Surface Roughness and Assessment Methods of Surface Roughness

Surface roughness

The surface roughness grade affects the overall performance of the coating. Surface height (measured from peak to valley) determines aspects such as adhesion, coverage thickness and total amount of paint applied.

If the roughness value is too high, the paint needs to be increased to ensure adequate coverage, otherwise the raised spots will not be covered and rust spots will result. If the roughness value is too low, sufficient adhesion may not develop, causing premature failure of the coating.

With the correct surface preparation, the performance of the coating and the application of the material can be optimized.

There are four different methods for testing surface roughness:

Surface comparison method:

Use the surface comparison board to compare the freshly painted surface with the defined surface. There are sandblasting type, shot peening type or fine sand type for comparing boards, and the comparison is made by visual or tactile sense. A very rapid reference to roughness can be made in this way.

Test strip profiling method:

Foam-backed plastic test strips are pressed into the sprayed surface. Measure the test strip to determine surface roughness. This test provides a digital assessment of roughness and can provide proof of test, as test strips can be included in manual reports.

Surface Profiler:

Surface profilers include analog and digital types. After "zero calibration", the profile can be measured, and the instrument records the value from the top to the bottom of the valley. The digital instrument minimizes the intermediate error of the reading, and the measurement is fast and accurate. Memory models can store readings and download them to a computer via Bluetooth® wireless technology.

Surface Roughness Tester:

Contains a stylus attached to an arm that automatically moves over the surface to record and measure the profile. The instrument is ideal for testing during production as part of quality control.