METHOD OF FORMING OXIDE PASSIVATION FILM AT WELD PORTION AND PROCESS APPARATUS

摘要

This invention provides a welding method capable of forming an oxide passivation film having corrosion resistance and an extremely small emission quantity of an outgas during welding at a weld portion and portions nearby, and a process apparatus requiring an ultrahigh-clean atmosphere. A back-seal gas comprising an inert gas contaning 1 ppb to 50 ppm of oxygen gas in caused to flow during a welding process and an oxide passivation film comprising chromium oxide as a principal component is formed on the surface of a weld portion. In a process apparatus using welding for installing the apparatus, a back-seal gas comprising an inert gas containing 1 ppb to 50 ppm of oxygen gas is caused to flow during a welding process and an oxide passivation film comprising chromium oxide as a principal component is formed on the surface of a weld portion.