Powder Spray Profile Inspection and Technical Standards
ã€China Aluminum Industry Network】 Check items and sampling rules for powder-sprayed aluminum alloy profiles are shown in Table 6-3-23, in which the chemical composition, room temperature mechanical function, dimensional errors, appearance quality, and coating thickness, gloss, color and color difference, pressure Trace hardness, adhesion, impact resistance, and cupping test are mandatory items for each batch, resistance to tortuosity, hydrochloric acid resistance, solvent resistance, mortar resistance, salt spray corrosion resistance, moist heat resistance, artificial accelerated weather resistance The boiling water resistance, and the thickness of the chemical conversion coating of the pre-treatment are regular inspection items. The thickness of pre-treatment chemical conversion film is usually checked once a week. Resistance to tortuosity, hydrochloric acid resistance, solvent resistance, mortar resistance, salt spray corrosion resistance, heat and humidity resistance, artificial weather resistance, and boiling water resistance Checked once every quarter.
All coating function tests should be conducted after the coating is cured and placed for 24 h.
Table 6—3-23 Inspection items and sampling rules for powder-sprayed aluminum alloy profiles
Items
Checking nature
Sampling rules
chemical composition
Factory inspection
No less than 1 per melting or batch (per 1,000kg of merchandise)
Room temperature mechanical function
Factory inspection
2 batches (furnace), 1 each
Scale error
Factory inspection
L% per batch, not less than 10
Appearance Quality
Factory inspection
View by root
Coating color and color difference
Factory inspection
View by root
Coating thickness
Factory inspection
Sample according to Table 6-3-3
Coating gloss
Factory inspection
2 profiles per batch
Take one sample from each
Coating adhesion
Factory inspection
Coating indentation hardness
Factory inspection
Coating impact resistance
Factory inspection
Coating Cupping Experiment
Factory inspection
Coating resistance to bending
Regular inspection
Coating resistance to hydrochloric acid
Regular inspection
Coating solvent resistance
Regular inspection
Coating mortar resistance
Regular inspection
Coating salt spray resistance
Regular inspection
Coating moisture resistance
Regular inspection
Artificial coating accelerates weatherability
Regular inspection
Resistance to boiling water
Regular inspection
Chemical conversion film thickness
Regular inspection
Take 2 150 mm×75 mm test plates per batch
First, chemical composition, room temperature mechanical function and scale error checking
The chemical composition, room temperature mechanical function and standard error checking method of powder sprayed profiles can be found in Chapters 1 and 2 of Chapter 6 of this book. Check the following questions when checking:
1 Check the chemical composition, room temperature mechanical function and scale error test sample should first remove the outer coating before inspection.
2 When measuring the cross-section dimension of the powder sprayed profile, the method of subtracting the thickness of the coating layer from the measured value may be used, and the measurement method may be selected after the powdered profile is removed from the coating.
Second, the substrate pre-treatment inspection
In order to improve the adhesion of the aluminum alloy profile substrate and coating, it is necessary to use a multi-stage cleaning and pre-treatment system to remove the organic and inorganic dirt and accumulated oxides of the metal surface, and apply a layer before the substrate is sprayed. The chemical conversion film is so that the organic coating can be firmly attached. When chromate treatment is used, the thickness of the chromic conversion coating should be controlled within the range of 200 mg/m2 to 1300 mg/m2, and should not show the appearance of chromed powder.
The quality of the pre-treatment of the substrate can directly affect the relevant function of the coating. Therefore, it is very important for the routine and fast pre-treatment check. The inspection of the substrate pretreatment is usually divided into inspection of the deoiling effect and inspection of the appearance and thickness of the chemical conversion film. Inspection of the degreasing effect can be performed by visual inspection. Check whether the surface of the aluminum substrate is stained or not, and whether the water film is connected in succession or not. The surface of the aluminum substrate that has been deoiled prior to its disposal should be free from stains, and the water film should not be hung. Inspection of the chemical conversion film can be found in GB/T9792 "Measurement of weight of film on unit area of ​​chemical conversion film on metal materials" for inspection. Chrome or phosphorus chrome film should not be used for powder.
Because of the importance of substrate pretreatment quality for coating function, there are clear rules for the quality of substrate pretreatment in the leading foreign countries. For example, BS 6496 in the United Kingdom, AAMA 2604 in the United States, and QUALICOAT in Europe all regulate the substrate pretreatment. The quality of the chemical conversion film and cleaning needs, the specific rules are shown in Table 6-3-24. Because of the pollution to the environment caused by the treatment of chromium or phosphorus chromium, all countries in the world are dedicated to the study of a chromium-free chemical conversion film that can replace the chromated or phosphorus-chromium film. The chromium-free disposal will be the future for the pre-treatment of the powdered profile material. Skills development direction. Because of environmental reasons, the European Union and the United States have gradually applied rules concerning the environmental protection of aluminum products, such as the European Union's WEEE Directive and the ROHS Directive, which restricts the production and application of chromium-containing conversion coating aluminum profiles to certain extent.
Table 6—3-24 Quality Requirements for Pretreatment of Aluminum Substrates for Powder Coating Profiles at Home and Abroad
Specification variety
Pre-treatment cleaning needs
Chemical conversion film
disposal method
Chemical conversion film quality
/mg·m-2
Pre-treatment time
/h
GB5237.4—2004
There is no specific pre-treatment cleaning requirement, only the regular substrate before spraying
Appearance should be pre-treated
Chrome treatment
200 to 1300
Meet the needs of chemical suppliers
AAMA2604:2002
It is necessary to use a multi-level cleaning and pre-treatment system to remove the organic, inorganic and accumulated oxides of the metal.
Chrome or phosphorus chromium
Disposal
The smaller value is 323
Synergy with chemical suppliers
Demand
Chromium-free disposal
Chemicals
Demand from suppliers
BS6496:1984
After cleaning with acid or alkali, the conversion membrane is cleaned with deionized water. The conductivity of deionized water dropped from the profile is less than 100μs/cm.
Chrome or phosphorus chromium
Disposal
Synergy with chemical suppliers
Demand
Do not exceed 48
QUALICOAT
After the conversion film is formed, it is cleaned with deionized water. The conductivity of the deionized water dropped from the profile is less than *30μs/cm.
Chrome or phosphorus chromium
Disposal
Synergy with chemical suppliers
Demand
Do not exceed 16
Third, appearance quality inspection
The coating on the decorative surface of the powder coating profile shall be smooth and uniform. No wrinkles, air bubbles, flow marks, stickiness, pinholes, exposed bottom, loose powder, incomplete powder, dust particles, scratches, falling films, or bones shall be allowed. And concave and other shortcomings. There should be subtle orange peels, shrinkage holes, color mixing, and grain appearances. The degree of acceptance should normally be indicated by the physical standard sample agreed upon by the supply and demand sides.
The appearance quality of powder-sprayed profiles was examined using normal vision. Under natural scattered light conditions, the distance from the coating lm was measured and the coating appearance was examined at a viewing angle of 90°. Because the shapes of the profiles are not the same as the types of coatings, different survey intervals and different viewpoint orientations are different. Table 6—3—25 is a comparison of the inspection methods for the appearance quality of coatings in domestic and foreign specifications.
Table 6-3-5 Domestic and Foreign Specifications for Appearance Inspection Method Comparison Table
specification
GB5237.4
BS6496
AAMA2604
QUALICOAT
Visual inspection
Check method
Investigate coating appearance with normal vision under natural scattered light conditions
Under natural scattered light illumination, eyes with bare eyes or proofreading eyes with a certain bevel angle of about 1 m
3m interval from coating, view into 90° point of view
3m interval from coating, view into 60°
Fourth, check the color and color difference
The color of the powder spray coating should be common with the standard swatches of the contract rules. When the instrument is used to measure, the color difference between the monochromatic powder coating and the normal color plate ΔEab ≤ 1.5, and the color difference between the same lot of goods ΔEab ≤ 1.5.
There are two ways to check the color and color difference, namely visual method and color difference meter method. Normally, the visual method is used. According to the 3.2 and 6.1 rules in GB/T 9761-1988 "Visual Comparison of Paints and Varnish Paints", the standard swatches are checked. Monochromatic coating timing selection using colorimeter, according to GB/T lll86.2 "paint film color measurement method" rule determination.
Factors that affect the color of the coating are the coating species, the illumination source, and the human eye. Different people have different degrees of sensitivity to color. To prevent errors caused by human factors, the color and color difference of a single-color coating are determined using a color difference instrument. As to the coating of pearl powder, mica powder and metal aluminum powder, because the directionality of the metal sheet placed in the coating has a greater influence on the color, the use of the instrument to determine the color and chromatic aberration is more error-prone and is not suitable for the determination of the instrument. The color and color difference are usually viewed visually.
Visual method
1) Colorimetric Light Source Requirements For everyday colorimetric work, natural daylight or artificial daylight can be used. However, the nature of natural light is unstable, and the investigator's judgment is also susceptible to the influence of colorful objects around it. It is also impossible to select natural daylight for the quality control of the production company's night production site. Therefore, it is usually selected by comparison of artificial sunlight and natural daylight of the color box, and the artificial color light of the color box is the main colorimetric light source. The distribution of the spectral energy that the cuvette's light source illuminates on the test plate should be similar to the CIE specification light source D65.
2) Investigator Needs Investigators cannot have visual shortcomings. In order to prevent the effects of binocular fatigue, do not look at light colors immediately after watching intense colors. When comparing brightly lit saturated colors, if you can't make a quick determination, you should look at the next neutral grey for a few seconds and then perform colorimetry later.
3) Colorimetric Place the test plates side by side, so that the corresponding sides touch or stack each other. The interval between the two eyes to the template is 0.5 m. Survey at an angle of 45°. The orientation of the test plate is exchanged from time to time. Both ends of the profile should be viewed. ,Prevent the color difference of the head and tail of the profile. Regarding multicolor coatings or high-gloss coatings with pearl powders, mica powders, and metallic aluminum powders, the investigation point of view should try to prevent the sunlight emitted by the coating mirrors from entering the human eye.
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