| No. | Description | Possible causes | Suggestion |
| 1 |
Crispy film: Finished coating surface showing cracking texture with crispy coating layer
|
Powder is not well cured. | Increase curing temperature or extend curring time or both. |
| 2 | Powder clogging/lumping
|
Storage temperature too high.
Powder exposured to high humidity environment. Powder is stressed under high force. |
Move the powder to the proper temperature and dry area.
Avoid heavy force above the powder while storing. |
| 3 | Cratering – The formation of small bowl-shaped depressions in the paint film.
|
Porous metal substrate like Cast iron, Aluminium alloy contains air bubbles
Contaminated with other powder. Inadequate pretreatment of coating substrate. Contamination with incompatible materials from the spraying area. Compressed air infected with oil, moisture, wax or silicon residues. |
Preheat porous substrate to release trap bubbles.
Clean the spraying system and start with the virgin powder. Check pretreatment process. Check the spray area for presence of incompatible materials. Check compressed air line and air filter. |
| 4 | Off color coating (Color difference)
|
Oven temperature too low or too high.
Baking time in the oven too long or too short. Improper oven exhaust Variation in film thickness. Coating itself. |
Adjust the oven temperature.
Review the baking schedule from the powder supplier, adjust the oven temperature or conveyer speed. Check the exhaust ventilating fan. Manage consist film coating. Clean application equipments thoroughly while changing color. Contact powder supplier. |
| 5 | Orange peel: The smoothness’ too poor and look like Orange-peel
|
Improper film thickness.
Air pressure too high. Incompatible powder contamination Micro -pinholding from gassing. Bad powder free-flow properties. |
Adjust the film thickness as per recommendation from powder supplier.
Cease the air pressure on the spraygun control unit. Clean application equipment before changing powders. Check substrate for porosity. b. Check substrate for moisture. c. Check powder for moisture from reclaim or compressed air. d. Check film thickness, coating too thick. Contact powder supplier |
| 6 | Poor adhesion of cured film
|
Inadequate cleaning or pretreatment of substrate.
Under-cured coating film |
Check the pretreatment process.
Increase oven temperature or oven dwell time |
| 7 | Poor powder penetration into recessing area or deep corner due to Faraday cage.
|
Poor powder delivery.
Poor ground. Improper spray pattern. Voltage too high or too low. Powder output too high or the pressure for the transport air too high, which blows the powder from the object. Poor gun positioning. Powder particle size too fine or too coarse. |
Improve Powder delivery.
Check ground from conveyor rail (or rub bar when used ) through hanger to part. All contact areas must be free from heavy grease and other insulating material Select proper deflector or spray nozzle. Adjust Voltage settings. Turn air pressure on pumps and guns to the proper setting. Turn the spraygun into right position so that powder builds on necessary area. Too much reclaim added to virgin powder. Or contact powder supplier for assistance. |
| 8 | Poor impact resistance / poor flexibility
|
Under-cured coating film.
Poor cleaning or pretreatment. Too heavy coated film. Coating substrate changed Uneven formation of the phosphate layer and residues from the pre-treatment. |
Improve baking schedule.
Check pretreatment process. Reduce film thickness. Consult with powder supplier Check the surface pretreatment |
| 9 | Gloss too low for High gloss powder or Gloss too high for Matt powder |
Virgin powder contaminated.
Overcured or Under-cured. Defective spray equipment. Moisture in the compressed air might kills the gloss |
Clean application equipment before changing powders.
Adjust curing oven setting. Check with spray equipment supplier. Checking compressed air filter. |
| 10 | Yellowing: The color is yellower than standard color. |
Too high baking temperature or baking duration too long.
Different in coating film thickness. |
Suitable baking condition should be ensured.
Adjust the film thickness evenly. |
| 11 | Pinhole: Tiny holes appear on the coating surface after curing. |
Compressed air infected with oil, moisture, wax or silicon residues.
Moisture remains on the metal substrate Porous substrate |
Check compress air quality, clean air filter system.
Dry out metal substrate before coating. Using appropriate powder coatings which are especially designed for diffusing gas on the coating surfaces. |
| 12 | Bits: Small sand dots defect. |
Foreign materials that does not melt and flow out during curing process.
Failure on the substrate cleaning. |
Check the contamination issue from powder, conveyor chain, spray booth and curing oven.
Check the pretreatment process to make sure the prepared metal surface is totally cleaned. |
| 13 | Poor color and Opacity |
Insufficient coating film thickness.
Powder quality problem (pigmentation uneven) Coating film is overbaked cause pale color |
Apply appropriate film thickness as per given Data sheet
Contact powder supplier Review baking condition on substrate |
| 14 | Picture framing: Occurs around the outer edge of a part |
Too much powder is applied on the edge of workpiece
Powder spray dispersal during the application process Heating rate in the oven too low (Especially on Thick metal) Powder property too much flow |
Reduce film thickness or powder volume
Adjust the settings on powder gun to reduce powder flow, and consider lowering your KVs Improve oven heating capacity or pre-heat workpiece before coating (thick substrate) Contact powder maker to adjust flow property |
| 15 | Outgassing: Usually happen on cast steel or cast aluminum
|
Moisture or contaminants rupture on the surface of the substrate break through the baking coating | Consider appropriate surface pretreatment methods or pre-heat metal prior to coating application to release gas.
|
| 16 |
Poor charging – inadequate powder build or wrap on part
|
High voltage source not providing enough KV at charging electrode or grid
Poor ground
Powder delivery air too high
Powder too fine |
Check high voltage source is on. Systematically check electrical continuity from voltage source to electrode(grid) including cable resistors and fuses. Check ground from conveyor rail (or hub bar when used) through hanger to part. All contract areas must be free of powder build, heavy grease and other insulation materials Turn down air setting or move gun position further away from part Too much reclaim added to virgin powder. Virgin powder pulverised too fine by manufacturer.
|
| 17 |
Mud cracking – The cracks appear as a network that can vary in size and amount. |
Generally, overapplication of heavily pigmented primers such as inorganic zinc silicates or water-based coatings, although can occur with other overthick systems. |
Apply only the recommended coating |
| 18 |
Rush rashing – The initial
|
Low film thickness, often in combination with a high surface profile. |
Ensure that an adequate thickness of a |
| 19 |
Rust Spotting – Individual spots of rust that appear on a paint film and frequently start as localized
|
Low film thickness (more likely creating rust rashing), voids and holidays (more likely creating rust rashing), but also defects in the steel, such as laminations and inclusions. Too high a surface profile may cause penetration of peaks through a paint film and cause rust spotting. May also occur from metallic contamination of a coated surface by grinding dust and so on. |
Ensure that an adequate thickness of a |
| 20 |
Rust staining – A light staining on the surface of the coating caused by the precipitation of ferrous oxide from adjacent exposed steel.
|
Water runoff from a rusty surface above a soundly coated surface. Rust staining occurs when the rust is wetted-out and contaminated water runs over and discolors other items or locations. Usually more of an eyesore than a defect. The coating itself may not be defective, only stained. |
Ensure adequate design and suitable maintenance. |
| 21 |
Alligatoring – Large crazing/cracking that resembles the skin of an alligator or crocodile. Cracks may penetrate through to the undercoat or down to the substrate.
|
Internal stresses in the coating where the surface shrinks faster than the body of the paint film. Excessive film thickness and limited paint flexibility. Application of a hard topcoat over a more flexible softer undercoat. Application of topcoat before the undercoat has dried. |
Use correct coating specification and |
| 22 |
Blistering – Dome-shaped projections or blisters in the dry paint film through local loss of |
Many mechanisms can be involved, including osmotic gradients associated with soluble salts, soluble pigments, corrosion products, retained solvents, and solvents from cargoes. Nonosmotic blistering is associated with cathodic disbonding, thermal gradients related to cold-wall effects, and compressive stress. |
Ensure correct surface preparation and |
| 23 |
Chalking – A friable, powdery layer on the surface of a paint film. A change of color or fading is |
Insufficient cured film.
Disintegration of the paint binder on exposure to weathering and/or ultraviolet light. |
Assured sufficient curing film.
Apply a suitable topcoat with high |
