AVS 46th International Symposium
    Vacuum Technology Division Thursday Sessions
       Session VT-ThM

Paper VT-ThM1
A Comparison of Outgassing Rates from Stainless and Carbon Steels

Thursday, October 28, 1999, 8:20 am, Room 610

Session: Outgassing, Leaks, and Mass Flow Controllers
Presenter: H.F. Dylla, Thomas Jefferson National Accelerator Facility
Authors: H.F. Dylla, Thomas Jefferson National Accelerator Facility
W.R. Blanchard, Princeton University
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Various types of stainless steels (ANSI type 300 series) are the most commonly used materials for the construction of high and ultrahigh vacuum vessels and associated vacuum hardware. As a result of this widespread use, numerous outgassing studies of stainless steels have been published in the literature. The available information on outgassing from carbon steels is relatively meager. Carbon steels are usually not considered for use in high vacuum systems because of the propensity for corrosion (oxidation) in ambient environments and the assumption that standard surface preparation techniques would be less effective on carbon steels in comparison to 300 series steels. During consideration of a number of vacuum applications of carbon steels we reviewed the outgassing literature and found that an often quoted measurement significantly overestimates the outgassing from properly cleaned material. We describe outgassing measurements we have performed on both types of steel in order to get a direct comparison of the materials on the same apparatus and using the same surface preparations techniques. Results show that the short-term (<100 hr) outgassing rates from clean carbon steel are only a modest factor (times two to four) larger than from similarly prepared stainless steel. The increased outgassing rate appears to be in direct proportion to the passivation oxide layer thickness. @FootnoteText@ This work was supported by US DOE Contract No. DE-AC02-76-CH-03073.