UFC 3-240-13FN
25 May 2005
Table 4-11. Guidelines for Passivation Film Formation
and Subsequent Maintenance
Dosage (ppm)
Film-Formation
Corrosion Inhibitor
Time (Days)
Maintenance
Initial
Cathodic Inhibitor
Polyphosphate1
40-60 as PO4
10-20 as PO4
5-6
Zinc salts2
10-20 as Zn
3-5 as Zn
5-6
Polysilicate3
40-60 as SiO2
10-20 as SiO2
10-12
Molybdate
40-60 as Mo
5-20 as Mo
10-12
Anodic Inhibitor
Orthophosphate1
40-60 as PO4
15-20 as PO4
5-6
Orthosilicate3
40-60 as SiO2
10-15 as SiO2
10-12
Copper Corrosion Inhibitor
Tolyltriazole
10-20 as TTA
1-2 as TTA
5-6
NOTES: General: Maintenance dosage shifts to lower part of range as pH rises.
1. May require polymeric calcium phosphate dispersant.
2. Rarely used alone. Requires zinc solubilizer above pH 7.8.
3. Do not use if natural silica is 150 ppm or greater.
4-6
DEVELOPING AN EFFECTIVE COOLING WATER TREATMENT
PROGRAM. An effective and complete cooling water treatment program addresses
many factors, including those associated with compliance and safety, protection of
equipment, and cost. Compliance and safety considerations are mandatory components
of the program. Achieving or exceeding minimally acceptable equipment protection at
the lowest possible cost is an advisable outcome for a well-designed program. The
overall cost of the treatment program includes not only the cost of chemical treatment,
but also the costs of water, disposal, manpower, and equipment. Development of an
appropriate cooling water treatment program is dependent upon knowledge of both the
specific equipment to be protected and the quality of the water to be used (source water
and system water).
4-6.1
individual pieces of cooling system equipment. Typical systems include equipment
components of different metals. For example, systems may include smooth and
enhanced copper tube bundles, mild steel transfer piping, and galvanized cooling tower
components; therefore, to select the proper corrosion inhibitor, it is important to identify
all metals contacted by the cooling water. (See Table 4-10 for corrosion inhibitor
selection criteria.)
4-6.2
Operational Features and Parameters. Operational features and
parameters of the cooling water system must be known to select the proper scale and
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