Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Hydrochloric dew point corrosion (DPC) behavior of 304 and 316L stainless steels was investigated using a novel DPC simulation set-up with in situ measurements of electrochemical impedance spectroscopy and electrochemical noise. The results indicated that the DPC resistance of 316L stainless steel was superior to 304. The difference of the corrosion performance for the two stainless steels can be ascribed to the following two aspects: the ratio of Cr/(Cr+Fe) is higher and the concentration of Fe is lower in the passive film of 316L stainless steel. There exists Mo in the passive film, which can enhance its pitting resistance of 316L stainless steel.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: A novel chromium-free titanate- zirconate conversion coating on 2024 aluminum alloy was prepared, the corrosion resistance of the coatings was evaluated by means of potentiodynamic measurement, NSS test and AC impedance spectra. The morphology and composition of the coatings were characterized by means of SEM with EDS. The results showed that the titanate – zirconate conversion coating is made up of micro particles and shows a smooth flat surface with a few defects. After NSS test for 168 h, only a little corrosion products can be observed on the surface of the titanate- zirconate conversion coating on 2024 aluminum alloy, implying that the conversion coating possesses passivation ability to a certain extent. Therefore, the prepared chromium-free titanate-zirconate conversion coating can provide excellent corrosion protection for 2024 aluminum alloy efficiently.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Effect of pre-treatment processes including acid pickling and acid pickling plus alkaline cleaning on the corrosion resistance of achromium-free zirconate-titanate based conversion coating on AZ91D magnesium alloy was systematically investigated. The results indicated that the acid pickling could induce the preferential dissolution of α phase and thereby increase the surface roughness of AZ91D magnesium alloy, but which was not conductive to the enhancement of the corrosion resistance of the conversion coating. However, the acid pickling plus alkaline cleaning could appropriately modulate the surface chemical state of AZ91D magnesium alloy, and therefore effectively improve the corrosion resistance of the zirconate-titanate based conversion coating.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: none
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Incident involving failure occurred for a 40 months old upright type tee of gas filed gathering and transmission pipeline in a west natural gas field. The tee consisted of a main pipe of 16Mn steel and branch pipes of bimetal composite of 316L stainless steel+L416 steel. Examinations were performed to identify the cause of the failure, which include visual physical inspection, pipe thickness measurement and acquiring the galvanic corrosion behavior of 16Mn steel and 316L stainless steel in an oxygen-free medium containing chloride ion concentration 150 g/L with CO2 partial pressure 0.1 MPa at 65 ℃ using electrochemical methods, as well as Computational Fluid Dynamics (CFD) analysis of the tee with assumed angles as 90°, 45°and 30°respectively between the branch pipe and main pipe along the direction of inlet using the FLUENT software. Investigations revealed that for the present tee design, there existed galvanic couple of the metallic materials and the straight cutting structure of the tee caused the fluid changes radically. Gas field water gradually adhered to the inner side of the pipe due to the low velocity that caused by the vortex which was formed nearby the pipe explosion site. Corrosion then ensued as CO2 dissolved in the water. The area around the explosion site suffered from large wall shear stress caused by the fluid scouring action. Because of the synergy of galvanic corrosion and fluid flow erosion the pipe gradually thinned, and then perforated.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Dew point corrosion (DPC) behavior of rolling Q235 steel was investigated using simulative equipment and electrochemical noise. The results indicated that mass loss of Q235 steel along the rolling direction (RD) is more than that along the normal direction (ND). The main reason was that the cementite was not so easily broken off along normal direction during the corrosion process because of the net-like characteristic of ferrite and pearlite. And weight loss resulting from galvanic corrosion in the two directions was nearly the same with each other.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: A novel enamel coating of 20~40 μm thick was prepared on γ-TiAl intermetallics. Of which the air oxidation and (Na, K)2SO4+25%NaCl (mass fraction) deposits induced hot corrosion were studied in air at 700 ℃ for 1000 and 600 h respectively. It is revealed that the enamel coating was stable, and able to prevent the substrate from high temperature oxidation and hot corrosion during tests. Neither cracks nor spallation of enamel coatings was observed after tests. Interfacial reactions at the coating/substrate interface took place during the coating preparation and high temperature tests, thereby resulted in the formation of a thin oxide layer consisted of α-Al2O3, TiO2, Al2SiO5 and Al2TiO5.