Can the PE pipe still be welded after oxidation?

many friends in the PE pipe construction or maintenance will encounter such confusion: the original milky white PE pipe has been placed outdoors for a long time, the surface slowly becomes yellow brown, rough and brittle to the touch, can this oxidized PE pipe be welded normally? To answer this question, we must first understand the nature of PE pipe oxidation and the impact of oxidation on welding.

PE pipe is mainly composed of polyethylene, which is a polymer material. Long-term exposure to ultraviolet rays, high temperature or oxygen environment, the molecular chain on the surface will break, forming a dense oxide layer - the structure of this oxide layer is completely different from that of fresh PE. Not only does it have a higher melting point, but it also loses its original flexibility and becomes hard and brittle.

Can the oxidized PE pipe be welded? The answer is: It depends on the degree of oxidation.

If only the surface is slightly oxidized (for example, if it is left for 1-2 months, the surface color is slightly darker, and the powder will not be removed by scraping with fingernails), this situation can be welded - but the oxide layer must be thoroughly polished off first. Because the core of welding is "hot melt fusion of PE materials", if the oxide layer remains on the surface, it cannot be fully combined with fresh PE material during hot melt, which will lead to "fake welding" at the weld: it looks welded, but the actual strength is extremely low. A little pressure will crack and leak water. The treatment method is also very simple: use a wire brush, sandpaper or angle grinder to gently polish the surface until the fresh milky PE inside is exposed, and then weld according to the normal process.

But if the oxidation is very serious (for example, if it is placed in the open air for more than half a year, the surface will turn black, the powder will be removed by hand, or even broken after being gently bent), this situation must not be welded. Because the oxidation has penetrated deep into the pipe at this time, even if the surface is polished off, the internal PE molecular chain has been damaged, and the strength of the weld after welding cannot meet the requirements at all, and it is likely to cause leakage or even pipe bursting later.

How to quickly judge the degree of oxidation of PE pipe? Teach you two simple methods: ① Look at the color: fresh PE pipe is uniform milky white, and it will turn yellow-brown, dark-brown or even black after oxidation; ② Do a "scratch test": scrape the surface with nails or coins. If the powder can be scraped off, it means that the oxide layer is thick; if only scratches are left,

Finally, I would like to remind you that preventing the oxidation of PE pipes is more important than treatment. Anti-ultraviolet agents are generally added when PE pipes leave the factory, but they will still age when placed in the open for a long time. So it is best to bury them in the ground or cover them with shading cloth and protective cover when storing. Try to avoid exposing the pipes to the sun for a long time during construction. If they must be stored in the open air, the time should not exceed 1 month.

To summarize: PE pipes cannot be welded after oxidation. The key is to judge the degree of oxidation - they can be welded after slight oxidation and grinding, and replaced directly after severe oxidation. Take an extra 2 minutes to check the surface of the pipe before construction to avoid a lot of trouble in the later stage. After all, the safety of the pipeline system is always determined by the details. 11727798