【ALUMINIUM NETWORK】All coated products are used in the atmospheric environment and are eroded by moisture and other chemical components in the air. The purpose of painting the products is to make them resistant to the use of the products. The ability to erode and extend its useful life. Therefore, the chemical resistance of the coating is an important quality indicator and must be tested.

The chemical resistance and corrosion resistance of the coating film are mainly tested as follows: the resistance to damage caused by exposure to chemical media, such as water resistance, salt water resistance, petroleum resistance, chemical resistance, etc. Resistance to material damage in the atmosphere is measured, such as resistance to moisture, resistance to contamination, resistance to chemical gases, and resistance to mold. The ability to prevent the medium from causing corrosion of the substrate, such as corrosion resistance, rust resistance, etc., is usually expressed in terms of damp heat test, salt spray test and water vapor permeability test.

1, water resistance coating coating testing products in actual use are often in direct contact with the humid air or water, with the expansion of the film and water permeability, there will be blistering, discoloration, loss, adhesion and other destructive destruction The phenomenon directly affects the service life of the product. Therefore, the water resistance of the coating must be tested. The main factors influencing the water resistance of the coating film are: the component materials that make up the coating; the surface treatment quality and coating quality of the coated product;

At present, the commonly used methods for measuring water resistance include normal temperature immersion method, immersion boiling method, and accelerated water resistance method.

(1) At room temperature, water immersion method is widely used at room temperature. Applicable to the vast majority of varieties such as alkyd, amino paint. The national standard GB1733-93 (confirmed in 1988) specifies the method and requirements for specific inspection of the water resistance of coating films.

(2) Immersion boiling water detection method The immersion boiling water detection method is used for coating films that often contain hot water, hot soup and other utensils. During the measurement, the painted sample plate is immersed in boiling distilled water in 2/3 area, and the sample is taken out after a specified time of product to observe the change of the coating film to evaluate the water resistance of the coating film.

(3) Accelerated water resistance method In order to shorten the testing time, specific operations are performed according to the national standard GB5209-85 "Paint and Varnish - Determination of Water Resistance - Immersion Method". The results can be seen on the same day.

2. If the salt water resistance test film is not only immersed in water but swelled in salt water, it is also subject to the strong corrosion damage caused by the penetration of chloride ions in the solution. Therefore, the salt water resistance test can be used to detect the corrosion resistance of the coating.

At present, the sodium chloride solution with a mass fraction of 3% is used to soak the 2/3 area of ​​the test plate, and the change of coating film is taken out after the time specified by the product. It can also be tested according to the specified method according to the national standard GB1763-79 (confirmed in 1989).

3, resistance to oil product testing due to the development of the petroleum industry, petroleum products have been widely used, a variety of oils and solvents, these products have a certain degree of erosion of the coating. Different products stipulate the tolerance standards for different petroleum products, and the most common one is gasoline resistance.

The gasoline resistance test is to determine the coating film's resistance to gasoline. Tested under the specified conditions, observed whether the coating film discoloration, loss of light, white, foaming, softening, falling off and other changes. The specific test method can be carried out according to the GB1734-93 “Determination of paint film gasoline resistance”. It can also be tested according to the test method specified in the paint product standard.

4. Test of chemical resistance In the process of use, the coating film is often destroyed by dry etching of industrial chemicals such as acids, alkalis, salts, and organic solvents, and the coating resists the “dry etching”. "The ability is chemical resistance. This is also one of the important items for coating film performance testing. The main test content such as acid resistance, alkali resistance, solvent resistance, pollution resistance (resistant to household chemicals) and so on.

Specific test methods can be determined according to GB 1763-79 (confirmed in 1989) "Determination of chemical resistance of paint film", G ratio 9274-88 "Determination of liquid paint resistance of paints and varnishes", GB 9265-88 "Architecture paint coating "Alkaline resistance measurement" and other methods specified by the standard.

5. Corrosion resistance of coating film The corrosion resistance of the coating film refers to the corrosion resistance of the coating film to the wet environment. This property is an important performance that is very much needed for coating products used in the tropics or subtropics. Can be tested according to the requirements of the product.

6. Contamination resistance of the coating film In the course of use, the coating often exposes and contacts harmful media in the atmosphere. The coating is subject to various damages to varying degrees, such as dust, oil spots, dirt, and the like. This is where the coating is contaminated, and the ability of the coating to resist this contamination is called contamination resistance.

This kind of performance is very important for some paint products, such as architectural coatings, transportation vehicles, cars' surface coatings have higher requirements for pollution resistance, so this is also one of the major testing items.

The method of detection is to expose the test panel to the atmosphere for a certain period of time, and then use a color difference meter to measure the reflection value before and after the exposure of the paint film. The difference can be considered as the result of the pollutant. The smaller the difference is, the better the stain resistance is. Strong.

7, anti-fungal film coating test If the coating product in the (15 ~ 35) °C, relative humidity of more than 80% of the environment used, more susceptible to all kinds of mold erosion, so that the coating was destroyed. The anti-mycotic requirements for coating products used in this environment are necessary. Therefore, the coating must be tested for anti-fungal properties.

The method for detecting the anti-mold of the coating film shall be tested according to the environmental conditions in different regions and the mold species using the corresponding test methods. The method may also be tested according to the method specified in the coating product standard.

8. Corrosion test of the coating film The corrosion resistance of the coating film means that the coating film resists the effect of foreign media to prevent the substrate from being corroded. There are many factors that cause stories and they are ubiquitous, often resulting from a combination of actions. For this reason, it is difficult to be able to objectively and correctly corrode the corrosion resistance of paints, and it is also one of the more complex issues of corrosion resistance when designing and producing paint products.

The actual method for evaluating the corrosion resistance of a coating film is a physical test. The physical test conditions are complex, the time is long, and there is considerable difference with the actual use environment. At present, more methods such as salt spray test, damp heat test, water vapor permeability test, etc. are simulated using methods such as laboratory tests, but they are still not perfect. Several methods were performed simultaneously, and the obtained test results were comprehensively evaluated for the corrosion resistance of the paint film.

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