Discharges in powder coating: identifying causes and eliminating them safely
Electrostatic discharges – also known as voltage breakdowns – can cause significant quality and safety problems in powder coating. They occur when too much charge builds up and suddenly escapes at a conductive point. This can not only lead to surface defects, but also to sparking and dust explosion hazards.
1. Inadequate grounding of workpieces
The most common cause of discharges is poor or missing grounding of the object to be coated. Without clean ground contact, the electrostatic charge cannot be dissipated.
Solution: Ensure that each workpiece has a defined, bare metal contact to earth. Rust, paint residues or poor suspension contacts must be avoided.
2. High voltage setting too high
If the high voltage of the coating gun is set too high, the risk of voltage breakdown increases – especially with thin or sharp-edged parts.
Solution: Reduce the high voltage in the critical area. GEMA recommends using PCC mode (Precise Charge Control) for sensitive geometries in particular in order to be able to finely control the charge.
3. Component spacing too small
If two conductive components are too close together, the high field strength between them can cause sparking.
Solution: Maintain sufficient distance between the workpieces, especially with rotating product carriers or automated systems.
4. Insulating coatings or contamination
Pre-treatment residues, oil films or powder coatings on the contact surfaces can interrupt the grounding.
Solution: Check and clean the contact points regularly. Use suitable test equipment to check the grounding resistance.
5. Powder quantity and air flow
Excessive powder application or incorrectly adjusted air flows can lead to the formation of powder clouds with high charge potential.
Solution: Reduce the amount of powder, optimise the air flow and regularly check the condition of the injectors and nozzles.
With consistent grounding, correct system settings and clean handling of the workpieces, you can avoid dangerous discharges and ensure high-quality coating results in the long term.
