I. Common Symptoms and Solutions of Paint and Coatings - Sagging

Causes of symptoms:

1. Too much dilution water is added.

2. Too much paint is too thick each time, and the re-spraying time is not appropriate.

3. The surface is uneven, unclean, complicated in shape and contains oil and water.

4. The nozzle is too large, and the distance between the nozzle and the object surface is too close.

5. The spraying speed is uneven and the interval between layers is not enough.

Solutions for symptoms:

1. Add diluent in proportion.

2. It should be sprayed twice, with an interval of ten minutes between each time, and each coating should not be too thick.

3. Treat the sprayed surface without water and oil.

4. Correctly select the diameter of the spray gun. The spray gun should be kept at a distance of 20cm-25cm from the object.

5. Adjust the viscosity of the spraying brush and master the speed of brushing and spraying.

2. Common Symptoms and Solutions of Paints and Coatings - Orange Peel

Causes of symptoms:

1. The paint is too thick, the thinner is too much, the spray pressure is too high and the distance is too close.

2. The temperature of the construction site is too high or too low.

3. The substrate is uneven or the thinner evaporates too quickly.

4. One coat is too thick.

Solutions for symptoms:

1. Add diluent in proportion, mix curing agent, and adjust the pressure and distance of the spray gun.

2. Adjust the temperature of the construction site.

3. The substrate should be as flat as possible.

4. Each coating should not be too thick.

Three. Common Symptoms and Solutions of Paint Coatings - Pinholes

Causes of symptoms:

1. Too much dilution water is added.

2. Too much paint is too thick each time, and the re-spraying time is not appropriate.

3. The surface is uneven, unclean, complicated in shape and contains oil and water.

4. The nozzle is too large, and the distance between the nozzle and the object surface is too close.

5. The spraying speed is uneven and the interval between layers is not enough.

Solutions for symptoms:

1. Add diluent in proportion.

2. It should be sprayed twice, with an interval of ten minutes between each time, and each coating should not be too thick.

3. Treat the sprayed surface without water and oil.

4. Correctly select the diameter of the spray gun. The spray gun should be kept at a distance of 20cm-25cm from the object.

5. Adjust the viscosity of the spray brush and master the speed of coating and spraying.

Prevention and control measures for whitening of paint film:

After the coating dries to form a film, the coating film is cloudy and white, resulting in dullness and turbidity. The preventive measures are as follows:

1. The construction can be carried out when the relative humidity is 80% and the ambient temperature is lower than 5°C. If it is needed urgently, it can be heated by infrared lamps around the object to be coated, and the coating can be done after the ambient temperature rises.

2. Strictly prevent the mixing of water in paint production.

3. The condensed water in the spraying equipment must be completely removed, and the water separation of the oil-water separator must be checked.

4. The substrate to be coated should be dry, and the sealing primer should be applied.

5. Strictly the ratio of main paint, curing agent and thinner to prevent polymer precipitation during the brushing process. Be sure to use thinners wisely.

6. For the whitening phenomenon of the paint film, slowly heat the object to be coated, or spray a thin layer of moisture-proof agent, or use a combination of the two methods. For severely whitened and irreparable paint films, lightly sand the stone with fine-grit sandpaper to remove dust and, in a suitable environment, repaint.

Fourth, common faults and treatment methods of paint coatings - blackening and yellowing

    The blackening of polyester furniture paint products generally has nothing to do with the quality of the paint itself. It is often due to the dark spots on the wood itself, which become obvious after painting. When wood is exposed to moisture, the degree of yellowing of the paint is mainly related to the composition of the paint and the environment in which the paint is used. From the perspective of the composition of the paint, the degree of yellowing from large to small is: nitrocellulose. TDI or its derivatives?? Other components of resin. The addition of white pigment A nitrocellulose, on the one hand, can improve the brushing performance of polyester paint, on the other hand, it brings the disadvantage that the paint film is easily yellowed when exposed to sunlight and ultraviolet rays, such as Byron semi-matte formula paint, in summer sunlight Severe yellowing after half a day of exposure. B aromatic urethane bond is decomposed and oxidized by ultraviolet light to produce quinone chromophore, thereby making the paint film yellow, which is represented by TDI. These curing agents using TDI as raw materials, due to the difference in production process, the color of the finished product is determined by water. White to brownish-yellow, but they all have yellowing superpotential under the irradiation of ultraviolet rays, super-yellowing series curing agents, and other polyester curing agents belong to this type of curing agent. C yellowing is not only related to sunlight ultraviolet rays, but also related to the baking time of the paint film. The longer the baking time and the higher the temperature, the easier the paint film is to yellow. For white or light-colored polyester and polyurethane paints, if the curing agent is TDI products. Therefore, when using white enamel outdoors, please avoid using S04-1 white color poly, or use A04-9 white amino plus A component to choose C04-42 white alkyd enamel, A04-9 white amino drying enamel, white acrylic Amino drying enamel or white acrylic biuret polyester enamel.

V. Common faults and treatment methods of paint and coatings - bleeding

After the topcoat is applied to the primer, the color of the primer penetrates into the surface due to the action of the topcoat solvent, which is called "bleeding". Most of the topcoat is light in color, and the primer is dark Appears:

1) The primer contains oil-soluble pigments or dyes

For example, when spraying A04-9 red amino paint, painters often pour the red thinner from the sprayer into F06-1 red-gray phenolic primer or other red primers in order to save money, thinking that they are all red anyway. This often ends up being reddened when light-colored topcoats are applied.

2) Spray paint with strong solvent such as nitro paint on the undercoat that is not dry.

Six. Common faults and treatment methods of paint and coatings-bite the bottom

The solvent in the topcoat can easily soften the primer film and even affect the adhesion between the primer and the surface. After the topcoat is applied, the phenomenon of biting the primer is called "biting" Bottom", a slight underbite is very similar to paint film wrinkling.

1) Topcoat before the primer is dry

For example, H06-2 Iron Red Epoxy Ester Primer, F53-31 Hongdan Antirust Paint perform well at high temperature in summer, but as the temperature drops, especially in winter, it is difficult to paint on them There are more and more complaints about wrinkling and biting the bottom of the topcoat, mainly because the drying speed of these two kinds of paints is closely related to the temperature. It will be dry, and spraying the topcoat containing strong solvent will not bite the bottom and wrinkle, and in the low temperature in winter, its self-drying and hard-drying time will take 5 days or longer. We recommend that the iron red epoxy primer should be dried at 120 degrees Celsius for 1 hour in winter. If there is no drying equipment, it is recommended to extend the drying time or choose other quick-drying primers.

2) The primer and topcoat do not match

If the primer itself is a paint that is not resistant to strong solvents, such as red red phenolic antirust paint or iron red phenolic antirust paint, and the topcoat is a strong polar solvent, such as nitraldehyde paint, polyurethane paint, even if the primer After the paint dries, there will still be a biting phenomenon.

3) The two-component paint curing agent leaks air, causing a certain degree of resin gelation or paint preparation after too long before painting, which will reduce the final film quality of the paint and resist the penetration and swelling of the topcoat solvent. Decreased ability, causing bottom bite.

4) The bottom layer uses volatile putty or paint with poor resistance to strong solvents, while the top layer uses polyester and polyurethane thermosetting resin paint. Even after the first topcoat is fully dried, the bottom-biting phenomenon occurs when the second topcoat is applied. produce bottom bite.

5) Impasto

The thick coating of the primer prolongs the drying time of the primer, and at the same time, as the primer resists the penetration of strong solvents, the ability to swell and soften decreases, thereby greatly increasing the probability of biting the bottom. The thick coating of the topcoat will make the solvent in the topcoat penetrate into the primer, and the softening time will be prolonged accordingly, and the probability of being bitten by the primer will increase.

7. Common faults and treatment methods of paints and coatings - particles

1) The construction tools are unclean, the new brushes have dust on them, the old paint brushes are used to not wash the paint in time, and the paint-holding utensils are unclean.

2) The construction environment and construction personnel are not clean, the coating material is not clean or the construction weather is bad, and the surrounding environment is not good, so that impurities such as dust, mesh sand, yarn wool and other impurities fall into the paint, or soak in the wet paint film Graining the paint film.

3) The paint thinner has poor diluting ability, which causes the precipitation of some resin components in the paint. Particles can occur, for example, in semi-matte topcoats or clear primers, when the thinner leaks out or when the thinning capacity is poor.

Solution: Add strong solvents such as butyl acetate and cyclohexanone to the diluent, and filter it after matching the paint.

Eighth, common problems and treatment methods of paint and coatings - wrinkling

1) If the drier is not properly matched or added too much, the inner and outer layers will dry unevenly, resulting in wrinkling.

2) Thick coating and pouring coating, among which C04-42 alkyd enamel is the most representative. Poor thick coating of C04-42 alkyd enamel will cause wrinkling and slow drying.

3) After painting, the drying temperature is too high in strong sunlight.

4) Slight bottom bite.

Nine, common faults and treatment methods of paint coatings - shrink paint

1) The surface to be coated is contaminated (dust, sweat, oil, wax, etc.) and moisture. For steel workpieces, use solvent to clean them and then paint them. For wooden furniture, first wash them with soapy water, then wipe them with water to dry them, and then paint them.

2) The compressed air sprayed contains oil or water

3) The surface of the coated object is too smooth, and the surface should be sandblasted and polished for pretreatment.

4) Two-component paints are sometimes mixed and applied immediately after being mixed, and shrinkage and fermentation will also occur. After the paint is mixed, it is fully mixed and matured before painting.

5) The high temperature in summer greatly increases the volatilization rate of the solvent in the paint, resulting in uneven dispersion of the additives in the paint film, resulting in shrinkage of the paint. The solution is to reduce the construction humidity or add a strong solvent with slow volatility, such as cyclohexane. ketone.

6) The paint is not matched. When the polyester paint uses primers and topcoats from different manufacturers, because the additives used by each manufacturer are not necessarily compatible systems, sometimes the phenomenon of shrinkage will occur.

10. Common faults and treatment methods of paint and coatings - cracking

1) The paint itself has poor weather resistance and is not easy to use outdoors. For example, our factory's phenolic white blend and bright white aluminum powder will crack after 1-2 months of outdoor use in summer.

2) Thick coating and pouring floor paint are used in the process of use, and the possibility of cracking of the paint is greatly increased. Generally speaking, the total amount of paint used per square meter does not exceed 0.8 kg. , cracking is unlikely.

3) The ratio of curing agent is too high, or the hardness of the paint itself is too high and the toughness is insufficient.

4) The bottom layer itself is loose and cracked, causing the upper paint film to fall off and crack.

Eleven. Common faults and treatment methods of paint and coatings-powder removal

1) Excessive addition of diluent will lead to separation of resin and powder, resulting in powder removal.

2) The paint with white pigment has poor weather resistance, resulting in chalking when used outdoors

3) The paint is precipitated and stirred unevenly, and the paint with high silty content in the lower layer is used to remove powder.

4) Quick-drying paint sprays large workpieces, and the paint mist in the air falls on the workpiece and generates dust, so this type of paint is generally not easy to spray large workpieces. In the actual construction process, we may also encounter rust, floating color, pan-golden and other problems, which will not be explained one by one here.

In short, whether it is furniture polyester paint or ordinary industrial paint or latex paint, the following matters should be paid attention to in the construction process:

1) The substrate must be clean to ensure no water, no oil, dust and other pretreatment quality.

2) Construction paint base, surface matching, solvent matching.

3) Pay attention to the construction environment and the influence of temperature on the specific construction.

4) The two-component and three-component paints are ready for use, and will be discarded after expiration. The colored paint should be fully stirred before use.

5) For non-thick-coat paint, it is not allowed to pour thick-coat in order to shorten the working hours.

6) After the construction is completed, ensure that the paint film has a certain maintenance period, and do not use it immediately.

Twelve, common faults and treatment methods of paint coatings - slow drying, sticky

1) The surface of the object contains oil stains, water vapor causes slow drying, or the plasticizer in the plastic penetrates into the paint

2) Improper diluents used, such as engine oil, diesel diluents and other less volatile substances are brought into the paint, which can cause the paint film to become stickyDry slowly.

3) The influence of thick coating on polyurethane paint is not very prominent, but it is very prominent on alkyd and phenolic. Under constant temperature and constant pressure, C04-42 white alkyd enamel of 20 microns can be dried in 18 hours. , but when its paint film is 50 microns, it cannot be completely dried for three days, and it is prone to wrinkling. For this type of paint, it is better to apply several coats more than to apply too thick at one time.

4) The oxidizing primer, putty or primer is not dry and then the second layer of paint is applied, resulting in interlayer isolation, air drying and solvent volatilization are blocked, thus causing the paint film to dry slowly.

XIII. Common faults and treatment methods of paint and coatings - peeling and peeling

1) After the primer is fully dried, a smooth and hard paint film has been formed. When the upper paint is applied, it is not sufficiently polished, resulting in peeling off between layers. In theory, the shorter the construction interval between matching paints, the better The stronger the adhesion between layers, but considering that the primer is too short to dry, it may cause the problem of biting the bottom, so the painter generally let the primer fully dry when the last coat of paint is thickened, which is very important for the polishing of the primer. put forward higher requirements.

2) In addition, in order to improve the construction performance of modern paints, the addition of a large number of additives also reduces the interlayer adhesion of the paint.

3) The bottom and the surface are not matched. For example, if the polyester or polyurethane varnish king has formed a certain fullness, paint nitro wood varnish, even if the polyester paint film is polished, the layer will still be formed after a long time. shedding phenomenon. The same reason applies to the matching use of 9311 quick-drying acrylic paint and polyurethane paint.

4) The bottom layer is not thoroughly treated, there is floating dust, oil stains or the bottom layer itself is loose. The phenomenon that the bottom layer is loose and leads to shedding accounts for a large proportion of the reasons for the shedding of latex paint.