Regarding the corrosion issue of ammonia pipelines
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Our factory is equipped with 4 sets of low-temperature methanol washing units and 4 sets of mixed refrigeration units; the mixed refrigeration units provide cooling capacity for the low-temperature methanol washing units. At present, the mixed refrigeration equipment and pipelines are suffering from severe corrosion. I would like to know the reasons for this. Does anyone with experience have any insights I can refer to?
Ammonia itself is corrosive to carbon steel pipes, but the issue is mainly stress corrosion cracking; this tends to be more severe at the weld areas. If cracking occurs at the welds, the first thing to consider is whether the hardness of those welds is too high. If it is uniform corrosion thinning, then we need to check whether the flow rate in the pipeline is too high Test the composition of the medium to check for any other corrosive substances
It should be dehydrogenation corrosion. There is no oxygen in ammonia; ammonia captures the metal cations in the metal crystal to form complex ions, which can be considered as a replacement of hydrogen. This process has nothing to do with dissolved oxygen. Ammonia water, NH4+·OH-, is likely responsible for dehydrogenation corrosion