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Step into the production workshop of Kunshan Yingliyue Electronics, and you’ll witness a remarkable scene: inside a high-vacuum chamber, an invisible “magic” is quietly unfolding. Ordinary metal, plastic, or ceramic components, through a series of physical transformations, “grow” a uniform, dense, a
We provide professional one-stop surface treatment services including PVD vacuum coating, sandblasting, precision polishing, and laser engraving. We focus on metal and plastic parts such as aluminum alloy, stainless steel, and engineering plastics, widely used in 3C electronics, automotive inter
Core Answer: Clarifies that PVD coating can simultaneously meet environmental compliance and performance standards. Environmental Advantages: Briefly describe the core environmental characteristics of the PVD process. Performance: Summarize the key performance standards required for mobile phone components. Customer Assurance: Supplementary certification and service support.
PVD (Physical Vapor Deposition) and CVD (Chemical Vapor Deposition) are two major thin-film coating technologies. PVD vaporizes materials through physical means (e.g., heating or sputtering), resulting in strong adhesion but slower deposition rates. CVD forms coatings via chemical reactions, off
As a new polishing process, plasma polishing is a trend in stainless steel polishing. If we can make good use of plasma polishing will save us a lot of time and costs.
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PVD coating is not simply about creating color. It is the result of optical behavior, film structure, substrate condition, electrochemical stability, and process control working together. Kunshan Yingliyue Electronics Co., Ltd. continues to focus on improving the appearance, wear resistance, corrosion resistance, and reliability of PVD-coated products, providing customers with more stable and competitive surface treatment solutions.
In metal components, electronic parts, hardware products, precision components, and consumer product decoration, PVD coating is widely used due to its high gloss, high hardness, rich color options, and environmentally friendly characteristics. However, the true quality of a PVD coating is not determined only by the color seen on the surface. It depends on the optical principles, coating density, substrate compatibility, and corrosion resistance mechanism behind the film.
The color of a PVD-coated surface often comes from complex interactions between light and the thin film. The most common optical phenomena include reflection, refraction, diffraction, and interference.
Reflection occurs when light reaches the coating surface and returns to the air. The mirror effect, brightness, and metallic appearance of a product are closely related to reflectivity and surface roughness.
Refraction occurs when light enters the coating from air and changes direction because of different refractive indexes. Different PVD materials have different refractive indexes, which influence visual brightness, transparency, and color depth.
Diffraction occurs when light encounters fine structures, edges, or periodic textures and spreads or disperses. When surface structures are close to the wavelength of light, angle-dependent color changes or rainbow-like effects may appear.
Interference is one of the most important reasons for color formation in thin PVD films. When light is reflected multiple times at the upper and lower interfaces of the film, some wavelengths are enhanced while others are weakened. This creates the color perceived by the human eye. Film thickness, refractive index, incident angle, and coating uniformity all directly affect color stability.
Therefore, color control in PVD coating is not simply “color adjustment.” It is a comprehensive process involving film thickness, deposition rate, vacuum condition, target material, process parameters, and product geometry.
Salt spray testing is a common method used to evaluate the corrosion resistance of PVD-coated products. Many people assume that rust means the entire PVD coating has failed, but the real situation is usually more complex.
Rust in salt spray testing is often related to the following factors:
Poor corrosion resistance of the substrate
If the substrate is iron, carbon steel, or a low-corrosion-resistant alloy, it may oxidize rapidly once corrosive media penetrate the coating.
Pinholes, microcracks, or particle defects in the coating
If pinholes, pores, cracks, or particle contamination exist in the PVD film, water, chloride ions, and oxygen from the salt spray can reach the substrate.
Insufficient coating coverage at edges and corners
Sharp corners, holes, edges, and grooves are more likely to have thin or uneven coating coverage, making them high-risk areas for corrosion failure.
Incomplete pretreatment
Residual oil, oxide scale, polishing wax, cleaning agent, or particles on the substrate surface can reduce coating adhesion and create hidden corrosion risks.
Insufficient film density
If a single-layer coating contains columnar structures or microvoids, corrosive media can penetrate more easily. Therefore, multilayer films, interlayers, denser deposition, and sealing treatments are important for improving salt spray resistance.
Chloride ions in salt spray environments are highly aggressive. They can damage the passive film on metal surfaces and promote localized pitting corrosion. Once corrosion begins at pinholes, cracks, or edges, it can spread laterally under the coating, eventually leading to blistering, blackening, red rust, or coating delamination.
In addition to physical defects, rust in PVD-coated products is also related to an important electrochemical mechanism: potential difference corrosion, also known as galvanic corrosion.
When different metals or conductive layers are in contact with an electrolyte, a micro-corrosion cell may form. In a salt spray environment, the water film and sodium chloride solution act as the electrolyte. If there is a potential difference between the PVD layer, interlayer, and substrate, an anode and a cathode can form.
The material with lower potential and higher activity becomes the anode, where oxidation occurs and corrosion proceeds faster. The material with higher potential becomes the cathode, where corrosion is slower.
For PVD-coated products, the most dangerous situation is:
A large PVD-coated area acts as the cathode, while a small exposed substrate area at a pinhole acts as the anode.
This creates an unfavorable “small anode / large cathode” area ratio. Since corrosion is concentrated in a very small anodic region, the local current density becomes high, and the exposed substrate at the pinhole dissolves rapidly, forming pitting corrosion. The corrosion can then spread underneath the coating. As a result, the surface may only show a small rust spot, while a larger hidden corrosion area has already developed beneath the film.
This is why PVD products often show the first rust points at holes, sharp edges, scratches, particle bumps, welded areas, or regions with insufficient pretreatment after salt spray testing.
Improving the salt spray performance of PVD-coated products cannot rely only on making the coating thicker. A truly effective solution requires optimization of the substrate, pretreatment, coating design, process control, and post-treatment.
Kunshan Yingliyue Electronics Co., Ltd. believes that stable PVD quality should focus on the following areas:
First, select the right substrate.
Different substrates have very different corrosion resistance. For products with high salt spray requirements, substrate composition, surface condition, and coating compatibility must be considered together.
Second, strengthen pretreatment quality.
Cleaning, degreasing, dewaxing, activation, drying, and surface cleanliness form the foundation of coating adhesion and corrosion resistance.
Third, optimize interlayers and bonding layers.
A proper transition layer can improve adhesion between the coating and substrate, reduce corrosion risks caused by potential difference, and enhance the overall barrier effect.
Fourth, improve coating density.
By optimizing deposition parameters, vacuum conditions, target condition, and film structure, pinholes, microcracks, and columnar voids can be reduced. This is critical for improving salt spray performance.
Fifth, pay attention to edges and complex structures.
Edges, holes, grooves, and sharp corners are more likely to fail than flat areas, so they must be considered during process design.
Sixth, apply sealing or composite protection when necessary.
For products with high corrosion resistance requirements, sealing treatment, composite coatings, multilayer structures, or other post-treatment methods can further block the penetration of corrosive media.
The competitiveness of PVD-coated products lies not only in whether the color looks attractive, but also in whether the color is stable, the film is firmly bonded, the salt spray performance is reliable, and the batch quality is consistent.
From an optical perspective, reflection, refraction, diffraction, and interference together determine the visual appearance of PVD coating. From a corrosion perspective, pinholes, cracks, weak edge coverage, pretreatment contamination, and potential difference are the main risk factors for salt spray rust.
Kunshan Yingliyue Electronics Co., Ltd. will continue to optimize PVD coating processes around appearance performance, film structure, corrosion resistance, and quality stability, providing customers with surface treatment solutions that combine aesthetics and reliability.
PVD coating is not a single process. It is a complete system. Only by controlling optics, materials, electrochemistry, and process stability together can high-quality coating products truly withstand market requirements and reliability testing.
