Take a look! Your paint peeling might be because of this
Paint film adhesion refers to the ability of a coating to firmly adhere to another coating or to the surface of a substrate through physical action or chemical reaction. It indicates the firmness between the paint film and the coated substrate. Coating thickness, drying conditions, substrate condition and properties directly affect the paint film adhesion. A paint film with good adhesion is durable and has the required performance; a paint film with poor adhesion is prone to cracking and peeling and cannot be used.
So what does paint adhesion have to do with? Below, Jin Feima Coatings will show you some basic factors related to the strength of adhesion:
Substrate Treatment
Polishing the substrate not only increases the mechanical bonding strength, but also facilitates surface wetting. If the substrate surface is not treated to increase adhesion, and the substrate is extremely smooth or rusty, the coating cannot find an anchoring point, resulting in a lack of adhesion, and is prone to peeling, delamination, and cracking. A rough surface has a larger contact area with the coating, thus strengthening the paint film adhesion.
Influence of Coating Viscosity
When the coating viscosity is low, it is easy to flow into all parts and pores of the substrate, resulting in higher mechanical bonding strength; when the coating viscosity is too high, it will cause coating waste or even blockage of the spray gun nozzle. Therefore, please refer to the matching ratio provided by the manufacturer for the dilution of the coating.
Coating Condition of the Substrate Surface
To obtain good adhesion, it is necessary that the coating completely wets the substrate surface. Pure metal surfaces usually have high surface tension, while coatings generally have lower surface tension, so they are easy to wet. However, the actual metal surface is not pure, and oxides are easily formed on the surface, and various organic or inorganic pollutants can be adsorbed. If organic substances are adsorbed on the surface, the surface tension can be greatly reduced, making wetting difficult. Therefore, the substrate needs to be treated before coating. For substrates with low surface energy, appropriate treatment is even more necessary.
Influence of Internal Stress
The internal stress of the coating is an important factor affecting adhesion. There are two sources of internal stress: ① shrinkage stress generated by volume shrinkage during coating curing; ② thermal stress generated by the difference in thermal expansion coefficients between the coating and the substrate when the temperature changes. No matter what method is used to cure the coating, some volume shrinkage will inevitably occur. Shrinkage can be caused by solvent evaporation or chemical reaction. Internal stress affects the paint film. Internal stress is an important factor affecting adhesion. If the internal stress is too large and greater than the cohesive force of the coating, the coating will crack; if it is greater than the adhesion of the coating, the coating will peel off and other damage will occur, losing its protective function. Reducing volume shrinkage during the curing process is of great significance to improving adhesion.
Influence of Coating Matching
During the drying process of the paint film, the solvent of the upper coating will have a certain degree of dissolving effect on the lower coating. At this time, if the connecting coatings are not related and cause a chemical reaction, it will cause a decrease in adhesion, or even peeling of the paint film. Therefore, please be sure to consult the relevant matching and construction process before construction.
Contact Us
Phone:18541015000
Address: No. 21, 102 National Highway, Yilu Garden, Tieling County Industrial Park, Tieling City, Liaoning Province
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