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Analysis of the Process Flow for UV Vacuum Plating

Release time:

2026-05-25 17:18

Analysis of the Process Flow for UV Vacuum Plating

UV vacuum plating is a composite surface‑treatment technology that combines ultraviolet‑curing techniques with vacuum‑coating processes. This process enables the formation of decorative layers with a metallic luster on non‑metallic substrates such as plastics. The complete process comprises key steps including substrate pretreatment, primer application and curing, vacuum coating, topcoat application and curing, as well as post‑processing and quality inspection. Mastering the operational essentials of each stage is fundamental to producing high‑quality coated products.

I. Substrate Pre-treatment

Substrate pretreatment is the first step in UV vacuum plating, and its quality directly affects the adhesion of subsequent coatings and the surface finish.

Substrate cleaning is the primary task of the pretreatment process. The workpiece surface may harbor contaminants such as release agents, oil, and dust, which must be removed by wiping with alcohol or a dedicated cleaning agent, or by ultrasonic cleaning. Inadequate cleaning can result in poor primer adhesion and the formation of pinholes or delamination in the coating layer.

For certain plastic substrates, surface activation is required. Corona treatment or plasma treatment is employed to introduce polar functional groups onto the substrate surface, thereby increasing surface energy and wettability and enhancing the adhesion of the primer. This step is particularly critical for low‑surface‑energy materials such as PP and PE.

Dust removal is performed after cleaning. An ion air gun or an electrostatic dust‑removal device is used to eliminate static charge and fine particles from the workpiece surface, thereby preventing dust contamination from compromising coating quality.

II. Primer Spraying and Curing

The primer is the initial coating in a UV vacuum plating system, serving to seal substrate defects and enhance adhesion.

Primer spraying is typically carried out in a dust-free spray booth. Using air spraying, the UV primer is applied evenly to the workpiece surface. The coating thickness must be precisely controlled: too thin will fail to seal substrate defects, while too thick may result in sagging or incomplete curing. After primer application, a sufficient leveling time is required to allow the coating to spread spontaneously across the surface, forming a smooth, even wet film.

After leveling is complete, the workpiece enters the UV curing unit for irradiation. Under ultraviolet light, the photoinitiators in the primer decompose to generate free radicals, initiating the polymerization of resins and monomers and causing the coating to transition from a liquid to a solid state within seconds. Once cured, the primer forms a smooth, even substrate, providing an excellent surface condition for subsequent coating deposition.

III. Vacuum Coating

Vacuum coating is the core process of UV vacuum electroplating, forming a metallic thin film on the primer surface and imparting a metallic luster to the workpiece.

Before coating, place the primed workpiece into the coating chamber of the vacuum deposition system, close the door, and activate the vacuum pumping system. Once the required vacuum level is achieved, commence the coating process.

Thermal evaporation coating involves heating a metallic material to vaporize it; the metal vapor then diffuses and deposits onto the substrate surface in a vacuum, forming a metallic thin film. Aluminum is a widely used coating material due to its low evaporation temperature, excellent adhesion, and low cost.

Magnetron sputtering utilizes ions generated by glow discharge to bombard the target material, causing atoms from the target to be sputtered and deposited onto the substrate. The resulting sputtered coating is dense, exhibits strong adhesion, and offers more consistent coating quality.

During the coating process, the film thickness can be monitored in real time using an online thickness gauge. The coating typically measures only 0.01 to 0.1 micrometer—extremely thin yet sufficient to produce a metallic luster.

IV. Topcoat Spraying and Curing

The topcoat is the outermost layer in a UV vacuum-plating system, serving to protect the metallic coating and resist external abrasion and corrosion.

Topcoat application is performed after the coating process is completed. An air‑spray method is used to evenly apply the UV topcoat onto the surface of the coated layer. Colorants may be added to the topcoat as needed to achieve a variety of color effects. The coating thickness should be moderate: too thin will provide insufficient protection, while too thick may result in sagging or incomplete curing.

After the topcoat is applied, it also requires a leveling period to ensure uniform spreading across the coating surface. Once leveling is complete, UV curing is performed; under ultraviolet irradiation, the topcoat cures within seconds. The cured topcoat exhibits high hardness and excellent abrasion resistance, providing effective protection for the coating layer.

V. Post-Processing and Inspection

After the topcoat has cured, the workpiece proceeds to the post‑treatment and inspection stages.

Quality inspection is a critical step in ensuring product compliance. Visual inspection is conducted under standardized lighting conditions, with the coating surface examined for defects such as runs, orange‑peel texture, bubbles, particles, and areas of incomplete plating. Performance testing encompasses adhesion, hardness, and chemical resistance assessments to verify that the product meets customer specifications. Qualified products are cleaned, packaged, and then stored in inventory.

VI. Conclusion

The UV vacuum plating process comprises key steps such as substrate pretreatment, primer application and curing, vacuum coating, topcoat application and curing, and post‑treatment and inspection. Pretreatment ensures a clean substrate and surface activation; the primer provides adhesion and a smooth base; vacuum coating forms a metallic‑luster layer; the topcoat offers protection and decorative finish; and post‑treatment and inspection safeguard product quality. Each stage is interrelated, and precise control of process parameters is essential for ensuring product quality. Mastering the complete process flow is the foundation for producing high‑quality UV vacuum‑plated products.

Disclaimer: The above content has been compiled from publicly available sources and is provided for reference only. If any infringement occurs, please contact us, and we will address it promptly.

Bosheng’s Recommended Products – Vacuum Plating
Primer
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-113	Bisphenol A epoxy acrylate	High hardness, high gloss, high fullness, contains 20% TPGDA.
B-151	Modified epoxy acrylate	Low halogen, yellowing-resistant, excellent plating performance, and strong adhesion.
B-160D	Modified epoxy acrylate	Good flexibility, yellowing resistance, and excellent adhesion.
B-163	Modified epoxy acrylate	Good flexibility, excellent pigment wetting, and strong adhesion.
B-165	Modified epoxy acrylate	Good flexibility and strong adhesion
B-212A	Aromatic polyurethane acrylate	High cost-performance, excellent plating adhesion, good toughness, and resistant to boiling water.
B-221	Aliphatic polyurethane acrylate	Fast curing, resistant to boiling water
B-268M	Aliphatic polyurethane acrylate	Good flexibility, excellent adhesion, superior plating performance, and strong hiding power.
B-574C	Polyester acrylate	Low viscosity, low odor, excellent wettability, suitable for LED UV.
B-619W	Aliphatic polyurethane acrylate	Fast curing, high hardness, excellent toughness, wear resistance, and chemical resistance.
Intermediate coat
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-374	Aliphatic polyurethane acrylate	Good flexibility, excellent leveling, resistant to abrasion and chemicals, and yellowing‑resistant.
B-601	Aromatic polyurethane acrylate	High hardness, scratch resistance, chemical resistance, and excellent cost-effectiveness.
B-6020	Special functional group acrylate	Resistant to boiling water, excellent color development, and strong interlayer adhesion.
Topcoat
Product Model/English Abbreviation	Product Name/Product Type	Product Features
B-221	Aliphatic polyurethane acrylate	Fast curing, resistant to boiling water
B-301	Aromatic polyurethane acrylate	Fast curing, excellent toughness, and good sandability.
B-302	Aromatic polyurethane acrylate	Fast curing, high strength, excellent toughness, and good grindability.
B-368	Aliphatic polyurethane acrylate	Good toughness, excellent leveling, excellent bend resistance, and excellent heat resistance.
B-374	Aliphatic polyurethane acrylate	Good flexibility, excellent leveling, resistant to abrasion and chemicals, and yellowing‑resistant.
B-574C	Polyester acrylate	Low viscosity, low odor, excellent wettability, suitable for LED UV.
B-601	Aromatic polyurethane acrylate	High hardness, scratch resistance, chemical resistance, and excellent cost-effectiveness.
B-6016C	Special functional group acrylate	Easy to apply, resistant to yellowing and boiling water, and improves the appearance of the paint film.
B-6019	Special functional group acrylate	Good leveling, excellent wettability, resistant to boiling water, and superior color dispersion.
B-609	Aliphatic polyurethane acrylate	Fast curing, high hardness, scratch resistance, and chemical resistance.
B-615A	Aliphatic polyurethane acrylate	Fast curing, excellent toughness, wear resistance, and chemical resistance.
B-619W	Aliphatic polyurethane acrylate	Fast curing, high hardness, excellent toughness, wear resistance, and chemical resistance.
B-6210	Aliphatic polyurethane acrylate	Low viscosity, chemical resistance, environmental resistance, and dual photocatalytic–thermal curing.
B-6211	Aliphatic polyurethane acrylate	Fast curing, high hardness, scratch-resistant, and free of organotin.
B-919B	Aliphatic polyurethane acrylate	Fast curing, high hardness, excellent toughness, and superior chemical and wear resistance.
Monomer Recommendation
Product Model/English Abbreviation	Product Name/Product Type	Product Features
BM2223 (TPGDA)	Di(propylene glycol) diacrylate	Good flexibility and low volatility
BM3231 (TMPTA)	Trimethylolpropane triacrylate	High crosslink density, high hardness, high gloss, and excellent wear resistance.
BM3235 (PET3A)	Pentaerythritol triacrylate	Fast curing, high crosslink density, high hardness, and chemical resistance.
BM3380 (3EO-TMPTA)	Pentaerythritol triacrylate	More flexible and less irritating than TMPTA.
BM6261 (DPHA-80)	Dipentaerythritol hexaacrylate	High crosslink density, high hardness, chemical and wear resistance, and water resistance.
BM6263 (DPHA-90)	Dipentaerythritol hexaacrylate	High crosslink density, high hardness, chemical and wear resistance, and water resistance.

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