During the storage and use of oxidative drying varnishes and basecoats, crusting often occurs, which not only affects the film-forming performance and color stability of the coating, but also may lead to the degradation of the construction quality of the coating. Therefore, the determination of crusting property has become one of the important indicators to evaluate the storage stability of coatings. In this article, we will introduce the two main methods for determining the crusting properties of coatings and their operation steps.
The containment test is designed to simulate the possible crusting of the paint after prolonged storage in an airtight container.
Test Equipment and Specimen Preparation:
Use a 125mL wide-mouth grinding glass bottle or a 0.33L lacquer can.
The specimen is packed into a glass bottle or lacquer can, and the sample amount should be accurate according to the standard requirements.
When the glass bottle is tightly capped, the paint can is open, but the specimen should be 15mm away from the top of the can.
Test conditions:23±2℃, protect from light for 48 hours.
At the end of each 48-hour cycle, the lid is opened to check the surface of the paint for crusting.Three consecutive cycles of the examination were performed, with a 5-minute ventilation time between each cycle.
Result:If no crusting is observed within three cycles, it is confirmed that the coating has good anticrusting properties under closed conditions.
The open can test is designed to simulate the crusting velocity of the paint during its actual use after the can has been opened.
Test Equipment and Specimen Preparation:
The specimen is loaded into a paint can, usually to a depth of half the volume of the can.Keep the lid of the paint can open and keep the paint surface in condition.
Test process:
At room temperature, always observe whether the surface of the paint in the paint can begins to form crusting. suggestionAt the same time, an open-tank test of a sample of known properties is carried out for comparison.
Result:
The timing and morphology of crust onset can be used to evaluate the crust properties of coatings, often compared to samples of known properties.
Through the airtight test and the open tank test, the crusting tendency of oxidation-dry coatings during storage and use can be comprehensively evaluated. These measurement methods can not only help manufacturers optimize coating formulations and improve the stability of coatings, but also help users choose products with consistent quality when purchasing and using, so as to ensure good application and long-term use of coatings. In practical application, combined with standardized detection methods and instrument-assisted measurement, it can more accurately evaluate the crust performance of coatings, and provide scientific basis and technical support for the development and application of the coating industry.