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Aluminum Alloy Electrostatic spaying techniques

Electrostatic spraying techniques
A powder coating method is the use of static uniform spray to the surface after blasting, degreasing, descaling, chromium, zinc and other pre-treatment on the melt under the provisions of the curing temperature and time conditions, leveling pay - linking the surface to form a uniform, dense and solid coating combined with the workpiece. Second, the use of precautions, process? Good condition and ground of the painting equipment, oil-free compressed air and gas, water;? Between products from different manufacturers or different products may have interference, change the line to be thoroughly cleaned; ? different products, coating thickness, plain powder 50-70 microns, texture powder 60-80 microns, special varieties when the case may be;? than the heavy workpiece heat capacity, heat up the slower the corresponding need to extend the baking time curing conditions, curing temperature is the temperature of the workpiece;? to ensure that the workpiece is clean, keep the environment clean and tidy;? uniform spray seamless point to prevent corrosion and shorten the service life; safe? spray room should have good dust recovery operations prohibit the use of fire;? operating personnel should be equipped with the necessary protective equipment such as dust masks, overalls, work hats, gloves. Transport and storage? Powder coating solvent evaporation, the main material is non-toxic, non-flammable, environmentally friendly, efficient and secure new coating material, is a non-dangerous goods, you can transport a variety of modes of transport;? Storage, transport should be avoid heat, moisture, avoid contact with chemicals. , Affecting factors and countermeasures of the powder coating quality (a) spray voltage within a certain range, the spray voltage increases, the powder attached to the amount of increase, but when the voltage is more than 90KV powder attached to the contrary, with the increase of the voltage reduction smaller. 2, the voltage increases, the increase in the initial growth rate of the powder layer, but with the increase of the spraying time, the voltage on the rate of increase of the thickness of the powder layer is smaller. 3, when the spray distance (referring to the distance of the gun head to the workpiece surface) increases, the voltage on the powder layer thickness is smaller, the general distance lies between 150-300mm. 4, the spray voltage is too high, makes the powder layer breakdown, quality of the coating. The spray voltage should be controlled between 60-90KV. (B) for the powder pressure for the air pressure is lost in the powder pressure means for the powder in the powder tube, the other conditions remain unchanged, 0.05Mpa (1.96 kgf pressure) is the best. (C) dusting the amount of dusting is the amount of gun mouth of the amount of powder per unit time. The initial growth rate and dusting is proportional to the amount of the powder layer thickness, but with the increase of the spraying time, the dusting on the growth rate of the powder layer thickness is not only smaller, but also the deposition efficiency decreased, so dusting the amount of grasp 100-200g/min more appropriate. (D) The spray from the spray distance refers to the distance of the gun mouth to the workpiece surface, imposed when the gun electrostatic voltage constant spray distance changes, the electric field strength changes. Therefore, the spraying distance directly affects the size of the powder layer thickness of the workpiece adsorption and deposition efficiency. The optimum distance is about 250mm. (E) coating the ambient temperature and film thickness, dusting amount 170-200g/min; voltage 70KV spray gun with painted distance of 200 mm. Powder paint transfer efficiency is better when the temperature is 20-30 ℃, humidity of 60-80%, and the thick coating. (Vi) the formation of the coating powder coating, the coating thickness of the thicker, the surface tends to the more formation. The powder paint coating formation, the main factor is the particle size distribution of the scattered state of the melt viscosity, paint and curing agent. Melt viscosity resins to obtain smooth coating of the coating thickness of 40μm, the maximum particle size of the powder size is about 60μm. (G) of the coating thickness distribution in the electrostatic powder coating, due to the inhomogeneity of spray powder coating thickness non-uniformity of about twice that of the solvent coating, proper understanding of the spray beam coating equipment graphics, control, good spray indirect time to prevent the non-uniformity of the spray. Was painted area is greater than of the spray pattern of coating equipment, reciprocating spray gun structure is more appropriate. When the arrangement of parallel long stroke, the central parts of the painted coating is thin, while the use of a series of short stroke arrangement, to be painted the central part of the coating is thicker. (H) The transfer efficiency of powder coating transfer efficiency of the main factors is charged way of painting equipment to paint, powder particle size distribution, coating temperature and humidity of the environment. To this end, the appropriate particle size range of powder coatings for the 10-80μm. The relationship between coating efficiency and particle size is roughly: particle diameter (μm) 150 transfer efficiency (%) 35.0; 150-100 35-60; 100-74 60-70; 74-20 of 70 - 90, it is relative to the weight of the particles, the static electricity with the reduction of the particle diameter increases, the particle diameter of 36-100μm (150-400 mesh) powder can be completely attached to the cold state to be painted, the larger 74-177μm (80-200 mesh) particles in the spray, the powder may be coated to fall. Epoxy resin particle size of 20-100μm, should be the balance of the particle diameter distribution standard for the 10-80μm, the smallest lower limit of less than 10μm less than 10% particles below 60μm 60%, preferably into a sharp particle size distribution of 20-50μm 20μm below the micro-powder is easy flying, paint loss. (I) coating the particles causes cause for entering into the gel of insoluble particles and other impurities in the powder coating. The fine particles in the powder coating easy accumulation of parts to change the airflow direction in the gun head or pipe coating equipment, accumulation and to some extent, the agglutination state of spray attached to the painted above, do not bake melting into a particle diameter of 0.5-3mm. Attached to the dusting chamber wall and recycling equipment, plastic compounds, manufacture of the powder coating process due to the pigments to produce the condensate in the melt mixing process some of the resin curing reaction of gel particles, these particles will form a coating on the particles electrostatic spray, environmental dust problems should also be taken seriously enough. Dust from the air, flaking material on the fiber and baking equipment operator on the work of plastic bag recycling equipment such as dust in the process of electrostatic powder coating can also cause pollution and bring the particles. (10) less than 1, curing, baking time is too long; 2, the temperature is too high; 3, mixed with other harmful gases in the oven; 4, the surface is too rough; 5, the former approach is the inappropriate choice of coating gloss. (11) coating color repeatedly baking; 2, mixed with other gases in the oven; 3, curing overbake. (12) coating the surface of orange peel, spraying thin coating thickness is uneven; 2, powder atomization bad gun phenomenon of accumulated powder;, low curing temperature or time;, powder moisture The powder particles are too thick; 5, poorly grounded workpiece; 6, the baking temperature is too high; 7, the coating is too thick. (13) film inappropriate concave hole, surface treatment, degreasing without a net; 2, the gas source of contaminated compressed air, oil, water removal is not complete 3, the surface is not flat; by the dust or other impurity contamination. (14) film bubbles, surface treatment, water is not thoroughly dry, leaving the pre-treatment residue;, degreasing, descaling is not complete; 3, the underlying volatiles did not go to the net; 4, the surface pores;, powder coating is too thick. (15) coating uneven, uneven powder spray; too close to 2, the spray gun and the workpiece; 3, the high voltage output instability. (16) film impact strength and poor adhesion of a phosphate film thick; 2, the curing temperature is too low, too short, so that the curing is not complete; 3, bottom metal unhandled clean;, coating the workpiece flooding will reduce adhesion. (17) coating pinholes contain foreign matter, the residual oil in the air; 2, the gun voltage is too high, causing coating breakdown; 3, the spray gun too close to the workpiece distance, resulting in coating breakdown; 4, Tu layer is too thick; 5, the coating is not fully cured. (Xviii) the film surface a small amount of sand, spray blockage or poor airflow; 2, poor atomization; dusting indoor powder dripping; 4 other debris contaminated the surface. (19) coating off a surface treatment is not good degreasing rust completely; 2, high-voltage electrostatic generator output voltage; 3, the workpiece is poorly grounded; dusting when the air pressure is too high. Uneven (20) for the amount of powder for powder tube or dusting tube blockage, powder adhesion hardening in the nozzle; 2, air pressure, pressure instability;, air compressor, mixed with oil or water; 4 for the Powder Flow instability for powder powder over less; for the powder tube is too long, the powder flow resistance increases. (21 a) of the powder flying adsorption poor 1, no high-voltage electrostatic generator; 2, the workpiece is poorly grounded;, air pressure is too large; recovery stroke airway obstruction. (Xxii) dusting less 1, less than atmospheric pressure, the gas is not enough; 2, the pressure is too high, the high proportion of air in the mixture of powder and airflow; 3, the air in the mixed water gas and oil; 4, the spray gun head partially blocked. (Xxiii) dusting duct obstruction therefore dusting tube material, the powder easily attached to the wall; 2, the output tube heat, causing the tube in powder agglomeration;, pink tube bend, twist; 4 powder mixed with particles of impurities

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