Automotive Paint TestingOctober 3, 2018
Automotive paint is expected to put up with a lot over the course of its lifetime. It needs to endure through dings, scratches, smudges, hand prints, bird droppings, nasty weather and so much more. It must be durable, and it must be long-lasting if it’s going to keep performing well over the course of your vehicle’s lifespan. After all, cars are expected to last 10, 15 or even 20 years. While there’s nothing wrong with getting a new coat of paint during that time, the ideal expectation is that the paint should hold up this long as well.
Of course, this kind of durability and longevity doesn’t just occur by accident. Instead, extensive testing and trials go into making sure the paint holds up to the level of stress it will be asked to endure in the real world. These tests and measures are known as automotive paint testing, and they’re designed to make sure the paint on your car is as tough as the car itself — and ready to handle just about anything you can throw at it.
Before most automotive paint even touches the surface of a vehicle, it will need to pass these tests to ensure it’s at the level it should be and is up to standard enough to be road ready.
What Are Some of the Automotive Paint Tests Used Today?
There are so many different environmental and human factors that will come together to stress the paint on the exterior of a car. We mentioned a few of them earlier, such as weather, bird droppings and scratches, but the list could go on indefinitely. The simple fact is that there is a vast multitude of hazards out there just waiting to damage exterior paint.
Because of this, it only makes sense that there should be a number of different tests automotive paint needs to pass to prove it’s up to the task of resisting and repelling all these hazards. These tests are intended to evaluate things like the paint’s thickness, hardness, color, glossiness, resistance to weather, corrosion and chemical agents and more.
Let’s look at a few of those tests now and see how they evaluate a paint’s performance level.
1. Abrasion Resistance
The purpose of this test is to gauge how well paint can hold up against scrapes, scuffs and scratches. In cases like these, what’s really being tested isn’t necessarily the colored paint itself. Rather, the testers are concerned with the clear coat that rests on top of the colored paint. It’s this clear layer that’s being tested for its ability to withstand abrasions.
Testers will purposefully scuff the paint and then examine the damage, measuring it and evaluating it. If the results are not satisfactory, they’ll update the formula or the method of the painting and try again. This process is repeated until the testers are satisfied that the damage from minor scrapes and scuffs is either nonexistent or is as minimal as possible given the limitations of current technology.
2. Accelerated Corrosion
During the winter months roads in many areas are typically covered with road salt to keep the snow and ice at bay. While this is great for driving, it’s less wonderful for a vehicle’s paint. The chemical structure of the road salt can, unfortunately, tend to have a corrosive effect when it’s left in prolonged contact with your car’s paint. This leads to a dull, patchy appearance in your paint, almost as though something has been eating away at it. To test a paint’s resistance to this type of corrosive damage, testers will expose paint to a salt fog. This replicates the conditions where an automobile might be exposed to road salt in the winter.
3. Accelerated Weathering
It should come as no surprise that automotive paint will need to hold up against severe weather of all types. Automotive paint will need to brave high winds, snowstorms, rain, hail and ice as well as extended exposure to the harmful rays of the sun.
Of course, because the type of weathering that might damage a car takes place over months and even years, this makes it difficult to simulate in a lab as technicians attempt to gauge how well the paint withstands this type of strain. To best simulate this type of damage, they will usually expose the paint to 1,000-2,000 hours of ultraviolet light and water cycling exposure at specific temperatures designed to mimic extreme weather conditions.
4. Chemical Resistance
Road salt isn’t the only chemical compound automotive paint might encounter. Other potential chemical hazards include antifreeze, windshield wiper fluid and gasoline. Any of these compounds, if splashed in excess on a car’s painted exterior, has the potential to eat away at the paint’s finish. And while a car’s paint might not purposefully be exposed to gasoline or antifreeze, their natural proximity means it’s more than likely these substances will contact the paint over the vehicle’s lifespan.
To combat this, these chemicals are tested on the paints until the results are satisfactory enough to prove that a paint job will be able to withstand them.
5. Environmental Exposure
While this type of hazard is similar to the ones we discussed as weather concerns, it’s ultimately its own category. When we talk about environmental exposure, this tends to mean things like extreme heat, humidity or cold. Think of things like a scorchingly hot and humid summer day or a bitterly cold day that freezes and cracks everything in its path.
If paint hasn’t been tested and prepared properly, these types of extreme weather might cause irreparable damage. Heat and humidity might cause paint to melt, whereas extreme cold might cause it to crack and even peel away from the exterior of the vehicles themselves.
To perform these types of tests, technicians subject the paint to thermal shocks and extreme temperature and humidity fluctuations. Through this process, they attempt to speed up the effects of weather exposure that would normally take months or years, as they try to see how well the paint holds up against the damage.
6. Paint Adhesion
Depending on the chemical makeup of the paint, as well as the surface it’s been painted on to, paint can have an unfortunate tendency to want to separate from the surface it’s supposed to be covering. Think of paint that you might have ever seen flaking or peeling off of a surface, like the exterior of a building, and you’ll have a better picture.
As this is not a desirable outcome, paint is stressed and tested to ensure it can remain adhered and won’t weaken or flake off. Paint might be tested by way of cross-cuts, or by peel-off. If the paint appears to easily succumb to these stressors, then it will likely need to return for more development.
7. Paint (Film) Hardness
While the name of this test might be a bit obscure, it’s simple enough in practice. If a paint is soft and flimsy, it will be highly susceptible to scratches that reveal the surface of the car beneath the paint. A harder paint, on the other hand, will be well-equipped to hold up against scratches while exposing the bare surface of the car.
These tests, then, measure how hard the surface layers of the paint are and determine whether or not this hardness is sufficient to withstand a reasonable amount of scratching and wear-and-tear.
8. Paint Thickness
Most original equipment manufacturers (OEMs) require that paint must be a very specific measure of thickness. If the paint varies too far to either side and is either too thick or too thin, a whole variety of issues could follow. It might be more susceptible to scratching, more vulnerable to extreme weather or even more difficult to clean.
Because of these risks, manufacturers have determined the precise level of thickness that is most appropriate and most adept at protecting itself from damage. The tests in this category will measure whether or not the paint in question has achieved this level of thickness.
What Are Some of the Common Testing Categories?
One way to look at paint testing is in terms of what the paint is being tested for. When you look at it this way, you might tend to lump tests like accelerated weathering and thermal exposure together — because of the significant overlap in these two factors that could potentially damage the paint.
This isn’t the only way to look at testing, however. Another way to examine these testing processes and compare them to one another is by looking at the actual means of testing, not just at what the tests are trying to prepare the paint to withstand.
Broadly speaking, these tests can be grouped together into specific categories:
1. Chemical Analysis
These types of tests are concerned with evaluating the performance and composition of the various surface layers of the paint. Through an accurate understanding of these layers and the elements that build them, engineers and technicians can then be better equipped to manipulate the layers to withstand outside concerns.
2. Physical and Mechanical Tests
On the surface, these tests may initially seem less “scientific,” as they aren’t designed with the purpose of testing chemical composition or anything similar. Instead, these tests are a little more physical in nature. They involve the testers literally attempting to physically damage the paint to see how well it holds up.
The qualities these tests are usually looking to evaluate are physical, visible traits such as a paint’s adhesive abilities, its hardness, color, glossiness and more.
A few examples of these types of tests include:
- Cross-cut test to measure paint adhesion
- Pull-off test to measure paint adhesion
- Pencil test to measure paint hardness
- Glossameter, designed to measure pain glossiness
- Spectrophometer, designed to evaluate paint color
- Bend test to measure how well paint moves and adheres
- Impact test to measure impact resistance
- Microscopic examination of a section to measure paint thickness
- Various methods to determine the thickness of the film on the paint’s surface
These tests are less concerned with physical, immediately visible properties and are instead more focused on how a paint holds up over time, especially when subjected to less-than-ideal conditions. These conditions include factors like extreme temperatures and severe weather patterns. To determine whether or not paint can withstand snow, ice, rain, heat and humidity, conditioning tests are usually employed.
What makes these tests difficult to devise and perform is that much of this type of weather conditioning doesn’t occur in just one day. It takes place over a period of months and even years. Because of this, it’s difficult to simulate in a lab.
To combat this problem, testing facilities work to replicate the long-term effects of weathering in a greatly accelerated timeline. In a lab, they’ll produce environments that can simulate years of sun, rain and other elements to illustrate what paint might look like after exposure to these conditions.
Just a few of these potential tests include:
- High-temperature conditioning
- Low-temperature conditioning
- Thermal cycles, moving from one temperature to another on a controlled schedule
- Climate cycle, with a controlled pattern rotating between different levels of heat and humidity
4. Resistance to Corrosion
Corrosion is a very real concern both for the car itself and for the paint covering it. A vehicle’s paint will likely come into contact with high levels of chemicals during its lifetime. All of these various compounds have the potential to break down the smooth finish of paint, damaging it or even destroying it entirely.
Again, however, these are often difficult conditions to simulate in a laboratory, as much of this corrosion results from salt or other chemicals sitting on the paint’s surface for an extended period of time — all while coupled with extreme weather conditions, in many cases.
To best replicate these types of conditions and contaminants, these are a few of the tests that will likely be used:
- Neutral salt spray test
- Acetic acid salt spray test (copper accelerated and non-copper accelerated)
- Cyclic corrosion test
- Continuous condensation in hot and humid conditions
- Water immersion resistance test
Aging is yet another category that will inevitably cause damage and general wear-and-tear to a car’s paint. No matter how well a car is cared for, paint will wear out with age, and there isn’t much any of us can do about it.
From a manufacturing point of view, then, the goal is to create a paint that will last as long as possible before it begins to show signs of aging and wearing out. As with several of the other categories we’ve discussed, however, the inherent difficulty is in how to test for a process that would ordinarily take years to complete.
To best simulate the type of timeline that would cause aging damage, and to speed this timeline up into a workable scenario, the following tests will typically be employed:
- Accelerated aging by solar radiation, using artificial simulation
- Weathering, using artificial simulation
- Aging, using UV radiation
- Alternate cycling between weathering and corrosion
6. Resistance Test to Chemical Agents
These types of resistance tests have a lot in common with corrosion-resistance tests, although those are typically more focused on how the corrosion will affect the paint over time. In resistance tests, as they apply to chemical agents, the greater focus is on the wide range of chemical materials that paint is likely to encounter over its lifetime and how they will react with one another.
Just a few of the types of chemicals paint-manufacturers are concerned about that would fall into this category include chemicals like antifreeze, gasoline and windshield wiper fluid. Because these are all chemicals that relate directly to cars and are handled near, on or even in them, the likelihood of these compounds coming into contact with the surface of the paint is highly likely. Because of this, it’s imperative to test how the paint will react to these chemicals.
The types of tests commonly employed to test a paint’s level of chemical resistance include:
- Resistance tests by drop application
- Resistance tests by immersion
- Resistance tests by application of a soaked cloth
What makes this category unique is that every test is evaluating the same thing: how paint reacts when it comes into contact with a substance. The only difference between tests is the variety of ways the chemical is applied to the paint.
In the drop application test, a chemical substance such as windshield wiper fluid would be dropped onto the paint. In an immersion test, the paint might be plunged into a container of this fluid. Finally, in a soaked-cloth test, a rag might be soaked in this fluid and then rubbed onto the paint. In each test, the goal is the same — to gauge the paint’s reaction and resistance ability.
Automotive Paint Measurements
While the types of testing discussed here are absolutely critical to the long-term success and durability of automotive paint, it isn’t the only way manufacturers can assess paint and determine how well it succeeds in durability and reliability.
Manufacturers are also interested in obtaining direct “measurements” for the paint. In this way, they’re able to base their improvements and research not just on qualitative properties and general impressions, but also on real, quantitative data. This results in more accurate and actionable data that leads to more reliable and sturdy paint overall that can hold up under testing and, eventually, real-world conditions.
In terms of collecting this solid data, two parameters that manufacturers and developers will often look at to measure are color and gloss. Within these parameters, number values are determined and assigned. Different numbers designate things like the current levels of color and gloss, as well as the ideal level of color and gloss.
When paint undergoes the various tests described above, these numbers will be measured and compared to one another as the technicians attempt to evaluate how well the paint is holding up against the different contaminants. With these numbers, they’re better able to assign real data to what would otherwise be mere impressions and guesswork.
Contact NTS to Request Your Quote Today
Here at NTS, our testing programs help you feel confident in your paint’s capabilities. Whether you’re looking to learn more about your paint’s chemical resistance abilities or its aging abilities, our tests can give you the answers you’re looking for. Not only that, but we’re also recognized as one of the largest commercial test laboratories in the U.S., meaning you can be certain you’re getting your money’s worth. We test everything from software to aerospace technology, and we’d love to test your paint as well.
To get started with our testing programs, request a quote and learn more about what the process of testing with us would look like. And if you have any additional questions about our services or our programs, don’t hesitate to contact one of our experts to find out more.