THE POWDER COATING, WHICH SHOULD ELECTROSTATICALLY ADHERE TO THE SUBSTRATE, FALLS OFF – NO RELEVANT COATING THICKNESS CAN BE ACHIEVED.
NEEDS TO REMOVE POSSIBLE CAUSES:
- The use only recycled powder (recuperator) without adding the original powder. The recuperator must not exceed 50% of the original value;
- too high speed of air flow, the gun is too close to the painted part (the optimal distance is 20-30 cm);
- insufficient charging of the powder (low voltage on the corona electrode or its absence);
- too high a yield of a powder (it does not have time to be charged because of a large flow);
- too high voltage (reverse ionization effect occurs);
- insufficient grounding of components or lack thereof.
DECISION.
The Adjustment of parameters for staining, optimization:
- air flow velocity;
- hanging parts;
- voltage;
- grounding;
WHY ARE CRETERS ON READY PRODUCTS?
Craters possible causes:
- Incompatibility with powder coatings from other manufacture (compatibility of different powder systems is determined by chemical structure, surface tension, difference in reactivity and viscosity);
- Outgassing from substrate (the presence of cavities and pores may lead to defects because of chemical residues from the surface preparation);
- On structure surface: insufficient coating thickness;
- Insufficient pretreatment;
- Work piece moist/wet (Increase drying time/temperature);
- Residues of oil, grease, wax or silicone;
- Surrounding air contaminated with oil.
WHAT PERMISSIBLE MIN / MAX THICKNESS COATING? (Structure, coarse texture, antique)?
RECOMMENDED THICKNESSES
- For coatings of structure type: 70-120 μm;
- For coarse texture coatings: 60-110 μm;
- For smooth coatings: 60-80 μm;
- For antique cover coatings: depending on the structure, from 80 to 200 μm;
- at a recommended thickness of a structured coating of more than 110 μm, impact strength is not regulated.
LIFTING OF THE POWDER COAT LAYER?
CAUSES:
- Under or over curing of the powder coating film
- Insufficient/inappropriate pretreatment: adhesion-preventing substances such as silicone, oil, grease, wax, various contaminants, rust, grinding dust, scribing layers or oxide films remained on the surface
- Very high film thickness (insufficient mechanical properties). If the recommended thickness is exceeded, the physical and mechanical characteristics of the coating deteriorate, so that when the impact (mechanical action) occurs, the coating may lift or crack.
CORRECTIONS, TESTING, PROCEDURES:
- Observe curing parameters which are recommended for the powder paint manufacturer (the manufacturer indicates the temperature of the metal, not the air);
- Reduce film thickness or use more flexible powder coatings
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