Oxidation
and / or clear coat failure
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.
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
The
resin system's binder holds all the other components together, while the film
former creates a dense surface, which among other things, hold the ultra violet
blockers in place. Paint usually comprise three different solvents-one is just
a carrier, the second is the binder and the third is the tailing solvent, which
flows out the materials" to create a smooth, glossy surface
The
tailing solvent defines if a final surface is smooth or has orange peel. The
curing bake temperature is the cause of paint density issues, the misnamed hard
and soft paint
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% 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 TiO2leads 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 SiO2and
Al2O3
Clear Coat Failure
A chalk like appearance on the paint surface or small triangular marks
(crow’s feet) or other similar marks on the paint surface - basically the
chemical integrity of the paint has been degraded by ultra violet (UV-B)
radiation, stress, environment fall out, acid rain and etc.
Oxidation is sometimes confused with clear coat failure; 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
Oxidation really amounts to a
weakening of the resins that bind paint, which results in the micro-pores
becoming exposed and a larger area of paint becomes oxidized. Once the paint
has been breached in this manner, applying waxes and polishes temporarily wets
the surface making it appear better. The oxidation residue can be removed with Swissvax Cleaner or Duragloss DG
501
Correction- usually
entails a re-paint of the affected panel, although sometimes wet-sanding may
remove it, if it’s not too deep
Removing more than 0.3 mil (7.5ยต) of clear coat will cause premature
paint film failure as the ultra violet (UV) protection percolates to the top of
the clear coat, there is ultra violet (UV) protection all the way through the
paint, but the majority of it migrates to the top of the clear coat along with
the thinner solvents and particles.
Therefore removing clear coat ultra violet protection is not a
linear process; by removing a small percentage of the clear coat paint tends to
remove a larger percentage of UV inhibitors. So once you remove too much clear
coat you'll have no paint UV protection other than what you apply with a LSP
Oxidation is sometimes confused with clear coat failure; 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
1. Ultra violet radiation is the prime cause of clear
coat failure, infrared radiation (IR) represents part of the ultra violet solar
spectrum (approximately 55%-60%). The remaining heat source comes from visible
and ultra violet light Infrared radiation infrared radiation (IR) that
transmits heat that will cause oxidation by drying out materials, like the
paint (binder) resin system, the plasticizers in vinyl, moisture evaporation of
leather and the elasticity of rubber causing these materials to dry out and
become brittle and compromise their structural integrity
2. Ultra violet light; UV-B radiation is known to contribute to the chemical modification, photosensitize
(fading) of exposed paint surfaces resulting in loss of gloss, colour change,
chalking, flaking and along with infrared heat radiation infrared radiation
(IR) eventually the destruction of the clear coat paint film.
First, the paint take on a cloudy
appearance, then as time progresses, we observe small hairline marks start to
appear; that's the clear breaking down.
Oxidation
Oxidation is caused by environmental pollutants (acid rain,
ozone, industrial pollutants, hydrocarbons, etc)t UV- B radiation is known to
contribute to the chemical modification of exposed paint surfaces resulting in
loss of gloss, colour change, chalking, flaking and eventually destruction of
the paint film. Inclement weather or the use of harsh detergents in commercial
car washes using strong detergents will leach out the oils in the paint and dull
the paint film surface even faster
It starts as
a chemical reaction that causes the paint film surface to overheat, dry out and
oxidize leaving microscopic surface imperfections and micro pores in the paint
film surface that are vulnerable to deterioration
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, the top most layer of clear coat paint contains ultra violet
(UV) protection. 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.
Clear-coat dulling has the appearance of
oxidation, i.e. paint surface has little or no gloss and may exhibit a slightly
‘grey’ colour but can usually be rectified without the need to re-paint.
This can be brought
about by abrasive washing which simply dulls the paint; touch less carwash
washing, which uses an acid that dulls the clear-coat and / or simply from
exposure to industrial fallout and UVR, etc.
• Wash the paint
surface and dry thoroughly
• Clean the paint with chemical paint cleaner (Autoglym Paint
Renovator
or Swissvax
Cleaner)
using an orange foam pad at speed #4, this may take 2-3 applications
• Apply a paint
surface protection
For highly oxidized paint try the following;
this may help to eliminate some of the oxidation-
• Wash the paint
surface and dry thoroughly
• Clean the paint with chemical paint cleaner (Autoglym Paint
Renovator
or Swissvax
Cleaner)
using an orange foam pad at speed #4, this may take 2-3 or more applications
• Once the oxidation
has been removed use a decontamination system (C.Quartz IronX)
• Apply an oil rich product to stabilize the
paints binder system (3M Imperial Hand Glaze) apply a thick coat and allow to dwell time for 12-24 hours
before buffing, repeat as necessary until surface has an ‘oily’ sheen.
• Remove residue with 1:10 solution of isopropyl alcohol and
distilled water
Finally apply a coating (Opti-Coat™) a pre-polymer that cross
links and forms a semi-permanent continuous film on the surfaces it is applied
to similar to a single component isocyanate that forms a clear coating finish.
Single stage paint systems (base and colour
coat) – 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 ultra violet (UV)
heat radiation, which causes it to dry out and/or fail, further 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.
A dark coloured
vehicle parked in the sun can attain a surface temperature in excess of 200° F
With both types of paint system the application of a Carnauba wax provides a
sacrificial and easily renewable barrier against airborne contaminants, which
means the wax is compromised not the paint system
Single stage is
easier to correct than most clear coats, as a general rule use a more
aggressive pad before moving up the scale in an abrasive polish. Start with a Lake County (LC) Orange (light)
cutting foam pad with Optimum Polish or Menzerna Intensive Polish (IP) you may also want to try an
LC yellow cutting foam pad.
If you need a more
abrasive polish; use a high speed rotary and try Optimum Hyper or Menzerna Power Gloss with a LC White polishing foam pad,
if the results are not satisfactory then
step up by to going to a LC Orange
(light) cutting foam and then if needed a LC Yellow cutting foam pad.
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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(Established 1980) all rights reserved
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