This is a practical guide to Surface Science for researchers working in the Automotive Industry.
In this all-new guide you’ll learn all about:
Let’s dive right in.
In automotive production, many paint and bond defects start at a surface you cannot see. A trace of silicone causes a crater. An under treated bumper sheds its paint. A rain repellent that no longer clears glass becomes a warranty claim.
These are the places where wetting decides yield in automotive work:
The Dropometer drop shape analysis kit measures contact angle, surface and interfacial tension, surface free energy and sliding angle with one portable setup. Its method was validated against a KRUSS DSA100E in two peer reviewed papers. If you are new to the terms, start with wettability.
We use the following surface properties to understand the behavior of Automotive products and improve their quality.
Sample Image taken from Droplet Lab Tensiometer.
Young – Laplace Method
Polynomial Method
Ideally, when we place a drop on a solid surface, a unique angle exists between the liquid and the solid surface. We can calculate the value of this ideal contact angle (the so-called Young’s contact angle) using Young’s equation. In practice, due to surface geometry, roughness, heterogeneity, contamination, and deformation, the contact angle value on a surface is not necessarily a single consistent value but rather falls within a range. The upper and lower limits of this range are known as the advancing and receding contact angles, respectively. The values of advancing and receding contact angles for a solid surface are highly sensitive to many parameters, such as temperature, humidity, homogeneity, and minor contamination of the surface and liquid. For example, the advancing and receding contact angles of a surface can differ at different locations.
Practical surfaces and coatings naturally show contact angle hysteresis, indicating a range of equilibrium values. When we measure static contact angles, we get a single value within this range. Solely relying on static measurements poses problems, like poor repeatability and incomplete surface assessment regarding adhesion, cleanliness, roughness, and homogeneity.
In practical applications, we need to understand how easily a liquid spreads (advancing angle) and how easily it is removed (receding angle), such as in painting and cleaning. Measuring advancing and receding angles offers a holistic view of liquid-solid interaction, unlike static measurements, which yield an arbitrary value within the range.
This insight is crucial for real-world surfaces with variations, roughness, and dynamics, aiding industries like cosmetics, materials science, and biotechnology in designing effective surfaces and optimizing processes.
Learn how Contact Angle measurement is done on our Tensiometer
For a more complete understanding of Contact Angle measurement, read our Contact Angle measurement: The Definitive Guide
These reference measurements show how deionized water wets four standard substrates measured with the Droplet Lab Dropometer. Use them as visual and numerical benchmarks when you're checking your own sample preparation, treatments, and chemistry.
Full contact angle and surface energy datasets (including additional liquids and statistics) are available on our dataset hub.
The droplet images above are taken from the same benchmark series as our open dataset. For each substrate and probe liquid we report:
● Advancing and receding contact angles (and hysteresis)
● Derived surface energy (SFE) values based on multi-liquid measurements
● Measurement conditions, uncertainties, and sample preparation details
Comparing your own droplet shapes and angles against these references is a fast way to spot contamination, treatment drift, or unexpected changes in wettability.
This property measures the force that acts on the surface of a liquid, aiming to minimize its surface area.
Sample Image taken from Droplet Lab Tensiometer
Dynamic Surface Tension
Dynamic surface tension differs from static surface tension, which refers to the surface energy per unit area (or force acting per unit length along the edge of a liquid surface).
Static surface tension characterizes the equilibrium state of the liquid interface, while dynamic surface tension accounts for the kinetics of changes at the interface. These changes could involve the presence of surfactants, additives, or variations in temperature, pressure, and composition at the interface.
When to use Dynamic Surface Tension Measurement
Dynamic surface tension is essential for processes that involve rapid changes at the liquid-gas or liquid-liquid interface, such as droplet and bubble formation, coalescence (change in surface area), the behavior of foams, and the drying of paints (change in composition, e.g., evaporation of solvent). It is measured by analyzing the shape of a hanging droplet over time.
Dynamic surface tension applies to various industries, including cosmetics, coatings, pharmaceuticals, paint, food and beverage, and industrial processes, where understanding and controlling the behavior of liquid interfaces is essential for product quality and process efficiency.
Learn how Surface Tension measurement is done on our Tensiometer
For a more complete understanding of Surface Energy measurement, read our Surface Tension measurement: The Definitive Guide
Sample Image taken from Droplet Lab Tensiometer
Learn how Surface Energy measurement is done on our Tensiometer
For a more complete understanding of Surface Energy measurement, read our Surface Energy measurement: The Definitive Guide
For benchmark contact angle and surface energy values on glass, nylon, PMMA, and Teflon, see the Open Benchmark Data panel above or visit our Dataset Hub for full CSV downloads.
The sliding angle measures the angle at which a liquid film slides over a solid surface. It is commonly employed to assess the slip resistance of a surface.
Sample Image taken from Droplet Lab Tensiometer
Learn how Sliding Angle measurement is done on our Tensiometer
For a more complete understanding of Sliding Angle measurement, read our Sliding Angle Measurement: The Definitive Guide
Within the Automotive industry, several case studies exemplify the advantages of conducting surface property measurements.
A good paint finish needs a substrate the paint can wet and a paint batch that behaves like the last good one. Orange peel can follow a shift in paint surface tension or viscosity, even with the same spray settings. Pendant drop surface tension of the paint as sprayed, compared with a reference batch, catches that shift. See fixing orange peel.
On the substrate side, ASTM D7334 covers wettability by advancing contact angle. Plastic parts usually need activation first, so check them after plasma treatment or flame treatment. Most orange peel still comes from application, so check spray setup too.
Rain repellent coatings keep water from building up on the windshield, but wipers, washer fluid and sun wear them down. Static contact angle shows how strongly the coating repels water. Sliding angle shows whether drops actually run off. Compare both with bare glass and a reference coating on the same day.
The glass must be clean before any coating goes on. ASTM C813 uses water contact angle to detect hydrophobic contamination on smooth glass; see also glass cleaning verification. For glass and lamps that must stay clear, see anti fog coating validation.
If you are interested in implementing these or any other applications, please contact us.
In an industry where precision reigns supreme, how can Automotive manufacturers ensure their products withstand scrutiny? The answer lies in standards and guidelines: the compass that guides them through the complex maze of quality and performance.
A combined characterization workflow that pairs ISO 25178 areal (3D) surface texture parameters with quantitative wettability and droplet-mobility metrics to explain whether functional performance is driven mainly by surface chemistry/contamination or by texture/roughness state. Dropometer provides the wettability/mobility measurements; ISO 25178 texture metrology must be performed separately using a profilometer/interferometer.
Use when a part fails or drifts and you need to separate “chemistry/contamination” causes from “texture recipe/process” causes with measurable evidence.
Use when establishing PPAP/APQP-ready limits by correlating texture parameters + wetting/mobility outputs to real performance outcomes.
Note: Correlation thresholds must be calibrated per part family + process by tying texture + wettability outputs to actual functional outcomes (adhesion test, clearing/fogging performance, defect/return rates). Treat Wenzel/Cassie interpretations as diagnostic models with assumptions, not as universal truth.
We hope this guide showed you how to apply surface science in the Automotive industry.
Now we’d like to turn it over to you:
Feel free to leave a comment below—we’d love to hear from you.
Start with the defect you see most often. Use water contact angle on substrates before painting or bonding. Use paint surface tension by pendant drop for craters and orange peel. Add surface free energy from two or more probe liquids for plastics and adhesives. Use sliding angle for glass coatings. Our contact angle and surface tension guides explain each method.
DIN EN 828 describes contact angle and surface free energy as wettability indicators before bonding, not bond strength. ASTM D7334 covers advancing contact angle, and ASTM C813 covers contamination on glass. The Dropometer uses the sessile drop method. Keep your peel, lap shear and paint adhesion tests for acceptance.
Measure water contact angle at a fixed time after treatment, at several spots per zone, and log the time since treatment. Treated polypropylene drifts back toward its original state in air, so timing matters. Set gates from parts that passed your adhesion tests. See reliable polypropylene bonding and, for metals, reliable aluminum bonding.
It can flag a risk that is consistent with silicone, such as a high angle or a large spread between zones. It cannot name the contaminant; that needs FTIR or XPS. Use the contact angle screen to decide which parts to hold and which to send for chemical analysis. See silicone contamination detection.
Texture and chemistry both change how liquids spread and pin. ISO 25178 defines 3D surface texture parameters, measured with a profilometer or interferometer. The Dropometer does not measure texture. Pairing texture data with contact angle and sliding angle helps you tell a texture problem from a chemistry problem. See surface roughness.
Yes, for wetting. Pendant drop gives electrolyte surface tension, and sessile drop gives contact angle on separators and electrodes. Together they help rank electrolyte additives before cell builds. They do not measure conductivity or cell performance. Moisture changes LiPF6 electrolytes, so control the air around the test. See electrolyte and separator wetting.
The drop shape method was validated against a KRUSS DSA100E in two peer reviewed papers, one in Review of Scientific Instruments and one in Colloids and Surfaces A. Published contact angle accuracy is 0.35 degrees. Automatic edge and baseline detection gives the same reading from the same image. See our validation papers.
