The Corrosion Behaviors Of X80 Pipe Line Steel And Q235 Steel In Coastal Tidal Flats

In the 21 st century,for the shortage of resources and the deterioration of environment, tidal flats as one of the six major reserve land rapidly fade into people’s sight. The construction of the coastal tidal flats port towns and the development of petrochemical industry cannot leave a lot of iron and steel facilities. But the corrosion problem of these steel facilities seriously threatens people’s life and property, especially in the coastal tidal flats which with high salt, temperature and humid. So the corrosion problem of metal material in coastal tidal flats can not be ignored.Q235 steel was commonly used in engineering facilities. And X80 pipeline steel is commonly used in long distance oil and gas pipelines. In this research, the electrochemical corrosion behaviors of X80 pipeline steel and Q235 steel in coastal tidal flats simulated soil solution was studied by using the polarization curves, electrochemical impedance spectroscopy and corrosion morphology observation. Moreover, the effect of temperature and concentration of coastal tidal flats simulated soil solution to the corrosion of X80 pipeline steel and Q235 steel was studied. The results indicated that immersion time and corrosion products had a significant impact on the corrosion behavior of X80 pipeline steel and Q235 steel in coastal tidal flats simulated soil solution. The corrosion of X80 pipeline steel and Q235 steel in coastal tidal flats simulated soil solution experienced three stages. At the initial immersion, the corrosion film was not continuous and dense; At medium corrosion stage, the continuous and compact corrosion product film was formed and had good protection. So the corrosion rate of X80 pipeline steel and Q235 steel sharply reduced. But then layer off of the loose outer rust caused corrosion rate increased. In the range of 25℃~60℃,temperature can accelerate the corrosion rates of X80 pipeline steel and Q235 steel in coastal tidal flats simulated soil solution(concentration of 20g/L~80g/L). In higher concentration coastal tidal flats simulated soil solution, the concentration of dissolved oxygen is lower, which result the corrosion rate of Q235 steel decreased with increasing concentration of coastal tidal flats simulated soil solution. For X80 pipeline steel, in the temperature range of 25℃~50℃, the corrosion rate of X80 pipeline steel decreased with concentration. But when the temperature reached 60℃, the effect of concentration was not obvious.