Chemistry: electrical and wave energy – Processes and products – Electrostatic field or electrical discharge
Patent
1991-11-12
1993-02-23
Valentine, Donald R.
Chemistry: electrical and wave energy
Processes and products
Electrostatic field or electrical discharge
204140, 148276, 148277, 148280, C25F 324, C21D 174, C23C 1100
Patent
active
051887142
ABSTRACT:
The present invention provides a method for surface passivating stainless steel articles against the effects of corrosive materials having activities anywhere from aqueous salt solutions to corrosive gases such as hydrogen chloride and silane. Additionally, after the treatment and exposure of the article to moisture, when the article is subsequently flushed with a dry gaseous fluid, the time that the article takes to exhibit an acceptable moisture outgassing rate is reduced over an untreated article. In accordance with the present invention, the surface to be passivated is flushed with a dry gaseous fluid, chemically non-reactive with the stainless steel and containing essentially no oxygen. During such flushing, the articles is baked and cooled. The baking is accomplished at a predetermined temperature and time (preferably between about 250.0.degree. C. and 500.0.degree. C. for about 4.0 hours) to effect, within the oxide layer, a reduction in absorbed moisture and hydroxide content and an increase in chromium content. The article is allowed to cool after the baking step. Such gaseous fluid can comprise argon having a moisture content of no greater than 10.0 ppb and an oxygen content of about 10 ppb.
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Davidson Jeffrey
Paciei Richard
Sherman Robert
Cassett Larry
Rosenblum David M.
The BOC Group Inc.
Valentine Donald R.
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