3.1.3
Protection
Cleaning, metallizing, and painting shall be so programmed that dust, dry
spray, or other contaminants from the cleaning and painting operations do
not contaminate surfaces ready for metallization or painting. Surfaces not
intended to be metallized shall be suitably protected from the effects of
cleaning and metallizing operations. Machinery shall be protected against
entry of blast abrasive and dust into working parts.
3.2
METALLIZING APPLICATION
Metallizing equipment shall be set up and operated in the same manner as
used to prepare the JRS. Equipment set up and operation shall be validated
using a bend test. The bend test is acceptable if the coating shows no
cracks or exhibits only minor cracking with no lifting of the coating from
the substrate. If the coating cracks and lifts from the substrate the
results of the bend test are unacceptable. Compressed air used to atomize
the metallized coating shall be clean and dry.
3.2.1
Metallizing Application Technique
Surfaces to be flame sprayed shall be preheated to prevent condensation of
the flame on the surface to be coated. Arc spray application does not
require preheating of the substrate. Surfaces to be metallized shall be
free of all visible contaminants including grease, oil, soot, and dust
prior to receiving the first and subsequent coats of metallizing. All
metallizing coats shall be applied in such a manner as to produce an even,
continuous film of uniform thickness. Edges, corners, crevices, seams,
joints, welds, rivets, and other surface irregularities shall receive
special attention to ensure that they receive an adequate thickness of
metallic coating. Metallizing equipment shall be operated by qualified
applicators in accordance with the manufacturer's recommendations. The
sprayed metal shall overlap a minimum of 40 percent on each spray pass to
ensure uniform coverage. Manual spraying shall be done in a block pattern
not exceeding 600 by 600 mm 2 by 2 feet square. Specified thickness of the
coating shall be built up in multiple layers. Fewer than 2 spray coats
(overlapping at right angles) shall not be accepted. The application gun
shall be held at such a distance from the work surface that the metal
remains plastic until impact with the surface. Metallizing shall not
extend closer than 20 mm 3/4 inch to surfaces that are to be welded.
3.2.2
Metallizing Appearance
The thermal-sprayed coating prior to sealing shall have a uniform
appearance. The coating shall not contain any of the following: blisters,
cracks, chips or loosely adhering particles, oils or other internal
contaminants, pits exposing the substrate, or nodules.
3.2.3
Metallizing Thickness
Surfaces shall be coated with the systems indicated in the metallizing
schedule and/or as noted on the drawings in accordance with the following:
a.
System No. 1-Z: This metallizing system shall be applied to a
minimum average thickness of 0.15 mm 6.0 mils for the completed
system; the thickness at any one spot shall not be less than 0.12
mm 5.0 mils.
b.
System No. 2-Z:
This metallizing system shall be applied to a
SECTION 09971A
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