Causes of common defects in the hottest electrosta

Common defects, causes and corresponding preventive measures of electrostatic powder coating

causes and preventive measures of powder coating: 1. Insufficient amount of leveling agent and defoamer. 2. The leveling agent and defoamer are mixed unevenly. 3. The powder coatings with poor compatibility in the manufacturing process pollute each other. 4. The compressed air contains oil and water during the manufacturing process

reasons of spraying process and corresponding preventive measures: 1. Unclean degreasing. 2. The surface of the workpiece is uneven. 3. Insufficient drying after surface treatment. 4. When changing the type of powder, the cleaning is not complete. 5. The compressed air used for spraying contains oil and water or the chain is polluted by oil falling. 6. The powder is damp or the air in the workshop is damp

II. Particle

defect characteristics: protruding particles on the surface of the coating

powder coating causes and preventive measures: 1. The quality of raw materials is poor, and the resin contains gelatinized particles. 2. Pigments, fillers or additives contain mechanical impurities. 3. The self-cleaning effect of the extruder is not good, and partial gelatinized particles without melting are brought in. 4. Dust and other mechanical impurities in the environment are brought into the powder coating

reasons of spraying process and corresponding preventive measures: 1. There are burrs on the surface of the workpiece, or the surface is rough, with micro pits, etc. 2. Impurities such as chromium residue in the surface treatment solution are still attached to the surface of the workpiece. 3. The surrounding environment of the spraying room is not clean, and some dust and particles in the air are brought into the powder coating or spraying room, or charged impurities are adsorbed on the workpiece due to electrostatic induction. 4. The coating is too thin to hide the tiny non molten particles on the film. 5. The recycled paint has not been screened or the sieve is too coarse. 6. Particles of the solidified powder coating on the conveyor chain hanger fall into the film

III. film thickness out of tolerance

defect characteristics: the film thickness of the same workpiece exceeds the range specified in the contract

reasons of spraying process and corresponding preventive measures: 1. Arrangement of the number of spray guns in the powder spraying air. 2. Powder output and air pressure of spray gun. 3. The running speed of the conveyor chain. 4. Hanging mode and arrangement of workpieces. 5. The proportion of recycled powder is improper or the mixture is uneven

IV. no powder application

defect characteristics: the ratio of the amount of powder on the surface of the workpiece to the amount of powder sprayed is less than 60%

reasons and preventive measures for powder coatings: 1. For corona discharge system, filler varieties with good electrostatic performance should be selected, or special additives such as electrification agents should be added to improve the electrostatic performance of coatings; 2. For friction charging system, friction charging additives should be added to the formula; 3. The high mass fraction of pigments and fillers leads to high density and coarse particles, making the gravity greater than the electrostatic adsorption force; 4. Or the particle size is too small, the charge is less, and the electrostatic adsorption force is small

reasons of spraying process and corresponding preventive measures: 1. The voltage of corona spray gun is too low or too high; The workpiece resistance is too large (grounding focuses on the development of new material technology and utilization technology according to the needs of downstream users, or the hanger is not cleaned); 2. Excessive powder spraying; 3. The air pressure is too high

v. loss of gloss and yellowing

defect characteristics: the lower limit of 60 ° gloss exceeds the standard

reasons and preventive measures for powder coatings: 1. Interference between powder coatings of different resin types. 2. Powder coatings prepared by two resins with different activities are also easy to interfere with each other

spraying process reasons and corresponding preventive measures: 1. The powder spraying system is not thoroughly cleaned. 2. The curing temperature is too high and the curing time is too long, which exceeds the heat-resistant temperature of the coating

VI. color difference

defect characteristics: the color difference between the coating and the standard color plate exceeds the specification

reasons and preventive measures for powder coatings: the heat resistance of raw materials selected in the formulation design, such as pigments, matting curing agents, etc., is not ideal, and there is a certain gap between the baking curing conditions of coating plants and those of powder manufacturers when mixing colors. The real-time display of the display is convenient and fast

reasons for the spraying process and corresponding preventive measures: 1. Uneven film thickness. 2. The furnace temperature is uneven. 3. The thickness is 1. The speed regulation range is narrow. If there is high speed, there will be no low speed or if there is low speed, there will be no low speed. When the workpiece with large difference in high speed is hung in the same curing furnace for curing, the heating time of the workpiece material with thick thickness is longer than that of thin material, resulting in color difference. 4. The powder spraying system is not cleaned thoroughly

VII. Reasons and preventive measures for unqualified physical properties

powder coating: the matching of resin and curing agent in the formula design is unreasonable, such as the selection of resin reactivity or the variety and dosage of curing agent is unreasonable, and the mass fraction or volume fraction of filler is too large

reasons of spraying process and corresponding preventive measures: 1. The curing temperature required by the coating is not reached. 2. The curing time required by the coating cannot be reached. 3. The surface treatment of the workpiece is not good. 4. The film thickness is too thick. 5. The test temperature is too low. 6. The curing temperature is too high and the baking time is too long

VIII. Unqualified chemical resistance

powder coating causes and preventive measures: in the formula design, the matching of resin and curing agent system, the chemical stability of pigments and fillers and the mass fraction in the formula are inappropriate

reasons of spraying process and corresponding preventive measures: 1. Poor quality of surface treatment. 2. Incomplete curing. 3. The film is thin and uneven

IX. poor covering power

reasons and preventive measures for powder coating: the coating formula does not use enough pigments with covering power, so that the coating film does not have enough covering power

reasons of spraying process and corresponding preventive measures: the film thickness is too thin

(Note: 1. Physical properties refer to indentation hardness, impact resistance, adhesion and cupping test values. 2. Chemical properties refer to hydrochloric acid resistance, solvent resistance, mortar resistance, salt spray corrosion resistance, damp heat resistance, boiling water resistance and artificial acceleration weather resistance.)