Cleaning Recommendations

  • 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.

Theoretical Powder Coating Coverage Chart

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) 

Guide Lines For Powder Coating Application

SOLID POWDER

To achieve smooth and consistent surface finish, one should have regular maintenance of application equipment and be sufficiently aware of any factorys that could affect the quality of surface ie. pretreatment process, types of spraying head, distance between gun and applied surface, gun speed, gun movement pattern-vertically/horizontally, grounding, optimum air flow and air pressure, KV setting, reclaim-to-virgin ratio, types of powder coatings, chargeability and fluidization of powder coatings, curing temperature and time, dusting from environment and spray booth, and humidity atmosphere.
 

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 

Gold, Brass and Copper effects need to be cured according to precisely maintained curing schedules. Slight temperature changes might discolor the metallic flakes used.
 

Application equipment positioning

To achieve an even metallic effect, the distance between spraying gun to the part should be maintained throughout the entire spraying process.
 
 
 

TWO COAT PROCESS

In case the two-coat colors (ie metallic powder coatings with clear or other specialty colors) are required, it is advisable to spray the Base Coat, go though only half the regular curing cycle (underbake is desired) and spray another coat (Top Coat) before finishing up with a full curing cycle.

Powder Coating Application

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.

Guide Lines For Pretreatment

Aluminum Yellow  Chromating

1. Clean 5.0 – 10.0 minutes 60°C- 70°C    
2. Rinse 1.0 – 2.0 minutes room temperature
3. Etching 0.5 – 1.0 minutes 60°C
4. Rinse 1.0 – 2.0 minutes room temperature
5. Deoxidizing 0.5 – 1.0 minutes room temperature
6. Rinse 1.0 – 2.0 minutes room temperature
7. Yellow Chromate 1.0 – 2.0 minutes 20°C
8. Rinse 1.0 – 2.0 minutes room temperature
9. DI Rinse 0.5 minutes 40°C- 50°C

COMMENT

  • Coating weight should be between 30-100 milligrams pers sq.ft.
  • Dry-off with warm blowing air at a temperature of 90°C
  • The degreasing step will remove only a fresh light coat of white rust
  • The etching step is required to remove heavier coats of white rust.
  • The chemical supplier should be consulted for optimum time and temperature

 

Aluminum Green Chromate

1. Clean 5.0 – 10.0 minutes 60°C- 70°C 
2. Rinse 1.0 – 2.0 minutes room temperature
3. Etching 0.5 – 1.0 minutes 60°C 
4. Rinse 1.0 – 2.0 minutes room temperature
5. Deoxidizing 0.5 – 1.0 minutes room temperature
6. Rinse 1.0 – 2.0 minutes room temperature
7. Green Chromate 1.0 – 2.0 minutes 20°C
8. Rinse 1.0 – 2.0 minutes room temperature
9. DI Rinse 0.5 minutes 40°C- 50°C

COMMENT

  • Coating weight should be between 30-250 milligrams per sq.ft.

 

Galvanized steel    Transparent Chromate

1. Clean 5.0 – 10.0 minutes 60°C- 70°C 
2. Rinse 1.0 – 2.0 minutes room temperature
3. Etching 0.5 – 1.0 minutes room temperature
4. Rinse 1.0 – 2.0 minutes room temperature
5. Deoxidizing 0.5 – 1.0 minutes room temperature
6. Rinse 1.0 – 2.0 minutes room temperature
7. Transparent Chromate 1.0 – 2.0 minutes 20°C
8. Rinse 1.0 – 2.0 minutes room temperature
9. DI Rinse 0.5 minutes 40°C- 50°C

COMMENT

  • Chromating is the best pretreatment for Galvanized steel. Transparent Chromating has proved to be the best for this purpose.

 

Remark

  • Outdoor use of steel requires an excellent pretreatment because steel is highly corrosive.
  • We recommend two types of pretreatment; Zinc phosphate or Iron phosphate.
  • Zinc phosphate is used for automobiles and arhitectural products.  

The Powder Manufacturing Process

The process starts from melt mixing of raw materials using extruder or compounder. This mixed material is then flattened, cooled and fine grounded to the appropriate particle size for application. Hence, there are three principal stages: Premixing, Extrusion and Grinding. 
 
(a) Premixing 
A homogeneous mixture of the raw materials is prepared prior to extrusion. Careful weighing of all raw materials are combined and mixed as homogenous as possible to yield powder of the required color and specification.
 
(b) Extrusion 
The approved premixing ingredients are passed through an extruder to ensure maximum dispersion, short residence time and controlled melting temperature. The extrudate, discharged from the extruder, is rapidly cooled through rollers to become a thin sheet and its temperature is reduced further. The sheet is then kibbled into small chips ready for the next stage.
 
(c) Grinding 
The granulated chips are then fed through a grinding mill, consist of a rotor, classifier and cyclone, to become Powder Coatings with proper particle size distribution. Control of PSD is essential for successful application.

Introduction To Powder Coating

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.
However, applicator should be cautious of contamination when changing colour. The utmost care is essential in cleaning the application equipment, spraybooth and recovery unit.
 
Powder Coatings are applied in custom job shops to large manufacturers. Metal, plastic, wood, composite and glass substrates can be coated provided that the curing temperature does not distort or deform the parts. Office Furniture, General Metals, Engine Parts, Light Fixtures, Industrial Shelving, Computer Cases, Toolboxes, Medical Equipment, Barbeque and Gas Grills, Appliances, Kitchen cabinets, Automotive components, Aluminium extrusions and sheets, Coil coating and Reinforcing bars for concrete, Valves and pipeline fittings and many other items can be successfully powder coated.