Coating adhesion test standard for thermos cups: the key to ensuring product quality

Coating adhesion test standard for thermos cups: the key to ensuring product quality

In the production and wholesale procurement process of thermos cups, coating adhesion is a crucial quality indicator. It not only affects the appearance and service life of the thermos cup, but also the safety and reliability of the product. This article will explore the various standards for the adhesion test of thermos cup coatings in depth to help you better understand this key link.

The importance of coating adhesion
Protective function: The coating can prevent the metal surface of the thermos cup from corrosion and oxidation, and extend the service life of the product. Good adhesion can ensure that the coating is not easy to fall off during long-term use and continues to play a protective role.
Aesthetics: A uniform and firm coating can make the thermos cup more beautiful and colorful. Coatings with poor adhesion are prone to peeling and fading, affecting the visual effect and market competitiveness of the product.
Safety: If the coating falls off due to poor adhesion, it may be mixed into food or beverages, posing a potential threat to consumers’ health.

Common test standards for the adhesion of thermos cup coatings
GB/T 29606-2013 “Stainless Steel Vacuum Cups”
This is a national standard widely followed by the stainless steel vacuum cup industry in my country. It specifies the test method for the adhesion of thermos cup coatings, that is, using a single-edged cutting tool with a blade angle of 20°~30° and a blade thickness of (0.43±0.03) mm, vertically and evenly apply force on the surface of the tested coating to scratch 100 (10×10) 1mm² checkerboard grids with a depth of bottom.
Then stick a 25mm wide pressure-sensitive adhesive tape with an adhesive force of (10±1)N/25mm on it, peel off the tape with force at right angles to the surface, and calculate the number of residual checkerboard grids that have not been peeled off. Generally, the coating should retain more than 92 checkerboard grids.
GB/T 40355-2021 “Stainless Steel Vacuum Insulated Containers”
This standard applies to daily stainless steel vacuum insulated containers that come into contact with food. The test method and requirements for the adhesion of the coating on the thermos cup are similar to GB/T 29606-2013. The test is also carried out using the cross-cut method, requiring the coating to have high adhesion to ensure the quality and safety of the product.
EN12546 “Thermal Insulated Containers”
This is one of the commonly used European test standards for thermal containers, and it also has clear provisions for the adhesion of the coating on the thermos cup. It requires that the coating must have sufficient adhesion to withstand various conditions that may be encountered during normal use, such as temperature changes, mechanical shock, etc.
The test method may include placing the thermos cup in a specific environment, such as high or low temperature environments, and observing the changes in the adhesion of the coating to ensure the stability and reliability of the product in different environments.

Specific methods for coating adhesion testing
Cross-cut method
The cross-cut method is currently one of the most commonly used, simple and effective coating adhesion test methods. During the test, a special gridding tool is used to scratch a grid pattern of a certain size on the surface of the coating. The depth of the gridding should penetrate the coating to the substrate.
Then stick the tape on the grid, and then quickly tear off the tape to observe the coating being stuck by the tape. The adhesion level of the coating is evaluated by calculating the percentage of the number or area of ​​the remaining grids to the total number or area of ​​the grids.
Tape sticking method
Stick the tape directly on the surface of the coating, and then quickly tear off the tape at a certain angle and force to observe whether the coating is torn off from the substrate. This method is simple and quick to operate, but the test results are relatively subjective and are greatly affected by factors such as the stickiness of the tape and the tearing angle.
Circle method
Use a rotating circle device to make the needle draw a circular track on the surface of the coating while applying a certain pressure. The adhesion of the coating is judged by measuring the depth and width of the scratches and the shedding of the coating.
Pendulum drop method
The coated thermos cup is fixed on a specific device, and the pendulum is made to fall freely from a certain height, hitting the surface of the thermos cup, and observing the shedding of the coating under impact. This method is mainly used to test the adhesion performance of the coating when it is subjected to mechanical impact.

Factors affecting coating adhesion
Material factors
The quality and performance of the coating are one of the key factors affecting the adhesion of the coating. High-quality coatings have better adhesion and adhesion, and can form a uniform and firm coating on the surface of the substrate.
The surface treatment condition of the substrate also has an important influence on the adhesion of the coating. If there are impurities such as oil, dust, and oxide layer on the surface of the substrate, it will hinder the adhesion between the coating and the substrate, resulting in a decrease in the adhesion of the coating.
Process factors
The control of coating process parameters is crucial to the adhesion of the coating. For example, parameters such as temperature, humidity, and pressure during spraying will affect the leveling and curing effect of the coating on the surface of the substrate.
The temperature and time during baking or drying also need to be strictly controlled. If the temperature is too high or the time is too long, the coating may be over-cured, making the coating brittle and reducing adhesion; if the temperature is too low or the time is too short, the coating will not be fully cured, affecting the performance of the coating.
Environmental factors
During the use of the thermos cup, it may be affected by various environmental factors, such as temperature changes, humidity, ultraviolet radiation, etc. These factors may cause the adhesion of the coating to decrease, causing the coating to peel off, fade and other problems.
How to improve the adhesion of the coating
Strictly control the quality of materials
Choose a suitable coating supplier to ensure that the coating used has good quality and performance. At the same time, strictly inspect and treat the substrate to ensure that its surface is clean and free of impurities to improve the adhesion of the coating.
Optimize the coating process
According to the characteristics of the coating and the material of the thermos cup, formulate reasonable coating process parameters, and strictly control the temperature, humidity, pressure and other conditions during the coating process. At the same time, pay attention to the temperature and time control during baking or drying to ensure that the coating can be fully cured to form a uniform and firm coating.
Strengthen environmental adaptability design
In the design and production process of the thermos cup, consider the diversity and complexity of its use environment and carry out corresponding environmental adaptability design. For example, adding additives such as UV absorbers can improve the UV resistance of the coating; using special moisture-proof and rust-proof treatment processes to enhance the adhesion and anti-corrosion performance of the coating in a humid environment.
Quality Inspection and Control
Establish a complete quality inspection system to strictly inspect the adhesion of the thermos cup coating. In addition to routine testing in accordance with national standards and industry specifications, some test items that simulate the actual use environment can be added according to actual conditions, such as high temperature and high humidity testing, salt spray testing, etc., to comprehensively evaluate the adhesion performance of the coating.
Carefully analyze and evaluate the test results to promptly discover and solve problems with coating adhesion. For products with unqualified adhesion, the causes should be investigated and improved to ensure that the product quality meets the requirements.

Application of coating adhesion test in thermos cup quality control
Quality monitoring during production
On the production line of the thermos cup, regular sampling and testing of coating adhesion is carried out to promptly discover coating adhesion problems that may occur during the production process. By adjusting and optimizing raw materials, process parameters, etc., ensure that each batch of products has good coating adhesion and improve the stability and consistency of product quality.
Product quality acceptance
In the factory inspection and wholesale purchase acceptance of thermos cups, coating adhesion test is an important quality control indicator. Buyers can determine whether the product meets the quality requirements and whether it can meet market demand by testing the coating adhesion of the product. For products whose adhesion does not meet the standard, buyers can ask the manufacturer to make rectifications or return them to safeguard the rights and interests of consumers and their own business reputation.
Product improvement and research and development
The coating adhesion test results can provide an important reference for the improvement and research and development of thermos cups. By analyzing the test data, R&D personnel can have an in-depth understanding of the impact of different materials, processes and design schemes on coating adhesion, so as to develop more competitive thermos cup products.

Summary
The coating adhesion test standard for thermos cups is an important basis for ensuring product quality and performance. Whether it is the domestic GB/T 29606-2013, GB/T 40355-2021 standards, or the international EN12546 standards, the test methods and requirements for coating adhesion are clearly defined. In the actual production and wholesale procurement process, we should strictly follow these standards, adopt scientific and reasonable testing methods, and strengthen the quality control of coating adhesion.