Hi all I have a problem about Tank & pipe material made from SS316L have a red color on the surface. The red color color look like rust but it not rust. When i clean it by tissue have some residue red color but it still remain on SS surface can't move all. For the process cleaning and sanitize. We use Hot DI water(>82C) for cleaning and some time we use Hot DI water+detergent(Pan solf clean). Sanitization we use only Hot DI water(>82C) 30 min. SS316L don't have reaction with other chamical righ? So I can't find the potential root cause that impact to 316L change to red color.I have a piture but i can't paste on this.

What you are getting is a surface degredation called rouging. There are MANY opinions on exactly what the rouge contains, but it is fairly well accepted that it is a combination of things including iron oxides. This is a very common phenomenon when using hot DI water on stainless steel, especially in the pharmaceutical industry. The source of the problem is several things, including usually a source of iron rust somewhere in the system, but also just degredation of the surface by the hot DI water (nature abhors a vacuum). The solution to the problem depends on how bad the rouging is. It can be fairly simple using safe chemisty in a CIP system, or it can be quite difficult using more hazardous chemicals if the rouging has gone too far. There are a number of contractors around the country who deal with this problem on a regular basis. If you need help finding someone, please contact us. Lee Kremer Stellar Solutions, Inc.