1.How to strictly control the quality of raw materials?
Substrate Cleanliness:
Ensure the surface of the galvanized or aluminum-zinc plated substrate is free of rust, oil, dust, or residue. Use a cleanliness testing instrument (e.g., contact angle test) during incoming inspection.
Avoid moisture and dust contamination during storage; rust-proof packaging and a dry environment are recommended.
Coating Quality Control:
Filter the coating thoroughly before use (5-10μm filter recommended), ensuring the coating viscosity and solids content meet process requirements.
Regularly check coating compatibility to avoid mixing different batches or brands, which can lead to particulate reactions.
2.How to optimize the pretreatment process?
Cleaning Section Management:
Ensure the degreasing solution concentration and temperature are within the process range (typically 2-4% concentration, 40-60℃), and change the bath solution regularly.
Strengthen the monitoring of rinsing water quality (conductivity ≤50μS/cm) to prevent chemical residue.
Check the condition of the squeeze rollers and replace worn rollers promptly to prevent moisture from being carried into the next process.
Chemical Formation Treatment:
Control the pH, temperature, and film thickness of the passivation solution (e.g., chromium-free passivation) to ensure coating adhesion and reduce subsequent coating defects.
3.How to control the coating process
Coating Uniformity:
Adjust roller coater parameters (roller speed ratio, pressure) to ensure uniform coating thickness. After initial setup, use a film thickness gauge to check at multiple points.
Avoid excessively high or low paint viscosity (adjust according to the paint supplier's recommendations; typically, an application viscosity of 20-30 seconds for a 4-cup coating) is sufficient.
Curing Process Control:
The oven temperature profile must precisely match the paint requirements. Rapid heating may cause solvent evaporation and bubble formation; segmented heating (preheating, curing, cooling) is recommended.
Ensure oven nozzles are clean and airflow is uniform to avoid localized overheating or residual volatiles.
4.How should the environment and equipment be managed?
Painting Room Cleanliness:
Maintain positive pressure in the painting area and install an air filtration system (ISO Class 8 or higher cleanliness level recommended).
Regularly clean roller coaters, paint lines, spray guns, and other equipment to prevent dried paint particles from falling off.
Equipment Maintenance:
Inspect the wear and balance of coating rollers (feed rollers, application rollers), and grind or replace them as needed.
Ensure the drive rollers are clean to prevent impurities adhering to the roller surface from transferring to the panel surface.
5.How are process monitoring and testing conducted?
Online Monitoring:
Install a high-resolution surface inspection system (such as a line scan camera) to identify defects such as pitting in real time and trigger alarms.
Periodic sampling for laboratory analysis (such as microscopic observation and energy dispersive spectroscopy) to determine the composition of pitting (zinc particles, dust, resin particles, etc.) and trace its root cause.
Process Records and Traceability:
Record detailed process parameters for each roll of material (cleaning parameters, coating amount, curing temperature, etc.) to facilitate rapid troubleshooting when defects occur.