The short-term corrosion behavior of API X100 steel in an acidic simulated soil was investigated by electrochemical measurements and soaking experiments,followed by corrosion morphology observations and X-ray photoele...The short-term corrosion behavior of API X100 steel in an acidic simulated soil was investigated by electrochemical measurements and soaking experiments,followed by corrosion morphology observations and X-ray photoelectron spectroscopy analyses.The results show that X100 steel exhibits an obvious pitting susceptibility in an acidic soil environment.Pits nucleate after approximately 10 h of immersion.Along with the nucleation and growth of the pits,the charge-transfer resistance and open-circuit potential first increase sharply,then decrease slowly,and eventually reach a steady state.The maxima of the charge-transfer resistance and open-circuit potential are attained at approximately 10 h.The evolution of the electrochemical process is confirmed by the analysis of the product film.The product film exhibits a porous and loose structure and could not protect the substrate well.The product film is primarily composed of ferrous carbonate and ferrous hydroxide（Fe（OH）2）.The concentration of Fe（OH）2 in the product film increases from the inside to the outside layer.展开更多
E32 grade corrosion resistant steel was welded with welding wires with three different S contents. The mi crostructure, mechanical properties, inclusions, and corrosion behavior of welded joint were investigated. The ...E32 grade corrosion resistant steel was welded with welding wires with three different S contents. The mi crostructure, mechanical properties, inclusions, and corrosion behavior of welded joint were investigated. The joint coupon corrosion test and potentiodynamic polarization test were carried out under the simulated corrosion environ- ment of the inner bottom plates of cargo oil tanks. The pitting initiation and propagation mechanism of the weld metal were studied by scanning electron microscopy and infinite focus. The results indicated that the microstructures of three kinds of weld metals are all composed of acicular ferrite, ferrite side-plate and proeutectoid ferrite. The micro- structure of heat affected zone is composed predominantly of bainite. Joint welded with low S filler wire has good me- chanical properties. S can decrease free corrosion potential and increase the corrosion tendency. The pitting initiation is oxide inclusion or sulfide oxide inclusion complex. S can induce the formation of occluded area and promote the corrosion propagation. The chemical compositions of weld metal is similar to base metal, which can limit the galvanic corrosion between weld metal and base metal, and avoid formation of corrosion step.展开更多
Corrosion behavior of low-alloy steel was investigated in simulated cargo oil tank （COT） bottom plate service environment （10% NaCl solution, pH = 0.85）. The corrosion behavior of inclusion was studied by in-situ ...Corrosion behavior of low-alloy steel was investigated in simulated cargo oil tank （COT） bottom plate service environment （10% NaCl solution, pH = 0.85）. The corrosion behavior of inclusion was studied by in-situ scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS）. It was found that pitting corrosion was inclined to occur around the place where inclusions exist. After initial corrosion, an area of 10-20μm in diameter was formed as a cireinate cathode around the edge of inclusion. MnS inclusion dissolved in the simulated COT corrosion solution before low-alloy steel matrix, and pitting was formed at the place where MnS dissolved. TiO2 inclusion dissolved in the simulated COT corrosion solution after low alloy steel matrix, and pitting was formed at the place where steel matrix dissolved. The corrosion tended to occur at the area where the curvature radius of inclusion is smaller. The size of round TiO2 inclusions had little influence on corrosion behavior in this certain environment.展开更多
基金financially supported by the National High-Tech Research and Development Program of China (No.2012AA040105)the National Nature Science Foundation of China (Nos. 51131001 and 51741034)the Beijing Higher Education Young Elite Teacher Project
文摘The short-term corrosion behavior of API X100 steel in an acidic simulated soil was investigated by electrochemical measurements and soaking experiments,followed by corrosion morphology observations and X-ray photoelectron spectroscopy analyses.The results show that X100 steel exhibits an obvious pitting susceptibility in an acidic soil environment.Pits nucleate after approximately 10 h of immersion.Along with the nucleation and growth of the pits,the charge-transfer resistance and open-circuit potential first increase sharply,then decrease slowly,and eventually reach a steady state.The maxima of the charge-transfer resistance and open-circuit potential are attained at approximately 10 h.The evolution of the electrochemical process is confirmed by the analysis of the product film.The product film exhibits a porous and loose structure and could not protect the substrate well.The product film is primarily composed of ferrous carbonate and ferrous hydroxide（Fe（OH）2）.The concentration of Fe（OH）2 in the product film increases from the inside to the outside layer.
基金Sponsored by National Key Technology Research and Development Program of China(2011BAE25B01)
文摘E32 grade corrosion resistant steel was welded with welding wires with three different S contents. The mi crostructure, mechanical properties, inclusions, and corrosion behavior of welded joint were investigated. The joint coupon corrosion test and potentiodynamic polarization test were carried out under the simulated corrosion environ- ment of the inner bottom plates of cargo oil tanks. The pitting initiation and propagation mechanism of the weld metal were studied by scanning electron microscopy and infinite focus. The results indicated that the microstructures of three kinds of weld metals are all composed of acicular ferrite, ferrite side-plate and proeutectoid ferrite. The micro- structure of heat affected zone is composed predominantly of bainite. Joint welded with low S filler wire has good me- chanical properties. S can decrease free corrosion potential and increase the corrosion tendency. The pitting initiation is oxide inclusion or sulfide oxide inclusion complex. S can induce the formation of occluded area and promote the corrosion propagation. The chemical compositions of weld metal is similar to base metal, which can limit the galvanic corrosion between weld metal and base metal, and avoid formation of corrosion step.
基金Item Sponsored by National Science and Technology Major Project of the Ministry of Science and Technology of China(2011ZX05016-004)National Key Technology Research and Development Program of the Ministry of Science and Technology of China(2011BAE25B00)
文摘Corrosion behavior of low-alloy steel was investigated in simulated cargo oil tank （COT） bottom plate service environment （10% NaCl solution, pH = 0.85）. The corrosion behavior of inclusion was studied by in-situ scanning electron microscopy （SEM） and energy dispersive spectroscopy （EDS）. It was found that pitting corrosion was inclined to occur around the place where inclusions exist. After initial corrosion, an area of 10-20μm in diameter was formed as a cireinate cathode around the edge of inclusion. MnS inclusion dissolved in the simulated COT corrosion solution before low-alloy steel matrix, and pitting was formed at the place where MnS dissolved. TiO2 inclusion dissolved in the simulated COT corrosion solution after low alloy steel matrix, and pitting was formed at the place where steel matrix dissolved. The corrosion tended to occur at the area where the curvature radius of inclusion is smaller. The size of round TiO2 inclusions had little influence on corrosion behavior in this certain environment.
