protect the substrate from visible and UV light.  Today’s primers include both solvent and water-based.  Colour-keyed primers are often used to allow minimum basecoat film thickness, to optimize the painting process and to minimize defects related to stone-chip damage


The basecoat is either solvent or water-based and this coating layer provides colour and aesthetic effects.   Modern requirements for vehicles aesthetics often require micas, aluminium flakes and other effect pigmentation.  These can be incorporated in one basecoat layer or in a separate layer (for example in two-tones).
 If two basecoat layers are used, the sandwich with the clear coat is called a tri-coat topcoat. DuPont Automotive Systems is the world leader in wet-on-wet tri-coat application in both solvent and water-based basecoat topcoats.

Clear coat

The clear coat is the coating layer that forms the last interface to the environment.  It carries the biggest part of the technological performance and must be able to resist environmental etch, bird droppings, car wash machines and other outside influences.  

To improve performance against all these influences, OEM coating systems move from colour topcoats to basecoat/clear coat (BC_CC) systems.  The clear coat in combination with the basecoat forms the automotive topcoat, which gives the vehicle its aesthetic colour appearance.  One and two component clear coats (1K and 2K) are applied over both solvent and water-based basecoats

Clear coat paint was originally formulated to protect the base coat from ultra violet (UV) radiation damage. Once vehicle mfg. started to use metallic paint a clear coat was necessary to cover the metallic flakes that are subject to oxidation.

Based upon the studies of PPG, DuPont, BASF and Sherwin Williams, the average vehicle's paint system will absorb up to a pint of water into the substrate when subjected to rain or car washing

Based on DuPont Automotive Paint Systems

Typical OEM Paint Thickness

·         E-Coat 33 µ (1.3 Mil) - an anticorrosion coat applied to both sides of the steel to prevent corrosion

·         Primer 18 µ (0.7 mil) - Initial protection layer with texture to assist the pigment layer in bonding to the metal beneath

·         Base Coat 15 µ (0.6 mil) - The basecoat is usually 0.5 to 1 mil thick

·         Clear Coat 48 µ (1.9 mil) - The clear coat provides gloss plus physical protection from the elements, including ultraviolet rays

All paint has three major components: a pigment for colour and hiding powder; a binder that holds the pigment to the surface; and a carrier to maintain the pigment and binder in liquid form. 

Current Information

To be of real practical use, a subject like automotive detailing requires a great deal of research, and updating as new products become available. The advent of materials like detailing clay, micro fibre technologies and finely milled micro diminishing abrasives, suitable for ceramic nanotechnology paints are examples of why it’s so important to monitor the industries new products, chemical technologies and ideas that are constantly being introduced, as are the techniques for applying them, hence all of the in-depth articles will be up-dated and revised on a regular basis

Always be willing to learn; because the more you learn, the more you’ll realize what you don’t know. It is said that knowledge is power, with the caveat that it includes access to a reliable information sources. I would like to think that these articles become an asset to anyone who is new to detailing and to professional’s alike, as well as industry experts who seek to advance their knowledge.

I hope these articles are informative. They are based on the current status of technical development as well as my experience with the products.

By having some understanding of the ‘What’ and ‘Why’ as well as the ‘How’ along with a little science to help you understand how the chemicals we use react, you can achieve the results you desire.

I would appreciate it if you would share these articles as it helps other detailers further their knowledge.

As always if you have questions, I’ll do my best to answer; bear in mind the only stupid questions is the one that was unasked. Questions and/ or constructive comments are always appreciated

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