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W W W . B A L T I M O R E A I R C O I L . C O M . A U
M A R 2 1 0 - 2
NOTE: Stainless steel cold water
basins do not require passivation.
However, if the upper structure is
galvanized steel, passivation is
required on the galvanized area
including any Hot Dip Galvanized
After Fabrication (HDGAF) coil(s).
Corrosion and Scale Control
1. To control corrosion and scale, maintain the water chemistry of
the re-circulating water within certain parameters. The specic
measures required vary from system to system and are dependent
on the chemistry of the make-up water, the metallurgy of the piping
and heat transfer devices exposed to the re-circulating water and the
temperatures at which the system will be operating.
2. Bleed/blowdown, the continuous ow of a small portion of the re-
circulating water to drain, is used to control the concentration of
dissolved solids. On rare occasions, this may be adequate to control
scale and corrosion. More often, however, chemical scale and
corrosion inhibitors are necessary, which raise the allowable level of
dissolved solids without the risk of scale and corrosion.
3. Keep the chemically treated water within the guidelines given in the
below table. Your water treatment specialist may recommend more
conservative limits than those shown in the table.
SST ZAM / Galvanised Steel
PH 6.5 to 8.5 7.0 to 9.0
Hardness as CaCO3 300 to 500 ppm 300 to 500 ppm
Alkalinity as CaCO3 500 ppm max. 500 ppm max.
Total Dissolved Solids 1200 ppm max. 1000 ppm max.
Chlorides 250 ppm max. 125 ppm max.
Sulphates 250 ppm max. 125 ppm max.
Table 2. Recirculated Water Quality Guidelines
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