The most common pvdf coating process are three sprays (referred to as 3 COAT) and two sprays (referred to as 2 COAT).
PRETREATMENT
Before coating the aluminum, the surface of the aluminium piece should be degreased and chemically treated to creat a chrome film, which help to increase the adhesion and oxidation resistance of the coating and the aluminum surface.
1 COAT – PRIMER COATING
A primer coating can improve the coating’s resistance to penetration, enhance the protection of the substrate, stabilize the metal surface layer, and enhance the adhesion of the top coat to the aluminum surface. The thickness of primer coating is generally 5-10 microns.
2 COAT – COLOR TOP COATING
The color top coating is the key layer of the spray coating. It provides the decorative color required for the aluminum to meet the design requirements and protect the metal surface from the external environment, acid rain and pollution. The color top coating is the thickest layer of paint in the spray, generally 25-30 microns.
3 COAT – CLEAR TOP COATING
The main purpose of the clear top coating is to more effectively enhance the lacquer coating’s resistance to external erosive, protect the color coating, increase the metallic luster of the coat color, and make the appearance more vivid and brilliant. The coating thickness is generally 10-15 microns.
CURING
3 Coat process generally requires two times curing. The curing temperature in the oven is generally between 230°C and 250 °C, and the curing time is generally 10-15 minutes. Different PVDF coating manufacturers will have their own instruction on curing temperature and time. Some coating plant adapts one time curing according to their own experience.
For 2 COAT process, there’s a little difference from 3 COAT process. 2 COAT process is followed by a color top coating after primer coating, and it only require one time curing.
PVDF Coating manufacturers generally can guarantee a coating life of 20 years or even 30 years. Also , FONNOV ALUMINIUM should emphasize that high-quality paint materials, proper production process, strict quality controlling, as well as regular effective maintenance on PVDF coated aluminum final product are all essential factors for long-term weatherability.