Part I - Applying a Polymer Sealant or Waxing Re-Painted Surfaces
Be cognizant that OEM and refinish paint used by body shops are different formulations, even if it’s the same paint manufacturer; this is partly due to the way the paint is cured. OEM paint is applied to a body that has no wiring, upholstery and etc so it can be subjected to elevated temperatures that would not be possible on a refinished vehicle
Drying / hardening time varies by paint manufacturer, paint type and how it was dried; so quoting specific times are dependent upon some variables. Some paint shops use ultra violet light heating ovens, some just allow it to air-dry. Most paint manufactures recommend waiting at least thirty (30) days air-cure before sealing the paint and some recommend up to sixty to ninety (60-90) days to ensure that the paint has sufficiently hardened.
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
Solvent-based paints use water as its carrier system (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. Water-based paint is, much more prevalent in European imports than domestic (US) mfg vehicles.
That distinctive smell of paint is actually dibutyl and diethyl phthalate out-gassing- two very volatile compounds
New paint needs to be allowed to harden for approximately 90 days, 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 and take 16 hours to be stable enough to polish
a) Polishing or Waxing Post-production Paintwork
Due to EPA volatile organic compounds (VOC) regulations most auto body paint shops use down draft paint booths and high volume low pressure (HVLP) paint guns for spray painting. A spray booth is a positive pressure, controlled closed environment, used to paint vehicles in a body / paint shop. To ensure the ideal working conditions (temperature, air flow and humidity), these environments are equipped with forced air ventilation, consisting of one or more air fan / motors and one or more burners to heat the supply air. In order to assist in the removal of the over sprayed paint from the air and to provide efficient operation of the down-draft, water-washed paint spray booths utilize paint detackifying chemical agents.. They filter the air flow and provide heat for paint drying; this heat is not sufficient to bake the paint but only helps in the drying process.
A down draft system provides sufficient air movement around the painted vehicle or parts, to accelerate the evaporation of both the solvents and its water carrier system. Paint specifications require a certain amount of heated air (usually 180-185.OF over a given time period to enable outgassing, drying and cross-linking. Be cognizant that paint is not fully hardened for 60-90 days
The added heat, is also regulated, but on average is never over 180-185F. (See Item 4 and OEM bake temps), as it aids in accelerating the evaporation of the carrier solvents, (water and some hydrocarbon mixtures)
Body / paint shops that use this type of equipment operated by trained and certified operatives will provide a warranty on the paint they apply (baked by PPG, DuPont and others)
Before you seal a repainted finish it needs to fully outgass, that is to say the solvents need to evaporate and the paint needs to cross-link with the surface, then the paint needs to dry and finally harden before you seal the surface.Ask the paint shop to check the P-Sheet as this is specific to the actual paint used and states the recommended outgassing, drying and hardening times in accordance with the actual methods used. A paint warranty (if provided) is usually conditional with these recommendations being strictly adhered to.
Most product data sheets (P-Sheet) state paint will air dry in 12 hours and take 16 hours to be stable enough to polish
Notes:
1. Refinish paint products, materials and paint drying methods are very different from original equipment materials (OEM) specified materials.
2. Paint system require heat to dry and time to harden
3. 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 with water as its carrier system)
4. 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.
5. The base cost of materials (paint) can be quite expensive, it`s not unusual to pay $1000 plus for base coat, clear coat, hardener and reducer needed to paint (PPG, DuPont, Glasurit) a medium sized car when you`re using decent materials
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% un-reacted 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 polyureas, which is much harder than polyurethane adding solvents to the paint, hindering this reaction, while water-based products can help the (moisture) curing process.
Some 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); 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?
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)
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.
c) 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.
Be cognizant that there are many levels of paint / body shop repair, they range from skilled paint spray operatives that work in EPA compliant spray booths to the guy down the road who paints cars. If in doubt ask the body shop or the person who painted your vehicle
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, Griot’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
