The impact of the environment on the coating
Galvanized metal structures are used both indoors and outdoors. The more the surface will be exposed to moisture, the sooner the protection will decrease. Over time, the protective function can be reduced by various contaminants (both the surface and the surrounding atmosphere). As a rule, the air ceases to be clean due to a number of factors, these include:
- precipitation (rain, snow, hail);
- the level of humidity;
- the temperature in the room or on the street;
- the level of salts and sulfur dioxide in the air.
Separately, they do not play a special role, but together take part in the formation of corrosion on the surface. To track how the zinc coating behaves in certain conditions, experts conducted a number of studies. Several environments were taken into account: rural, tropical-marine, industrial, moderate-marine, suburban. Such studies have demonstrated the real characteristics of the steel, which was galvanized by the hot method. At the same time, the tests were carried out not in an accelerated, but in the usual mode. Some manufacturers accelerate inspections, which can not have a positive impact on the quality of galvanized metal.
In fact, the rate of corrosion of zinc in almost all conditions does not go beyond 0.3 for 12 months. And, of course, if the galvanized structure is used indoors, its service life will be several times higher. As mentioned above, during the tests 5 natural environments were created, each of which has its own characteristics, and we will dwell on them in more detail. It is necessary to classify the corrosion.
- Industrial environment-is considered the most aggressive, because its atmosphere contains chemicals. Among them are phosphates and sulfides. A simple example is the exhaust gases of vehicles. That is why the structures used in urban environments, which belong to the moderate-industrial zone, corrode the most.
- Moderate-marine environment-the degree of corrosion is slightly lower than tropical-marine, because the humidity level is much less. The rate of corrosion is most often influenced by the speed and direction of the wind, the distance from the sea, as well as chlorides contained in the air.
- Tropical-marine environment – it is often equated with industrial, because it is characterized by an increased level of corrosion due to the high content of salts, chlorides in the air. It rarely reaches the temperature of freezing water, which means that the atmosphere is a lot of moisture, which adversely affects the galvanized coatings.
- Rural environment-the most gentle environment, which is typical for areas with residential and technical buildings. It did not find a high content of sulfur, so it is considered quite favorable.
Suburban environment is a zone typical for suburban areas where there are no industrial facilities. In such an environment, zinc-coated metal structures can be used for as long as possible.