refers to the elimination of dirt, debris, paint, rust, concrete..or other contaminates leaving the surface in an ideal state for the application of future coating or bonding. When Sandblasting steel for the purpose of coatings applications the sandblaster needs to follow specific specifications provided by the coatings manufacturer. Steel surface preparation standards measure two critical specifications : Surface profile and Degrees of Cleanliness.
Surface Profile:
Profile refers the scratch depth that the abrasive leaves on the steel surface. Abrasives cut into the steel forming peaks and valleys. The depth of the profile is controlled by the size of the abrasive, angle of nozzle, distance of nozzle to surface and compressed air flow. The profile provides a mechanical method of positive, uniform bonding between the coating and the surface.
Coating manufacturers test their coatings on various profiles making sure that their products perform as intended. Adhesion and performance of coatings are guaranteed if specifications are followed. Contractors must adhere to these specifications. When profiles exceed the maximum specifications, the peaks may protrude through the coating system, causing it to fail.
Sandblasting Steel: removes rust, dirt, concrete, debris and other contaminates. Sandblasting new steel removes the mill scale. Blasted surface leaves profile.
Contact SSPC http://www..sspc.org/contact.html
Phone
Toll Free:
1.877.281.7772 (US Only)
All Others: 1.412.281.2331
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Administrative: 412.281.9992
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Publications,
Membership: 412.281.9995
The Steel Structures Painting Council (SSPC) has established four degrees of
cleanliness for blasting, ranging from removal of all contaminants to removal of loos materials only. The four degrees are White Metal
Blast, Near White Metal Blast, Commercial Blast, and Brush off Blast For detailed descriptions of each refer to the SSPC's Visual
Standards for Abrasive Blast Cleaned Steel.
White Metal Blast
Viewed without magnification, a shite metal blast cleaned surface is
free of all visible rust, mill scale, paint, and foreign mater. This degree of cleanliness is usually required where sophisticated
points; such as, zinc-rich coatings, will be applied to surfaces exposed to highly corrosive environments. Chemical plants, offshore
drilling rigs, and bridges over salt water are typical applications.
Near White Metal Blast
Viewed without magnification, at least
95% of the surface is free of all visible residue after blast cleaning. This is similar to White Metal but some slight staining on
the metal is allowed. This degree of cleaning is required where high performance coatings will be applied to steel exposed to harsh
elements and heavy usage.
Commercial Blast
Viewed without magnification, at least two thirds of a commercial blast cleaned surface
is free of visible residue. It allows some tightly adhering old paint to remain, based on the premise that paint adheres after blasting
is unlikely to fail. For most applications where standard coatings will be applied, commercial blast is specified.
Brush Off Blast
Viewed without magnification a brush off blast cleaned surface may have only tightly adhering residues of mill scale, rust, and coatings remaining and must have numerous evenly distributed flecks of underlying metal exposed. This method is acceptable for surfaces not subjected to sever environments or where long-term coating life is not expected
|
Degrees of Cleanliness |
SSPC Std. |
NACE Std. |
SIS Std. |
|
White Metal Blast |
SSPC-SP 5 |
NACE No. 1 |
SA-3 |
|
Near White Metal Blast |
SSPC-SP 10 |
NACE No. 2 |
SA-2 1/2 |
|
Commercial Blast |
SSPC-SP 6 |
NACE No. 3 |
SA-2 |
|
Brush-off Blast |
SSPC-SP 7 |
NACE No. 4 |
SA-1 |
dust, dirt, mill scale, rust, coating, oxides, corrosion products, and other foreign matter. ...more...
procedures necessary to achieve and verify the end condition....more...
