YS/T 714-2020Technical Specification for Process of Organic Polymer Spraying on Aluminium Alloy Extruded Profiles for Architecture (English PDF)

3.1 Etching Degree

Mass loss per unit area of the sample before and after the etching process.

5.1 Production Facilities

5.1.1 General requirements

5.1.1.1 Powder coating production lines should be equipped with volatile organic compound (VOC) treatment devices; paint coating production lines shall be equipped with volatile organic compound (VOC) treatment devices.

5.1.1.2 Pretreatment production lines utilizing an alkaline degreasing process shall be equipped with ventilation devices.

5.1.1.3 When wastewater is treated at the manufacturing facility, the facility shall be equipped with appropriate wastewater treatment equipment (such as units for acid-base neutralization, flocculation, sedimentation, and pressure filtration).

5.1.2 Pretreatment equipment

5.1.2.1 The production line shall be equipped with the production equipment for spray or immersion pretreatment, as well as necessary pretreatment tanks (such as degreasing, water rinse, and chemical pretreatment tanks) and drying ovens.

5.1.2.2 The lining material of chemical pretreatment tanks shall be resistant to corrosion by the tank solution and shall not contaminate the tank solution. The layout of chemical pretreatment tanks shall be designed to prevent contamination of the tank solution.

5.1.2.3 Chemical pretreatment tanks shall ensure tank solution uniformity; horizontal production lines should be equipped with agitation devices, and vertical production lines should be equipped with malfunction alarm devices.

5.1.2.4 The dimensions of the pretreatment production equipment shall meet the requirements regarding the cross-sectional dimensions and lengths of the profiles.

5.1.2.5 The temperature difference between the top and bottom of the drying oven should be less than 10°C, and an over-temperature alarm system shall be installed.

5.1.3 Electrostatic powder coating equipment

5.1.3.1 Powder coating booth

5.1.3.1.1 The interior wall surfaces of the powder coating booth shall be flat, smooth, and free of dead zones; corners and edges should be designed with rounded contours to facilitate cleaning and color changes.

5.1.3.1.2 Conductive facilities within the powder coating booth and a 5-meter radius around it shall be grounded to prevent the accumulation of electrostatic charges.

5.1.3.1.3 The powder coating booth shall comply with the environmental requirements specified by the powder coating supplier.

5.1.3.1.4 The opening dimensions of the powder coating booth shall match the airflow rate of the recovery system to prevent powder leakage.

5.1.3.1.5 The powder coating booth shall be equipped with properly designed exhaust equipment.

5.1.3.1.6 Compressed air entering the powder coating booth shall be treated using a refrigerated dryer and an oil-water separator to prevent adverse effects on coating quality.

5.1.3.1.7 Materials used to construct the powder coating booth typically include metal sheets, plastic sheets, plastic films, or PE curtains; silicate-based materials shall not be used.

5.1.3.2 Electrostatic spray gun

5.1.3.2.1 The electrostatic spray gun is the core component of powder coating equipment; its selection shall take into account factors such as stability, powder transfer efficiency, safety, and charging characteristics.

5.1.3.2.2 Electrostatic spray guns may include high-voltage electrostatic spray guns or triboelectric spray guns. When a high-voltage electrostatic spray gun is selected, its high- voltage electrostatic generator must be safe, stable, reliable, and durable, and must be equipped with protection devices against electric leakage and short circuits.

5.1.3.3 Powder supply unit

5.1.3.3.1 The powder supply unit shall be capable of delivering powder coating to the spray gun continuously, uniformly, and at a controlled rate.

5.1.3.3.2 Powder supply units are classified into pressure-fed, mechanical, and fluidized- suction types. Currently, the fluidized-suction type is the most widely used; the fluidized- suction type powder supply unit consists of a powder hopper, a fluidizing plate, and a Venturi powder pump.

5.1.3.4 Powder recovery unit

5.1.3.4.1 Powder recovery units directly impact powder coating utilization rates and environmental protection; therefore, high-efficiency powder recovery units shall be designed, typically employing two-stage, three-stage, or multi-stage recovery units. Powder recovery units shall meet the following requirements.

a) High recovery efficiency;

b) The equipment is easy to clean;

c) Small footprint;

d) Low noise level;

e) Safe and reliable, equipped with explosion-proof facilities.

5.1.3.4.2 Recovery units shall be grounded for protection.

5.1.4 Electrostatic paint coating equipment

5.1.4.1 Paint coating booth

5.1.4.1.1 The air supply and exhaust systems shall be properly matched to maintain a slight negative pressure within the paint coating booth.

5.1.4.1.2 Paint coating booths are classified into dry-type and wet-type based on the method of paint mist treatment.

5.1.4.1.3 Dry-type paint coating booths filter paint mist particles using methods such as baffle plates or filter paper.

5.1.4.1.4 Wet-type paint coating booths separate paint mist particles from the air through the interaction of air and water. The thickness of the water curtain must be uniform; the structural design of the upper water trough, the water supply piping distribution, and the distance from the bottom of the water curtain panel to the liquid level in the water trough must ensure proper water circulation within the paint coating booth.

5.1.4.1.5 Compressed air entering the paint coating booth shall be treated using a refrigerated dryer and an oil-water separator to prevent adverse effects on coating quality.

5.1.4.1.6 Safety devices shall be installed in the paint coating booth to prevent fires caused by spark discharges; electrical components within the booth shall be of the explosion-proof type.

5.1.4.1.7 The paint coating booth shall be equipped with lightning protection and explosion- proof devices for static electricity and sparks (such as explosion-proof lights and switches) and provided with fire-fighting facilities.

5.1.4.2 Electrostatic spray gun

5.1.4.2.1 The selection of electrostatic spray guns shall take into account factors such as the structural characteristics of the product’s mill finish profiles, coating material and quality requirements, equipment stability, and transfer efficiency.

5.1.4.2.2 Electrostatic spray guns may include high-voltage electrostatic spray guns and rotary- bell electrostatic spray guns.

5.1.4.3 Paint supply unit

5.1.4.3.1 The paint supply unit shall be capable of delivering paint to the electrostatic spray gun accurately, continuously, and uniformly.

5.1.4.3.2 Paint supply units are classified based on their delivery principles into gravity-fed, pressure-fed, and metering paint supply units, as well as centralized pressure-fed paint supply stations. The gravity-fed paint supply unit is suitable for the electrostatic paint coating of small- cross-section profiles in small batches.

5.1.4.3.3 The paint supply unit shall utilize air agitation.

5.1.4.4 Paint mixing booth

The paint mixing booth shall maintain constant temperature and humidity, and be equipped with ventilation, explosion-proof, lightning protection, and fire prevention devices.

5.1.5 Air compressor

5.1.5.1 The air compressor shall be equipped with an oil-water separator and a refrigerated dryer

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