RP0176-2003
NACE International 23
12.2.9 Hand cleaning should be discouraged and
should be used only for small areas where other meth-
ods of surface preparation cannot be used. Methods
resulting in polishing of the steel surface, e.g., wire
brushing, shall not be used.
12.3 NACE Surface Preparation Standards
12.3.1 The selection of the degree or grade of surface
preparation should be determined by the requirements
of the coating selected. Following are descriptions of
the four degrees of abrasive blast-cleaned surfaces as
given in joint NACE/SSPC standards.
12.3.1.1 NACE No. 1/SSPC SP 5
15
states that a
white metal blast-cleaned surface, when viewed
without magnification, shall be free of all visible oil,
grease, dust, dirt, mill scale, rust, coating, oxides,
corrosion products, and other foreign matter.
12.3.1.2 NACE No. 2/SSPC SP 10
16
states that a
near-white metal blast-cleaned surface, when
viewed without magnification, shall be free of all
visible oil, grease, dust, dirt, mill scale, rust, coat-
ing, oxides, corrosion products, and other foreign
matter. Random staining shall be limited to not
more than 5% of each unit area of surface (ap-
proximately 58 cm
2
[9.0 in.
2
]), and may consist of
light shadows, slight streaks, or minor discolora-
tions caused by stains of rust, stains of mill scale,
or stains of previously applied coating.
12.3.1.3 NACE No. 3/SSPC SP 6
17
states that a
commercial blast-cleaned surface, when viewed
without magnification, shall be free of all visible oil,
grease, dust, dirt, mill scale, rust, coating, oxides,
corrosion products, and other foreign matter. Ran-
dom staining shall be limited to no more than 33%
of each unit area (approximately 58 cm
2
[9.0 in.
2
])
of surface and may consist of light shadows, slight
streaks, or minor discolorations caused by stains
of rust, stains of mill scale, or stains of previously
applied coating.
12.3.1.4 NACE No. 4/SSPC SP 7
18
states that a
brush-off blast cleaned surface, when viewed with-
out magnification, shall be free of all visible oil,
grease, dirt, dust, loose mill scale, loose rust, and
loose coating. Tightly adherent mill scale, rust,
and coating may remain on the surface. Mill scale,
rust, and coating are considered tightly adherent if
they cannot be removed by lifting with a dull putty
knife.
12.3.1.5 A cross-index of various surface prepar-
ation standards is provided in Table 2.
Table 2: Surface Preparation Standards
Standard White Near-White Commercial Brush-Off
NACE No. 1 No. 2 No. 3 No. 4
SSPC SP 5 SP 10 SP 6 SP 7
ISO
(A)
8501-1
19
Sa 3 Sa 2-1/2 Sa 1
___________________________
(A)
International Organization for Standardization (ISO), 1 rue de Varembe, Case Postale 56, CH-1121 Geneve 20, Switzerland.
12.4 Centrifugal Wheel Cleaning—This method is applic-
able to a fabrication plant where new weldments can be
processed through an automated, wheel-type machine
using metal abrasives. The cost of wheel blast surface pre-
paration is significantly lower than the cost of air blast sur-
face preparation work.
12.4.1
Good Painting Practice, SSPC Painting Man-
ual
,
20
should be referred to for centrifugal blast clean-
ing.
12.4.2 Special consideration should be given to:
12.4.2.1 Abrasive material—Steel grit of the
appropriate mesh size and hardness should be
used to produce the required surface profile using
the equipment selected to perform the work. Steel
shot is not recommended for surface preparation
for coatings to be used in severe surface applic-
ations.
12.4.2.2 Surface profile tests should be conducted
and recorded on a regular agreed basis to ensure
that the prepared surface of the components
meets the cleanliness and profile requirements of
the coating to be applied.
12.5 Air Blast Cleaning—This method is used when com-
ponents are not suitable for the available automated mach-
ines, when cleaning is performed on the job (field) location,
or when maintenance work is performed on offshore struc-
tures. Abrasives used are described in Paragraph 12.5.2.
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