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The Practical Guide to Surface Science (2026)

D54c15105cfe94f786c500e4091d6ea65457608fde49ba183c8f862814a54249?s=100&d=m
Escrito por
Dr. Amit Pratap Singh
PhD, Delhi University Post Doc - AIST Japan
Guest Author
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alidad
Reviewed by
Dr. Alidad Amirfazli
Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.
Scientific Advisor & Co-founder
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D54c15105cfe94f786c500e4091d6ea65457608fde49ba183c8f862814a54249?s=100&d=m
Written By

Dr. Amit Pratap Singh

Guest Author

PhD, Delhi University

Post Doc - AIST Japan

alidad
Reseña escrita por

Dr. Alidad Amirfazli

Scientific Advisor & Co-founder

Dr. Amirfazli, a leading expert in surface wetting and superhydrophobic coatings, has 250+ publications, edits Advances in Colloid and Interface Science, and has received multiple research awards.

Esta es una guía práctica de la Ciencia de Superficies para investigadores que trabajan en la Industria del Transporte.

En esta nueva guía aprenderás todo sobre:

  • Principios cruciales de la ciencia de superficies
  • La importancia de las mediciones de la ciencia de la superficie para la industria del transporte
  • Normas y directrices ASTM aplicables

Vamos a sumergirnos en ello.

Buque de carga en el río

Executive Summary

What it covers: How transport engineers use contact angle, dynamic contact angle, sliding angle and surface tension on coatings, metal surfaces and battery materials. Each topic links to a use case or a standard.
Key insights: A high contact angle shows that a surface repels water, but not that drops will run off. Sliding angle and contact angle hysteresis answer that second question, which matters for rain, spray and ice.
Business value: Ranking coatings and surface treatments on flat coupons narrows the field before costly rig and road testing. A wetting check before bonding catches poor surface preparation while the part can still be cleaned again.
Standards to follow: ISO 19403-6 describes dynamic contact angle by changing drop volume, giving advancing and receding angles and hysteresis. ISO 19403-7 describes roll off angle on a tilt stage. Neither sets pass limits, so build them from your own parts.
Bottom line: Measure both contact angle and sliding angle when a surface must shed water or ice. Start with the coating or bond that fails most often, then book a 15-minute consult about testing it on your own coupons.

Capítulo 1: Introducción

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:

  • Rain repellent glass. Contact angle, sliding angle and hysteresis show whether a windshield coating still clears water after wiper and washer wear. See windshield rain repellent performance.
  • Aluminum bonding. Water contact angle at a fixed time after surface preparation flags oxide drift and contamination before the adhesive goes on. See reliable aluminum bonding.
  • Battery electrolyte wetting. Electrolyte surface tension and contact angle on separators and electrodes help rank additives before cell builds. See electrolyte and separator wetting.

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.

Capítulo 2: Medición del ángulo de contacto

El ángulo de contacto cuantifica la humectabilidad de una superficie representando el ángulo entre la superficie de un líquido y una superficie sólida.
Investigación de Dropletlab

Sample Image taken from Droplet Lab Tensiometer.

Joven – Método Laplace

Método polinómico

Ángulo de contacto dinámico

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.

Ángulo de contacto dinámico frente a ángulo de contacto estático

Las superficies y los recubrimientos prácticos muestran naturalmente histéresis de ángulo de contacto, lo que indica un rango de valores de equilibrio. Cuando medimos ángulos de contacto estáticos, obtenemos un solo valor dentro de este rango. Confiar únicamente en mediciones estáticas plantea problemas, como una repetibilidad deficiente y una evaluación incompleta de la superficie con respecto a la adherencia, la limpieza, la rugosidad y la homogeneidad.

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.

Esta información es crucial para las superficies del mundo real con variaciones, rugosidad y dinámica, lo que ayuda a industrias como la cosmética, la ciencia de los materiales y la biotecnología a diseñar superficies efectivas y optimizar los procesos.

Aprenda cómo se realiza la medición del ángulo de contacto en nuestro tensiómetro

Para una comprensión más completa de la medición del ángulo de contacto, lea nuestra medición del ángulo de contacto: la guía definitiva

Open Benchmark Data: Contact Angle & Surface Energy

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.

Glass - DI Water
Glass - DI Water
Nylon - DI Water
Nylon - DI Water
PMMA - DI Water
PMMA - DI Water
Teflon - DI Water
Teflon - DI Water

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.

Capítulo 3: Medición de la tensión superficial

Esta propiedad mide la fuerza que actúa sobre la superficie de un líquido, con el objetivo de minimizar su superficie.

Medición de tensión superficial

Sample Image taken from Droplet Lab Tensiometer

Tensión superficial dinámica

La tensión superficial dinámica difiere de la tensión superficial estática, que se refiere a la energía superficial por unidad de área (o fuerza que actúa por unidad de longitud a lo largo del borde de una superficie líquida).

La tensión superficial estática caracteriza el estado de equilibrio de la interfaz líquida, mientras que la tensión superficial dinámica explica la cinética de los cambios en la interfaz. Estos cambios podrían implicar la presencia de tensioactivos, aditivos o variaciones en la temperatura, la presión y la composición en la interfaz.

Cuándo utilizar la medición dinámica de la tensión superficial

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.

La tensión superficial dinámica se aplica a diversas industrias, incluidas las cosméticas, los recubrimientos, los productos farmacéuticos, la pintura, los alimentos y las bebidas, y los procesos industriales, donde la comprensión y el control del comportamiento de las interfaces líquidas son esenciales para la calidad del producto y la eficiencia del proceso.

Aprenda cómo se realiza la medición de la tensión superficial en nuestro tensiómetro

Para una comprensión más completa de la medición de la energía superficial, lea nuestra medición de la tensión superficial: la guía definitiva

Capítulo 4: Medición de la energía superficial

La energía superficial se refiere a la energía requerida para crear una unidad de área de una nueva superficie.
231

Sample Image taken from Droplet Lab Tensiometer

Aprenda cómo se realiza la medición de la energía superficial en nuestro tensiómetro

Para una comprensión más completa de la medición de la energía superficial, lea nuestra medición de la energía superficial: la guía definitiva

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.

Capítulo 5: Medición del ángulo de deslizamiento

El ángulo de deslizamiento mide el ángulo en el que una película líquida se desliza sobre una superficie sólida. Se emplea comúnmente para evaluar la resistencia al deslizamiento de una superficie.

Ángulo de deslizamiento 1

Sample Image taken from Droplet Lab Tensiometer

Aprenda cómo se realiza la medición del ángulo de deslizamiento en nuestro tensiómetro

Para una comprensión más completa de la medición del ángulo de deslizamiento, lea nuestra medición del ángulo de deslizamiento: la guía definitiva

Capítulo 6: Aplicaciones en el mundo real

Dentro de la industria del transporte, varios estudios de caso ejemplifican las ventajas de realizar mediciones de propiedades superficiales.

Ice build up on aircraft wings

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.

Ice build up on aircraft wings

Low wetting surfaces on titanium alloys

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.

Low wetting surfaces on titanium alloys

Somos sus socios en la resolución de su negocio y tecnología Desafíos

Si está interesado en implementar estas u otras aplicaciones, póngase en contacto con nosotros.

Capítulo 7: Normas y directrices

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 19403-6:2024, Dynamic Contact Angle (Advancing/Receding) by Drop-Volume Change

What it is

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.

When to use it

Ready-to-coat / ready-to-bond verification:

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.

Root-cause triage & process drift monitoring

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.

In-scope / Out-of-scope

In scope
  • Sessile-drop optical measurement with controlled volume increase/decrease (e.g., needle-in-drop dosing) to obtain dynamic angles.
  • Dynamic advancing (θₐ) during volume increase and dynamic receding (θᵣ) during volume decrease under a defined volume-change program.
  • Derived hysteresis (Δθ = θₐ − θᵣ) and spot-to-spot variability as diagnostic outputs for non-uniform surfaces.
  • Coated panels/substrates (common in transportation finishing and bonding workflows) using a documented SOP to lock controllables.
Out of scope
  • Universal pass/fail thresholds (limits must be calibrated to your downstream outcomes for each coating family + substrate + pretreatment).
  • Surface energy component analysis or direct liquid surface tension measurement (use other standards/methods for those).
  • Uncontrolled porous/absorbing surfaces where absorption dominates the droplet-volume/contact-line behavior without additional controls.
  • Alternative contact-angle methods (e.g., tilting plate, captive bubble, Wilhelmy) and replacing your instrument’s operating instructions.

Minimum you must report (checklist)

  • Standard + edition used (ISO 19403-6:2024) and your internal SOP ID (if applicable).
  • Substrate/coating description (material, finish) and pretreatment/treatment history, including time since treatment/cure.
  • Test liquid (identity, grade/concentration if relevant) and liquid temperature.
  • Drop/dosing geometry: sessile configuration, needle-in-drop (if used), needle type/size, and imaging/optics setup.
  • Volume-change program: start volume, step size or continuous rate, advance/recede rate, and dwell/settling rule.
  • Results: θₐ, θᵣ, and Δθ = θₐ − θᵣ, plus number of spots/replicates.
  • Statistics across spots: median + IQR (or mean + SD) and spot rejection/re-run criteria (edge fit QC, non-axisymmetric drops, vibration, unstable receding due to pinning).
  • Environment + controls: temperature/RH (if controlled) and reference (“golden”) panel or other run control results.

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.

How to interpret results (guardrails)

  • θₐ increases vs baseline → poorer initial wetting; investigate treatment decay, low-energy residues, or contamination before coating/bonding.
  • θᵣ decreases or becomes unstable and/or Δθ increases → stronger pinning/dewetting tendency consistent with heterogeneity, roughness, contamination, or cure gradients; treat as a diagnostic signal, not a single-cause verdict.
  • High spot-to-spot variability (large IQR/SD) → non-uniform pretreatment/coating/additive distribution or localized contamination; use a panel map to locate outliers.
  • Always anchor interpretation to controls (golden panel stability) and calibrate Green/Yellow/Red limits to downstream metrics (adhesion, crater/fisheye rate, rework/scrap) for each process window.

Ahora te toca a ti

We hope this guide showed you how to apply surface science in the Transportation industry.

Ahora nos gustaría entregárselo a usted: 

Feel free to leave a comment below—we’d love to hear from you.

Frequently asked questions

Which surface measurement should a transport engineering team start with?

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.

Why measure sliding angle as well as contact angle?

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 y hysteresis entries.

Which standards apply to wetting tests on transport coatings?

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.

Can lab tests predict how a rain repellent will perform on the road?

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.

How do I check a metal surface before bonding?

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.

Can the Dropometer measure battery electrolytes?

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.

How accurate is the Dropometer?

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.

Standards, evidence and resources

1. Use cases
  • Reliable aluminum bonding: Water contact angle on prepared aluminum panels and brackets, checked against joints that passed, catches poor surface preparation before bonding in rail and vehicle builds.
  • Windshield rain repellent performance: Static contact angle, sliding angle and hysteresis show whether a windshield rain repellent still clears water after wiper, washer fluid, UV and cold cycles.
  • Electrolyte and separator wetting: Pendant drop surface tension of electrolytes and contact angle on separators and electrodes help rank additives for lithium ion cells before long wetting and formation runs.
Case studies Example scenario: checking aluminum panels before bonding in rail car assembly. A rail car bonding team sets a water contact angle baseline on aluminum panels from joints that passed lap shear testing. Operators then read several spots on each panel after cleaning and hold any panel outside that baseline for cleaning again. The check catches poor surface preparation while the panel can still be reworked. Client citations (our analysis of each paper) Example scenario: ranking anti icing coatings for exposed transport surfaces. A university research group developing anti icing coatings for aircraft and rail surfaces measures water contact angle, hysteresis and sliding angle on flat coated coupons. The readings rank candidate coatings before the best few go to icing tests, and repeat readings after abrasion show which coatings keep their repellency. Use case collections Further resources