Some standard content:
GB/T 18178--2000
Appendix A is the standard appendix.
Appendix B is the indicative appendix.
This standard is proposed by the State Machinery Industry Bureau.
This standard is under the jurisdiction of the National Technical Committee for Standardization of Metallic and Non-metallic Coverings. The responsible drafting unit of this standard: Wuhan Institute of Material Protection. The main drafters of this standard: Li Xinli, Chang Yuxin, Jia Jianxin, Li Anzhong, Ye Lei. 103
National Standard of the People's Republic of China
General rules of the selection for painting system of water paint
General rules of the selection for painting system of water paint1Scope
This standard specifies the basic principles for the selection of water-based paint systems. This standard applies to the painting of steel parts.
2 Cited standards
GB/T 18178—2000
The provisions contained in the following standards constitute the provisions of this standard through reference in this standard. When this standard is published, the versions shown are valid. All standards will be revised, and parties using this standard should explore the possibility of using the latest versions of the following standards. GB/T1731—1993 Determination of flexibility of paint films GB/T1732—1993 Determination of impact resistance of paint films GB/T1733—1993 Determination of water resistance of paint films GB/T1763-1979 (1989) Determination of chemical resistance of paint films GB/T1771--1991 Determination of neutral salt spray resistance of paints and varnishes (egvISO7253:1984) GB3186—1982 Sampling of coating products
GB/T5206.1-1985 Paints and Varnish Vocabulary Part - General terms (eqv ISO 4618.1:1978) GB6514-1995 Safety regulations for painting operations Safety of painting process and ventilation purification GB/T6739-1996 Determination of paint film hardness by pencil method GB/T6807-1986 Technical conditions for phosphating treatment of steel workpieces before painting GB7691-1987 Safety regulations for painting operations Labor safety and labor hygiene management GB7692-1999 Safety regulations for painting operations Safety of pre-treatment process for painting and ventilation purification GB/T 8264--1987
Coating technical terms
GB/T8923-1988
Rust grade and rust removal grade of steel surface before painting (eqvISO8501.1:1988)GB/T 9286-1998
Scratch test of paint and varnish film (eqvISO2409:1992)GB/T 11376--1997
GB/T 13312-1991
Phosphate conversion film of metal (eqvISO9717:1990)Test method for degreasing degree of steel parts before painting (oil test paper method)JB/T6978-1993
Surface preparation before paintingAcid pickling
3 Definitions
This standard adopts GB/T 8264 and the following definitions. 3.1 Water-based paint Water (based) paint Paint that is completely or mainly water-based (GB/T5206.1--1985 1.15). 3.2 Coating system Coating system
Multi-layer coating formed after coating and curing. Approved by the State Administration of Quality and Technical Supervision on August 28, 2000 101
Implementation on January 1, 2001
3.3 Painting system Painting system
General term for surface pretreatment, coating and coating construction. 4 Information to be provided by the purchaser
Unless otherwise specified, the purchaser shall provide the following information: 4.1 Number of this standard.
GB/T 18178--2000
4.2 Description, drawing or sample of the shape, size and surface condition of the workpiece to be coated. 4.3 The use environment and purpose of the workpiece. 5 Surface pretreatment
Surface pretreatment mainly includes degreasing, rust removal and phosphating processes. According to the surface state of the workpiece, the construction requirements of water-based paint and the use environment of the workpiece, all or part of them can be adopted. 5.1 Degreasing
After the workpiece is degreased, the surface should be free of grease, oil, acid, alkali, salt solution, etc. The degreasing effect shall be carried out in accordance with the provisions of GB/T 13312 or Appendix A (Appendix of the standard).
5.2 Rust removal
After the workpiece is derusted, the surface should be free of oxide scale, molding sand, rust, etc. Mechanical rust removal can be used, chemical rust removal can be used, or a combination of the two (such as ultrasonic rust removal, etc.).
5.2.1 Mechanical rust removal
Mechanical rust removal includes spraying, projectile, flame, hand tool and power tool rust removal, etc. Mechanical rust removal shall be carried out in accordance with the provisions of GB/T8923, and can be selected according to the specific situation. The surface of the workpiece after rust removal should reach Sa2-
5.2.2 Chemical rust removal
Chemical rust removal is usually called pickling. The surface state achieved after chemical rust removal and workpiece rust removal should comply with the corresponding regulations in JB/T6978. 5.3 Phosphating
Different water-based coatings have very different requirements for the phosphating process. Self-phoretic coatings do not require phosphating; unless otherwise specified, other water-based coatings are recommended to use phosphating when used as the base layer. The phosphating film formed on the surface of the workpiece after phosphating should comply with the corresponding regulations in GB/T6807 or GB/T11376.
6 Coatings
6.1 Classification
Currently, water-based coatings are classified as follows: a) Type I is latex coating;
b) Type II is self-phoretic coating;
c) Type V is electrophoretic coating;
d) Type V is water-based coating other than Type I, Type I, and Type I. The types and uses of commonly used water-based paints are shown in Appendix B (suggestive appendix). 6.2 General requirements
6.2.1 The color, composition, packaging, and marking of the paint should comply with the product standards or corresponding technical specifications. 6.2.2 The paint should be able to dry naturally or be oven-dried.
6.2.3 Before using the paint, a sample should be taken for re-inspection, and it should comply with the product standards or corresponding technical specifications. 6.2.4 When multiple paints are used in combination, the supplier should conduct matching tests approved by the purchaser. 105
6.3 Technical requirements
GB/T 18178—2000
Unless otherwise specified, the technical requirements for paints are shown in Table 1. Table 1 Technical requirements
Pencil hardness
Flexibility, mm
Impact resistance, cm
Adhesion, grade
Water resistance (method A), h
Salt water resistance (method A), h
Salt spray resistance, h
Comply with product
Technical requirements
Comply with product
Technical requirements
6.4 Selection of coatings in coating system
Comply with product
Technical requirements
≥240
Anodic electrophoretic coating: ≥H
Cathode electrophoretic coating: ≥2H
Anodic electrophoretic coating: Comply with product technical requirementsCathode electrophoretic coating: ≥1000
Polybutadiene anodic electrophoretic coating: 240
Acrylic anodic electrophoretic coating: ≥120
Other anodic electrophoretic coatings: ≥24
Thick film cathode electrophoretic coating: ≥10 00
Other cathode electrophoretic coatings: ≥720
Meet product technical requirements
Meet product technical requirements
Water-based alkyd coatings: ≥48
Water-based epoxy coatings: ≥120
Water-based acrylic coatings: ≥120
Other water-based coatings: ≥48
Meet product technical requirements
The corresponding coatings for each layer of the coating system should be selected according to the corresponding substrate surface conditions, coating properties, workpiece use environment and purpose, etc. The selection of commonly used water-based coatings in the coating system is shown in Table 2. Table 2 Varieties of commonly used water-based paints in coating systems
Acrylic metal latex paint
Styrene acrylic metal latex paint
Vinyl chloride self-phoretic paint
Acrylic self-phoretic paint
Acrylic anodic electrophoretic paint
Epoxy anodic electrophoretic paint
Polybutadiene anodic electrophoretic paint
Epoxy cathode electrophoretic paint
Acrylic cathode electrophoretic paint
Water-based alkyd paint
Water-based acrylic paint
Water-based epoxy anti-rust paint
Water-based polyester paint
Intermediate layer
Note: Y means can be selected, N means cannot be selected, Y/N means selection or non-selection is determined by negotiation between the supply and demand parties. 106
Bottom and one layer
6.5 Test method
6.5.1 Sampling
According to GB/T3186.
6.5.2 Pencil hardness
According to GB/T6739.
6.5.3 Flexibility
According to GB/T1731.
6.5.4 Impact resistance
According to GB/T1732.
6.5.5 Adhesion
According to GB/T9286.
6.5.6 Water resistance
According to GB/T1733.
6.5.7 Salt water resistance
According to GB/T1763.
6.5.8 Salt spray resistance
According to GB/T1771.
7 Coating application
7.1 Surface pretreatment
Surface pretreatment shall be carried out in accordance with Chapter 5.
7.2 Construction conditions
GB/T 18178—2000
Water-based coatings shall generally be applied in clean, well-ventilated and well-lit places. The temperature, humidity, mixing method, recoating interval and other parameters shall be selected according to the characteristics of various water-based coatings. 7.3 Construction method
According to the characteristics of the water-based coatings and the requirements of the workpieces to be coated, one or a combination of dipping, brushing, rolling, electrophoresis, self-coating, spraying, etc. shall be selected.
7.4 Curing
The curing temperature, time, method, etc. shall be selected according to the characteristics of various water-based coatings. 8 Inspection
The supplier shall accept the inspection and approval of the purchaser for the materials and technical documents provided in accordance with this standard. In case of disputes, the arbitration or mediation method specified in the negotiation documents shall be followed, or other appropriate methods of mediation or arbitration shall be adopted. 9 Safety
Some water-based paints also contain organic solvents, which are also flammable under certain conditions. Some components of water-based paints may be harmful. When operating, the corresponding provisions in GB/T7691, GB/T7692 and GB/T6514 shall be observed. 107
GB/T 18178—2000
Appendix A
(Appendix to the standard)
Simple determination method for degreasing effect
Simple determination method for degreasing effect includes water immersion method and finger test method, etc. See Table A1. Table A1 Simple method for judging degreasing effect
Water immersion method
Test method
Operation method
After cleaning, immerse the workpiece in tap water, take it out and observe whether the water film on the surface is continuous or has water beads. If there is residue on the surface, it should be soaked in weak acid, and then taken out to observe whether the water film is continuous or has water beads. When cleaning with surfactant, it should be repeatedly soaked in tap water for 2 to 3 times, and then taken out to observe whether the water film is continuous or has water beads
Those with continuous water film and no water are qualified, and those with discontinuous or water beads are unqualified
After cleaning, wipe the workpiece with white cloth or white paper, and observe whether there is no stain on the white cloth or white paper, which is qualified, and those with stains are unqualified. When the dust and dirt on the surface of the workpiece are heavy, it is not recommended to use this method as a non-conforming method
Appendix B
(Suggestive Appendix)
Common water-based paint varieties and uses
Common varieties and uses of type I, type I, type III and type V water-based paints are shown in Table B1, Table B2, Table B3 and Table B4 respectively. Table B1 Common varieties and uses of type I water-based paints Paint varieties
Styrene acrylic metal latex paint
Acrylic metal latex paint
Polyurethane latex paint
Paint varieties
Acrylic self-phoretic paint
Vinyl chloride self-phoretic paint
Film-forming conditions
Surface drying: 1h, actual drying: 24h.
Drying: 140~160℃, 1h
Surface drying: 1h, actual drying, 24h.
Drying: 90~110℃, 1 h
Surface drying: 1h, hard drying, 24h
Performance and use
The coating is resistant to water washing, wear and weathering, and its anti-rust performance exceeds that of alkyd and perchloroethylene anti-rust coatings. It is suitable for coating steel substrates, aluminum alloys and galvanized sheets. The coating has good anti-rust performance and can be used with percyanethylene, alkyd, nitro and acrylic topcoats. It is suitable for coating machine tools, castings, iron furniture, flanges and other products. It has good coating effect on aluminum alloy surface, galvanized sheet surface and damp metal surface. The coating has excellent durability, wear resistance and rust resistance. It can be used as a primer and is mostly used in the automotive industry. Table B2
I type water-based coatings Common varieties and uses
Film forming conditions
Drying: two-stage drying,
110C, 15 min, 170C
Drying at: 100~110℃, 20
~30 min
Performance and Application
The coating has excellent salt spray resistance, acid resistance and alkali resistance, and is suitable for coating automobile frames and parts, instruments and meters, agricultural machinery and implements, etc. The coating has better salt spray resistance than acrylic self-phoretic coating, and its adhesion is slightly lower than that of acrylic self-phoretic coating, and is suitable for coating automobile frames and parts, instruments and meters, agricultural machinery and implements, etc.
Coating Varieties
Epoxy anodic electrophoretic coating
Acrylic anodic electrophoretic coating
Polybutadiene anodic electrophoretic coating
Epoxy cathode electrophoretic coating
Acrylic cathode electrophoretic coating
Coating Varieties
Water-based alkyd coating
Water-based acrylic coating
Water-based epoxy anti-rust coating
Water-based epoxy polyester coating
Water-based polyester coating
GB/T 18178—2000
Common varieties and uses of type III water-based coatings
Film-forming conditions
Electrophoresis voltage: 60~~100V
Electrophoresis time: 2~~3 min,
Curing temperature: 150~170C,
Curing time: 20~30minwwW.bzxz.Net
Electrophoresis voltage: 130~170V,
Electrophoresis time: 2~~3min,
Curing temperature: 170~190℃,
Curing time: 20~30min
Electrophoresis voltage: 80~200V,
Electrophoresis time:2～3 min,
Curing temperature 150～180℃,
Curing time: 20～30min
Electrophoresis voltage: 150~250V,
Electrophoresis time: 2～3min,
Curing temperature: 160~190℃,
Curing time: 20~~30min
Electrophoresis voltage: 120~200V,
Electrophoresis time: 2~ 3min,
Curing temperature: 170～190℃,
Curing time: 20~~30min
Performance and use
The coating has good adhesion and physical and mechanical properties, and is suitable for coating steel, aluminum and alloys. The coating has good rust resistance, weather resistance and light resistance, and is used for coating light industry, home appliances, aluminum materials, etc.
The coating has good rust resistance, excellent physical and mechanical properties, and good tank liquid stability. It is suitable for coating steel plates, steel bars, metal parts, automobile bodies, etc. The coating has good water resistance, moisture resistance and excellent physical and mechanical properties. It is used for coating metal products in military, automobile, agricultural machinery, home appliances, instrumentation and other industries
The coating has excellent weather resistance and decorative properties, and the varnish coating is bright, smooth, transparent and clear. It can be used as a transparent finishing coating for metal finishing parts. Adding various color pigments can make the coating colorful
Table B4V type water-based paint common varieties and uses Film-forming conditions
Drying: 130~150℃, 20min
Drying: 120~160℃, 30min
Drying: 80~100℃, 30min
Drying: 130~140℃, 30min
Drying: two-stage drying, 80℃, 10min, 160℃, 20min
Performance and use
Pencil hardness: ≥HB, impact strength: 50cm, flexibility: 1mm, used for coating steel structures, mechanical parts, automotive parts, etc. Pencil hardness: ≥H, impact strength: 50c m, adhesion (cross-cut method): ≤1 level, the coating has good salt spray resistance, water resistance and adhesion, and can be used not only as a base layer but also as a combined base layer. It can be used for coating automobiles, household appliances, instruments, the inner wall of food cans, etc.
Pencil hardness: ≥H, impact strength: 50cm, adhesion (cross-cut method): 0 level, the coating has good water resistance and rust resistance, and is suitable for rust-proof primer for ferrous metals. Pencil hardness: ≥H, impact strength: 50cm, adhesion (cross-cut method): ≤1 level, the coating has excellent adhesion, and is suitable for coating automobile and agricultural vehicle frames, chassis and parts, household appliances and instruments, etc. Pencil hardness: ≥2H, impact strength: 50cm, adhesion (cross-cut method): 1 level, the coating is hard and tough, plump and bright, and has good pollution resistance. Suitable for coating of coils, automobile bodies, light industrial products, etc.
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