This article systematically introduces the concept, types, features, functions, application areas, selection considerations, and solutions to common problems of BONDING metallic powder coating. It focuses on the specific applications of BONDING metallic powder coating to help you better understand what BONDING metallic powder coating is and what its characteristics and functions are.
What Is BONDING Metallic Powder Coating
BONDING metallic powder coating is a metallic-effect powder coating that uses a thermomechanical process to firmly adhere flake metallic-effect pigments, such as aluminum powder and pearlescent pigments, to the surface of base powder particles at a controlled temperature, thereby solving the pigment separation problem associated with the traditional dry-blending method.Features of BONDING Metallic Powder Coating
The main features of BONDING metallic powder coating are as follows.1. Stable Metallic Effect
Metallic pigments are bonded with the base powder particles into an integrated system and are deposited simultaneously during spraying, avoiding fluctuations in pigment ratios caused by differences in electrical charging properties. It provides high consistency between color batches and a uniform metallic effect, avoiding shade differences or color-difference patches.
2. Reclaimed Powder Can Be Used
This is the most prominent advantage of BONDING compared with the dry-blending method. Because the ratio of metallic pigments to base powder remains relatively stable, reclaimed powder can achieve nearly the same color as virgin powder, with a utilization rate approaching 100%.
3. Excellent Application Performance
(1) No gun clogging: The pigments are bonded and do not accumulate at the spray gun nozzle.
(2) Higher powder deposition rate: Metallic pigments and base powder become electrically charged simultaneously, improving the poor charging performance of metallic pigments encountered with the dry-blending method.
(3) Fingerprint resistance: The coating surface resists fingerprints, and metallic pigments are less likely to be rubbed off.
(4) Higher metallic pigment loading: Dry blending is usually subject to limitations, while bonding technology can accommodate a higher proportion of metallic powder to achieve a stronger metallic sparkle effect.
4. Stable During Storage and Transportation
Metallic pigments do not separate from the base powder particles, maintaining powder uniformity without pigment settling or stratification during transportation and storage.
5. Mechanical and Protective Properties of the Coating
Mechanical properties are mainly determined by the resin system of the base powder. After bonding, uniform pigment distribution helps maintain performance consistency. Typical products can achieve a cross-cut adhesion rating of 0. impact resistance of 50 kg·cm, pencil hardness of ≥H, and salt spray resistance of ≥500 hours.
Functions of BONDING Metallic Powder Coating
The main functions of BONDING metallic powder coating are reflected in the following aspects.1. Stabilizing the Metallic Effect and Eliminating Color Differences
The BONDING process firmly adheres metallic pigments to the surface of base powder particles, allowing the two to be deposited simultaneously during spraying and avoiding fluctuations in pigment ratios caused by differences in charging properties. Therefore, coating colors remain highly consistent between batches, the metallic effect is uniform, shade differences or color-difference patches are avoided, and the sparkle effect is also brighter.
2. Enabling Normal Use of Reclaimed Powder
This is the most prominent economic value of the BONDING process. Because the ratio of metallic pigments to base powder remains relatively stable, reclaimed powder can achieve nearly the same color as virgin powder, with a reclaimed powder utilization rate approaching 100%. In contrast, reclaimed powder from dry-blended metallic powders is generally not recommended for reuse. BONDING technology directly reduces material waste and lowers overall usage costs.
3. Improving Application Performance and Safety
(1) No gun clogging: Metallic pigments do not accumulate at the spray gun nozzle and cause clogging during spraying.
(2) Higher powder deposition rate: Metallic pigments and base powder become electrically charged simultaneously, improving the poor charging performance of metallic pigments encountered with the dry-blending method.
(3) Fingerprint resistance: Metallic pigments on the coating surface are less likely to be rubbed off, avoiding fingerprint defects.
(4) Safer use: Metallic pigments are less likely to become airborne and accumulate in the workshop, improving operational safety.
Applications of BONDING Metallic Powder Coating
The main application areas of BONDING metallic powder coating are as follows:1. Architecture and Curtain Walls
This is one of the mainstream application areas for BONDING metallic powder. It is mainly used for aluminum profiles, curtain wall panels, and door and window frames, especially in high-end architectural projects that need to comply with weatherability standards such as AAMA 2604/2605.
2. High-End Furniture and Design Elements
The color stability and metallic appearance provided by the BONDING process make it highly suitable for outdoor furniture, office furniture, garden pavilions, fences, and other applications. The metallic effect can provide furniture and design elements with a “bright, high-end” decorative appearance, which is a typical selling point of bonded metallic powder.
3. Home Appliances, Automotive, and Transportation
For high-end home appliances, control panels, and consumer electronics housings, bonded powder can provide a stable metallic appearance. In the automotive industry, it is used for components such as wheels, decorative parts, and interior metal components. Fitness equipment is also one of its common application areas.
4. Lighting and General Industry
Lighting housings, reflectors, and decorative lighting components are traditional application scenarios for bonded metallic powder. In broader industrial applications, products requiring a metallic appearance, such as store shelves, display systems, tool cabinets, and safes, also commonly use bonded metallic powder.
How to Select BONDING Metallic Powder Coating
When selecting BONDING metallic powder coating, we may face the problem of not knowing how to choose. Based on our industry experience, we recommend focusing on the following aspects when selecting BONDING metallic powder coating.1. First Determine Whether BONDING Is Necessary
This is the starting point for product selection. BONDING is not the only option, but it is essential in the following applications:
(1) BONDING must be selected: Large workpieces, multi-batch production, outdoor architectural/curtain wall applications, applications requiring reclaimed powder, and applications with high color-consistency requirements. Bonded powder provides “stable color differences between batches, with no clouding or cloud-like patches in the coating film,” and “overspray powder can be reclaimed and reused.”
(2) Dry blending can be considered: Small workpieces produced in a single batch, applications that are extremely cost-sensitive, and applications with relatively low color requirements. However, the risks of pigment separation, unusable reclaimed powder, and easy gun clogging must be accepted.
2. Select the Resin System According to the Application Environment
The BONDING process itself does not determine weatherability; the resin system of the base powder is the key factor.
(1) Outdoor/architectural curtain wall applications: Weather-resistant polyester or super-durable systems must be selected. Attention should be paid to Qualicoat classes (Class 1/2/3) or AAMA 2604/2605 certification. Class 2/3 is suitable for south-facing facades, dark colors, or projects with high weatherability requirements.
(2) Indoor/general industrial applications: Epoxy-polyester hybrid or pure polyester systems can be used, with cost-effectiveness as a priority.
(3) Special requirements: If high-end metallic appearances such as electroplated or anodized effects are required, dedicated product series can be selected.
3. Verify Practical Application Capability Through Process Parameters
Bonded powder has a more tolerant process window than dry-blended powder, but it is still more sensitive than ordinary powder coating. When selecting a product, the following parameters must be confirmed to match your production line:
(1) Curing conditions: Typical curing conditions for bonded powder are 200°C/10 min, while low-temperature solutions such as 180°C/10 min can also be designed as required. It is necessary to confirm whether your oven can meet the requirements.
(2) Film thickness window: A recommended film thickness is 50~80 μm, with an applicable range of 40~150 μm. Film thickness fluctuations directly cause color differences: when the film is thin, more of the base powder shows through; when the film is thick, the silver powder color becomes more prominent. “A color difference becomes visible when the film thickness differs by approximately 15 μm.”
(3) Spraying voltage: Voltage directly affects the amount of aluminum powder deposited. The normal setting is approximately 65 kV, and “adjusting by 5~10 kV will produce a certain effect.”
(4) Spraying method: Corona charging is recommended rather than tribo charging. Tribo charging may cause pigment separation and weaken the metallic effect.
Common Problems and Solutions for BONDING Metallic Powder Coating
The most common problems encountered when using BONDING metallic powder coating are mainly reflected in the following aspects. Based on our industry experience, we propose corresponding solutions to help effectively solve powder coating problems you may encounter.1. Poor Bonding Effect (Pigments Not Effectively Bonded)
Appearance: After bonding, metallic pigments remain in a free state, resulting in a low powder deposition rate, weak metallic effect, and large color fluctuations in reclaimed powder during spraying.
Possible causes:
(1) The bonding temperature does not reach a level close to the softening point of the resin, so the powder particle surfaces are not sufficiently softened to adhere to the pigments.
(2) Insufficient bonding time results in insufficient contact time between the pigments and base powder. Some studies show that a fluidization time of approximately 10 minutes results in the smallest composition deviation, while both shorter and longer times are unfavorable.
(3) Excessively high bonding temperature causes powder particles to adhere to one another, resulting in “false bonding,” localized agglomeration, carbonization, or even bonding failure.
Solutions: Set a bonding temperature approximately 10°C above the glass transition temperature of the resin as the bonding temperature reference, and then fine-tune it through stability testing. Set the hot-water temperature approximately 10°C higher than the bonding temperature to accelerate heating while preventing material from adhering to the inner wall. Add metallic pigments when the material temperature approaches the bonding temperature to reduce the time during which the pigments are subjected to shear.
2. Metallic Pigment Breakage or Reduced Sparkle Effect
Appearance: The metallic sparkle effect is weak after bonding, or the sparkle effect is unstable between batches.
Possible causes: The shear force generated by the high-speed rotation of the mixing blades damages the structure of flake metallic pigments, resulting in smaller particle sizes and reduced sparkle. Conventional bonding processes generally have insufficient metallic sparkle and stability.
Solutions: Control the stirring speed during heating and minimize shear as much as possible while maintaining the required heating rate. For pigments that are easily broken, add them when the material temperature approaches the bonding temperature. A two-step bonding process can also be considered. By controlling the resin-to-curing-agent ratio and bonding conditions, the average color difference under different spraying conditions can be reduced by 26%, while the metallic area ratio under a microscope can be increased by 40%.
3. Uneven Color Caused by Improper Loading Amount
Appearance: Uneven color within a batch or between batches.
Possible causes: Excessive loading prevents the powder in the upper part of the bonding machine from being effectively stirred, resulting in insufficient mixing between the upper and lower powder. Insufficient loading can cause the material to adhere easily to the inner wall after heating, resulting in uneven dispersion of metallic pigments and base powder.
Solutions: Control the loading amount within the effective operating range of the bonding machine and keep the material quantity consistent for each bonding cycle to effectively reduce color differences between batches.
4. Color Fluctuation with Spraying Parameters
Appearance: The same batch of bonded powder shows differences in metallic effect and color under different voltages or spraying conditions.
Possible causes: Aluminum powder pigments have better charging properties than the base powder. At high voltage, more aluminum powder is deposited on the workpiece, while at low voltage, less aluminum powder is deposited. Changes in voltage directly alter the actual proportion of aluminum powder in the coating.
Solutions: Corona charging is recommended for spraying bonded metallic powder rather than tribo charging. Tribo charging can cause pigment separation and weaken the metallic effect. A normal spraying voltage can be set at approximately 65 kV. An adjustment of 5~10 kV can produce a visible effect on the aluminum powder ratio, so the voltage setting should be kept constant. The same charging method must be used throughout the entire process and should not be mixed.
5. Color Difference Caused by Film Thickness Variation
Appearance: Color inconsistency occurs in different areas of the workpiece, and a color difference becomes visible when the film thickness differs by approximately 15 μm.
Possible causes: The base powder and metallic pigments in metallic powder coatings have different hiding characteristics. When the film is thin, more of the base powder color shows through; when the film is thick, the silver pigment color becomes more prominent. Clouding in bonded powder is also directly related to uneven film thickness.
Solutions: Control the difference between the thinnest and thickest areas of the workpiece within 15 μm. Check and optimize the spray gun sine curve, high-voltage stability, and workpiece grounding to reduce film thickness variation.
6. Spray Gun and Nozzle Clogging
Appearance: The spray gun or nozzle becomes clogged, or powder spitting occurs during spraying.
Possible causes: Even with bonding, if the bonding is incomplete, free metallic powder may still accumulate at the spray gun nozzle. The higher the metallic pigment loading, the more likely gun clogging and poor leveling may occur.
Solutions: Use a nozzle system suitable for metallic powder, such as a spray disc with internal ventilation, to prevent powder accumulation on the back of the spray disc from intermittently falling off and forming “metallic spots.” Thoroughly clean the spraying equipment. When switching between metallic powders, the equipment must be cleaned; otherwise, deposited particles may be carried onto the workpiece surface with the powder and form spots.
Get Professional BONDING Metallic Powder Coating Solutions
If you are looking for BONDING metallic powder coating with a stable metallic effect, good application performance, and a high reclaimed-powder utilization rate, we can provide suitable powder coating solutions according to your application scenario, substrate type, color effect, weatherability requirements, and spraying process.Whether for architectural aluminum profiles, curtain walls, furniture, home appliances, automotive components, lighting products, or general industrial metal parts, we can provide product specifications, color solutions, samples, and technical support according to actual requirements.
Welcome to contact us for BONDING metallic powder coating product information, samples, and quotations, and let us work together to determine a suitable metallic-effect powder coating solution for your project.
