Reasons for rust or corrosion of gas tank

Reasons for rust or corrosion of gas tank

The gas storage tank is a part of the post-processing equipment of the air compressor, which mainly plays the role of gas storage, buffering, pressure reduction, and drainage. It will inevitably cause corrosion in the air, rain or humid atmosphere after long-term use or use for many years. These corrosions are caused by the action of water, oxygen, acidic pollutants and other substances in the atmosphere. The main material of gas storage tanks is steel. Steel rusts under natural atmospheric conditions, which is one of the most common atmospheric corrosion phenomena.

　　 Reasons for rust or corrosion of gas tank

　　 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 maintains luster.

　　B. Corrosion in humid atmosphere. It refers to the corrosion of metal under the invisible film layer. 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 thin water film on the metal surface, and uniform corrosion will occur. If there are pollutants CO2, H2S, SO2, etc. in the atmosphere, the corrosion will accelerate significantly. Steel corrosion under atmospheric conditions is actually electrochemical corrosion under water film conditions.

　　C. Visible corrosion of gas storage tanks under liquid film conditions. Refers to the relative humidity in the air at about 100% or corrosion caused by rain and other aqueous solutions. At this time, moisture 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 corrosive to steel in the atmospheric environment, water is the main factor (generally speaking, the higher the humidity, the stronger the corrosiveness). The corrosion principle is as follows: water is an electrolyte, and it can also dissolve a large number of ions. Causes metal corrosion; water can be dissociated into H and OH, and the difference in pH has a significant effect on the dissolution and 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. Exhaust gas fueled by petroleum, natural gas, and coal contains a large amount of sulfur dioxide, and the corrosion rate of gas storage tanks increases with the increase of the sulfur dioxide content in the atmosphere.

　　 3. The influence of ocean atmosphere. In the atmosphere near the ocean, there is a certain amount of salt, and its main component is NaCl, Cl-which is highly corrosive, so it can intensify corrosion. The farther away from the ocean, the less salt in the atmosphere, and the smaller the amount of corrosion.

　　 4. Other influences. In the atmospheric environment of oil production, there may be a lot of harmful substances such as Cl2, NH3, H2S solid dust particles, and their corrosion of gas storage tanks increases with the increase in content. The synergistic effect of several substances will lead to steel corrosion. Intensified.