Powder coating storage, application environment, gloss loss and treatment

For powder coating manufacturers, producing high-quality powder coatings relies not only on superior raw materials and advanced production processes, but also on crucial aspects such as powder storage, application environment management, and handling of gloss loss issues. Neglecting any of these aspects can lead to a decline in powder coating performance and substandard film quality, ultimately impacting the company's reputation and market competitiveness. Therefore, strict standards and procedures must be established for powder coating storage, application environment control, and handling of gloss loss to ensure that every step meets quality requirements.

1. Powder Coating Storage Management

The storage conditions of powder coatings directly affect their physicochemical properties. Improper storage can easily lead to moisture absorption, clumping, and performance degradation, resulting in defects such as poor leveling, insufficient adhesion, and gloss loss after spraying. Therefore, powder coating manufacturers need to strictly regulate storage procedures, focusing on the following aspects:

1.1 The storage environment must meet the core requirements of "ventilation, dryness, and temperature control."

Powder coatings have a certain degree of hygroscopicity. If the storage space is humid, the powder easily absorbs moisture from the air, leading to particle adhesion, reduced fluidity, and problems such as spray gun clogging and low powder application rate during spraying. At the same time, high-temperature environments will accelerate the aging of components such as resin and curing agent in the powder, affecting the curing performance and coating effect. Therefore, the warehouse for storing powder should have good ventilation conditions. Air circulation can be maintained by installing exhaust fans, ventilation windows, and other equipment to reduce indoor humidity (ideally, the relative humidity should be controlled between 40% and 60%). At the same time, the warehouse temperature must be strictly controlled below 30℃, avoiding direct sunlight or proximity to heat sources (such as heating systems, boilers, etc.). This can be achieved by installing air conditioners and thermometers to monitor and adjust the temperature in real time, ensuring that the powder is stored in a suitable temperature and humidity environment.

1.2 Powders of different types and manufacturers should be stored separately to avoid cross-contamination and mixing.

Different types of powders (such as epoxy powder, polyester powder, and polyurethane powder) differ in composition and formulation. Mixing them may alter powder properties due to physical adsorption or slight chemical reactions between particles. For example, mixing epoxy powder and polyester powder may result in abnormal curing speed and decreased coating adhesion. Even powders from different manufacturers of the same type may differ in resin grade, additive type, and pigment ratio. Mixing them can affect powder consistency, leading to uneven color and gloss in the sprayed coating. Therefore, the warehouse needs clearly defined storage areas, and powders of different types and manufacturers should be categorized and labeled (powder name, manufacturer, production date, and shelf life), ensuring batch separation. During application, powder should be used only after each batch is finished, avoiding mixing different batches. Unused powder should be sealed in packaging (e.g., using sealed bags or covered containers) to prevent moisture absorption or contamination. The remaining quantity and usage should be clearly labeled for subsequent use.

2. Construction Environment

Control for Powder Coatings The construction environment is a key factor affecting the spraying effect and production safety of powder coatings. Environmental conditions vary significantly among different powder coating contractors. Some contractors use open-air construction or open environments connected to production workshops, which are easily affected by external dust, humidity, temperature, and other factors, leading to unstable coating quality. A standardized construction environment should be independent, sealed, and safe. Specific requirements are as follows:

2.1 The construction environment must be independently set up and equipped with professional powder recovery equipment.

An independent construction environment (such as a sealed spray booth) can effectively isolate external dust and debris, preventing them from mixing into the powder or adhering to the workpiece surface, causing defects such as particles and impurities in the coating. Simultaneously, equipping the workpiece with powder recovery equipment (such as a cyclone separator or filter cartridge recovery machine) can recover and reuse overspray powder that did not adhere to the workpiece during the spraying process. This not only reduces raw material waste but also reduces dust concentration in the spray booth, improving the construction environment. The recovery equipment needs regular cleaning and maintenance (such as replacing filter cartridges and cleaning pipelines) to ensure recovery efficiency and powder purity, avoiding excessive impurities in the recovered powder that could affect its reuse.

2.2 The spray booth must be kept clean, and unrelated items are strictly prohibited.

The spray booth is the core area of ​​powder coating. Placing unused powder, tools, packaging materials, etc., inside can easily lead to powder contamination (such as debris mixing into the powder) or affect air circulation. Simultaneously, the spray booth floor and walls must be cleaned regularly. Before and after each shift, the floor should be mopped or dust removed with a vacuum cleaner to prevent dust accumulation. Long-term dust accumulation in the spray booth not only increases cleaning difficulty but may also cause dust to be stirred up by personnel movement and equipment operation, affecting coating quality.

2.3 Strictly control the dust concentration in the spray booth, eliminate open flames, and ensure production safety.

The main components of powder coatings (such as resins and pigments) are mostly flammable substances. When the dust concentration in the spray booth reaches a certain range (explosion limit), it can explode upon contact with open flames, static sparks, or high temperatures, posing a serious safety hazard. Furthermore, high concentrations of dust can harm the respiratory system of operators, and long-term inhalation may lead to occupational health problems such as pneumoconiosis. Therefore, a dust concentration monitor must be installed in the spray booth to monitor the dust concentration in real time (ideally controlled below 10g/m³), and the dust concentration should be reduced by strengthening ventilation and optimizing recovery equipment. In addition, open flames (such as lighters and cigarettes) are strictly prohibited in the spray booth, and equipment must be properly protected against static electricity (e.g., grounding, using anti-static hoses). Operators must wear anti-static clothing and shoes to avoid static electricity accumulation that could lead to safety accidents.

3. Gloss Loss Phenomenon and Treatment

Methods for Powder Coatings Gloss loss is one of the common appearance defects after powder coating spraying, manifested as a coating surface gloss lower than the standard requirements, seriously affecting the product's visual effect and market competitiveness. There are various reasons for powder gloss loss, and corresponding treatment measures must be taken for different causes, as follows: 3.1 Powder may lose its surface gloss if it is kept in the oven for more than the specified time and temperature.

Epoxy polyester (indoor) powder is generally kept at a constant temperature not exceeding 190 degrees Celsius. Pure polyester powder is generally kept at a constant temperature not exceeding 220 degrees Celsius.

Due to the different heat energy required by different materials, the time spent in the oven varies. For example, aluminum molds and thin iron plates should generally be placed in the furnace for no more than 15-20 minutes. Large metal parts generally only need to be placed in the furnace for 30-60 minutes.

3.2 During construction, to reduce waste, recycled powder is sometimes mixed with new powder.

This often causes the workpiece surface to lose its gloss. The correct method is to add about 3 kg of powder (normally), generally not exceeding 5 kg, otherwise the gloss will be lost.

3.3 Powder may clump due to high temperature or excessive compression. This often causes the powder to lose its gloss. This is usually solved by sieving the clumped powder and then combining it with unclumped powder.

3.4 Mixing powders from different manufacturers can also cause the powder to lose its gloss due to interference. If powders from different manufacturers are needed, the powder supply tank, spray gun, powder pipe, and surrounding environment of the electrostatic generator must be thoroughly cleaned before using powder from the other manufacturer.

3.5 Powder should generally not be stored for too long. Prolonged storage can cause changes in gloss. Generally, powders with high gloss will lose their gloss after prolonged storage. Powders with low gloss, such as matte black or matte gray, are likely to develop a wavy or sandy texture after prolonged storage.

3.6 Transparent powder can interfere with other powders. If you have used transparent powder and want to switch to another powder, you must thoroughly clean the spray gun, powder supply container, and spray booth.

4. Summary

To produce superior quality products, powder coating manufacturers need to comprehensively control multiple aspects, including powder storage, application environment, and gloss loss treatment. For powder storage, temperature and humidity must be strictly controlled, and powders from different types and manufacturers should be stored separately to avoid contamination and aging. Regarding the application environment, independent, clean, and safe spray booths should be established, equipped with recycling equipment, and dust concentration should be controlled to eliminate safety hazards. For gloss loss treatment, the causes of gloss loss must be accurately identified (such as improper baking parameters, powder mixing, or expired storage), and targeted measures (such as adjusting the baking process, cleaning equipment, and screening powders) should be taken to ensure the quality of the coating appearance. For a long time, some people have held the misconception that powder coating manufacturers' production environments are "dirty, messy, and unsanitary." This is related to the lack of standardized production standards and inadequate environmental control in the early days of the industry. Today, with technological upgrades and stricter environmental requirements, powder coating manufacturers need to proactively improve their production environments, establish standardized storage and application processes, strengthen employee training (such as operational procedures and safety awareness), and improve product quality and production safety through refined management. Only in this way can they break down traditional misconceptions, establish a positive corporate image, gain an advantage in fierce market competition, and drive the powder coating industry towards high-quality and green development.