Common pathological conditions and causes of paint film The causes and preventive measures of pathological coating Product Inspection Report
The causes of pathological coating
1. The effect of surface tension on the coating film.
2. The influence of the equilibrium degree of paint solvents should comply with the theory of solubility parameters.
3. The impact of paint leveling.
4. The influence of solvent volatilization during the coating film formation process.
5. The influence of coating film-forming substances.
6. The effect of additives added to coatings.
7. The impact of appliances and environment during the painting process.

The causes and preventive measures of the top ten common coating diseases
1、 Orange peel
Cause of occurrence:
1. High construction viscosity and insufficient atomization degree.
2. Improper flash time for baking paint.
3. Improper selection of diluent.
Preventive measures:
1. Adjust the appropriate construction viscosity.
2. Add a solvent with a slower evaporation rate.
3. Add modified silane leveling agent.

2、 Shrinkage cavity
Cause of occurrence:The surface tension of the upper and lower parts of the wet film is different.
Preventive measures:
1. Pay attention to the surface treatment of the substrate to improve its wettability.
2. Choose a resin with low surface tension and good wettability to the substrate.
3. Add leveling aids or low surface tension solvents.

3、 Whitening
Cause of occurrence:The drying coating absorbs heat, causing water in the air to condense on the surface of the coating.
Preventive measures:
1. Adjust the solvent used for the coating and increase the solvent with a high Buddha point.
2. Avoid construction on rainy days.

4、 Floating white
Cause of occurrence:
1. Mainly related to the variety of white pigments used.
2. The addition of another paint base is related to the variety of pigments.
Preventive measures:
1. For light gray and light blue paints, titanium white with large particle size, wide particle size distribution, and low surface charge should be selected, such as using R-820 instead of R-930.
2. Increase the consistency of the construction paint solution, improve the volatilization rate of the solvent, minimize the use of polar solvents, and use more fatty solvents.
3. Try to avoid using two different paint bases.
4. Add pigment dispersant.

5、 Bubbles
Cause of occurrence:
1. The gas or liquid adsorbed by the paint film is released when conditions change (such as temperature rise).
2. Due to the release of gases dissolved in coatings due to temperature rise, especially when adding curing agents during the preparation of two component coatings, the heat generated by the reaction is the most common.
3. Bubbles generated during production or construction.
4. Residual air on the surface of porous substrates.
Preventive measures:
1. Wetting and dispersing agents are used in coatings to replace surface air, and the wetting and dispersing time of pigments is appropriately extended to improve their wetting and dispersing state.
2. For drying type coatings, extending the flash time opens the surface of the coating film to ensure the escape of bubbles.
3. Adjust the proportion of diluent to gradient the solvent evaporation process.
4. Add defoamer additives.

6、 Wire drawing
Cause of occurrence:The viscosity of the coating application is high, and the solubility of the diluent is poor.
Preventive measures:Select appropriate solvents and adjust to the appropriate construction viscosity.

7、 Pinhole
Cause of occurrence:
1. For drying type coatings, the flashing time of the wet film is too short, and during the drying and heating process, the initial heating is too fast or due to the spraying process, the wet film is too thick, and the surface of the wet film is too dry, resulting in poor evaporation of the underlying solvent.
2. For two-component polyurethane coatings, the bubbles generated during paint preparation or spraying do not disappear. During the drying process of the coating film, when the bubbles overflow, the film loses its fluidity, resulting in pinholes.
3. When there is a trace amount of water in polyurethane coatings or solvents, pinhole pathology is more likely to occur.
Preventive measures:
1. Strict selection of diluents, strict control of construction viscosity, and appropriate selection of diluents with slower evaporation rates to improve surface leveling.
2. Strictly check the cleanliness of compressed air and the degree of contamination on the surface of the coating.
3. When using two component coatings, they should be left for a period of time after preparation before use.

8、 Wrinkling
Cause of occurrence:
1. The drying type coating is applied too thick, and the wet film flash time is not enough, resulting in sudden high temperature and accelerated drying.
2. For oily paint and alkyd paint containing dry oil, improper selection of desiccants, excessive use of cobalt and manganese desiccants, and lack of zinc desiccants can cause wrinkling of the coating film.
3. When using the impregnation method for construction, the thick edge coating film with sagging is more prone to wrinkling.
Preventive measures:
1. When making alkyd paint, a reasonable selection of drying agents should be made, and manganese dry materials should be avoided as much as possible. When choosing tung oil as the film-forming material, pay attention to the appropriate degree of refining of tung oil.
2. If the self drying paint needs to be heated and dried, a small amount of high boiling point melting should be used, and the wet film should be fully air dried at room temperature to prevent the wet film from wrinkling due to rapid heating.
3. During construction, the coating should not be too thick.

9、 Gelatinization
Cause of occurrence:
1. Pigments have high water content or contain alkaline substances, resulting in soap formation from fatty acids.
2. Excessive catalytic crosslinking of free acids in alkyd amino baking paint leads to thickening and gelation of the system.
3. Some additives exhibit strong thixotropy and gelation, such as BYK-203, which produces a phenomenon similar to gelation when encountering resins with high molecular weight and low polarity.
Preventive measures:
1. Carefully select pigments to avoid high moisture content or other alkaline impurities.
2. Increase the amount of butanol or add anti gelatinizing agents such as trimethylamine in alkyd amino baking paint. Especially in the summer when the temperature is high, attention should be paid.

10、 Poor interlayer adhesion
Cause of occurrence:
1. Improper matching of the primer or improper surface treatment during repainting can cause the topcoat to become brittle and peel off.
2. For amino baking paint, the second topcoat was not polished with sandpaper or wiped with solvent.
3. The use of inappropriate silane leveling agents and excessive amounts in coatings.
Preventive measures:
1. Pay attention to the matching of the primer and topcoat, as well as surface treatment of the primer. For example, for spraying a gloss varnish on a self drying aluminum powder paint, thermoplastic acrylic resin with a lower Tg point should be used as the paint base to avoid cracking of the topcoat.
2. Adopt the "wet to wet" process and try to use a one-time drying method. Choosing a resin with good recoating performance can also avoid the problem of poor interlayer adhesion.
3. Try to avoid or minimize the use of silane based leveling agents.
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