The performance requirements of high temperature paint and the corresponding test standards are analyzed

0 Introduction
paint, as the name implies, is to provide corrosion protection for steel structures at high temperature coatings. Its anti-corrosion protection performance is reflected in two aspects: first, for the steel structure in the environment of water vapor and other corrosive substances shielding effect, and second, for high temperature resistance, to ensure that the coating in high temperature environment, can still be firmly attached to the steel structure surface, to provide corrosion protection.
It is well known that the corrosion rate of steel structure is related to many factors, such as temperature and humidity, among which ambient temperature is the key factor: the higher the temperature, the faster the corrosion speed, the higher the performance requirements for anti-corrosion coatings . At the same time, however, the rate of corrosion is inversely inversely related to the moisture content in the environment, and in high temperature environments, the increase in temperature leads to a decrease in the moisture content in the surrounding environment, thus slowing the corrosion rate. The test results show that for steel structures in open environment, the ambient temperature is dominant to the corrosion rate below 150 degrees C, and the higher the ambient temperature, the more severe the corrosion, more than 150 degrees C, and the corrosion rate decreases gradually with the decrease of water content in the environment. At more than 200 degrees C, the water content in the environment is very low, its corrosion is very small. The NACESP0198-2010 and EFC 55 standards state that if the temperature of the equipment is below 175 degrees C, it needs to be protected against corrosion, and if the temperature of the equipment is above 175 degrees C, the corrosion rate is very low, even without corrosion protection.
the above theory, steel structures in high temperature environments above 175 degrees C can be protected from corrosion protection. However, in practice, the equipment can not always operate in high temperature environment, due to equipment maintenance and downtime problems, its temperature will always drop below 175 degrees C, or even room temperature. This condition determines that no matter how high the operating temperature of the equipment, it needs to be protected against corrosion, taking into account maintenance and downtime.1 Comparison of high temperature paint test standards at home and abroad
the characteristics of the operation of high temperature equipment, decided that anti-corrosion coating for equipment protection is mainly reflected in two points: First, the coating can withstand high temperature, to ensure that in high temperature environment, the coating does not crack and failure; At present, the test of high temperature paint has not unified standards, especially in China, for high temperature paint has no specific requirements, even in the petrochemical industry, the largest demand for high temperature paint, for high temperature paint support also only provides supporting guidance, and for coating performance has no clear requirements, usually on the basis of routine performance testing, testing its high temperature resistance performance.
test standards for high temperature paint in China are relatively simple, but simply test the performance of coatings at high temperatures. GB 1735-2009 "Color paint and varnish heat resistance determination" is the test standard for high temperature anti-corrosion coatings. The test method is to prepare the paint film on 4 thin steel plates, and after the paint film is dry, place 3 paint samples in a blowing thermostat or high temperature furnace at a set temperature. After reaching the specified temperature, the model will be taken out, compared with the original model, while checking whether there are layers, wrinkles, blisters, cracking, color change and other phenomena.
International standard ASTM D 2453 Performance test method for high temperature paint is to make a model according to the standard, put the model in a high temperature furnace, after reaching the specified time, quickly put the model in cold water cooling, and then put in a high temperature furnace, repeated circulation. The entire testing process is as follows: 205 degrees C (400 degrees F), 8 h, put in cold water to cool down quickly, 260 degrees C (500 degrees F), 16 h, put in cold water to cool down rapidly, 315 degrees C (600 degrees C) After 8 h, put in cold water to cool down rapidly, after 370 degrees C (700 degrees F), after 16 h, put in cold water to cool down quickly, 425 degrees C (800 degrees F), 8 h, put in cold water to cool down quickly. At the end of the entire cycle, look at the defects of the model and check for layers, wrinkles, blisters, cracking, color change, etc. At the same time, it is also recommended to carry out routine corrosion resistance test on the model after high temperature testing.
As can be seen from the above, the TEST method of ASTM D 2453 is closer to the actual operating conditions, which increases the temperature change and cycle testing process, and the corrosion resistance test is recommended for steel structure after high temperature testing, so that the comprehensive protection performance of the coating can be evaluated objectively.protection under the
2 insulation layer simulates the characteristics of steel structures in open environments and evaluates the corrosion resistance of coatings. However, no specific requirements are put forward for the steel structure under the insulation layer. In fact, the steel structure under the insulation layer, due to the high temperature and humidity of the environment, its coating in the high temperature environment corrosion performance requirements are more stringent. AsTM G 189 simulates the process under the insulation layer and evaluates the performance of the coating at high temperatures. The test method is as follows: In this standard, a high temperature and humidity environment is simulated for the component first, as shown in Figures 1 and 2.
test components to select a hollow steel pipe, the interior has an electric heating rod, the outer wall of the component coated with anti-corrosion coating matching. The entire outer wall has a insulation layer, while constantly replenishing the insulation layer to maintain a high temperature and high humidity corrosion environment on the steel surface. This device controls the temperature and humidity of the components, thus providing a comprehensive assessment of the corrosion resistance of the coating in a variety of temperature and humidity environments.3 Conclusion
The environment of the high temperature equipment determines its special requirements for anti-corrosion coating, which not only ensures the stability of the coating at high temperature environment, but also provides corrosion protection to the steel structure at room temperature, especially the steel structure under the insulation layer. In order to ensure the performance of coatings in practical applications, a comprehensive assessment of coating performance at high temperatures is required in the laboratory. In order to ensure the accuracy of the test results, it is necessary to simulate the experimental process of a real environment as far as possible, according to the actual application of operating conditions, select the corresponding high temperature test standards.