Study on Pitting Corrosion of L360 Steel in H2S/CO2 Solution
|School||Beijing University of Chemical Technology|
|Course||Materials Science and Engineering|
|Keywords||H2S/CO2 environment Pipeline steel Pitting Chloride ion Calcium Temperature Statistical analysis|
In this paper, static coupon weight loss method H2S/CO2 simulated oilfield - containing aqueous solution temperature , the concentration of Cl- and Ca2 concentration on the pitting corrosion of pipeline steel L360 using XRD, SEM, EDS, adhesion, electrochemical test methods study the characteristics of the corrosion product film , In addition , the paper also analyzes the probability and Statistics the eclipse point distribution characteristics . The main conclusions are as follows: 1, found by the XRD L360 pipeline steel in oilfield produced water containing H2S/CO2 simulation environment , the temperature of the solution , Cl- concentration , Ca2 concentration change had no significant effect of the corrosion product ingredients are FeS found no Fe reacts with CO2 . L360 pipeline steel corrosion performance of H2S corrosion . 2, Cl- concentration on the pitting corrosion occurred . When the Cl- concentration of 15 g / L , the corrosion specimens obvious pitting ; the sample uniform corrosion occurs mainly when the Cl-concentration greater than 20g / L , with the increase of Cl- concentration , the corrosion product film with good protective properties of metal matrix tetragonal FeS content declining , while the corrosion product film becomes more loose, causing the protective effects of corrosion product films decreased , the uniform corrosion rate increases . 3, Cl- concentration of 15g / L , and have a significant effect of temperature on the pitting corrosion occurred . In the range of 40-70 ℃ , L360 pipeline steel with varying degrees of pitting corrosion and erosion point density and depth with increasing temperature and increasing severe pitting and 70 ℃ ; L360 pipeline steel the uniform corrosion rate as the solution temperature increased and then decreased , and reached a maximum value at 60 ℃ ; observed different temperature corrosion product film , when the temperature rises to 70 ° C , the granularity of the corrosion products than other temperature is significantly smaller , at 70 ° C under corrosion product film becomes more dense . 4, at 60 ℃ , the corrosion rate increases with the increase in Ca2 + concentration increases, and when the Ca2 + concentration of 8.5g / L , the surface corrosion products easily fall off . At this concentration , pipeline not only pitting corrosion occurs , and the sheet-like local corrosion occurred . 5 , at 40-70 ℃ , the maximum depth of the pits pipeline steel obeys Gumbel approximate distribution . Calculated using the Poisson distribution at 70 ℃ pits density of 1237-1791 a / ??m2 , the width of the confidence interval is 553 / m2 . The depth distribution of the pits to follow a normal distribution .