RP0176-2003
24 NACE International
12.5.1 Air supply—Initial inspection of the air supply
should include the following:
12.5.1.1 Air supply capacity shall be sufficient to
obtain 690 kPa (100 psi) air pressure at all opera-
ting nozzles.
12.5.1.2 Compressor shall be equipped with all
properly operating safety equipment required.
12.5.1.3 Oil/moisture separators with properly
maintained filters must be used in air lines. These
shall be tested at least once each shift in accord-
ance with ASTM D 4285.
21
12.5.2 Abrasives—The blast-cleaning abrasive used
for surface preparation shall be limited to the type
specified in the contract documents and shall be of
appropriate size to produce the required profile using
the equipment available for the job. The abrasive must
be clean and graded to a uniform standard size. See
Good Painting Practice, SSPC Painting Manual.
20
12.6 Safety equipment for surface preparation should
include, but shall not be limited to, the following:
(a) Bureau of Mines
(10)
or equivalent agency-approved air-
fed blast hood, properly fitted, with good vision,
(b) Charcoal-filtered and regulated compressed breathing
air supply,
(c) Operator-controlled deadman remote control valves,
(d) Operator protective clothing, gloves, etc.,
(e) Operator safety belts,
(f) Proper scaffolding, and
(g) Proper lighting.
12.6.1 Air blast operators must have proper training
for effective operation of surface preparation and safety
equipment.
________________________________________________________________________
Section 13: Coatings
13.1 Introduction
13.1.1 This section outlines general considerations
relating to structure coatings and lists the generic com-
position of the coatings commonly used by offshore
operators.
13.2 General
13.2.1 Conventional paints, surface preparation, and
methods of application should not be used in extremely
corrosive offshore environments. Because the main-
tenance cost on location is extremely high, only high-
performance protective coating systems should be
specified. Proper application and performance require-
ments of these systems demand rigorous surface prep-
aration (see Section 12) and skilled craftsmanship in
coating application and inspection (see Section 14).
This can be achieved only through the enforcement of
detailed and complete job specifications.
13.2.2 Proper application of high-performance coating
systems requires that personnel observe and adhere to
all applicable safety rules and regulations.
13.3 Coating Systems
13.3.1 Offshore coating systems are normally com-
posed of primer, intermediate, and finish coats. Many
generic coating materials are available but only a few
are considered by many owners and coating consult-
ants to be suitable for offshore service.
13.3.2 Most coating systems are based on a highly
inhibited prime coat designed to have superior wetting
and adhesion properties to retard undercutting by rust,
and to passivate the surface. Commonly used prime
coats include:
13.3.2.1 Wash primers—These are conversion
coatings consisting of a vinyl butyrate resin solvent
solution, pigmented with zinc or strontium chrom-
ate. Prior to application, these coatings are mixed
with a second component consisting of a solution
of alcohol and phosphoric acid. They are applied
as very thin films not to exceed 13 µm (0.50 mil)
dry. On contact with the iron surface, they gener-
ate a passive iron phosphate layer. Wash primers
must be quickly topcoated for maximum effective-
ness and to prevent rust breakthrough.
13.3.2.2 Zinc-rich primers—These primers are
organic or inorganic coatings with a high loading of
zinc dust. When there is a rupture or discontinuity
in the coating system, the zinc pigment particles
protect the substrate by galvanic action. Because
zinc reacts readily with both acids and strong alka-
lies, zinc-rich primers must be topcoated with
chemically resistant coatings when used offshore
because of exposure to alkaline drilling mud and
acidic well-completion fluids. Zinc-rich primers are
___________________________
(10)
Bureau of Mines, 2402 E. Street NW, Washington, DC 20241.
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