Corrosion of natural gas pipelines
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There are two identical natural gas pipelines: one is in normal use while the other is shut down but kept under pressure with nitrogen. It’s not clear which one corrodes more rapidly
It’s just my personal understanding. Why? If the pipeline isn’t in use, the medium inside it doesn’t flow; if there is water in the pipeline, local corrosion can occur easily. It would be better to completely drain the water and then use nitrogen for protection
It’s definitely normal wear and tear that leads to faster corrosion. Natural gas is a mixture primarily composed of methane, and it contains varying amounts of substances that can corrode metals; compared to what someone mentioned above about water remaining in the pipelines, I believe natural gas is more likely to cause pipeline corrosion. Additionally, when shutting down pipelines, steam purging and nitrogen flushing are generally carried out, which reduces the amount of moisture present to almost negligible levels; however, it’s not completely eliminated. Moreover, the compressed nitrogen is not pure nitrogen as it also contains oxygen, so local corrosion of the pipelines as mentioned earlier is not entirely impossible. In my opinion, pipelines that are used under normal conditions are more prone to corrosion, and this does not occur only in localized areas.
Theoretically, what you say is true, but in practice, the decommissioned natural gas equipment corrodes more rapidly, mainly due to inadequate maintenance