These recommendations cover anticorrosion protection of internal surface of tanks and equipment in the system of centralized cold and hot potable water supply (reservoirs for storage of potable water, storage tanks, tanks- de-carbonators, de-aeration towers).
Application of anticorrosion zinc-rich two-package ZFES composition is recommended for anti-corrosion protection the internal surface of the tanks and equipment in the systems of centralized cold and hot potable water supply, in ship building and ship repair.
Protection systems and schemes.
Following protection systems with one dry layer thickness for ZFES #2 30-40 µm are recommended:
1.System of protection of the tanks for storage of cold water, including potable water (for new tanks and tanks under repair):
ZFES# 2 - 3 layers with total thickness 100-120 µm.
Total thickness can be increased to 160 µm (4 layers) to extend service life.
2.Systems of protection of the surfaces contacting with hot water:
Standard scheme of protection (No1)
ZFES #2 - 3 layers with total thickness 100-120 µm
Enhanced scheme of protection 1 (No 2)
- side surface of the tanks: 4 layers of ZFES # 2 with total thickness 30-160 µm.
- the bottom and roofing: 3 layers of ZFES #2 with total thickness 100-120 µm.
Enhanced scheme of protection 2 (No 3)
- side surface of the tanks: 5 layers of ZFES #2 with total thickness 180-200 µm.
- The bottom and roofing: 4 layers of ZFES # 2 with total thickness 150-180 µm.
Bottom and roofing are for storage tanks.
Total thickness of the coating should be checked when applying ZFES coating.
Selection of protection system for tanks with hot water is made taking into consideration the initial state of the surface of the tank to be painted and corrosion activity of water.
Finishing materials in a complex system.
| Tank surface state before painting |
Medium corrosion activity* |
# of protection scheme |
Expected service life of the system**, not less, years |
| New tanks |
low |
1 |
3-4 |
| 2 |
6-8 |
| high |
2 |
3-4 |
| 3 |
6-8 |
| Tanks under repair |
low |
2 |
3-4 |
| 3 |
6-8 |
| high |
3 |
3-6 |
Water is considered to be high corrosion-active, if concentration of oxygen is more than 50 mkg/l, carbonic acid - 10 mkg/l, index of saturation (to Langelye) is negative, pH is out of limits for ZFES coating.
** Service life stated in the table relates to the coatings which are applied in conformity with the technological requirements on the surface degreased , cleaned from oxides to grade Sa 2,5 to ISO 8501-1:1988.
The proposed schemes are developed on the basis of intensive and full-scale corrosion tests, their efficiency is confirmed by usage at the actual objects.
Choosing the system of protection for the particular object it is advisable to consult the experts of the plant.
Application technology
Composition preparation
ZFES composition is prepared before application by mixing the binder (element A) with zinc powder (component B).
Empty zinc powder from the package into the metal pail containing the binder continuously stirring the mix. After intensive stirring for 2-3 minutes allow the mix to stand until gas bubbles stop to evolve (about 20-30 minutes). Then stir it again thoroughly. After that the compound is ready for application, its viability is 8 hours at least at the temperature of 200C.
Surface preparation
ZFES composition should be applied to the prepared surface. The preparation of the surface should include the following operations:
- Removal of dirt, loose and laminated rust;
- Degreasing;
- Removing oxides to grade Sa 2,5 to ISO 8501-1:1988;
The time interval between the surface preparation and coating application should be not more than 6 hours outdoors and 24 hours indoors.
Composition application
Painting work should be done when the ambient air temperature is between -150 and +400C and relative humidity is 30-80% (optimum is 50% at least). The painted surface should be free of moisture condensation. During the work the composition should be periodically stirred to prevent sedimentation of zinc powder.
Consumption of ZFES # 2 compound is 170-230 g/m in theory when the thickness of the dry coating is 30-40 µm.
Actual consumption will depend on the method of application, roughness of the surface and conditions of painting.
ZFES composition is applied in several layers by spraying (pneumatic or airless), with a brush, with a roller with natural drying between layers.
The subsequent layers are applied after the previous one dries until tack-free (a slight pressure on the coating does not leave a trace and it is not sticky to touch). At the air temperature (200+20)C and humidity of (65+5)% it takes the layer not more than 30 minutes to dry.
The maximum time interval between the application of subsequent layers on the primed surface can't be limited provided that the moisture penetration is prevented.
ZFES coating is maintainable. Defective parts of the coating should be removed, the surface should be conditioned to metal luster, degreased and painted.
The coating can be used in water not earlier than 7 days after painting.
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