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The different factors to affect the working life of PVDF Pipe
- Jul 18, 2018 -

           It is well known that the corrosion resistance of PVDF materials is very strong, so people think that the service life of PVDF pipes will be infinitely long, but the service life of PVDF pipes used in chemical anticorrosion industry is related to the corrosion resistance and aging resistance of PVDF materials. It is also related to the application conditions of materials, such as the concentration of corrosive medium, the temperature gradient, the flow rate of the medium and the pressure force of the material. In general, the higher the temperature, the lower the resistance of PVDF pipes to corrosive media, because the higher the temperature, the more intense the action between plastics and corrosive media, and the faster the chemical reaction or dissolution swelling. When the temperature of the medium is higher than the temperature of the plastic lining or the outer substrate of the coating, the permeation of the medium is in the same direction as the thermal diffusion caused by the temperature gradient, and the medium will reach the matrix faster through the plastic, leading to the bulging. 

          The flow of medium will speed up the dissolution and destruction of plastics, and the higher the flow rate, the worse the corrosion resistance of PVDF pipeline: when the plastic pipe products are subjected to external stress, the corrosive medium is more likely to infiltrate through the surface into the material. The corrosion resistance of the material decreases with the increase of the interaction area, and the service life of the material decreases greatly when the material is subjected to larger stress.

          Due to the fact that the materials are subjected to very different forms of action in different use situations, it is difficult to have a unified test index to reflect the exact effect of various actions on the service life of anticorrosive materials. The best way to do this is to choose the same (or similar) conditions and corrosion media as used to test the service life of the plastic specimen, Of course, this is difficult to complete in many cases. General dynamic corrosion resistance test methods include chemical stress relaxation test of constant strain, chemical creep test of constant stress, chemical fatigue test of alternating stress and so on. These tests were used to observe and determine the tolerance of plastic samples to chemical reagents (time) when subjected to a simple form of stress. There are some more standardized or standard test methods to observe the duration of the damage (cracking), The time (life) of environmental stress cracking of the specimen in this medium is expressed by the time of cracking of 50 laminated specimens. This result is useful for the service life of PVDF materials under similar conditions. The tail gas pipeline and chimney chemical acid production tail gas contains many kinds of corrosive medium such as sulphuric acid discouraging sulfur dioxide and so on in the sulfuric acid tail gas. But on the whole, the concentration is not very large, corrosion is not very strong. At the same time, the temperature is not too high, the pressure is close to normal pressure, so PVDF material should be selected first, which can not only meet the requirements of corrosion resistance, but also have the characteristics of cheap, light, easy maintenance, long life and so on.

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