One of the
most often asked question (besides Leather care and Glass cleaning) and a
subject that results in a great deal of confusion and misinformation regarding
polishing or waxing re-painted panels.
Many paint company now say
the 30-90 day recommendations are based on old paint formulations and the
p-Sheets need to be up-dated in line with the latest paint specifications,
although to my knowledge this has not been done. Most paints can have a paint
protection product (wax / sealant/coating) applied within 36 – 48 hours of
painting. However I would still abide with the
manufacturers official recommendations
Part I - Applying
a Polymer Sealant or Waxing Re-Painted Surfaces
a) Polishing
or Waxing Post-production Paintwork
1.
Refinish
paint products, materials and paint drying methods are very different from
original equipment materials (OEM) specified materials.
2.
This
is only relative to re-painted surfaces that use a solvent –based paint. Modern
environmentally friendly paint systems being utilized today are mostly
water-base (EU- Sikkens, BASF, and Brillux), which evaporates quickly from the
paint during the baking and drying process (US, only a limited number of
painters are utilizing water-based pain, most are utilizing solvent based
urethane)
3.
Unlike
the oven baking process used by OEM painting t he process used in body shops is
just a speed cure. Urethanes drying causes an exothermic reaction, that means
they produce a small amount of heat as they cure, by adding to the reaction, you accelerate it but if you
don't it will just take more time but will eventually completely cure on its own.
The majority of refinish
paint is supplied by BASF DuPont, PPG and Sherwin Williams is 2K (2 component
paint + activator) polyurethane systems; one component is polyisocyanate and
the second is a polyol (acrylic or polyester polyol). Solvent-based paints
(which still constitutes the majority of what is still being used, low solvent
content VOC compliant) once the two components react they form a strong polymer
chain. Or a water-based paint, much more prevalent in European imports than US
mfg vehicles
Newly applied paint is soft, much softer than OEM paint, dehydration (drying) is a different process
from cross-linking; while newly refinished paint is about 90% cured within 24
hours, even with the help of a drying oven and various additives, and will fully harden (dehydrate) after 60-90
days dependent upon local environmental conditions
That
distinctive smell of paint is actually dibutyl and diethyl phthalate
out-gassing- two very volatile compounds
New paint needs to outgas
for approximately 90 days (i.e. the solvents need to evaporate) if this is
hindered by an inappropriate product application the clear coat may form a
'hard film' on top and the clear coat matrix may remain 'soft'. Most product
data sheets (P-Sheet) state paint will air dry in 12 hours to buff and take 16
hours to fully dry.
Automotive paint is
classified as a semi-permeable membrane; some chemicals, especially solvent
based will penetrate a paint surface easily, others will just remain on the
surface. A solvent or oil solvent emulsion will permeate the paint and fill the
molecules causing them to swell. This will have an effect on the mechanical
strength effecting both the paints tensile strength and elasticity
Current 2k (2
component paint + activator) polyurethane systems use chemical reactions to cross-link
the clear-coat. Some body shops will oven cure them at approx 65.oF
for 30 minutes and air dry over night or use an accelerator catalyst.
Regardless, they still need to time for the solvents to evaporate (outgas) from
the finish. By not allowing this process can create solvent-pop ‘like ‘fissures
of the paint film and other issues.
During this period, using
waxes or sealants that use a solvent as their carrier system should not be used
since the solvents permeate the paint and soften it and if the wax or sealant
contains abrasives, it can cause micro marring on the softened paint. The best
products to use during this period are therefore water-based systems that are
both solvent and abrasive-free.
Most paint shops use 10-20%
more isocyanate component (hardener) than the polyol component. The reaction
between these two (isocyanate and alcohol) is fairly rapid and that accounts
for the 90% curing rate of the refinish paint within 24 hours. That leaves
about 10% unreacted isocyanate, some of these isocyanate groups slowly react
with moisture (hence the term moisture cure) and form amine groups (releasing
CO2).
The newly formed amine
groups rapidly react with isocyanate groups to form urea or polyurea, which is
much harder than polyurethane adding solvents to the paint, hindering this
reaction, while water-based products can help the (moisture) curing process.
Professional painters add
chemicals; accelerants and compounds to their paint mix prior to painting to
improve flexibility, reduce paint imperfections, increase hardness, and improve
gloss and some body shops heat it in a paint oven to harden the ‘shell’, it
doesn’t reduce cross-linking times (this process is both temperature and time
dependent) But I would suggest waiting for approximately ten to fifteen days
before any abrasive product application, which should be more than sufficient
time to enable paint off gassing and aerobic curing
a) When a body shop wet sands and buffs out a newly painted panel
they will hopefully polish out any sanding scratches, unfortunately this is not
usually the case.
Polishing paint that is at least 24 hours old is
perfectly fine.
As a conservative estimate I
would suggest waiting for approximately ten to fifteen days before any abrasive
product application, which should be more than sufficient time to enable paint
off gassing and aerobic curing
Unless you are a very
experienced detailer I would strongly advise against the use of heavily applied
pressure and overtly abrasive products as they behave more aggressively on soft
fresh paint. I would suggest you allow the fresh paint to fully cross-link
(cure) before you attempt to remove any surface imperfections
b) Automotive paint is classified as a semi-permeable membrane; it
has both tensile strength and elongation (elasticity) newly painted surfaces
are soft and full of out gassing solvents, resin binders and additives, as well
as and water. Polish contains solvents, which soften the paint film, kinetic
surface friction and applied downward pressure transfers its energy into heat /
torque (force to rotate an object about an axis);
c) Which causes the soft paint film to become thinner by
elongation and the pad rotation to transmit shear stress (torque=
Force (radius) torque is twisting force, which could result in the alteration
of the paint films bond between its substrate, causing it to delaminate or
tear?
d) The heat makes the gasses expand (pV = nRT) the expanding gases go through a phase
transition (change in density) and to relive this increased pressure they (a)
rupture the paint film surface, causing small fissures (similar to solvent pop)
e) The heat may cause the gaseous vapours to expand, but not
enough to break through the hardening clear coat. Once the vapour has evaporated, it may leave
a void between the basecoat and the clear.
Therefore you have a cloudy
spot where the clear and base is no longer adhered together. If this is the
case, the clear coat will delaminate in the future.
f) Once the outgas process
is complete automotive coatings (paint) becomes a semi-solid permeable
membrane, Being a polymer (elastomers) it remains flexible while retaining its
tensile strength, to enable it to expand and contract to follow temperature
fluctuations (elongation) kinetic friction and its associated heat can cause a
rapid temperature rise (i.e. initial surface temp 80.oF, heat
attained with a cutting foam pad at 1,100 RPM for approx. ten seconds is
approx. 104.oF) the paint temperature can be checked by utilizing an
instant read-out infra-red ‘gun’ thermometer, paint surface ‘spot’ temperature
should be limited to 110.oF <
In accordance with the Society of
Automotive Engineers (SAE) a temperature of 115.oF will cause the
urethane clear coat to soften and the foam pad will cause scratching that is
forced deep into the clear coat.
Also be aware that plastics
and those surfaces that have flex agent additives have a different thermal
rating and will be negatively affected by applied heat very rapidly.
Fresh paint safe glaze’ - while a paint is cross linking,
using solvent- based waxes or sealants is not ideal since the solvents
penetrate the paint and soften it and will interfere with the outgas / cross
linking process.
The common ingredients in a’
fresh paint safe’ glaze are: water,
glycerine or mineral oils(to produce a
high shine) and a mild abrasive Kaolin
(China clay) to burnish the surface and produce a gloss, some polymers are also
formulated as ‘fresh paint safe’ for the same reasons
The application of a
specific ‘fresh paint safe’ water-based or polymer type product, Zaino
Polishes (exclude the use of either Z1 or ZFX™) Optimum Car Wax is
water-based and is safe on fresh paint, or use Presta Fast it’s a liquefied
paste wax manufactured with premium, natural and synthetic ingredients. This
unique wax can be applied over 24-hour old clear coat and single-stage finishes
without risk of die back, because it creates a breathable film that permits
solvents to cross the wax film. Allow an ‘initial gas off’ (evaporate) /cure
aerobic process of 7 days before application
These products are
completely safe for any fresh paint system as they allow the solvents in a
water-based paint to outgas / aerobic cure process and provide some protection
for any type of paint surface. After thirty days (30) the paint surface can be
protected with a regular polymer sealant and/or Carnauba wax.
Notes:
1.
Both
DuPont and PPG recommend a 90 day period whereas BSAF advise 30 days; but any recommendation
is dependent upon what paint, hardener, drying system, additives etc were used,
the body-shop / paint manufactures know their products; seek their advice Paint
manufacturer have specific technical guidelines (see ‘Product Sheet’ or P-Sheet)
on how to use their products to affect a warranted spot/panel/ repairs or a
full repaint. This preserves both the paint manufactures and factory warranty
(if offered)
2.
Abrasive
polish should be avoided until the paint has cured (an abrasive polish will not
necessarily harm the soft new paint but unless it’s absolutely necessary I
would avoid it)
3.
Vehicle
washing is encouraged but avoid car wash concentrates that contain any harsh
detergents, alkali, acids, wax (recommended products- Zaino Z-7™ Show Car Wash,
Groit’s Car Wash) also avoid car washes that uses a high-pressure spray, harsh
detergents or brushes
4.
Don't
use a car cover until the paint is fully cured?
5.
A
paint film surface is a delicate thin coating easily dulled and very easily
scratched, so choose carefully the advice you listen to and most importantly
what advice you act upon.
6.
Some
Carnauba wax contains paraffin wax, which effectively ‘seals’ the paint surface
more than a polymer due to its formulation.
7.
The
use of water-based products is highly recommended
Part II -
Applying a Polymer Sealant or Waxing OEM Paint
b)
Polishing or Waxing Production (OEM oven cured) Paintwork
Original equipment materials (OEM) specified materials are very
different from refinish paint products and materials
One of the most often asked question and a subject that results
in a great deal of confusion regarding polishing or waxing OEM paint, Once you
brought a new vehicle “How
soon can I wax my car”?
To find out how long ago
your vehicle was painted; check the driver's side door jamb, a sticker should give
the month and year the vehicle left the plant. Paint curing process; new cars
go through the painting and baking process without any of the rubber, plastic,
and cloth components installed. This is why they can expose the cars paint to
such high temperatures, these high temperatures and special paints used at the
factory level ensure the paint is fully cured by the time the car leaves the
assembly line.
Original Equipment
Manufacturer (OEM) paint is cured at high temperatures; OEM paints are cured in
a paint oven at around 320. °F (160. °C) for 20 minutes, in multiple oven zones
where the paint is baked with radiation and convection heat, or infrared so
that 90-95% of the paint systems out gassing has taken place, the additional
5-10% will cure within 2-3 days, it will probably be stored for one or two days
before transportation, it is then shipped or transported over the road (OTR) to a dealership
and most likely be on the lot for a few weeks or more. So the vehicle’s paint
can be waxed as soon as you take delivery.
By not applying some sort of
paint protection soon after purchase the customer is actually damaging the
paint surface instead of helping it. Salesmen that advise a customer not to wax
a car for 3-6 months are relying on old paint methods and are misinformed about
the latest paint technology. The newer paints are catalyzed (a chemical
reaction that cures the paint) lacquers and enamels needed an extensive time
for the solvents to release, with modern water-based or reduced solvent content
paints this is not necessary.
This is a huge problem in
dealerships because customers tend to take the advice offered by a salesman who
usually knows nothing about paint, rather than a trained paint professional.
This goes a long way to understand why fairly new vehicles paint surfaces are
in such bad shape even after a relatively short period of time.
Twenty years ago, cars were
typically painted with lacquer or enamel paints. These were single stage
paints, with a large volume of solvents that needed to escape before the paint
would fully dry. These paint systems dried from the outside in. The paint would
look and feel dry, but the layers underneath could still be a bit wet and soft
because all the solvents in the paint had yet to escape. Therefore, if wax was
applied to the paint surface before it was fully dried, there could be
problems. There could have been solvent pop, which occurs from solvents pushing
up through the paint and the wax, giving the paint a crater-like appearance.
The paint could also have
“died back” or faded a bit because of the trapped solvents clouding the paint.
Also, solvents that did not escape would leave the paint softer and more
susceptible to scratches and blemishes.
Twenty years ago this was correct;
you should not to wax a new car with these paint systems. However, that was 20
years ago and no longer applies with today’s base-coat/clear-coat paint
systems.
I
would like to think that these articles become an asset to anyone who is new to
detailing and to professionals alike, as well as industry experts who seek to
advance their knowledge.
I hope the above article was
informative. 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 this article as it helps other detailers further their knowledge.
Questions and/ or constructive
comments are always appreciated.
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2012 TOGWT® (Established 1980) all rights reserved
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