Clear Coat Failure

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Clear Coat Failure (Paint Oxidation)

Oxidation (Reduction): [Oxidation simply means that oxygen is added to a molecule with an electron being displaced,which in turn dries the paint surface ]

Water-based paint is very porous, the paint film surface on a microscopic level has many surface imperfections, and is convoluted (a series of peaks and valleys) with time and use, plus normal wear and tear, the surface becomes more permeable, thus allowing ingress. High solid clear coat during the first couple of months, following factory painting will allow moisture to enter the clear and become trapped. This is most noticeable in vehicles that are transported, using transit wrap, when the surface has some moisture and the wrap is placed over it.

On average, a high solid clear coat will absorb approximately one pint of water when the vehicle is subjected to a heavy rain or a car wash. If there is a "clouding" of the clear, simply applying isopropyl alcohol (IPA) to the area, allowing it to dwell and with a heat gun or hair dryer, heat the area (do not exceeding 100oF spot temperature) The IPA acts as a "drying" agent, and when combined with the heat the moisture will evaporate.

An oxidizer is any compound that spontaneously emits oxygen either at room temperature or under slight heating. Many chemical compounds react vigorously at ambient temperatures as the oxidizing process takes place. Oxidation is caused by environmental pollutants (acid rain, ozone, industrial pollutants, hydrocarbons, etc) the suns heat, which also causes paint colour fading from ultraviolet radiation (UVR) inclement weather or the use of harsh detergents, all of which attack the paints binder system(resin)

It starts as a chemical reaction that causes the resin binder system to overheat and dry out, leaving microscopic surface imperfections and micro fissures in the paint film surface that are vulnerable to deterioration. Once the air borne contaminates and pollution compromises the paint surface they accelerate the oxidation (reduction) or paint failure process.

Two stage paint system- (base, colour and clear coat) - a clear-coat finish does not oxidize in the true sense of the word (meaning that the pigments and resins mix together and the pigments are exposed to the sun's ultra-violet rays, which causes them to dry out or oxidize. The clear coat is applied to protect against this but the finish will become ‘dull’ by using harsh (abrasive) or if acidic car washing solutions as used in ‘touch less’ car washing systems, or from industrial airborne pollutants compromising the clear coat allowing the suns heat to dry out (oxidize) the paint.

The clear coat layer is extremely thin (1.5 – 2.0 Mils) it is not a solid coating and is to some extent porous, oxygen interacts with substances in the paint layer (i.e. mica flakes as in metallic paints) and trigger the oxidation reaction. It's just that the amount of oxidation taking place is minimal in comparison to single stage paint.

For oxidized paint try the following;

•Wash the paint surface and dry thoroughly

•Clean the paint with chemical paint cleaner (Klasse All-In-One) using an orange foam pad at speed #4, this may take 2-3 applications

•Once the oxidation has been removed use a decontamination system (Auto International A B C System (Automotive International - Valugard Product Line)

•Apply an oil rich product to stabilize the paints binder system (3M Imperial Hand Glaze) apply a thick coat and allow to dwell for 12-24 hours before buffing, repeat as necessary until surface has an ‘oily’ sheen.

•Remove residue and apply a Carnauba wax (Zymol Concourse)

•Try to keep vehicle paint surface away from UV heat radiation

•Keep paint surface waxed on a regular basis.

Single stage paint systems (base and colour coat) – (note-single stage paint is usually very ‘soft’) without a clear coat to provide protection, primarily a hostile environment will attack the paint surface causing microscopic gaps and valleys (micro fissures) and it becomes compromised both chemically; by industrial fallout (IFO) acid rain, brake /rail dust and etc., and by UV heat radiation, which causes it to dry out and/or fail, causing the clear coat to expand and often separate from the base coat, allowing environmental pollutants to penetrate.

Acids enter the breach formed in the clear coat and attack the resin binder system, which accelerates the degrading of the paint film surface, eventually leading to oxidation and/or failure. Oxidation can appear as a dull and somewhat hazy, or `chalky' appearance to the paint surface, a paint film surface that is adequately protected with wax or a sealant actually has a lower surface temperature than one that is not.

Clear Coat Failure (Cause and Effect):

When a clear coat area appears to have an opaque ‘white or grey chalky’ or ‘cloudy’ look, this is the resin or paint binder system, which is indicative of clear coat failure, sometimes due to;

(a)Polishing the clear coat too often or using an aggressive abrasive polish / compound that has compromised the clear coat down to the colour (base) coat (sanding through) this can be checked with a paint thickness gauge. Clear coat that is too thin looses its ability to adhere effectively (delaminating) to the underlying paint layer and will flake off.

(b)Clear coat failure becomes noticeable when a section becomes opaque as it reflects less gloss than surrounding areas; this can be ascertained very clearly with an inspection light. More often than not this condition cannot be corrected by buffing or levelling the surface, it requires the refinishing of the paint system

Oxidation- clear coat clear coated paint does not oxidize; it fails and requires compound polishing to remove paint and re-painting to correct it.

Delaminating - Clear coat that is too thin looses its ability to adhere effectively to the underlying paint layer and will flake off; you need to remove the entire clear coat and re-apply a base coat and finally a clear coat. If you don't the new paint will separate due to delaminating of the original clear coat under the new paint you applied.

Other causes-

• Ultraviolet Radiation (UVR):

Ultra violet (UV-B) radiation is a paint film surface's greatest enemy, causing more damage than any other airborne contaminant and affecting both the interior and exterior of a vehicle. The light in this spectral range is responsible for photo degradation.

Photo degradation results in discoloration, fading, embitterment, cracking, chalking and/or loss of mechanical properties. Chalking gel coat fibreglass, yellowing plastics, fading and weakening fabrics and sunburned skin are all familiar problems caused by UV light. Infrared radiation (IR) is a light source that transmits heat that when combined with a UV source will cause oxidation by drying out the material.

Before UV light can cause harm, it must first be absorbed. If it is not turned into heat or transferred to a nearby stabilizer molecule called a quencher, it breaks weak chemical bonds. This is the beginning of UV damage; some materials absorb UV light more readily than other materials. Materials that readily absorb UV light are quickly damaged...rubber, vinyl, gel coat fibreglass, and many other plastics. Acrylic is slow to absorb UV light and accordingly very resistant to photo degradation.

Competitive absorbers (i.e. the carbon black in tyres) provide protection by converting UV light to heat so it can dissipate harmlessly. All UV stabilizers are consumed as they do their job. In a way, they serve as sacrificial molecules, taking the abuse from UV light instead of the material they are protecting. When UV light is absorbed, it starts to break (cleave) weak chemical bonds, which leads to bleaching (fading), discoloration, chalking, brittleness and cracking - all indications of UV deterioration

Information resource-

• “Automotive Detailing Inside & Out, A Knowledge Base for the Perfectionist"– by Jon Miller