Sulfuric acid corrosion at the ppm level
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Dear sea friends, a medium at 50 degrees Celsius and atmospheric pressure, containing 20 ppm of sulfuric acid, 4% water, with the remainder being dimethyl ether gas； It is compressed to 0.3 MPa by a compressor for transportation, and the temperature rises to around 160°C during the compression process. Will it corrode the cast-iron cylinder block? Will coolers exported and made of 304 material corrode? I would appreciate your guidance. Thank you!
There will be corrosion. Graphite heat exchangers are recommended for the outlet cooler.
This post was last edited by qugd on 2019-7-11 at 17:37. Does your 20 ppm refer to the amount present in the entire system, or does it mean the amount present in the 4% water solution? This is not the same; the concentration of the former is 25 times higher than that of the latter. In other words, if those 20 ppm of sulfuric acid remained in the 4% of water present in the entire system, the sulfuric acid concentration would be around 0.05%. There is a concentration effect of sulfuric acid in the aqueous phase, as sulfuric acid is much less volatile than dimethyl ether and therefore remains preferentially in the aqueous phase. 0.05% sulfuric acid is quite acidic; the pH is likely to be 3 or lower. Cast iron certainly cannot withstand such conditions, while 304 or 316 stainless steel should be able to handle it.
Thank you for your answer. 20PPM is present throughout the entire system. If 316L can be used, are there any corresponding corrosion data sheets or charts available? Thank you
If the sulfuric acid concentration in the entire system is 20 ppm, then stainless steel will definitely be fine. However, you need to consult experts in materials science for the corrosion data; I don’t have time to look up such basic information for you. One should not be too lazy.