Common problems and solutions of coatings!
1、 Pulverization
Phenomenon: there is a thin layer of powdered substance on the membrane surface, which will fall off immediately after wiping.
reason:
2) Excessive dilution, the paint film is too thin, and the resin can not effectively bond the pigments and fillers;
3) The substrate is too loose and too much resin penetrates into the substrate, which can not effectively bond the pigments and fillers;
4) The substrate temperature is too low and the film formation is poor during construction
5) The substrate and ambient humidity are too high, the recoating time is short, the ventilation is poor, and the film cannot be completely formed;
6) The base is too alkaline and the paint film is damaged;
7) The 7-day film forming period was not enough during the test.
resolvent:
1) Remove the pulverization layer;
2) Select appropriate paint;
3) Follow the construction specifications and do not dilute excessively;
4) If necessary, appropriate primer shall be selected to seal the substrate;
5) Ensure that the construction environment meets the construction requirements.
2、 Uneven gloss
Phenomenon: uneven gloss of coating film, light and dark distribution, often appearing in mercerized and semi-gloss products
reason:
1) The porosity of the substrate is uneven, and the adsorption of resin is different;
2) The construction thickness of primer and finish coat is uneven;
3) Local dry spraying during spraying;
4) Use different construction tools for the same wall;
5) The same wall uses products of different batches;
6) Failed to effectively "wet connect", with obvious connection marks;
7) The substrate temperature is too high or the paint dries too fast.
resolvent:
1) The primer, especially the local repair part, must be the same as the surrounding primer before applying the finish coat;
2) Ensure that the thickness of each layer is consistent and there is no brush leakage;
3) Make sure to use the same tools, use the same batch of products on the same wall, and ensure wet connection in the division area.
4) Ensure that the construction conditions and process meet the requirements;
5) Select appropriate diluent according to different climate to adjust the drying time of paint.
3、 Blistering and peeling
Phenomenon: blistering or cracking of coating film.
reason:
1) The base putty is mainly composed of gypsum powder, talcum powder and double-fly powder, which will swell in case of water and lift up the paint film, especially the exterior wall;
2) The base moisture is too high, and its pressure will bulge the paint film when it diffuses outward, especially for products with poor permeability;
3) The waterproof treatment of civil engineering is poor, rainwater enters the base through cracks or unpainted base surface, or water leakage damages the paint film
resolvent:
1) Remove the blistering and peeling parts. If it is caused by putty, remove the putty and re-scrape it with appropriate putty;
2) Comply with the construction specifications, make the base waterproof layer, repair the base cracks before construction, ensure that the moisture content of the base meets the construction requirements, and add paint layer in local areas if necessary to prevent rainwater infiltration.
4、 Fading and discoloration
Phenomenon: The color of the coating film changes uniformly or unevenly, and the overall hair is blossoming, especially red or yellow.
reason:
1) Organic pigments have poor weather resistance and discoloration under ultraviolet radiation;
2) The base alkalinity is too high, and the pigment in the paint film will be damaged after exudation;
3) Saline and alkali precipitate on the surface;
4) If the dark paint film is powdery, it will also show that the color becomes lighter.
resolvent:
1) Choose darker color, which usually has better weather resistance and alkali resistance;
2) Follow the construction specifications to ensure that the base alkalinity meets the construction requirements, especially the post-repair part;
3) Seal the substrate with a suitable primer.
5、 Pantothenate
Phenomenon: salt and alkali precipitation occurs on the surface of the coating film, forming white sags on the surface or damaging the adhesion of the coating film.
reason:
1) The base is not clean, with grease, release agent, etc;
2) The moisture content of the substrate is too high, or there is saline-alkali precipitation;
3) The base is severely pulverized or not dusted after grinding
4) The selected primer is not compatible with the substrate.
resolvent:
1) Remove all affected paint films that lose adhesion, clean the wall and wait for drying;
2) If the base is seriously pulverized, it shall be sealed with suitable penetrating primer;
3) Follow the construction specifications, make the base waterproof layer, and ensure that the base conditions meet the construction requirements;
4) Use a suitable primer.
6、 Poor adhesion and flaky peeling
Phenomenon: After the coating is applied, the coating film can be peeled off in pieces or partially after being damaged.
reason:
1) The covering power of bright red and bright yellow is poor;
2) The color contrast between the bottom and top coating is obvious;
3) The paint is excessively diluted and the paint film is too thin;
4) The base is concave and convex, and the convex paint film is usually too thin.
resolvent:
1) Use the middle coat or primer that is similar to the color of the finish coat but slightly lighter;
2) Control the dilution ratio to ensure that the dilution is less than 5%;
3) The roller construction effect is good;
4) For some colors or substrates, the number of finishing coats shall be appropriately increased.
7、 Macrophyta
Phenomenon: There are gray-black mold or green algae growing on the surface of the coating film, which damages the appearance, especially in wet places.
reason:
1) The dust accumulated on the film surface carries nutrients, which is beneficial to the growth of mold or algae in the wet place.
resolvent:
1) The exterior wall is strongly washed with high-pressure water;
2) Clean the mildew and algae growing place with appropriate fungicidal water or bleach;
3) If the environment is particularly bad, special formula should be used to properly increase the anti-mildew and anti-algae ability.
8、 Watermark
Phenomenon: When looking at the coating film, it is found that there are irregular patches on its surface with low gloss.
reason:
1) The moisture content of the substrate is too high;
2) There is water leakage and seepage;
3) The ambient humidity is too high during construction.
resolvent:
1) Ensure that the substrate is dry;
2) Ensure no water leakage and seepage;
3) Ensure that various conditions meet the requirements during construction;
4) Use proper primer for sealing if necessary.
9、 Smudge
Phenomenon: The coating film is stained and sagging, which damages the beauty, and usually appears under the window and near the roof.
reason:
1) The pollution rate exceeds the stain resistance of the paint film;
2) The building structure makes it easy for the rain to wash down the accumulated dust and hang it on the wall.
resolvent:
1) Clean the wall;
2) Select products with stronger antifouling property;
3) Change the structural design of the building. The windowsill has dripping eaves and the roof has parapets.
10、 Pinhole
Phenomenon: A kind of hollow pin-tip pinhole phenomenon on the surface of the paint film. This pinprick hole is like a pinprick hole, with a diameter of about 100 microns.
reason:
1) The surface treatment of the board is poor, there are many wood hairs and thorns, and it is difficult to fill;
2) The bottom layer is not completely dry, so the second construction is required.
3) The prepared paint did not stand for a period of time, the viscosity of the paint was high, and the bubbles were not eliminated.
4) One-time construction is too thick.
5) Wrong matching of curing agent and diluent;
6) Too much curing agent is added.
7) High ambient temperature and humidity;
Wood has a high moisture content.resolvent:
1) The blank of the plate shall be polished and then sealed with Didebao;
2) In case of multiple construction, the recoating time shall be sufficient, and the second time shall be carried out after the lower layer is fully dry;
3) The prepared paint shall be left standing for a period of time, and the construction shall be carried out after the bubbles are completely eliminated;
4) The viscosity of paint should be suitable, not too thick;
5) One-time construction should not be too thick, and the "thin brush multiple times" should be achieved. Generally, the thickness of single layer should not exceed 20 μ m。
6) Use the specified curing agent and diluent, and construct according to the specified proportion.
7) Do not work when the temperature and humidity are high.
Before construction, the wood shall be dried to a certain moisture content, generally 10-12%.11、 Blister
Phenomenon: After the paint film is dry, there are raised round bubbles of different sizes, also called blisters. Blistering occurs between the coated surface and the paint film, or between two layers of paint film.
reason:
1) The treatment of base material is unsatisfactory, such as high moisture content of wood, or the aromatic oil contained in pine resin and wood itself is not removed, which will cause blistering when it volatilizes naturally.
2) When the oily or water-based putty is not completely dry or the primer is not dry, finish the surface coating.
3) The joints and holes of wood are not filled, and there are gaps, holes, etc.
4) The paint viscosity is too high.
5) Improper paint mix.
6) When brushing, drag the brush back and forth, and the resulting bubbles are not eliminated.
7) There are oil stains, dust, blisters, etc. on the surface of the substrate, and there is water around these dirty objects.
There is water in the compressor and air pipe, or water splashes on the construction surface.9) Most of the reasons are the same as pinholes.
settlement:
1) The wood shall be dried to a suitable moisture content and aromatic oil or rosin shall be removed from the wood.
2) The surface coating shall be applied after the putty and bottom coating are fully dried.
3) The gap and wood hole at the wood joint shall be filled with putty, and then painted after polishing.
4) Clean up the sundries on the surface of the base material. Do not touch it with your hands. After cleaning, the coated surface can be coated.
5) The construction viscosity of paint shall be appropriate.
6) When brushing, do not drag back and forth, first horizontally, then vertically, and finally straighten in the direction of wood grain.
7) Drain the water in the compressor regularly and install an oil-water separator.
Refer to pinhole countermeasures.9) The slight bubbles can be polished with abrasive paper after the paint film is dry, and then the top coat can be repaired. In case of serious bubbles, first pick up the bubbles, carefully polish them with sandpaper and clean them, and then repair them layer by layer according to the coating process.
12、 Blanching
Phenomenon: the film contains water or other liquid, the color of the film is lighter than the original, and the film appears white fog.
reason:
1) The moisture content of the board is too high, and the water volatilization remains in the paint film over time, resulting in whitening;
2) The ambient humidity is too high;
3) The construction surface, container and paint are mixed with water;
4) The diluent volatilizes too fast;
5) The moisture contained in the bottom paint film is not removed;
6) For dark boards such as black walnut, paint with poor transparency is used because of the transparency problem;
7) The paint is too thick;
The curing agent is wrongly matched, and it is not compatible with the paint and turns white.Solutions:
1) Before construction, the board shall be dried to control the moisture content of the board below 12%;
2) Paint with good transparency shall be used for construction of dark plates;
3) Do not apply paint at one time;
4) Do not work at high humidity. If necessary, add proper slow dry water;
5) The construction surface shall be clean and free from moisture;
6) Do not mix water in the paint and container;
7) Use the specified thinner and curing agent;
The water for the bottom coating should be dried, especially when using water grinding.13、 Undercut
Phenomenon: undercut refers to the peeling and uncovering phenomenon caused by the solvent in the upper coating softens and swells the bottom paint film, resulting in poor adhesion of the bottom paint film.
reason:
1) Apply the finish coat before the primer is completely dry, and the solvent in the finish coat will easily dissolve and soften the primer, causing undercut.
2) When brushing the top coat, the operation is not fast, and if the number of times of repeated brushing is too much, the phenomenon of undercutting will occur.
3) For oily paint film and some synthetic resin paint film modified by dry oil, once it meets with strong solvent, the primer paint film will be eroded before it is highly oxidized and polymerized. If the primer is phenolic paint and the finish is nitrocellulose paint, the solvent in the nitrocellulose paint will bite the oily phenolic paint and separate it from the original adhesive base.
4) The amount of curing agent for the previous coating is insufficient, and the crosslinking is not sufficient;
5) The two coats are not matched.
settlement:
1) The surface coating shall be brushed after the bottom coating is completely dry.
2) When brushing solvent-based paint, it is necessary to be skilled, operate accurately and quickly to prevent repeated brushing.
3) The primer and surface coating shall be used together.
4) For serious undercut, the coating shall be completely removed, and the same type of coating shall be applied after drying.
14、 Particles
Phenomenon: dust, flying flocs, foreign matters, etc. are attached to the film surface.
reason:
1) There are dust, sand and other sundries mixed into the paint.
2) When mixing paint, the bubbles generated in the paint liquid are not dispersed before construction, especially in cold weather, which is easy to cause the bubbles to not disperse, making the surface of the paint film rough after drying.
3) The construction environment is not clean, there are dust and sand particles falling in the paint, or there are sundries stuck on the brush tools such as oil brush.
4) The treatment of the base course is unsatisfactory, the grinding is not smooth, and the dust and sand particles are not cleaned.
5) Improper use of diluent, poor solubility, unable to completely dissolve the coating, causing particles.
6) Improper use of curing agent, incompatibility with paint, causing particles.
settlement:
1) The prepared coating must be filtered by filter cloth before brushing to remove sundries.
2) After the paint oil is prepared, it should be left for 10-20 minutes, and then used after the bubbles are dispersed.
3) Construction should not be carried out in windy weather or dusty places, and the paint just brushed should be dust-proof and contaminated.
4) The uneven part of the base layer shall be filled with putty, polished with sandpaper, and then brushed with paint after wiping off the dust.
5) Use matching thinner and curing agent.
6) The surface of the coating film has been rough, so it can be polished with sandpaper, and then brushed with finish paint again. For advanced decoration, sandpaper or sand wax can be used to polish it, and then polish, polish and polish it.
15、 Degreasing
Phenomenon: oil separation refers to local shrinkage on the surface of the coating film, as if water was sprinkled on the wax paper, and the speckles show the flower-like phenomenon of the bottom layer, which is also called fish-eye, laughing, shrinkage hole, etc.
reason:
1) The coating contains water, oil or oily wax;
2) The air compressor and pipeline are contaminated with water and oil;
3) The working environment is polluted, and the spraying facilities and tools are dirty.
4) Water, oil and other impurities are accidentally mixed in the paint;
5) Add defoamer and other chemicals without authorization;
6) The solvent vapor content in the environment is high and the ventilation is poor.
7) The bottom paint is of poor quality or contaminated.
settlement:
1) The coating shall be free from pollution and shall be polished thoroughly
2) Use oil-water separator and drain water regularly, once every two hours;
3) The workplace and tools shall not pollute the oil and wax, and the clothes and wiping cloth shall be cleaned before contacting the work objects. During the construction, pay attention not to let the sundries fall into the paint bucket. Keep facilities, paint mixing tanks and tools clean;
4) The old coating film shall be cleaned with solvent and polished thoroughly before painting.
5) Do not add other chemicals without authorization;
6) If "laughing" phenomenon is found during painting, stop painting immediately and wash the "laughing" part with solvent. After the surface is dry, paint again.
16、 No or slow
Phenomenon: After a period of time, the coating film still does not dry and does not harden
reason:
1) The coated surface contains water;
2) The amount of curing agent added is too small or the curing agent is forgotten;
3) Use thinner with water and high alcohol content;
4) The temperature is too low, the humidity is too high, and the drying condition is not reached;
5) The coating film is too thick at one time, or the interval between layers is short.
Countermeasures
1) Spray after the water is completely dry;
2) Add curing agent to mix paint in proportion;
3) Use the matching diluent provided by the manufacturer;
4) Spray in normal room temperature;
5) For two or more times of construction, the construction time between layers shall be extended. If the coating surface cannot be dried, the coating shall be removed or cleaned with cloth dipped with acetone.
17、 Loss of light
Phenomenon: the coating film is foggy and cannot obtain the expected gloss
reason:
1) The coated surface is rough and porous with large oil absorption;
2) Too much thinner and too little paint spraying;
3) Poor exhaust, spray paint mist falling on the sprayed film surface;
4) The diluent with low boiling point is selected, and the volatilization and drying are too fast;
5) The polished coating is polished without sufficient drying, or the polishing wax is too thick;
6) The construction environment is too high, the humidity is too high, the solvent volatilizes too fast, and the paint film whitens;
7) Rough grinding, or grinding with coarse sandpaper, with trachoma;
Dust is attached to the surface of the coating, and the paint powder is not removed;9) The paint is left for too long after adding curing agent.
Countermeasures:
1) Select a good plate, or first brush 1-2 times of primer (sealing paint) to seal the wood hole, apply putty to fill the gap, and polish it flat;
2) Control the proper viscosity of the paint and spray the proper amount of paint liquid with the correct method;
3) Maintain good exhaust;
4) Select the matching diluent provided by the manufacturer, or add the solvent with slow volatilization;
5) Polish the paint film after it is completely dry, and select the fineness of the wax;
6) There should be good temperature and humidity of coating operation, and slow drying solvent such as white water should be added properly;
7) Use fine sandpaper to carefully polish;
Clean the coated surface;9) After the paint is mixed, the construction shall be completed within 4 hours as soon as possible.
18、 Sagging
Phenomenon: the paint flows on the surface to be coated or at the groove of the line corner. The thickness of the paint film is uneven, and the serious one is like the paint curtain sagging, and the light one is like a string of tears.
reason:
1) Excessive diluent makes the viscosity lower than the normal construction requirements, and the paint can not be attached to the surface of the object to drop and flow.
2) The temperature of the construction site is too low, the drying speed of the coating is too slow, and the fluidity is large in the film forming process.
3) The selected paint brush is too large, too long, too soft, or too much oil is dipped in when brushing, and too much paint is brushed, which makes the paint thickness different, and the thicker part will flow.
4) The uneven brushing surface or the grooves of the edges, corners and line corners of the object are easy to cause uneven brushing and uneven thickness, and the thicker part will flow.
5) The surface to be brushed is not clean, with oil, water and other dirt, which can not adhere well and flow after brushing.
Countermeasures:
1) Select excellent paint materials and proper amount of thinner.
2) The construction environment temperature and humidity are appropriate.
3) The selected paint brush and bristles should be elastic, with thick roots and fine tips, and thick mane and neat mouth. The oil brush should be dipped less frequently.
4) During construction, the base course shall be leveled as much as possible and edges and corners shall be removed. When brushing, brush evenly with force, first vertically, then horizontally, and do not smear horizontally. Press lightly with an oil brush at the corners and edges of the line to dip the excess paint and brush it away, so as to prevent the paint film from being too thick and flowing.
5) The matching thinner of the paint shall be selected.
6) Thoroughly clean the debris, oil, water and other debris on the coated surface.
7) When the paint film is not completely dry and the paint falls on one side or one surface, the excess paint can be removed with a shovel and then brushed again. If the paint film is completely dry, the slight sagging can be smoothed with sandpaper, and the large area sagging can be smoothed with water mill, which has a good effect, but can only be operated manually.
19、 Brush mark
Phenomenon: There are traces of brush hairs on the paint film, and there are a few uneven brush lines after drying, making the paint film uneven in thickness.
reason:
1) The viscosity of the coating is too high, and the volatilization rate of the diluent is too fast.
2) In the wood products brushing, there is no parallel operation along the grain direction.
3) The selected oil brush is too small or the bristles are too hard or the oil brush is not properly kept, resulting in uneven or dry bristles.
4) The absorption capacity of the coated surface is too strong and it is difficult to brush.
Countermeasures:
1) Adjust the application viscosity of the coating and select the matching thinner.
2) During brushing, the first coat of paint shall be brushed along the direction of wood grain.
3) Soft oil brush should be selected and the oil handling action should be light. After use, the oil brush shall be cleaned with diluent and kept properly. The oil brush with uneven bristles shall not be used as much as possible.
4) Seal the base material with the sealing primer, and then brush the primer and finish coat.
5) The paint selected for brushing shall have good leveling property, and thinner with appropriate volatilization speed shall be selected.
6) When brush lines are found, they shall be gently polished with water abrasive paper, and dust shall be cleaned with clean rags, and then the paint shall be brushed again.
20、 Orange peel
Phenomenon: the surface of the coating film is not smooth, showing a concave-convex state such as orange peel
reason:
1) The paint is too thick and the thinner is too little;
2) The spraying pressure is too large or the distance is too close, the amount of spraying paint is small, and the distance is too long;
3) The temperature of the construction site is too high and the drying is too fast, and the paint cannot be fully leveled;
4) Excessive wind speed in working environment;
5) Use low boiling point thinner, and the solvent will volatilize when the paint mist reaches the coating surface;
6) After the curing agent is added, the construction will not be started until it is placed for a long time.
Countermeasures:
1) Pay attention to the paint proportion and paint mixing;
2) Fully skilled in the use of spray guns;
3) Improve construction site conditions;
4) Prevent painting in strong wind;
5) Use appropriate thinner to mix paint;
6) Use up as soon as possible after adding curing agent to mix paint.
21、 Cracking
Phenomenon: cracks of different depth and size appear on the surface of the paint film. If the lower surface can be seen from the crack, it is called "crack"; If the paint film shows a small crack in the pattern of tortoise back, it is called "chapping".
reason:
1) The primer is not matched with the top coat, and the film is subject to shrinkage stress due to external influences (mechanical action, temperature change, etc.), causing the film to crack or crack.
2) Apply (spray, brush, roll) the finish coat before the primer is dry, or the first coat of finish coat is too thick, and then apply the second coat of finish coat before the primer is dry, which makes the internal and external expansion of the two coats of paint inconsistent.
3) Interior paint is used for outdoor or metal surface primer is used for wood.
4) The pine resin contained in the wood substrate will seep out of the paint film and cause local cracking if it is not removed and treated.
5) The moisture content of the wood is too high, and it will deform over time and cause cracking;
6) Too much curing agent is added or wrong curing agent is used;
7) Construction is too thick;
The construction environment is harsh, the temperature difference is large, the humidity is large, and the paint film expands due to cold and heat, causing cracks.Countermeasures:
1) The primer and finish coat shall be matched, and the primer and base material shall be matched.
2) The next layer of paint shall be applied after the bottom layer is dry. The first layer of finish paint shall be thin and thin, and the second layer shall be applied after it is dry.
3) Select appropriate paint varieties, especially outdoor paint, and select paint with good weather resistance.
4) The pine resin of the wood substrate shall be removed, wiped with alcohol, and sealed with sealing primer.
5) Construction shall be carried out according to the specified proportion;
6) Do not overcoat, the total thickness should not exceed 150 μ m。
7) Construction shall be carried out under suitable environmental conditions, and the paint shall be fully mixed before painting.
The moisture content of wood shall be controlled below 12%.22、 Film peeling, peeling, bulging and peeling
Phenomenon: due to poor adhesion and bonding between layers of paint film, the paint film will fall off, peel off, bulge, peeling and other pathological phenomena.
reason:
1) The primer and topcoat are not matched, resulting in poor adhesion between layers.
2) The surface is dirty, stained with oil, water or other dirt.
3) Improper surface treatment. If the wood surface is embedded with putty or painted without polishing, so that the oil content of the finish paint is absorbed by it, resulting in falling off, and the wood surface is not effectively sealed.
4) The top coat is applied when the bottom layer is not dry, and cracks due to the inconsistent shrinkage rate of the bottom layer over time, thus affecting the adhesion between layers. The primer is too hard or the primer is very smooth, and the topcoat is applied directly without polishing.
5) The construction temperature is too low.
Countermeasures:
1) Select matching primer and finish paint.
2) Oil, water or other dirt shall be completely removed during the surface treatment of the substrate.
3) The base material shall be polished, trimmed and then putted. The primer must be dried and polished before applying (brushing, rolling, or spraying) the finish paint to increase the adhesion between layers.
23、 Rough paint film
Phenomenon: when the coating is applied on the surface of the object, there are many particles in the coating film. The particles are in the form of prickly prickly heat bumps, and the feel is rough and not smooth.
reason:
1) There are dust, sand and other sundries mixed into the paint.
2) When mixing paint, the bubbles generated in the paint liquid are not dispersed before construction, especially in cold weather, which is easy to cause the bubbles to not disperse, making the surface of the paint film rough after drying.
3) The construction environment is not clean, with dust and sand particles falling into the paint, or there are sundries stuck on the brush tools such as oil brush.
4) The treatment of the base course is unsatisfactory, the grinding is not smooth, and the dust and sand particles are not cleaned.
Countermeasures:
1) The prepared coating must be filtered by filter cloth before brushing to remove sundries.
2) After the paint oil is prepared, it should be allowed to stand for 15-20 minutes, and then used after the bubbles are dispersed.
3) Construction should not be carried out in windy weather or dusty places, and the paint just brushed should be dust-proof and contaminated.
4) The uneven treatment of the base layer shall be filled with putty, polished with sandpaper, and then brushed with paint after wiping off the dust.
5) The surface of the coating film has been rough, so it can be polished with sandpaper, and then brushed with finish paint again. For advanced decoration, sandpaper or sand wax can be used to polish it, and then polish, polish and polish it.
24、 Stickback
Phenomenon: After the coating film is dry, some or all of the coating surface has bonding traces
reason:
1) Too much slow drying solvent is added to the paint, and the solvent cannot volatilize;
2) Insufficient or no curing agent added;
3) The coating surface is polluted and dirty;
4) The climate changes suddenly during construction, and the humidity is high during construction in rainy season;
5) The coating is too thick, the interval between layers is not enough, and the paint film is not dry, that is, the packaging is overlapped.
Countermeasures:
1) Select proper dry solvent and do not add too much;
2) Add curing agent in proportion;
3) Keep the coated surface free from contamination;
4) During construction in bad weather, good ventilation shall be ensured to allow the solvent to volatilize fully;
5) Apply the upper layer after the lower layer is fully dry, and then pack and ship after the paint film is dry.
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