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FDA approved coating for stainless steel cleaned with chlorine

I have a 304 stainless steel insulated box (12ft by 8ft x 6ft) for storage of ice used in our process. There are two ice flaking units attached to the top which fill the box. Plastic shovels used to remove the ice have scratched the stainless and the cleaning divisions use of chlorine solution to clean has caused rusting to the inside of the box. Is there an FDA approved (we are a food plant) coating that can be applied after we polish the rust off so that the chlorine does not again cause rusting? Any other options that can be done in place? Please advise. Thanks.

Paul Junior
- Stuarts Draft, Virginia
 

Line the tank with polyethylene?

Dale Woika
- Bellefonte, PA, US

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I have had similar issues with chlorinated water on some of the equipment we produce. We ended up going to 316L stainless steel material that has been electro-polished. We also specify the CL level to be no more than 5 ppm, and rinsing in between production runs must be thorough. It sounds like the plastic shovels may have something embedded on the edge, to be scratching the stainless. With the chlorine involved if the rinsing operation is not thorough, you can get much higher levels in areas like the scracthes, which will cause corrosion.

Can you use a different method/chemical for sanitizing?

I do think a change in the method will resolve your dilemma.

Best regards,

Bradford P. Maas
- Northfield, MN, USA

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Paul:

Chlorine containing materials such as bleach are the worst thing that you can use on stainless steel. You need to see if you can convince your cleaning people to use a different solution to disinfect the unit. There are other materials available. Even electropolishing and passivation will not protect the surface from chloride attack long term, although this will improve it greatly. It does not make sense to spend the money to use stainless steel to build your unit and then cover it with a coating (which will probably get a hole in it and then cause a WORSE problem).

If you cannot convince them to use a different material, you may want to go to a different material of construction. If you need help getting the rust off and cleaning it up properly, let us know.

Good luck.

Lee Kremer
Stellar Solutions, Inc.

McHenry, Illinois

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Check into PVD coated SS. I heard of surgical instruments PVD coated to distinguish them apart.

Michael Liu Taylor
specialty stainless steel distributor - Dallas, Texas