Imagine you've been rear-ended. There's a little dent in your fender, but the paint has been damaged. When you go to get it fixed, what will matter more to you? The exact specifications of the process used to repair the dent or the guarantee that the paint will match your car's paint job?
Probably the paint!
Most car owners do care about their car's paint. It's upsetting when it gets chipped because it disrupts the car's appearance, decreases its value, and is expensive to fix!
But it's expensive to fix for a good reason. Properly painting a car (especially if it involves color matching) takes a lot of time and layers of paint. If not done correctly, you might notice imperfections in the paint texture, peeling, sun or environmental damage, or fading.
In order to avoid imperfections or bumps in the paint, it must be applied in a certain way in a specific setting.
Your car's paint job involves several layers of paint, including rust protection, primer, color coat, and clear coat.
The layer closest to the car is the ED Coat. This is an anti-corrosive coat that is typically 0.8-1.2 microns in thickness.
Next is the primer. This is a thicker layer, ranging from 1 to 1.5 mils in thickness. This layer prepares your car to receive the color coat. The color coat is usually 0.5 to 2 mils.
Lastly, a clear coat is added to give a vibrant finish and protect the paint. This layer is typically 1.5 - 2 mils.
The color coat contains the pigment that makes your car whatever color your heart desires! Over the last 100 years, manufacturers have experimented with different types of color coats. In the 1910s, they used oil-based paints. In the 1920s, they shifted to solvent-based nitrocellulose lacquer and, in 1928, added metal flakes. The 1950s introduced acrylic paint, and the 1970s brought polyurethane enamel. It wasn't until the 1980s that we began to prime before adding additional coats to provide protection.
Since the 1990s, manufacturers have commonly used a waterborne base coat. Environmental regulations forced the reduction of solvents and gave us the same basic system we use today!
While manufacturers in the early 1900s hand-painted cars, they quickly switched to a sprayer. To this day, paint is sprayed onto the vehicle. While this is a much more efficient process and creates a beautiful, seamless layer of paint, it opens the door for some critical issues.
How can a car's paint job be impacted? Simply: particles during the painting process. Now you might think this is a simple fix - just paint in a clean environment, right? But it's not just visible particles that can impact a car's paint job. Everything from the finest grain of sand to literally a blood cell can make a noticeable mark in the end product.
Potential contaminants can come from just about anywhere. But potential sources in the manufacturing process include:
Dust from dry sanding.
Poor quality masking paper.
Not using a tack rag before spraying.
Inadequate or faulty filtration of air.
Unclean compressed airlines.
Ill-maintained spray booths or fans.
Poor gowning protocols (specifically, booties for your feet).
All of these allow for particles to end up on the painted surface or in the compressed airline that is used to paint the car.
When a particle makes an appearance and impacts the paint job, you will notice a bump in the texture. In the base coats, a tiny particle will make a big impact. But the topcoats are more concerned about particles typically visible to the eye.
At the ED Coat, particles from 2 to 6.3 microns are of concern because they can cause an impact. These are particles that are smaller than a blood cell.
Similarly, at the primer coat, microns ranging from 2 to 9.5 microns are worrisome.
The color coat is concerned with slightly larger particles, ranging from 3 to 9.5 microns.
Lastly, the clear coat is concerned with the largest particles ranging from 9.5 to 25 microns. To note, this is still smaller than the eye can see, which is typically particles larger than 35 microns.
Now, at all points during the process, large particles can make a difference and create a visual impact. But at the base coats, even the smallest of particles will have a magnified impact on the final layer.
So how do you avoid even the smallest of particles from impacting your final product?
If you want the perfect car paint job, you have to do what the pros do: paint in a cleanroom.
In a 2018 Tweet, you can watch Tesla's paint applicator apply even coats of paint to their Model 3 in a cleanroom environment. A cleanroom requires gowning procedures for any personnel who enter and cleaning procedures for all materials that go in and out.
A properly run cleanroom also requires all equipment used to be carefully cleaned and maintained. This will prevent issues with clogged or dirty compressed airlines harming the new paint.
The cleanroom environment protects the new paint from any particles - no matter how small - so that manufacturers can get the perfect finish.
Curious about how else manufacturers use cleanrooms in the automotive industry? Check out our Knowledge Center! You can make a free account and instantly access dozens of articles, videos, and white papers, breaking down the cleanroom and particle counting industry.
Paint Shop Contamination Control Layout