Analysis of the influence of season on film stability

The test results of paint materials under natural conditions are determined to a large extent by both the exposure season of the samples and the meteorological characteristics of the year. The same color paint film samples placed on the roof test station have completely different performance in different seasons.

The most serious damage to the paint film occurs during the first few days when the film is not yet sufficiently strong against the action of the atmosphere. Of course what is mentioned here is about air-dried materials.

As our observations have indicated, the worst damage to the paint film tends to occur in early spring. Under the climate conditions of Moscow in this season, a sharp change in temperature can be seen, for example from +12 to -19°C; in Tashkent the average maximum temperature in March is +27.7°C, and the bottom is -11.3°C . Such sharp temperature changes cause frequent deformations of the metal and the paint film (alternating contraction and expansion), and in many cases mesh twisting and cracking of the paint film and the associated rusting of the painted metal.

The corrosion process on the surface of those coatings that have cracked in spring or summer can be significantly accelerated by autumn rain.

Yakubovich and Golidberger studied the influence of the season of exposure on the results of experiments on the stability of a number of oil-based paints to atmospheric action. For this purpose, every 3 months identically painted sheets of iron are placed on the house station (in Moscow). It can be seen that the corrosion of the samples placed in autumn (September) is not serious. This can be explained by cooler temperatures in September and no significant change in temperature. By the time of autumn rains and first frosts (October to November), the freshly painted paint has been quite firm enough to withstand the damaging effects of the atmosphere. (Related instruments: air quality Detector)

Most of the paints are damaged faster in spring (March), because the film is deformed by the sharp change in temperature in the first few days before it is solid. The damage rate of the coating film placed on the roof in summer (June) ranks second.

The kinetic curves of the expansion of the corrosion process of the coated oxide iron and bright white iron plates subjected to atmospheric action in different seasons can represent the results of the above experiments (Figures 203 and 204). From graphs 203 and 204, it can be seen that the condition of the paint film after 24 months of exposure depends significantly on the season in which the sample is exposed. For example, 95% of the painted panels exposed in the spring had rot, 75% in the summer, 50% in the winter, and only 20% in the fall. From this, it can be concluded that the most suitable season for sun-painted paint films (and the season for outdoor finishing) should be autumn. (Related instruments: aging Test Chamber)

We 46 have drawn curve diagrams of the distribution of various damage phenomena that occurred when various coating films were tested under the conditions of the Moscow exposure station of HNNN-4 over several years. As shown in Figure 205, almost all damage phenomena have two peaks: one in May and another in August. In November, December, January and February, there was no significant external damage to the paint film except for loss of light, which occurs to varying degrees throughout the year. The damage process proceeds almost uniformly during the remaining months.

According to our observations, within a few months of spring, the color cracking of certain materials can reach 88% of the total number of samples subjected to the cracking test. The chalking process, such as that of enamel coatings, starts earlier in July, the hottest month. The model that was exposed to the sun in spring and cracked in summer will corrode in the places where cracks and nets are formed in autumn (September to October). The specimens exposed in the autumn remain unchanged in the autumn and winter, and only begin to deteriorate in the spring.

In order to most accurately evaluate the weather resistance of the coating film, it is best to expose the same coating film twice, that is, once in autumn and once in spring.