- Proper maintenance and regular servicing of the coated metal facade require that it be cleaned at least once a year. Environment with higher pollution levels requires more frequent cleaning.
- Dirt shall be removed from the surface with clear cold or lukewarm water. Clean water must be used, to which slight amounts of neutral or slightly alkaline detergents may be added. Strong acid or alkaline detergents or surface-reactive agents must not be used.
- For a thorough cleaning soft, non-scratching cloths may be used. Abrasives must not be used. Use only soft cloths or industrial cotton for cleaning and do not exert too much pressure.
- Greasy or oily substances can be removed with the help of naphtha hydrocarbons free from aromatic compounds. Test on a small hidden area prior to application is recommended.
- Residues from glue, silicone or adhesive tapes could be removed with the help of naphtha hydrocarbons free from aromatic compounds. Test on a small hidden area prior to application is recommended.
- After each cleaning, rinse parts immediately with clear cold water.
HEORETICAL YIELD IN SQ.M. OF SURFACE TO BE COATED PER KG OF POWDER |
Specific Gravity ( g/cm3 ) |
Film Thickness | ||||||
50 um | 75 um | 100 um | 125 um | 150 um | 175 um | 200 um | |
1.0 | 20.0 | 13.3 | 10.0 | 8.0 | 6.7 | 5.7 | 5.0 |
1.1 | 18.2 | 12.1 | 9.1 | 7.3 | 6.1 | 5.2 | 4.5 |
1.2 | 16.7 | 11.1 | 8.3 | 6.7 | 5.6 | 4.8 | 4.2 |
1.3 | 15.4 | 10.3 | 7.7 | 6.2 | 5.1 | 4.4 | 3.8 |
1.4 | 14.3 | 9.5 | 7.1 | 5.7 | 4.8 | 4.1 | 3.6 |
1.5 | 13.3 | 8.9 | 6.7 | 5.3 | 4.4 | 3.8 | 3.3 |
1.6 | 12.5 | 8.3 | 6.3 | 5.0 | 4.2 | 3.6 | 3.1 |
1.7 | 11.8 | 7.8 | 5.9 | 4.7 | 3.9 | 3.4 | 2.9 |
1.8 | 11.1 | 7.4 | 5.6 | 4.4 | 3.7 | 3.2 | 2.8 |
1.9 | 10.5 | 7.0 | 5.3 | 4.2 | 3.5 | 3.0 | 2.6 |
2.0 | 10.0 | 6.7 | 5.0 | 4.0 | 3.3 | 2.9 | 2.5 |
Theoretical Yield in sq.m./kg = 1.0/(Specific Gravity) x (Film Thickness) |
SOLID POWDER
METALLIC POWDER
The spraying of metallic powder is subject to a few variables which will considerably influence quality of finish and may well often be the source for variations of color and surface smoothness. Some of these variables are as follows:
Application Equipment
Electrostatic and tribo application equipment exhibit different metallic effects. Automatic lines are preferred to hand guns. Short cutting in the gun could be prevented by using a so-called exterior-charging gun tip, as this type of gun has electrodes which protrude into the cloud. The recommended voltage (KV) for spaying metallic powder coating is in the lower range of say 70 or half of the maximum output and with air pressure of 150 gm per minute.
Ground
Sufficient grounding is imperative, possibly an additional ground wire directly connected to the part may be helpful.
Reclaim
Reclaim and virgin powder should be consistently fed into the system.
Cure Cycle
Application equipment positioning
TWO COAT PROCESS
Powder Coatings can be applied using one of three standard methods, Fluidized Bed, Electrostatic spray-Corona charge and Tribo charge.
Electrostatic Corona Gun
The corona gun requires a high voltage of 30-100 KV at the electrode around the tip of the gun. This creates a field of electrical attraction between the gun and the grounded parts.
As the powder are transported through the tip of the gun, the powder particles are negatively charged in the electrostatic field, repel each other and form a cloud before being attracted to the item to be coated.
The particles deposit on to the part and form a layer after layer of powder. The thickness of the deposition can be controlled by position of the gun, spray duration time, level of charging and velocity of the powder flow from gun to part and part aperture.
It is vital that parts to be coated are well grounded or earthed. Jigs or hangers must be kept clean to yield good grounding at all time.
Over spray or powder not adhering to the part is collected for recycled.
Electrostatic Tribo Gun
Powder Coatings, upon transported through barrel of the Tribostatic gun to the part to be coated, are positively charged with no electrostatic field created. This method of application eliminates faraday cage effect and back ionization. Hence, it is good for use in coating intricate parts such as detailed automotive rims and heatsinks.
Aluminum Yellow Chromating
COMMENT
Aluminum Green Chromate
COMMENT
Galvanized steel Transparent Chromate
COMMENT
Remark
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Powder Coatings are “solid paint” which can be melted to form a continuous film over the substrate. Each powder particle contains resin, pigments, modifiers, extenders and curing agent, in case of thermosetting.
There are two types of powder coatings, thermosetting and thermoplastic.
Thermosetting Powder Coatings cross link and polymerize when heated and form a finished film. Once cured and crosslinked, this polymer network will not melt and flow again if heat is applied. The primary resins used in the formulation of thermosetting powder are epoxy, polyester, acrylic. In general, we refer to only thermosetting type of powder coatings.
Thermoplastic Powder Coatings are non-reactive and do not chemically crosslink upon application of heat but melt and flow over the part in the oven. The film hardens once part cools down and will remelt upon application of sufficient heat. They are polyethylene, polypropylene, nylon, polyvinyl chloride, polyester and polyvinylidene flurides/fluorocarbons.
WHY POWDER COATINGS:
Powder Coatings offer significant advantages over liquid solvent-based stoving paints:
- Ready to use. No stirring, mixing or thinning is required.
- Solvents free. No thermal afterburning of solvents is required.
- Virtually no VOCs or negligible emissions to the environment.
- Excellent durability and weathering properties
- Safety and low fire hazard
- Cleaner working environment
- High utilization. Efficiency recovery of oversprayed powder can enable utilization figures of over 95% can be achieved.