This article systematically introduces the concept, types, characteristics, and functions of general-purpose industrial powder coatings, as well as key considerations for powder coating selection and solutions to common problems. It focuses particularly on the functions of general-purpose industrial powder coatings to help readers better understand what they are and their characteristics.
What Are General-Purpose Industrial Powder Coatings?
General-purpose industrial powder coatings serve industrial products that do not fall under architectural certification standards but have substantial requirements for outdoor durability or mechanical protection. They provide a "sufficient and economical" solution between basic indoor coatings and fully certified architectural coating systems.The value of general-purpose industrial powder coatings lies in meeting the minimum performance requirements of specific applications within cost constraints. Typical requirements include good adhesion and hardness, impact and scratch resistance, a certain level of outdoor weather resistance (without requiring a 25-year warranty), and the ability to provide edge and corner protection on complex-shaped workpieces.
Types of General-Purpose Industrial Powder Coatings
According to their resin chemical systems, general-purpose industrial powder coatings can be divided into the following types.1. Epoxy Systems
They offer excellent adhesion and corrosion resistance, as well as high hardness. However, their weather resistance is poor, and they are prone to chalking and yellowing outdoors.
They are suitable only for indoor applications or applications where corrosion protection is the priority, such as electrical components, automotive parts, and the inner walls of equipment enclosures.
They are also commonly used as powder primers. For example, zinc-rich epoxy primers provide outdoor workpieces with sacrificial anode protection.
Epoxy-Polyester Hybrid Systems
They combine the adhesion and corrosion resistance of epoxy with the decorative properties and overbake resistance of polyester. They offer good leveling, fewer pinholes and craters, and moderate costs.
They are also unsuitable for long-term outdoor exposure and are a major coating system for general indoor industrial products, such as warehouse storage racks, general metal products, and heavy electrical equipment housings.
2. Polyester Systems
These are an entry-level choice for outdoor weather resistance. According to the curing system, they can be further divided into the following types:
(1) TGIC-Cured Systems: They offer relatively balanced overall performance and are commonly used outdoor weather-resistant systems, but there are concerns regarding their biological toxicity.
(2) HAA-Cured Systems (TGIC-Free): They are environmentally friendly and comply with strict environmental regulations. However, they are more sensitive to film thickness, are prone to pinholes, and have slightly poorer yellowing resistance.
(3) Polyurethane (PU) Systems: They offer excellent weather resistance and solvent resistance and can be used for general outdoor applications, building materials, home appliances, and metal products.
3. Acrylic Systems
They offer excellent weather resistance, color retention, and stain resistance, along with outstanding coating appearance. They are suitable for industrial components with high decorative appearance requirements. Thermosetting acrylic powder coatings can be used as decorative topcoats.
Characteristics of General-Purpose Industrial Powder Coatings
The main characteristics of general-purpose industrial powder coatings are as follows.1. Adhesion and Hardness: Typical products emphasize excellent adhesion, hardness, and impact resistance, making them suitable for the physical protection requirements of industrial components during handling and assembly.
2. Weather Resistance: Mainly based on polyester systems, they can reliably withstand UV radiation, moisture, and mechanical stress. They are suitable for outdoor applications involving long-term exposure, such as construction machinery, garden furniture, and gardening tools, but are not specifically designed for architectural curtain wall certification.
3. Edge and Corner Coverage: The ability of powder coatings to form relatively thick films in a single application enables uniform edge and corner coverage on complex-shaped workpieces.
4. Diverse Surface Finishes: Available finishes include smooth high gloss (gloss 80–95+), semi-gloss (55–65), matte (15–25), as well as fine textures, coarse textures, and metallic effects.
5. Zero VOC: Powder coatings do not contain solvents, and no volatile organic compounds are released during the curing process.
Functions of General-Purpose Industrial Powder Coatings
The main functions of general-purpose industrial powder coatings are reflected in the following aspects.1. Physical Protection: Resisting Mechanical Damage
Industrial products are exposed to scratches, impacts, and abrasion during production, transportation, storage, and use.
General-purpose industrial powder coatings provide excellent adhesion, hardness, and impact resistance, effectively resisting scratches, knocks, and peeling while protecting the appearance and integrity of the substrate.
For supply chain components such as warehouse storage racks and shopping carts, the coating must also maintain its durability under intensive use conditions.
2. Corrosion Protection: Extending Workpiece Service Life
For steel components and equipment housings used outdoors or in humid environments, the coating provides a basic corrosion barrier.
Some products can meet the requirements of C5 corrosivity categories and protect metal substrates against corrosion through a single-coat system or a primer system.
For electrical equipment such as transformers and switchgear cabinets, the coating must also balance corrosion resistance and weather resistance to ensure the equipment operates reliably over an extended period.
3. Decorative Appearance: Providing Colors and Surface Finishes
General-purpose industrial powder coatings are available in various colors, gloss levels, and surface textures, including smooth, sand-textured, and hammer-tone finishes, to meet the appearance requirements of different industrial products.
Textured finishes can also conceal minor substrate defects, providing a practical benefit and reducing pretreatment requirements.
How to Select General-Purpose Industrial Powder Coatings
When selecting general-purpose industrial powder coatings, we may face difficulties in determining which products to choose. Based on our industry experience, we recommend focusing on the following factors when selecting general-purpose industrial powder coatings.1. Determine the Resin Chemistry According to Indoor or Outdoor Applications
This is the first major distinction in product selection and directly determines whether the coating can meet the requirements of the operating environment.
(1) Indoor Applications or Applications Prioritizing Corrosion Protection
Epoxy systems or epoxy-polyester hybrid systems are the preferred choices.
Epoxy provides excellent adhesion, hardness, and chemical resistance at an economical cost, making it suitable for indoor workpieces such as equipment enclosures, electrical cabinets, warehouse storage racks, and general metal products.
Hybrid systems balance corrosion protection and decorative performance, offering good leveling and fewer pinholes and craters.
Neither system is suitable for long-term outdoor exposure, as epoxy coatings chalk under UV radiation.
(2) Outdoor or Semi-Exposed Environments
Polyester systems must be selected.
Polyester powder coatings can reliably withstand UV radiation, moisture, and mechanical stress, making them suitable for applications such as construction machinery, garden furniture, gardening tools, and steel components.
General-purpose industrial applications typically do not require architectural curtain wall-level certification. Their positioning is "non-architectural outdoor polyester," filling the gap between indoor coatings and certified architectural coating systems.
Curing Agent Selection Within Polyester Systems: TGIC vs. TGIC-Free (HAA)
The core performance of TGIC and TGIC-Free (HAA) systems is comparable. The choice depends on regulatory requirements and production line conditions.
TGIC offers better overbake resistance, while HAA complies with environmental regulations but is more sensitive to film thickness. Excessive film thickness can easily cause pinholes.
2. Match Performance to Workpiece Characteristics
(1) Mechanical Performance Requirements
General industrial components are often exposed to collisions during handling and impacts during assembly.
When selecting coatings, pay attention to adhesion, hardness, and impact resistance data.
If the workpiece requires bending or stamping after coating, confirm its post-forming performance in advance. Most thermosetting powder coatings are not recommended for severe post-coating processing.
(2) Corrosion Protection Requirements
A single-coat system is sufficient for ordinary outdoor environments.
If the workpiece is exposed to deicing salts, fertilizers, or high-humidity environments, such as agricultural machinery and construction equipment, a primer-plus-topcoat system should be considered to improve salt spray protection.
3. Ensure Film Thickness and Curing Conditions Match the Production Line
(1) Classify Film Thickness According to Surface Finish
For smooth finishes, the typical film thickness is 60–80 μm; fine-textured matte finishes require 70–90 μm; and coarse-textured high-gloss finishes require 90–120 μm.
When selecting products, confirm that the coating line can consistently maintain the required range. Insufficient film thickness affects protection, while excessive thickness may affect mechanical properties or cause pinholes, particularly in HAA systems.
(2) Does the Curing Window Match the Production Line?
General-purpose industrial polyester coatings typically have a relatively wide curing window and can be cured using different combinations of temperature and time.
If the workpiece contains heat-sensitive components or energy savings are desired, low-temperature-curing products can be considered.
Be sure to measure the actual workpiece metal temperature rather than relying on the oven temperature, and strictly follow the minimum and maximum curing times. Otherwise, mechanical properties and warranty conditions may be affected.
Common Problems with General-Purpose Powder Coatings and Solutions
The most common problems encountered when using general-purpose industrial powder coatings are mainly reflected in the following aspects. Based on our industry experience, we propose corresponding solutions to help effectively address the powder coating problems you may encounter.1. Orange Peel (Uneven Surface)
Problem Description: The coating surface develops an uneven texture resembling orange peel, affecting surface smoothness. This is particularly noticeable on smooth, high-gloss topcoats.
Possible Causes: Excessive film thickness is the most common cause. When too much powder is applied, the coating begins to gel before it has sufficient time to level, locking the texture into the surface.
Excessively high electrostatic voltage can result in uneven powder distribution, creating localized thickness peaks and valleys. These irregularities may remain visible even after leveling.
Rapid heating during curing or an actual workpiece metal temperature that fails to reach the required leveling window can also cause orange peel because the coating enters the crosslinking stage before sufficient leveling has occurred.
Solutions: Reduce the total film thickness, control the spray gun voltage, and ensure that the workpiece metal temperature, rather than just the oven temperature, remains within the specified range for sufficient leveling time.
Use an oven temperature profiler to measure the actual heating curve of the workpiece and avoid relying solely on the oven temperature display when adjusting the process.
2. Pinholes
Problem Description: Small holes appear on the coating surface. In severe cases, they extend down to the substrate and affect protective performance.
Possible Causes: The substrate releases gas at high curing temperatures (outgassing), which breaks through the uncured coating.
Castings, galvanized steel, weld seams, laser-cut edges, and porous substrates are particularly susceptible.
Residual pretreatment chemicals, such as phosphating solutions that have not been thoroughly rinsed off, may also decompose and release gas at high temperatures, causing pinholes.
Attempting to cover the problem with a thicker coating may instead seal the gas escape channels and aggravate the defect.
Solutions: Preheating the workpiece is the most effective method. Before spraying, heat the workpiece to a temperature slightly above the curing temperature and hold it there to allow gases to escape in advance. Then cool it before applying the powder coating.
At the same time, improve pretreatment rinsing and appropriately reduce film thickness to leave sufficient channels for gas to escape.
3. Cratering
Problem Description: Circular depressions appear on the coating surface, sometimes exposing the substrate at the center with raised edges. This is one of the most typical defects indicating contamination in powder coating applications.
Possible Causes: Almost all cases are caused by surface contamination. Oil and water in compressed air, residual grease on the substrate (particularly tapping oil that has thickened after prolonged storage), silicone-based release agents or cleaning agents, and even fumes from nearby welding operations can cause localized surface tension imbalances, resulting in coating retraction.
Solutions: Inspect the oil and water removal systems for compressed air. Strengthen degreasing according to the actual type of contamination on the workpiece. For workpieces that have been stored for an extended period, preliminary baking or thermal treatment may be considered.
Isolate contamination sources around the spray booth, paying particular attention to silicone-based substances, which are highly detrimental to coating operations.
4. Cracking During Post-Coating Processing
Problem Description: The coating cracks along the processing lines when the coated workpiece undergoes bending, punching, or forming.
Possible Causes: Thermosetting powder coatings form highly crosslinked networks after curing, and their flexibility is inherently limited.
Excessive film thickness or overcuring can significantly increase brittleness, making it difficult for the coating to withstand deformation.
Solutions: Whenever possible, complete forming before coating.
If post-coating processing is unavoidable, strictly control the film thickness at the lower end of the recommended range and accurately verify the curing profile to avoid overbaking.
5. Poor Adhesion and Peeling
Problem Description: The coating peels off in large areas or fails the cross-cut adhesion test.
Possible Causes: Inadequate pretreatment is the primary cause.
Excessive sandblasting may cause surface flaking or embed contaminants, reducing the effective contact area instead of improving adhesion.
Inconsistent manual cleaning may leave residual grease or oxide scale, compromising adhesion.
Excessive film thickness can also increase internal stress, making the coating more prone to peeling when subjected to impact.
Solutions: Standardize the pretreatment process by controlling sandblasting intensity and ensuring uniform and thorough degreasing.
Maintain film thickness within the recommended range. Before production, use actual workpieces to perform cross-cut adhesion tests for verification.
Choose High-Quality General-Purpose Powder Coatings to Meet the Coating Needs of Metal Products Across Multiple Industries
Whether for metal products, industrial equipment, furniture, electrical cabinets, or hardware accessories, powder coatings with both protective properties and decorative performance are required.
We have more than 20 years of experience in powder coating research, development, and production. We can provide a diverse range of products and customized solutions according to different substrates, application environments, colors, gloss levels, and surface texture requirements.
Our products offer good adhesion, corrosion resistance, and decorative surface performance to meet the coating requirements of different industrial sectors.
Contact us to obtain professional product selection advice and customized powder coating solutions.
