Influence of Film Thickness on Coating Performance

Film thickness control is a key technical indicator in the surface treatment process, and its reasonable degree directly affects the coating quality and production costs.

I.Typical performance of thin coating film (recommended thickness: 60-80μm)

1.Apparent quality defects

- Poor leveling: the surface of the coating is easy to form orange peel pattern, similar to the dimpled texture of citrus skin.

- Insufficient coverage: light-colored coatings are prone to translucency, and the color difference value ΔE can be more than 1.5.

- Obvious particles: electrostatically adsorbed dust particles are difficult to be covered by thin coatings.

2.Physical property changes
- Impact strength: Pass rate of 1kg-cm test decreased by about 30%.

- Flexibility: 40% increase in the probability of cracking in the 1mm axial bar bending test.

- Adhesion: possible reduction in test grade from 5B to 3B by scratch method

3.Chemical protection shortcomings

- Salt spray resistance time: 200 hours will appear corrosion expansion (standard requirements ≥ 500h)

- Acid and alkali resistance: 5% NaOH solution immersion for 24 hours to appear obvious light loss

II.Negative effects of excessively thick coating film (upper limit recommended: 120μm)

1.Construction quality risk

- Hanging probability: when the local thickness exceeds 150μm, the incidence of drooping can reach 80%.

- Assembly interference: the fastener fit gap is reduced by 0.1-0.3mm.

- Curing defects: thermosetting coatings may produce the phenomenon of “entrapment”.

2.Economic losses

- Increase in powder consumption: every 10μm increase in thickness, the cost of a single piece rises by 5-8%.

- Rework rate: the cost of secondary processing of ultra-thick parts is 2-3 times higher than that of normal parts.

3.Performance turning points
- Internal Stress: Coating internal stress exceeds 3MPa for thickness >150μm.

- Impact resistance: Reverse decrease of approx. 15% (brittleness increase effect)

- Curing energy consumption: 20% increase in energy consumption per unit area

III.Precision control technology program

 1.Equipment selectionpoints
- Electrostatic generator: Pulse type is 30% higher than DC type in thickness uniformity.

- Recycling system: equipped with cyclone + cartridge secondary recycling, powder utilization rate of 98

2.Process optimization direction
- Pre-treatment: Phosphate film weight control at 2-3g/m² can improve adhesion by 20%.

- Curing curve: the use of step temperature (120 ℃ → 180 ℃ → 200 ℃) to reduce the hanging