The Tubing Steel High-temperature And High-pressure CO <sub> 2 </ Sub> / H <sub> 2 </ Sub> S And CO <sub> 2 </ Sub> Corrosion Behavior Research

Under high-temperature high-pressure environment, the corrosion behavior of X60,X70 and 16Mn in NACE solution saturated with hydrogen sulfide (H2S) and carbon dioxide (CO2) or carbon dioxide (CO2), with partial pressure of 2MPa or 1Mpa, are investigated using autoclave. The results show that: (l)Within the temperature range of researah, the materials in hydrogen sulfide (H2S) and carbon dioxide (CO2) corrosive media have high corrosion rate with different degree pitting or pitting groups, CO2 causes pitting corrosion, H2S accelerates cathode and anode reaction, resulting in severe pitting corrosion; the main structure of corrosion product scales of the samples is iron sulfide; there is large difference among corrosion rates; the relationship between corrosion rate and temperature is different. (2)Within the temperature range of research, the materials in carbon dioxide (CO2) corrosive media also have high corrosion rate; with the increasing of temperature, the corrosion rates of samples takes the similar manner as increasing â†' decreasing and have the biggest value at 120 ℃; the main corrosion product is Fe3C. (3)The characteristics of corrosion product scale, including thickness, density, content, structure, adhesion, ion selection and stability etc., can affect corrosion rate; the protective characteristics of a corrosion film/layer depend on both the carbon steel characteristics(microstructure, heat treatment history, alloying elements) and environmental variables(solution pH, temperature, solution composition, flow rate etc.). (4)The formation of pitting can increase corrosion rate; parameters affecting pitting include environmental parameters (corrosion media sort, Cl- concentration, temperature), material parameter(all kinds of alloying elements) and other parameter(machinery process, surface condition, band structure, inclusion etc.); the capacity of inclusion for initiating pitting is related of the shape of inclusion.(5) Cl- was the "exciter" of pitting and it's rich-gathered in pits so that causes different localized Cl- concentration gradients and galvanic corrosion, which enhancing pitting, is formed. (6)There is more easily form pitting where band structure is, so band structure is also the sensitive place; it need to avoid the formation of band structure during steel produce.