There are different levels of surface preparation, and not every job will require the same one.
(Surface prep example images used in video are courtesy of SSPC)
The SSPC, the NACE and the SIS have established four degrees of blast surface cleanliness. Understanding these standards will help you provide the best surface prep for your customers, and keep your costs down where possible.
For example, a car body and a dump truck bed don’t require the same level of cleanliness.
You’ll want to consult the owner, or the coating manufacturer, or both before the job to decide what level of cleanliness is needed.
1. White Metal Blast
Let’s start with the cleanest standard which is the White Metal Blast. Metal with this level of cleanliness is free of all visible paint, rust, mill scale, stains and foreign matter. It is completely clean, bare metal. Though it’s called a white metal blast, clean steel will be grey. This level is necessary for some advanced coatings that are exposed to harsh corrosive environments such as refineries and offshore drilling platforms. It’s also favored for auto bodies and antique restoration.
(Image Credit: SSPC)
2. Near White Metal Blast
A Near White Metal blast is similar to the white metal blast, except some staining on the metal is allowed. This surface should be at least 95% bare metal.
(Image Credit: SSPC)
3. Commercial Blast
This type of blast is important — it's at least 2/3 bare, clean metal. Some tightly adhering coatings can stay, because if they can survive the blasting, they’re not going to come off. This is the most common type of blast for commercial work, like metal stairwells, fire hydrants, machinery, etc.
(Image Credit: SSPC)
4. Brush Off Blast
This type of blast just brushes off all the loose material. Rust, mill scale, and coatings can stay behind as long as they’re tightly adhering. This method is really only used in situations where long term coating life is not expected.
(Image Credit: SSPC)
In our videos, people are always blasting down to white metal. But when doing this for a living, knowing the correct level of cleanliness to use can save you time and work.
Don't lose jobs because you overbid on a White Metal blast when a Commercial blast is all you need.
PRO TIP: For large-scale or government projects requiring adherence to specific surface preparation standards, you may need to work with an independent NACE certified coatings inspector. Here's an example of the language you might find in this type of job bid:
American Stripping Company will provide NACE coating inspections and verification to the customer of satisfactory performance meeting provided specifications throughout the coating process along with the objective quality evidence (OQE)...
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