Outgassing Rates of Stainless Steel and Mild Steel after Different Pretreatments

Abstract

Outgassing rates for stainless steel, mild steel and chromium plated mild steel were measured by the orifice method after different pretreatments. The orifice used was 3mm in diameter. The pretreatments were (1) to dry by a sirocco fan after degreasing with carbon tetrachloride ; (2) to make baking of stainless steel at 100450°C and that of mild steel and chromium plated mild sttel at 100°300°C : and (3) to expose to argon and atmosphere after baking. After pretrreatment (1), the outgassing rates for stainlees steel and chromium plated mild steel were of the order of 10-9 Torr·l·sec-1 cm-2 and that for mild steel was one order of magnitude higher than the first two. The stainless steel sample baked at 300°C for 3 hours showed an outgassing rate of 3 × 10-12 Torr·l·sec-1 cm-2 that was the lowest in the three materials. Baking at 450°C for 5 hours reduced the outgassing rate for stainless steel down to 1 × 10-13 Torr·l·sec-1·cm-2. The effect of baking is the highest for stainless steel and the lowest for chromium plated mild steel. After pretreatment (3), exposure to argon results in a lower outgassing rate than that to atmosphere