Title: Measuring 2 Important Surface Profile Parameters: Peak Height and Peak Density
Author: David Beamish
Steel surfaces are frequently cleaned by abrasive impact prior to the application of protective coatings. The resultant surface profile must be accurately assessed to ensure compliance with contract specifications. But is profile height alone, the most common measured parameter, a good indicator of long term coating performance?
This paper reports on remarkable recent testing that compared numerous profiles with pull-off adhesion. A low-cost field device obtained several profile parameters from one replica tape measurement including:
- H – Profile height - the average of the maximum peak-to-valley distances.
- Pd –Peak density in accordance with ASME B46.1.
Conclusions or recommendations
The nature of abrasive blast cleaned steel surfaces is predictive of long term coating performance. Empirical data refutes commonly held beliefs that increasing roughness will improve long term coating performance. Currently, only the most important parameter, peak height, is reported. While important, it does not fully describe the dynamics of a coating/substrate relationship. Peak density is also important. Together they provide a better prediction of long term coating performance.