1. The Past and Present of Appliance Coating

In the early days, the "outer garments" of everyday appliances like washing machines and refrigerators relied on spray painting—either "one coat, one bake" or "two coats, one bake." Epoxy or water-based paints were used as primers, and solvent-based acrylic or amino paints as topcoats. However, in the 1990s, environmental awareness grew, and people didn't want the volatile organic compounds in paints to "pollute the air." Solvent-free, high-utilization powder coatings became the new favorite.

After all, appliances are divided into "indoor" and "outdoor" models: refrigerators in the living room can use epoxy powder coatings, while air conditioner outdoor units on balconies require sun- and rain-resistant pure polyester powder coatings. Today, appliance coating not only requires careful management of materials, processes, and equipment, but also a focus on "environmental protection"—after all, no one wants appliance production to become "polluting manufacturing." "Safety, greenness, and automation" are the current mainstream.

2. The "Personalized Labels" and "Three Pillars" of Powder Coating for Home Appliances

The air conditioners, washing machines, and range hoods we use every day have quite a few "dressing requirements":

Aesthetics: Mostly placed in the home, their appearance needs to be pleasing to the eye;

Efficiency: As necessities, they need to be mass-produced on an assembly line;

Durability: Outdoor air conditioners and kitchen range hoods operate in harsh environments, so the coatings need to withstand the elements;

Cost-effectiveness: With such fierce market competition, coating costs must be kept low.

To meet these requirements, the "three pillars" of coating are crucial: materials, technology, and management. Choosing the wrong paint will render even the best process useless—for example, using a moisture-sensitive paint in humid southern weather will cause the coating to blister quickly; applying indoor paint outdoors will result in fading and peeling within days. Coating technology (such as equipment and environment) is key to "using paint well," while management ensures the process doesn't deviate and quality isn't compromised. These three aspects must work together. Whether it's the paint mixer, the process engineer, or the operator, everyone needs to understand each other's work. Otherwise, blindly working can easily lead to safety accidents or wasted materials.

3. Current Powder Coating for Home Appliances

3.1 The Intricacies of Substrate

The "skeleton" (substrate) of home appliances is mostly thin steel sheet:

For thicknesses within 1.5 mm, galvanized sheet is preferred (especially for the chassis and drip tray, hot-dip galvanized is best); in coastal areas or areas with high salt spray, hot-dip galvanized sheet with a thicker zinc layer, or alloy sheet with powder coating, should be used;

For thicknesses between 1.5 and 2.5 mm, galvanized sheet is also generally used. If unavailable, cold-rolled sheet must first undergo electrophoresis before powder coating, otherwise it is prone to rust.

3.2 Coating Process

The current mainstream process is "phosphorus-free degreasing + environmentally friendly conversion agent + electrostatic powder coating." Specific steps depend on the substrate:

Hot-dip galvanized sheet: On-line → 50℃ hot water wash for 1 minute → Two phosphorus-free degreasing cycles (50℃ spray for 2 minutes) → Two room temperature water washes → Environmentally friendly conversion agent treatment → Re-wash → Pure water wash → Drying → Cooling → Powder coating → Powder curing → Cooling inspection → Off-line;

Cold-rolled sheet: The initial steps are similar to hot-dip galvanized sheet, but with the addition of "cathode electrophoresis (soaking at around 30℃ for 2 minutes) → ultrapure water cleaning → electrophoretic drying," as cold-rolled sheet is more prone to rust and requires an additional "protective layer."

3.3 Upgrading Coating Equipment

Now, home appliance manufacturers are willing to invest in coating equipment—this is the "foundation for coating quality." From initial degreasing and cleaning equipment to electrophoresis and powder coating machines, and then to drying and curing equipment, a complete system can improve the appearance of home appliances, save materials and energy, and reduce pollution. Equipment acts like a "bridge," transforming paint into a usable coating, and it's also the "face" of the coating process.

3.4 How to control coating quality

To ensure problem-free appliance coatings, potential issues must be nipped in the bud during production: operators should inspect first, foremen should supervise, and quality inspectors should conduct specialized checks to ensure quality before the product leaves the factory. Coating quality mainly depends on "appearance" (looks, color difference, gloss) and "performance" (adhesion, hardness, thickness), which directly affect the appliance's lifespan and marketability.

4. The Future of Home Appliance Coating

With the national advocacy of "clean production," the home appliance industry is also pursuing "low-carbon emission reduction and green production." These technologies will be the "protagonists" of the future:

 Nanotechnology: More environmentally friendly protective films: Combining nano-ceramics and silane technology can solve the phosphorus pollution problem of traditional phosphating processes and form a composite film of 20 to 200 micrometers on the metal surface, making the coating stronger and more rust-resistant;

 Low-temperature curing + ultrafine powder: Economical and aesthetically pleasing: "Low-temperature curing" powder uses less energy, emits less waste gas, and increases production; "ultrafine powder" reduces powder particles from 30-50 micrometers to about 20 micrometers, allowing the coating to be as thin and smooth as paint, saving materials, reducing spraying costs, and resulting in a more delicate appearance;

 Robotic loading and unloading: Automation upgrade: Home appliance spraying is already automated, but loading and unloading haven't fully caught up—given the large differences in size and shape of home appliance parts. However, future robotics technology will solve this problem. Large-batch, flat parts can already be automatically loaded and unloaded; complex parts will also be possible in the future, leading to even higher efficiency.

5. Conclusion

From traditional spray painting to powder coating, the way home appliances are "dressed" has been constantly changing—meeting user demands for "good looks, durability, and affordability" while keeping up with the era's requirements for "green and low-carbon" products. Current coating processes are a collaborative effort involving substrates, processes, and equipment; in the future, technologies like nanotechnology, low-temperature curing, and robotics will drive towards a more environmentally friendly, efficient, and intelligent direction. Ultimately, upgrading home appliance coating is both a "must-do" for industry competition and a "bonus" for adding a touch of "greenness" to our lives.