Roxul Industrial Insulation Process - Manual (Page 23)

1.1 Planning and preparation 1.1 Planning and preparation
1.1.3 Corrosion prevention
In the case of cold insulation, if the object is
made of non-alloy or low alloy steel, it must be
protected against corrosion.
In the case of objects made, for example, of
austenitic stainless steel or copper, the
installation must be tested in each individual
case by the planner to determine whether
protection against corrosion is necessary.
Objects made from austenitic stainless steel do
not require protection against corrosion if the
temperature never – even for a short period –
exceeds 120 °F (50 °C)
Note
Protection against corrosion should be applied
in the case of all installations made from
non-alloy or low-alloy steel where the
operating temperatures are below
250 °F (120 °C). Protection against corrosion
may be omitted in the case of:
Installations operating continuously under
extremely cold conditions [below -50 °F
(-50 °C)] such storage tanks.
Insulated surfaces of power plant
components, such as boiler pressure
components, flue gas and hot air ducts and
steam pipe systems with operating
temperatures that are constantly above
250 °F (120 °C).
If austenitic stainless steel is insulated with any
type of insulation - For temperatures of up to
930 °F (500 °C), aluminum foil of not less than
.06 mm thick to be applied to the steel surface,
arranged to shed water with overlaps of not less
than 2" (50 mm) at the joints.
CINI Manual “Insulation for industries”
CINI recommends applying corrosion protection
prior to the insulation work at any time.
In all phases, pay attention to CUI (corrosion
under insulation) prevention: design,
construction, paint & coating work, application
of the insulation system, inspection and
maintenance. Equipment and piping sections
like nozzles, supports etc. should be designed
and maintained to prevent ingress of water into
the insulation system.
The “paint” specifications are split up into:
- Construction material
(carbon steel, stainless steel)
- Temperature ranges from -22 °F (-30 °C) to
1000 °F (540 °C) with special attention to the
temperature range between 0 °F (-20 °C) and
300 °F (150 °C).
The corrosion protection can be achieved using
aluminum foil wrapping, thermal sprayed
aluminum (TSA) or paint.
Protection against corrosion may be omitted in the
case of installations operating continuously under
extremely cold conditions [< -22 °F (-30 °C)]
Application
Before applying corrosion protection coating, the
surface must be free from grease, dust and acid
and, for better adhesion, the priming coat should
be roughened. Blasting is recommended as a
surface preparation method (with austenitic
stainless steel, use a ferrite free blasting
abrasive).
Observe the corresponding processing guidelines
of the coating manufacturer. If metals with
different electrochemical potentials, such as
aluminum and copper, come into contact with one
another, there is a risk of electrochemical
corrosion. If necessary, this can be avoided using
insulating, intermediate layers such as non-
metallic straps. The presence of moisture will
increase the development of electrochemical
corrosion.
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