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Effects of Ozone on SS304

 

To all metallurgical boffins,

I manage a large bottling plant where we intend soon bottling treated water. The water will be disinfected with ozone at concentrations of 0.5 - 3 ppm at various stages in the process. My concern is whether we will experience corrosion problems in our existing blending and filling plant which is SS304. What levels of corrosion can I expect and what is a "safe" level for SS304 (if any)?

Phillip Mallinson

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Coincidentally, I worked as a plant manager for years at a large water bottling plant. Ozonated water should not be a major concern to the 304 stainless. Infrequently, the ozone contact tank may develop some corrosion at the welds; the welds are the location to check for damage. If you are using an advanced oxidation process, another place to check the welds might be the inside of the post-ozonation u.v. unit.

Distilled/deionized water is corrosive to stainless & presents a corrosion problem; ozonated drinking water or spring water is completely compatible with 3xx stainless. BTW, unless your water is ultrapure and very cold, I doubt you will be seeing water ozone concentrations in the 3.0 ppm range. 0.2ppm is a safe disinfection level.

Dale Woika

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Thanks for the feedback. Just to clarify- I will be blending a stream of o3 water at 3ppm, with a non-ozonated stream to achieve a desired residual of 0.2-0.5 ppm in the final product. Also- my water is ex RO and has TDS of only 40. Does this change things viz. corrosion?

Phillip Mallinson
 

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You should be ok with a TDS above 15 ppm. The real corrosion problems are not severe unless the water is less than 10 ppm tds, even more so if the pH is allowed to drop below 5. Is it safe to assume you are going to be blending in a few minerals for taste? Distilled & low dissolved solids water tends to taste a bit insipid (but that is my own humble opinion, of course).

Watch the welds in the filler heads and it is prudent to check the welds in the system at pressure points once in a while, just to make sure. If the filler heads start to have corrosion problems, specify electropolished finishes the next time around.

Dale Woika