Ceramic Coating Basics3 min read

Coating Tests on Curved Panels: Record Drop Position and Local Slope

Improve coating comparisons on curved parts by recording local slope, drop location and camera geometry instead of treating every bead as equivalent.

Updated · NANOLAB Knowledge

Editorial illustration: A Practical Quality-Control Process for Ceramic Coating
Editorial illustration

Two water drops on the same coated panel can look different because they sit on different parts of a curve. A drop near a crown, crease or steep shoulder does not share the geometry of one on a flatter region. A comparison that ignores position can confuse part shape with coating behaviour.

Separate a visual demonstration from a measurement

A video showing water moving across a bonnet can document behaviour on that bonnet under the recorded conditions. It is not automatically a contact-angle measurement. Quantitative work requires a suitable instrument, a defined local surface reference and an appropriate analysis method.

Surface topography is another variable. KRUSS discusses how roughness can influence wetting and why simple corrections may not describe every structured surface. Local slope and microscopic roughness are different issues, but both argue against reading every visible drop as a direct chemical fingerprint.

Mark positions without altering the test area

Use a panel diagram and reference features outside the measured zone. Identify the crown, shoulder and any relatively flat area. Record part orientation and the direction of the surface fall at each location. Do not place adhesive, ink or a rough locating mark inside the drop footprint.

Control Record
Part position Fixture and overall orientation
Local location Distance from stable reference features
Water application Source, volume or controlled delivery method
Observation timing Time from placement to recording
Camera geometry View direction relative to the local surface

Compare equivalent locations

If product A is tested on the flatter centre while product B occupies a steep shoulder, position is entangled with product. Use equivalent parts, balanced locations or a suitable flat companion specimen to answer the product question. A companion coupon still needs its own documented preparation and cannot prove every aspect of performance on the actual curved part.

Repeat the observation at planned positions. If a result changes mainly with location, investigate geometry and preparation distribution before declaring one coating inconsistent.

Interpret movement separately from shape

A drop that moves away immediately cannot be compared with a stationary drop recorded after a long pause as though both had the same measurement history. Record whether it remained, spread, moved or merged with another drop. Keep video where motion is the endpoint.

For example, a shoulder may drain rapidly while the crown retains a droplet. That result can be useful for understanding real runoff. It does not, without additional controls, establish stronger chemistry on the shoulder.

Report the claim at the right level

Use wording tied to the tested part and conditions. Include the location map with the images and disclose any excluded positions. If the instrument cannot handle the geometry reliably, report a qualitative observation or choose another method. Precision written beside an unsupported angle does not make the underlying measurement valid.

Technical references

These sources support the identified technical concepts. The planning examples in this guide are illustrative and are not NANOLAB performance test results.

Discuss your surface and intended use with NANOLAB. Follow the current instructions for the exact product when planning application and care.