What are the causes of corrosion in metal storage tanks used for storing ethylene glycol?

We have encountered this situation before; the system needs to be nitrogen-sealed to prevent it

It is first oxidized to acetic acid; carbon steel corrodes easily in acids, and it is stainless steel that is prone to intergranular corrosion.

Let’s first understand the properties of ethylene glycol. Ethylene glycol contains hydroxyl groups; with prolonged use, it is first oxidized to glycolic acid, and then further oxidized to oxalic acid, that is, ethanedioic acid (oxalic acid), which has 2 carboxyl groups. Ethylene glycol oxalate causes corrosion of equipment, leading to leaks. The corrosion of metals by ethylene glycol: Under normal circumstances, ethylene glycol is highly corrosive. Ethylene glycol coming into contact with air during storage causes cavitation in the equipment. Erosion caused by cavitation tends to produce locally concentrated clusters of honeycomb-like pores, leading to corrosion of the equipment. At the same time, factors such as the instability of ethylene glycol due to its hydroxyl groups and its tendency to acidify can corrode carbon steel as well as ordinary stainless steels (304 stainless steel). Furthermore, during use, ethylene glycol aqueous solutions become acidic due to oxidation into organic acids, making them prone to electrochemical corrosion, underscale corrosion, acid corrosion, and other types of corrosion.

In addition to concentration and composition, temperature is also important for the occurrence of corrosion; if it is used merely as a refrigerant, there should be no corrosion issues (operating temperature below 0 degrees)