GB/T 23612-2017Technical specification for process of anodizing and electrodeposition painting on aluminium alloy extruded profiles for architecture (English PDF)

5.1 Manufacturing Equipment

5.1.1 Processing tank

5.1.1.1 Type of processing tank

Processing tank includes pretreatment tank (including degreasing tank, alkali rinsing tank and dust-removal tank), anodizing tank, electrolytic coloring tank, neutralization tank, dyeing tank, hole-sealing tank, post-cold-hole-sealing processing tank, electrophoretic painting tank and water rinsing tank, etc.

5.1.1.2 Materials and layout of processing tank

The lining material that the processing tank adopts shall not be corroded or contaminated by tank solution. The layout of the processing tank shall be reasonable. It shall prevent tank solution from being contaminated.

5.1.1.3 Capacity of processing tank

The capacity of the processing tank shall satisfy the requirements of manufacturing. In addition, it shall guarantee that the requirements of process parameters (such as electric current density and temperature) are satisfied.

5.1.2 Cooling equipment of anodizing electrolyte

Cooling equipment shall be able to absorb the heat generated during the electrolytic process and guarantee that the requirements of process temperature are satisfied.

Under the circumstance of normal manufacturing, the equipment's cooling capacity should reach the requirement in Formula (1): Where, K---cooling capacity, expressed in (J/h); I---maximum current, expressed in (A); V---maximum voltage, expressed in (V).

5.1.3 Agitation equipment of anodizing electrolyte

Anodizing electrolyte shall be properly agitated, so as to reach the effect of heat dissipation, and guarantee that the temperature of the electrolyte maintains uniformly stable. Generally speaking, the mode of agitation shall adopt Roots blower air agitation, circulating pump agitation, or a combination of Roots blower air agitation and circulating pump agitation. When air agitation is adopted, the air for agitation shall contain no grease; the amount of air agitation for each square meter of electrolyte surface area shall be not less than 5 m³/h, and preferably 12 m³/h. When circulating pump agitation is adopted, the circulating capability of the circulatory system shall be 2.5 ~ 4.0 times of the volume of the electrolyte per hour.

5.1.4 Heating equipment

In order to guarantee that the tank solution's manufacturing temperature reaches the process requirements, heating equipment shall be installed on processing tank which needs to be heated. In addition, the heating capability of the heating equipment is requested to guarantee that the tank solution's temperature is controlled within the range of the process requirements.

5.1.5 Power supply equipment

5.1.5.1 Power supply equipment shall satisfy the manufacturing requirements. Power supply equipment shall install corresponding voltmeter and ampere meter. The minimum scale of the voltmeter shall be not more than 2% of the nominal value; the minimum scale of the ampere meter shall be not more than 5% of the nominal value.

Furthermore, the voltmeter and ampere meter need to be validated and calibrated in accordance with the stipulated cycle of validation and calibration; the level of accuracy shall reach Level-1.5.

5.1.5.2 Generally speaking, anodizing power supply shall adopt direct current (DC) oxidizing power supply. Under general circumstances, silicon-controlled rectifier (SCR) or rectifier controlled by sliding brush automatic transformer is adopted to provide direct current in industry. The voltage drop from the anodizing power supply to tank-side busbar shall be not more than 0.3 V. The temperature rise at the conductive contact between the anode beam and the conductive seat shall be not more than 30 °C.

5.1.5.3 Anodizing power supply unit shall be equipped with an automatic fault diagnosis and protection system against overcurrent, default phase, output short circuit and equipment overtemperature, so as to guarantee equipment's safe operation.

5.1.5.4 Electrophoretic painting's DC power supply unit shall be equipped with an automatic fault diagnosis and protection system against overcurrent, default phase, output short circuit and equipment overtemperature, so as to guarantee equipment's safe operation. The ripple coefficient shall be less than 5%.

5.1.6 Recovery unit and waste-water treatment unit

5.1.6.1 Electrophoretic painting process and mono-nickel salt coloring process shall install recovery unit.

5.1.6.2 Processes that implement recycling, such as anodizing pretreatment process and anodizing process, should install recovery unit (such as sulfuric acid recovery unit, alkali recovery unit and secondary water utilization unit, etc.).

5.1.6.3 When waste-water is handled by manufacturers, anodizing profile manufacturers shall be equipped with corresponding waste-water treatment equipment (treatment devices like acid-base neutralization, flocculation, sedimentation and filter pressing). Anodizing electrophoretic painting profile manufacturers shall also be equipped with COD treatment unit (for example, elimination of COD through ozone or biological algae).

5.1.7 Hanger

5.1.7.1 Hanger shall have favorable electrical conductivity, so as to guarantee the satisfying and uniform conduction of working current to each aluminum alloy profile for architecture.

5.1.7.2 The cross-sectional area of aluminum hanger, which is soaked into the anodizing tank solution, shall be sufficiently large, so as to guarantee that in normal operation, the aluminum hanger's electric current density shall be not more than 5 A/mm2.

5.1.7.3 In the design of hanger, cross contamination among tank solutions shall be prevented.

5.1.8 Curing oven

5.1.8.1 Curing oven shall install temperature controller. The temperature controller shall be able to directly display temperature data inside the oven. The heating zone of the curing oven shall install an overtemperature alarming system.

5.1.8.2 Under normal operation, the temperature difference of the curing oven should not be higher than 20 °C.

5.1.8.3 Curing oven's operating temperature range shall satisfy the requirement of painting curing temperature.

5.1.9 Conductive cathode plate

5.1.9.1 Conductive cathode plate shall select suitable materials. For instance, anodizing cathode plate may select pure aluminum plate; electrolytic coloring cathode plate may select pure nickel plate or stainless-steel plate; electrophoretic cathode plate may select stainless-steel plate.

5.1.9.2 The surface area of the conductive cathode plate shall match with the designed and processed profile area, and the rated processing capacity of the rectifier.

5.1.9.3 The conductive cathode plate shall be reasonably arranged, so as to guarantee that electric current is uniformly distributed.

5.1.9.4 Anodizing and electrophoretic cathode plate shall be equipped with an electrode cover.

5.1.10 Workshop air cleaning unit

In zones of pretreatment process, anodizing treatment process, electrophoretic painting process and curing process, air ventilation and purification facilities shall be installed, so as to guarantee the internal environment in the workshop and avoid contamination of air.

5.2 Inspection Equipment

In accordance with different inspection items, inspection equipment shall be divided into instruments and equipment for daily inspection, and instruments and equipment for periodical inspection. Please refer to Table 1 for details.

7.1 General Requirements

7.1.1 When loading mill finish profiles, there shall be an appropriate spacing among the mill finish profiles, so as to guarantee that the anodizing oxide film is homogeneous.

7.1.2 When loading mill finish profiles in horizontal production lines, there shall be a certain inclination, which should be controlled at around 5°.

7.1.3 After each processing (pretreatment, anodizing treatment, coloring processing, hole-sealing processing and electrophoretic painting processing), water rinsing shall be conducted at least once. Some processing steps shall receive several times of water rinsing, for example, after alkali rinsing, anodizing treatment and electrolytic coloring treatment, water rinsing shall be conducted at least twice. Some water rinsing processes shall adopt deionized water. For example, before electrophoretic painting, deionized water, whose conductivity measured at 20 °C is less than, or equals to 30 µs/cm, should be adopted for rinsing. When condition allows, water in the water rinsing tank shall be filtered.

7.1.4 Cyclic utilization of water in the water rinsing tank should be taken into consideration.

7.1.5 Before anodizing treatment, the retention time of profiles, which have finished pretreatment, in the water rinsing tank should not be more than 30 min.

7.1.6 After anodizing treatment is finished, the profiles shall be placed into the water rinsing tank for water rinsing in time. After water rinsing is finished, the profiles shall be placed into the coloring tank for coloring treatment, so as to guarantee the uniformity of the applied colors.

7.1.7 When profiles in the horizontal production line are hanged into and hanged out of the tank solution, they shall be in a certain inclination. The degree of inclination should be controlled at around 30°.

7.1.8 In terms of water rinsing tank after nickel salt-containing coloring treatment and nickel-containing hole-sealing treatment, an exclusive drainage pipe shall be set up. After collection, Ni2+ in the waste-water shall be separately handled.

7.1.9 Please refer to Table 2 for the typical process of anodizing and anodizing electrophoretic painting.

7.2 Anodizing Pretreatment

7.2.1 Degreasing

7.2.1.1 Before anodizing treatment, degreasing treatment shall be conducted. The objective of degreasing is to eliminate grease on the surface of aluminum, so as to guarantee uniform effect on the surface of the profiles after alkali rinsing; […]