304 Chromium oxide

Date 04-27-2009 23:26

There are a few comments I'd like to do:

1st. I don't understand why do you need a temperature as high as 350 ºC for sterilizing bottles. Is there any specific requirement for that? "Sterilizing" means killing microorganisms, i.e., bacteria and viruses. No bacteria or virus withstands temperatures higher than 150 ºC.
2nd. What's exactly your problem? The glass bottles stick to the metal? Or the chromium oxyde formation on the 304 ss decking surface?
In the first case, of course the bottles stick to the metal. At 350 ºC glass starts getting soft and an inert gas won't change anything. In the second case, take into account that 304 s.s. is used for temperatures higher than 350 ºC. A thin film of chromium oxyde starts forming on the surface of 304 s.s. at room temperature, and this film sticks firmly to the surface.

Giovanni S. Crisi
Sao Paulo - Brazil

By MO139 Date 04-28-2009 12:30

350°C is the high end of FDA pharmaceutical sterilization temperatures, normal for this application is 320°C. The glass being used doesn't reach the transition temperature under 500°C, ie. it is considered hard and brittle at the temperaturesit is being soaked in. At ambient, the glass moves freely on a polished 304SS surface, non eventful. When the metal is brough up to the steriliing temperature, it developes a dull wheat straw color/surface and the glass stalls. Is there another austenitic or super alloy which is less likely to reduce in this enviroment?
Thanks

By G.S.Crisi (****)

Date 04-28-2009 19:27

Well, if that's the case, try to use some refractory (i.e., heat resistant) stainless steel. Get in touch with Sandvik www.sandvik.com They're Swedish but they have a subsidiary in the USA (Pittsburgh, if I rmemeber well).
If I were you, I'd take a little piece of that problematic 304 s.s. and run a chemical analysis to make sure that it's really 304.
Giovanni S. Crisi

By Joseph P. Kane (****)

Date 04-28-2009 02:17

Don't you mean 350 Degrees F.?