Electrophoretic coating and powder coating are two mainstream industrial coating processes, differing significantly in their principles, performance, and applicable scenarios. The following provides a detailed analysis of the core principles, process details, performance comparison, and applicable scenarios:
I. Core Principle Differences
1.1 Electrophoretic Coating:
Coating deposition is achieved through the action of an electric field. The workpiece, acting as an electrode (anode or cathode), is placed in an electrophoretic tank containing a water-soluble coating (containing charged resin particles). When a direct current is applied, the charged coating particles, driven by the electric field, migrate toward the workpiece surface, gradually depositing to form a uniform coating. Finally, the coating is dried and solidified into a film.
(Note: Based on the polarity of the workpiece, electrophoretic coating is categorized as anodic (the workpiece serves as the anode, and the coating is negatively charged) or cathodic (the workpiece serves as the cathode, and the coating is positively charged). The latter is more widely used due to its greater corrosion resistance.)
1.2 powder coating:
Coating adhesion is achieved through electrostatic attraction. Solid powder coating (a mixture of resin, pigment and additives) is charged with static electricity through a spray gun, and the workpiece being sprayed is grounded to form an electric field. The powder is adsorbed on the surface of the workpiece under the action of electrostatic attraction, and then baked at a high temperature (150-200℃) to melt, level and solidify the powder into a film.
2.Comparison of process steps:
| Link | Electrophoretic Coating | Powder Coating |
| Pretreatment | Strict treatment (degreasing, rust removal, phosphating/passivation) is required to ensure that the workpiece surface is clean and charged, otherwise the coating adhesion will be affected. | The pretreatment is relatively simple (degreasing and rust removal are sufficient), phosphating can be omitted in some scenarios, and the surface cleanliness requirements are slightly lower. |
| Paint application | The workpiece is completely immersed in the electrophoresis tank, and the paint is automatically deposited by the electric field without manual intervention. | When spraying with a manual or automatic spray gun, the spray gun distance and voltage must be controlled to ensure uniformity. |
| Post-processing | It needs to be washed with water several times (to remove undeposited floating paint) and then dried at low temperature (120-180℃). | No need to wash with water, direct high temperature curing (150-200℃, the specific temperature depends on the powder type). |
| Paint recycling | The undeposited coating remains in the electrophoresis tank for recycling, with a utilization rate of about 95%. | Excess powder can be collected and reused through a recovery system (such as a cyclone separator), with a utilization rate of about 90%. |
3.Key Performance Differences:
| Performance indicators | Electrophoretic Coating | Powder Coating |
| coating thickness | Thin (typically 10-30μm) with very high uniformity (deviation ≤ 2μm). | Thicker (usually 50-150μm, customizable to over 200μm), slightly less uniform (complex parts may have deviations of up to 10μm). |
| Adhesion | It has extremely strong adhesion to metal substrates (steel, aluminum alloy) (cross-cut test ≥5B). | It has good adhesion to metal (≥4B) and can also adhere to non-metals (such as treated plastics), but special pre-treatment is required. |
| Corrosion resistance | Cathodic electrophoresis coating has excellent salt spray resistance (500-1000 hours without rust), suitable for high corrosion resistance requirements. | Epoxy powder can withstand salt spray for more than 1,000 hours, while polyester powder has better weather resistance (not prone to powdering when exposed to outdoor sunlight). |
| Appearance texture | The gloss is uniform (mainly highlights), without sagging or pinholes, suitable for scenes requiring a delicate appearance. | A variety of textures can be achieved (matte, sand texture, hammer texture, etc.), but thick coatings may show orange peel (curing temperature needs to be controlled). |
| Corner coverage | Complex shapes (e.g. deep holes, grooves) can be covered evenly without “corner effects”. | Due to the “Faraday cage effect”, the coating may be too thin in recessed areas or corners (need to adjust the spray gun angle or add an auxiliary electrode). |
4.Comparison between environmental protection and cost:
| Dimensions | Electrophoretic Coating | Powder Coating |
| Environmental protection | The paint is water-based and VOC (volatile organic compound) emissions are extremely low (≤50g/L), but pre-treatment and water washing will produce phosphorus-containing wastewater, which requires professional treatment. | There is no VOC emission (the powder is solid), almost no wastewater, high paint utilization rate (≈90%), and better environmental protection; however, the curing temperature is high and the energy consumption is slightly higher. |
| Equipment costs | The initial investment is high (electrophoresis tank, rectifier, multi-stage water washing tank, etc. are required), and it is suitable for large-scale mass production. | The equipment is relatively simple (spray gun, curing oven, recovery system), with low initial investment, suitable for small and medium-sized batch production. |
| Running costs | The cost of wastewater treatment is high and the unit price of coating is high, but the utilization rate is almost 100%. | Powder coatings have a lower unit price and a recycling system that reduces consumables costs, but high-temperature curing consumes more energy. |
| Color change convenience | Color changing requires draining the electrophoresis tank and thoroughly cleaning it, which is time-consuming (4-8 hours) and costly, making it suitable for single color mass production. | Color changes require cleaning of the spray gun, pipes, and recovery system, which is time-consuming (1-2 hours). It is more flexible than electrophoresis, but still not suitable for frequent color changes. |
5.Summary and comparison table:
| feature | Electrophoretic Coating | Powder Coating |
| principle | Electrochemical Deposition (Electrophoresis) | electrostatic adsorption |
| Paint form | Liquid (water-based emulsion) | Solid powder (100% solids) |
| Construction method | Dip coating | Spraying (electrostatic) |
| Biggest advantage | Uniform coverage (cavity/gap/corner), ultimate corrosion protection | Decorative/diversity, thick film physical protection, environmental protection |
| Film Thickness | Thin (10-30 microns) | Thick (50-120+ microns) |
| Color/Effect | Limited (primarily single-color primer) | Extremely rich (various colors, sheens, textures, effects) |
| Corrosion resistance | Excellent (especially as a primer) | Good to excellent (thick film provides protection) |
| Weather resistance | General (mainly used as primer) | Excellent (especially weather-resistant powder) |
| Mechanical properties | good | Excellent (hardness, wear resistance, impact resistance) |
| VOC emissions | Very low (water-based) | zero |
| Material utilization | Very high (>95%) | High (recovery rate>95%) |
| Pretreatment | Extremely strict requirements | Strict requirements |
| wastewater | Yes (needs processing) | none |
| Color Change | Easy (bath) | Difficult (needs thorough cleaning) |
| Curing temperature | Higher (160-180°C) | Higher (160-200°C) |
| Typical Applications | Automotive body/parts primer, home appliance hardware primer, anti-corrosion primer | Home appliance exterior parts, building material profiles, furniture, decorative topcoats |
6.1 Electrophoretic Coating:
Suitable for applications requiring high coating uniformity, corrosion resistance, and a refined appearance, such as:
Automobile bodies and parts (cathodic electrophoretic coating is the industry standard);
Home appliance housings (refrigerator and washing machine linings);
Precision metal parts (hydraulic components and instrument housings).
6.2 Powder Coating:
Suitable for applications requiring high coating thickness, protective properties, and texture diversity, such as:
Outdoor facilities (guardrails, streetlight poles, traffic signs);
Furniture (metal tables and chairs, filing cabinets);
Pipes, agricultural machinery, and fitness equipment (requiring thick coatings for wear resistance).
Summary:
Electrophoretic coating represents “fineness and high corrosion resistance” and is suitable for mass-produced metal parts requiring strict coating uniformity. Powder coating represents “thick coating, high protection, and environmental protection” and has a wider range of applications, particularly suitable for outdoor applications and those requiring strong wear resistance.
Specifically in the tool cabinet industry, powder coating is not universally used in China, but it is currently a widely used surface treatment process in the industry, as it strikes an optimal balance between corrosion protection, wear resistance, aesthetics, and cost. Powder coating is a dominant process, accounting for approximately 70%-80%. The solutions we provide to our customers utilize powder coating.
In addition to powder coating, other spraying processes, such as paint spraying, are also used in the tool cabinet industry. Some companies may choose other processes due to small production scales, outdated equipment, or to reduce costs or meet special appearance requirements. For example, some tool cabinets that require extremely high gloss may use a baking varnish process. These are not mainstream spraying processes. When making a selection, a comprehensive judgment must be made based on the workpiece material, performance requirements, production scale, and environmental protection requirements.
