Influence of gas pressure on the long-term oxidation behaviour of mild and low-alloy steels in carbon dioxide atmospheres at 350°–450°c

Abstract

Long-term oxidation tests of mild and low-alloy steels in carbon dioxide atmospheres containing minor quantities of carbon monoxide and moisture show that as the gas pressure increases from 0–600 Ib/in² there is a decrease in the time to breakaway and possibly an increase in the post-breakaway oxidation rate. If the partial pressure of the moisture in the gas is kept constant, then the post-breakaway rate may be constant from 200–600 Ib/in² though there is an increased initial rate of development of excrescences. At 600 Ib/in², breakaway may occur in the virtual absence of moisture and carbon monoxide at 450° but may not occur at 350° even with significant quantities of both present. The form of the oxidation/time relationship is shown to depend on the initiation and development of excrescences. An attempt has been made to categorise the major types of excrescences observed.