The gas tank is part of the air compressor post-processing equipment, mainly for gas storage, buffering, pressure reduction, drainage and other functions. After long-term use or years of use, it is inevitable that corrosion from air, rain or humid atmosphere will occur. These are caused by the action of water, oxygen, acidic pollutants and other substances in the atmosphere. The main material of the gas tank is steel. The rust of steel under the natural environment of the atmosphere is one of the most common atmospheric corrosion phenomena.
Reasons for rust or corrosion of gas tanks
Three types of atmospheric corrosion:
a. Dry atmospheric corrosion. At this time, there is basically no water vapor in the atmosphere, ordinary metals form an invisible oxide film at room temperature, and the surface of steel remains glossy.
b. Humid atmospheric corrosion. It refers to the corrosion of metal under a thin film layer that is invisible to the naked eye. At this time, there is water vapor in the atmosphere. When the water vapor concentration reaches the critical humidity (the critical humidity of iron is 65%, and the critical humidity of copper is close to 100%), there is a very thin layer of water film on the metal surface, and uniform corrosion will occur. If there are pollutants such as CO2, H2S, SO2, etc. in the atmosphere, corrosion will be significantly accelerated. Steel corrosion under atmospheric conditions is actually electrochemical corrosion under water film conditions.
c. Corrosion of gas tanks under visible liquid film conditions. Refers to corrosion caused by relative humidity in the air of about 100% or in rain and other aqueous solutions. At this time, water forms droplets on the metal surface and there is a water film visible to the naked eye.
Factors affecting atmospheric corrosion:
1. The influence of water. Among the substances that corrode steel in the atmospheric environment, water is the main factor (generally speaking, the higher the humidity, the stronger the corrosion). The corrosion principle is as follows: water is an electrolyte and can also dissolve a large number of ions, thereby causing metal corrosion; water can dissociate into H and OH, and different pH values have a significant effect on the dissolution corrosion of metals and oxides.
2. The influence of sulfur dioxide. In areas polluted by industrial waste gas, sulfur dioxide has the most serious impact on steel corrosion. The waste gas fueled by oil, natural gas and coal contains a large amount of sulfur dioxide. The corrosion rate of gas tanks increases with the increase of sulfur dioxide content in the atmosphere.
3. Impact of marine atmosphere. The atmosphere near the ocean contains a certain amount of salt, the main component of which is NaCl, Cl- is highly corrosive, so it can aggravate corrosion. The farther away from the ocean, the less salt in the atmosphere and the less corrosion.
4. Other effects. In the atmospheric environment of oil production, there may be a large amount of harmful substances such as Cl2, NH3, H2S solid dust particles, which will also increase the corrosion of gas tanks with the increase of content. The synergistic effect of several substances will lead to the aggravation of steel corrosion.