Orange Peel

[Murr1525]

What is orange peel exaclty?

[the other pc]

Paint goes on as a mixture of solids held in suspension in a liquid carrier.

It's initially distributed on the substrate (the surface being painted) in the form of a wet film.

The wet film hardens into a solid film by a combination or outgassing of liquid carriers and chemical reacting/linking of liquid molecules into solid compounds.

As the hardening occurs the physical dimensions of the film change. When the resulting hard film tends to have greater surface area than the original wet film the outer surface must wrinkle in three dimensions to fit onto the two dimensional surface of the substrate.


PC.

[benhui86]

uhhhh yah that or..... paint surface that is not smooth and has a pattern that resembles the surface of a orange.....

[rusty bumper]

Originally posted by the other pc
Paint goes on as a mixture of solids held in suspension in a liquid carrier.

It's initially distributed on the substrate (the surface being painted) in the form of a wet film.

The wet film hardens into a solid film by a combination or outgassing of liquid carriers and chemical reacting/linking of liquid molecules into solid compounds.

As the hardening occurs the physical dimensions of the film change. When the resulting hard film tends to have greater surface area than the original wet film the outer surface must wrinkle in three dimensions to fit onto the two dimensional surface of the substrate.


PC.

Would that be another way of saying that the paint was applied too thick?

I've always wondered what the root cause of orange peel was.

[MandarinaRacing]

According to PPG:

Cause
Failure of the paint droplets to coalesce on the surface.
This may be due to:

a) Poor spraying technique, spray gun too far from surface, incorrect compressed air pressure, incorrect nozzle adjustment.

b) Excessively thick or thin film.

c) Paint incorrectly mixed, wrong viscosity, poor quality or incorrect thinner.

d) Insufficient drying time between coats, cold air fanning to speed drying.

e) Incorrect ambient or surface temperature, draughts.



Prevention
a) Use the correct spraying technique and ensure that equipment is correctly adjusted.

b) Apply paint in thin even coats.

c) Ensure that the paint is correctly mixed, use only recommended thinner with the correct grade.

d) Allow sufficient drying time between coats.

e) Spray within the recommended temperature range and ensure proper ventilation.

Rectification
Rub out the orange peel, compound and polish. In severe cases it may be necessary to flat and repaint the surface.

Some time ago I posted a link on the PPg website that deals with ALL types of paint defects, try it and see if it's still working...HERE

Alex

[rusty bumper]

Wow, there's a lot that can go wrong in the painting process after reading that list!

Thanks for the link......I just bookmarked it.

[the other pc]

Orange peel doesn’t come from one single root cause. Paint drying is a very complex physical/chemical phenomenon. Coating manufacturers and car makers spend billion of dollars on the technology and have armies of chemists, process engineers and technicians. It’s not like they haven’t read their own application notes, they wrote them. “Gee Bob, the instructions say not to put it on so thick. I guess we should have read that before we painted the last 50,000 cars.” If it were as simple as being “too thick” manufacturers would merely adjust the application process.

Orange peel in and of itself is not a defect. Orange peel is a characteristic of the coating process just like film thickness, gloss, hardness, color accuracy, optical opacity, dust free cure time, tack free cure time, etc. Excessive orange peel, greater than specified as acceptable for a given coating process, would be a defect.

A coating manufacturer must balance the divergent and conflicting parameters of all of those characteristics as well as application cost, application process robustness, process time, serviceability, service life, environmental regulatory compliance and more.

The characteristics are balanced to optimize value as defined by the OEM customer. If the car makers find that only 0.01% of customers care or even know what orange peel is but that they can cut 60 seconds off a paint process, 0.5% material volume, 0.2% waste disposal cost or 0.1% of post spray buffing processes what do you think they will choose?


PC.

[Murr1525]

Interesting.. thanks guys

[rusty bumper]

Originally posted by the other pc
The characteristics are balanced to optimize value as defined by the OEM customer. If the car makers find that only 0.01% of customers care or even know what orange peel is but that they can cut 60 seconds off a paint process, 0.5% material volume, 0.2% waste disposal cost or 0.1% of post spray buffing processes what do you think they will choose?


PC.

I guess that makes sense, considering all the vehicles they build in a year, and the high labor costs associated with automaking.

Great writeup PC.