This is a practical guide to Surface Science for researchers working in the Transportation Industry.
In this all-new guide you’ll learn all about:
Let’s dive right in.
In transportation, many coating and bonding problems come down to how water and other liquids meet a surface. A repellent coating that beads water but holds drops in place does not clear. A bond on a poorly prepared metal surface can fail after assembly.
These are the places where wetting decides yield in transportation 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 Transportation 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 Transportation industry, several case studies exemplify the advantages of conducting surface property measurements.
Coatings for wings and other exposed surfaces aim to slow ice formation and let ice release more easily. Water contact angle and sliding angle help rank candidate coatings on flat coupons. A low sliding angle means drops leave the surface before they can freeze in place.
ISO 19403-6 describes how to measure advancing and receding angles, and hysteresis, by changing drop volume. Hysteresis shows how strongly drops are pinned. Lab readings rank coatings; they do not replace icing wind tunnel or flight tests. Our sliding angle guide explains the method.
Titanium alloys are strong and light, but water and dirt that stay on the surface can still cause problems. Researchers make low wetting titanium surfaces by combining surface texture, such as anodizing or blasting, with a low energy surface chemistry. Contact angle and sliding angle show how well each process works.
Measure the bare alloy, then each treatment step, with the same drop volume and read time. For titanium parts that will later be bonded, the opposite goal applies, and a wetting check before bonding is the useful test. Our aluminum bonding page sets out that approach for light alloys.
If you are interested in implementing these or any other applications, please contact us.
In an industry where precision reigns supreme, how can Transportation 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.
ISO 19403-6 specifies an optical sessile-drop method to measure dynamic advancing (θₐ) and dynamic receding (θᵣ) contact angles by increasing and decreasing droplet volume. It’s used to quantify wetting/dewetting behavior and contact-angle hysteresis (Δθ = θₐ − θᵣ) to help diagnose surface heterogeneity, contamination, or pretreatment drift on coated panels and substrates.
Use dynamic θₐ/θᵣ (not just static angle) when you need early indication that surfaces will wet and resist dewetting before applying transportation coatings, adhesives, or sealants.
Use θₐ/θᵣ/Δθ trends and variability to separate likely chemistry/contamination drift from texture/heterogeneity/pinning effects when defects (e.g., fisheyes/craters, adhesion loss) start rising.
Dynamic contact angles are method-dependent, so your SOP must lock needle geometry, dosing rate, dwell, leveling, and fit/QC rules to keep trends comparable. If you see “ISO 19403-6:2023” internally, it commonly refers to a draft/DIS stage; the published ISO edition is 2024.
We hope this guide showed you how to apply surface science in the Transportation 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 failure you are trying to prevent. Use contact angle and sliding angle for repellent, anti icing and easy clean coatings. Use contact angle and surface free energy before painting or bonding. Use surface tension for battery electrolytes, paints and other process liquids. Our contact angle guide explains the core method.
A high contact angle shows that water is repelled. It does not show whether a drop will move. Some surfaces bead water at a high angle but pin the drop in place. Sliding angle on a tilt stage, together with contact angle hysteresis, shows whether drops roll off. See the roll off angle and hysteresis entries.
ISO 19403-6 describes dynamic contact angle by changing drop volume, which the Dropometer can run with its sessile drop modes. ISO 19403-7 describes roll off angle on a tilt stage; the Dropometer tilt stage reads up to 60 degrees. Neither standard sets pass limits, so build your own from parts with known field results.
Lab tests rank coatings and catch drift between batches, but they do not replace road testing. They do not capture airflow at speed, wiper chatter or haze. Measure bare glass and a reference coating on the same day, then retest after wiper, washer fluid and UV cycles. Our windshield repellent page sets out the steps.
Measure water contact angle at a fixed time after cleaning or treatment, at five or more spots per zone. Compare the median and the spread with parts that passed your lap shear or peel tests. There is no universal threshold, so gates are set per alloy and process. See reliable aluminum bonding.
Yes. Pendant drop gives electrolyte surface tension, and sessile drop gives contact angle on separators and electrodes. Porous samples absorb drops fast, so absorption time can be the better measure. Moisture changes LiPF6 electrolytes, so control the air around the test. These readings rank materials; they do not replace cell builds. See electrolyte 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.
