Material selection under chloride conditions
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I’ve built a set of solvent purification equipment; the medium contains high levels of chloride ions, with those levels being below 50 ppm. The temperature is below 55°C, and the pH value ranges from 3 to 7. For the materials used in these skid-mounted units, 304 stainless steel is commonly employed. Will 304 be suitable under these operating conditions? Some people suggest using 316L. I would like to know if there is any difference in corrosion resistance between 304 and 316L under these conditions? Is dual-phase steel or nickel-based alloy required for the material? Or should we use carbon steel?
For numbers below 50, there’s no major issue with 304
Use glass-lined equipment for chloride ions – it offers good cost-performance
It can definitely be used; it’s just a matter of how long its lifespan is\ud83d\ude03
Carbon steel + rubber/plastic/coating should all work; for more specific applications, it depends on the actual operating conditions
According to the data, 304 is suitable at 50 ppm and temperatures up to 60 degrees. It can be used if there are no other impurity ions present! It should be noted that being usable does not mean there is no corrosion; in ISO-CORROSION, a value of 0.1mm/Yr is considered sufficient for usability. If you want a permanent solution, upgrading to 316L and 2205 duplex steels is a safer option; this way, it doesn’t matter if the temperature occasionally rises to 65 degrees or even higher. Answers regarding Asmi alloy; hope this is helpful to you!
The answer above for Asmi alloy is already very complete； At a chloride concentration of 50 ppm, the rate for S30408 is approximately 0.005 mm/a; however, this is just an estimate, as chloride primarily causes pitting…… But! Under PH3 conditions, it’s not just an issue of chloride ion corrosion~~~ but acidic corrosion. Under these conditions, the corrosion rate is relatively fast. Since this test was not conducted, it is estimated that the value will not be lower than 0.3–0.5 mm/a ； This choice of material carries significant risks.