What causes rust or corrosion in gas tanks?

After the gas storage tank is used for a long time or for many years, it will inevitably cause corrosion from rain, air, or humid atmosphere. These corrosions are caused by the action of water, oxygen, acidic pollutants and other substances in the atmosphere. Steel rusting under atmospheric environmental conditions is a common atmospheric corrosion phenomenon.

There are three types of atmospheric corrosion

① Dry atmospheric corrosion. At this time, there is basically no water vapor in the atmosphere, and ordinary metals form an invisible oxide film at room temperature. The surface of the steel remains shiny.

② Moist atmosphere corrosion. It refers to the corrosion of metal under a thin film layer 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 the high standard), there will be a thin layer of water film on the metal surface, and uniform corrosion will occur. If pollutants such as CO2, H2S, SO2, etc. exist in the atmosphere, corrosion will be significantly accelerated. Steel corrosion under atmospheric conditions is actually electrochemical corrosion under water film conditions.

③The corrosion of the gas storage tank under liquid film conditions is visible. It refers to corrosion caused when the relative humidity in the air is around a high level or in rain and other aqueous solutions. At this time, the moisture forms droplets on the metal surface, and a water film is visible to the naked eye.