Grit blasting is the quickest and most cost-effective way of preparing a surface to receive a coating or lining. By introducing a surface profile, you ensure your coating adheres securely to the substrate, and avoid many of the common problems that can reduce the durability of a coating.
What is a Surface Profile?
A surface is rarely completely smooth, even if it appears so to the naked eye. There are always craters, pits, cracks and ridges that form a unique pattern, or surface profile, which must be taken into account when applying a coating or lining. When people talk about the surface profile they refer to the level of roughness of the substrate, also known as the anchor pattern.
As surface profile is not always clearly visible, care must be taken to verify the correct anchor profile prior to coating application.
Determining the surface profile is different from determining surface cleanliness – i.e. the presence of rust and other contaminants. Grit blasting can be used to either change the surface profile or remove contaminants – or both, should the need dictate. Please consult an abrasive blasting specialist, such as KUE Group, for their opinion on the choice of abrasive to ensure the correct cleanliness and surface profile is attained.
How to Determine Your Surface Profile
Determining the surface profile involves measuring the height/depth between the peaks and the troughs. This usually ranges from 40-100 microns. The higher the value, the greater the surface area to be treated, compared to an area of the same size that is completely smooth.
This makes a difference when determining the volume of coating or lining product you will need, as under-calculating the amount of material could result in the coating being applied too thinly across the surface, potentially leaving peaks uncoated.
There are several methods that can be used to measure surface profile under ISO 8503-1:
- Surface comparator – A flat, corrosion-resistant steel plate containing a number of referenced surface profiles.
- Replica tape – A strip that is compressed into the surface, after which the indentations in the strip replicate the anchor pattern of the substrate. The surface profile is then determined using a micrometer thickness gauge.
- Surface profile gauge – A handheld device, available in both digital and analogue versions, which extends to seek out the valley depth when held over a substrate. This provides an accurate average surface profile when 5 to 10 measurements are taken across the surface.
Choosing the Right Abrasive Media – Abrasive Blasting Profiles
Once the required surface profile is identified, you’re in a position to choose the correct type of abrasive blasting material and grade to achieve the surface profile required by the coating. The many types of blast media fall into two categories – rounded shot and angular grit. Shot particles have a tendency to flatten a surface profile, lowering the total depth, whereas angular grit creates a rougher surface, increasing the surface area. Large grit particles form larger surface indentations, whilst smaller grit particles create smaller surface indentations.
Find Out More
The correct surface profile is essential to ensure successful surface preparation and a good ROI from your coating or lining system. For the best results, we strongly recommend using an experienced provider/applicator with proven expertise in your industry. To find out more about our areas of operation and the sectors we work in, or to discuss your project requirements, please call 01274 033120, or click here to request a call back.