Clear Coat Paint
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Clear Coat
[Two stage paint; base (color) coat and clear coat was adopted as an automotive industry standard in 1982]
Modern clear coat paint finishes are so good today that they lull people into thinking that vehicle paint has protection and shine when in reality there is not really much there, other than the clear coat. The statement that “a sealant has no benefit to the paint ‘because’ there is a clear coat, is baffling, as clear coat is a polyethylene paint but without color pigmentation, its applied to provide the colour coat (base coat) with shine, if a clear coat did not need a protection applied, there would be no such thing as clear coat failure due to oxidation or any of a myriad of clear coat problems. To provide further improvements in appearance and durability the base-coat / clear coat systems were developed and introduced in the late 70’s. The base coat is comprised primarily of pigments held in place by a polymeric resin film (binder).
A smooth and transparent clear coat allows for more light to pass directly through the clear coat for optimal reflectance and shine.
Solvent-based paints
Solvent-based paints are categorized by the ratio of solids (resins, pigments, binders, etc.) to liquids (solvents) In the US manufacturers are required to use high solids paints, with a ratio of about 60% solids to 40% solvent. In order to produce a better flow rate a higher percentage of solvents is required, however due to recent volatile organic compound (VOC) limit restrictions; the 60/40 percentage cannot be exceeded. These restrictions stem from the Environmental Protection Agency (EPA) limits on volatile organic compound (VOC), which are in almost all solvents. In other countries, these restrictions either don't exist or are more lenient, allowing manufacturers to use low solids paints (as low as 30% solids to 70% solvent), which tend to have a smoother appearance. To combat these restrictions paint companies are developing new technologies.
High or low solid
* High or low solid, is a ratio of paint to solvents - High is 60/40) that leaves more material (coverage) once paint has cured. Low is (30/70, which means the paint contains more solvents, once they have out-gassed (evaporated) leaves a thinner coat (paint thickness)
Waterbased paints
* Waterbased paints, for example, are essentially low solids paints (up to 60% solvent), but they are legal because de-ionized water is used as the solvent, as opposed to volatile organic compounds (VOC). In addition to the low solids aspect, waterborne paints have many other neat properties that help improve the performance and appearance.
Clear Coat
* Clear Coats are two part systems (either a Urethane, or a good quality non-yellowing Polyurethane and an Epoxy) a solvent based urethane (a water-based clear coat is not yet available) is applied in two layers; it also contains UVR inhibitors Clear coat is not Armour plating but by adding UV blockers it provides a level of protection for the color pigmentation of the base (color) coat, but it must be protected, and the most durable protection is a polymer sealant.
Durability is really a very real concern for car owners today. With the increase in airborne pollution and other environmental factors, a car's finish is subject to serious damage. Acid rain; jet fuel fallout; industrial fallout; hard water, not to mention high acidic bird droppings; insect residue; tree sap all are very dangerous to a paint finish if not removed immediately. By adding UV blockers to the clear coat you have a new level of protection for the pigments (colour) in the base coat.
Once the outgass process is complete automotive coating (paint) becomes a semi-solid permeable membrane, being a polymer (plastic) it remains flexible while retaining its tensile strength, to enable it to expand and contract to follow temperature fluctuations (elongation) So pay attention to what you use on a paint surface; a polyurethane paint (high solid / low solvent) clear coat can absorb moisture; as water molecules are smaller than a cross-linked clear coats molecule. So be careful of the contents in car wash concentrates, sealant and waxes (i.e. low pH acids, high pH alkaline, Dimethylsilicone (DMS) or solvents that contain butyl, heptanes, and xylene or hydrocarbon Aliphatic solvents.
(See also MSDS, Potential of Hydrogen (pH)
The clear coat finish can become ‘dull’ by using harsh (abrasive) or if a high alkaline car washing solution as used in ‘touch less’ car washing systems, or from industrial airborne pollutants compromising the clear coat allowing the suns heat to dry out and oxidize the paint .
Bear in mind that a clear coat has a thickness of 1.5 – 2.0 Mils, removing more that 0.4 mil (0.0004") of clear coat will cause premature paint film failure. As a point of reference two sheets of Saran wrap placed on top of each other measure 1.5Mil (0.0015") a surface scratch that will `catch' your fingernail is approximately 0.004" deep and will usually require wet sanding and refinishing. There comes a point when you must judge wither removing a scratch will compromise the clear coat and if so you’ll have to ‘live’ with the imperfection
The clear coat is the final original equipment manufacturers coating applied to a vehicle to protect the (base) color coat while providing both depth and a durable, glossy appearance, originally designed to protect metallic paints, but is now applied to all colors. Any product applied on top of the clear coat needs to be transparent otherwise both the paint color and its depth of shine will be muted.
If you look at the vehicles on the road today that have a clear coat, they look great for a while, but scratches in the surface will cause white marks to appear, and dents smudge the finish, reducing the clarity of the top coat, which in turn affects both the depth of shine and paint color showing through. It doesn’t take long before the finish looks dull and lifeless because the clear coat isn’t reflecting light as it once did. A better finish can have a dramatic impact on the residual value of vehicles, and it certainly doesn’t hurt customer satisfaction.
(See also Paint Problems (Orange Peel) [Color Sanding / Polishing, and Polish])
No wax/sealant fluorine-type clear coat finish
The newest technological advancement in clear coat finishes is a fluorine-type clear coat that needs little or no waxing. Currently available on Nissan Motor Corporation's Infiniti luxury automobile, "no-wax" clear-coats are likely to be available on other cars and from other manufacturers in the future.
The fluorine-type clear coat finish requires special detailing, especially to correct damage to the clear coat, and should be treated exactly per the manufacturer's instructions in the owner's manual. Polishing and waxing in the usual detailing sense are not appropriate for these high-tech finishes. Because no-wax/minimum-wax finishes are so different from conventional finishes and from most other clear-coat finishes that have been available to date, it is likely that each manufacturer that produces such a finish in the future will also include very specific product and procedure recommendations for its individual formulation of no-wax clear coat.
Almost all original equipment manufacturers' (OEM's) automotive paint systems manufactured from 1990 on (with the exception of single stage paint systems) used today have a pigmented base coat protected by a thin layer of clear coat, that contains polymeric resin or binder, UV inhibitors, and generally one or more silicone additives. The base coat is comprised primarily of pigments or colorants held in place by a polymeric resin film (binder). Detailer’s should know, understand and be able to identify a two-stage paint finish. To check, take a cleaner type wax and in an inconspicuous place like a door jam rub the surface using a medium to heavy pressure and wipe off. If there is no paint colour (this is somewhat difficult to see with silver paint) on the cloth it has a clear coat finish.
There are three major paint suppliers to the automotive industry PPG Industries, DuPont Chemicals, and BASF Aktiengesellschaft, they have all have focused on creating super-hard clear coats. These "rigid" clears are more resistant to chemical etching which makes them less susceptible to acid rain spots and owner induced swirls from washing and drying improperly. The disadvantage of rigid clears is their susceptibility to chip when struck by stones or road debris; they also require a more abrasive polish to enable paint repairs. It should be noted that some car manufacturers use a harder clear coat then others, regardless of the cars paint colour (GM Corvette, VW, and Audi etc)
More resilient clear coat-a newer technology (2004) clear coat (CeramiClear) used by Mercedes-Benz and Chrysler, which provides an outstanding premium gloss, distinctness of image and long-lasting colour retention and a hard protective layer, some of the German (Audi, BMW, Porsche, etc) and European vehicle manufacturers have been using a BASF clear coat for some time.
When polishing a clear coat ‘spot’ surface temperature should be limited to 100oF (138oC) as urethane starts to soften at 115oF, just like any other plastic material, polishing at this or elevated temperatures will cause scratches to be driven deeper into the surface due to urethane expansion and foam / wool pad friction on the softened paint surface. Information resource: Heat Vs Urethane Coatings, The Society of Automotive Engineers (SAE) article
(See also Oxidation)
Reference source
- " Automotive Detailing; Inside & Out, A Knowledge Base for the Perfectionist – by Jon Miller
