Research On Corrosion Behavior Of 20# Steel In Gas Liquid Two Phase Stratified Flow Under Different Pressure And PH

The corrosion behavior o f 20# steel was studied under CO 2/H2 O so lut ion gas-liquid strat ified flow condit ion through CO2 dynamic corrosion experiment.the experiment was conducted in a horizontal pipe flow corrosion test apparatus which was designed and set up according to the experimental requirements and simulates the actual pipe flow corrosion environment. The corrosio n rate, corrosion appearance and the co mposit ion o f corrosion products were invest igated through SEM, XRD, XPS and EDS techno logies. The influence mechanism of pressure and p H on corrosion rate was discussed based on analyzing corrosio n morphology and co mposit ion o f corrosio n products.The results showed that the corrosion rate change trend with pressure of 20# carbon steel in the liquid medium varies under different p H. In the acidic environment, the corrosio n product film was loose and there were corrosion pits appeared, the depth and size o f corrosio n pits increase with the increase o f pressure in the low pressure range. With the pressure increase there was mesa products unevenly distributed on the surface in the liquid flow direct ion. In the neutral environment, the corrosion product film was distributed uniformly in the low pressure range, the corrosio n appearance was general corrosion at higher pressure, corrosion film was most ly flaky and there were irregular part icles attached on the surface when the co rrosion environment is alkaline. The corrosion rate change trend with pressure o f carbon steel in the gas medium also varies under different p H, corrosion film was mostly co mprised o f granular products, the granular products were appeared in nonuniform size at low pressure, and gradually turned uniform wit h the pressure increase. But when p H=6, there were bulge appeared and patchy products appeared when p H=8. The corrosio n rate o f 20# carbon steel in the liquid medium decreased with the increase o f p H,when p H=4 and 5, corrosion film was loose and micro cracks and cor rosion pits appeared o n the surface, the depth o f corrosion pit s increase and unevenly distributed corrosio n products appeared with the increase o f pressure. When p H=6, there were micro cracks appeared on the film but no corrosion pits under lower pressure. Unevenly distributed corrosio n products can be observed under higher pressure. When p H=8,unifor m corrosio n film can be observed and there were irregular p article attached on the surface. The corrosion rate of 20# carbon steel in gas medium changed diffe rent ly with p H under different pressure,when PCO2=0.06 MPa, granular particle product s appeared only when PH=5, corrosio n film was cont inuous massive wit h cracks under other p H, when PCO2=0.17 MPa, corrosio n film had relat ively rough surface with a small amount o f cracks when p H=4 and 5, when p H=6 corrosion film was co mprised of uniform granular particles,when p H=8, corrosio n film was co mprised o f granular part icles and also bulge shaped products, when PCO2=0.28 MPa, corrosion film was co mprised o f big nonuniform granular part icles when p H=4 and 5, corrosion film was co mprised o f small uniform granular part icles when p H=6 and 8. The corrosio n products were mainly co mprised o f iron oxides, and iron carbonate in different forms.