Whether ethylene glycol will corrode vacuum pumps
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Our company is preparing to launch a project that requires the use of dry vacuum pumps. The composition of the vacuum gas is as follows: 2.5% ethylene glycol, 4% water, with the remainder being air; the temperature of the medium ranges between 50 and 70 degrees. The solution proposed by the supplier at present is a screw pump, with both the rotor and the pump chamber made of cast iron. I would like to ask everyone whether ethylene glycol will corrode the rotor and pump chamber under these operating conditions If corrosion occurs, what should be done in such conditions?
Ethylene glycol solution – cast iron is not suitable for this; for more details, you can consult the experts in the corrosion section @WangWei2
@Wang Wei2, Mr. Wang, I have a question: will corrosion occur under this gas composition? How should this be solved?
This post was last edited by lwlkey on 2019-1-26 at 14:47. Let’s share the corrosion manual here: lol; it can be found, and the table refers to carbon steel and cast iron components, which are usable
This takes into account the oxidation of ethylene glycol by air to oxalic acid or glycolic acid. What you’re checking here is likely a single ethylene glycol solution under sealed conditions.
The last edit to this post was made by Wang Wei2 on 2019-1-27 at 11:44. It goes like this: Ethylene glycol contains hydroxyl groups; with long-term 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. Under normal circumstances, ethylene glycol is highly corrosive after oxidation. Ethylene glycol coming into contact with air during storage causes cavitation damage to the equipment. Erosion caused by cavitation tends to produce locally clustered honeycomb-like pore groups, 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). This also results in very high levels of impurities such as rust in the solution system, with the impurity content reaching around 1%. It leads to a decline in product quality. Furthermore, during use, ethylene glycol aqueous solutions become acidic due to oxidation into organic acids, which makes them prone to electrochemical corrosion, underscale corrosion, and acid corrosion. Therefore, carbon steel pumps are not recommended for use as pump bodies. Stainless steels such as 316L can be used.
This is a true expert; one rarely seen……
Excuse me, Mr. Wang, would it be acceptable if the screw pump is made of Hastelloy with a coating?