Localized residual strain develops within the metallurgical texture of 1018 carbon steel from metallurgical processes, such as fabrication, annealing, and shaping. This residual strain results in accelerated localized...Localized residual strain develops within the metallurgical texture of 1018 carbon steel from metallurgical processes, such as fabrication, annealing, and shaping. This residual strain results in accelerated localized pitting due to the formation of anodic sites at these locations. Once initiated, micron-sized corrosion pits can coalesce to form sites of potential catastrophic failure. In this contribution, we focus on the localized biocorrosion which initiates and grows in areas of localized strain such as the interfaces between manganese sulfide (MnS) inclusions and ferrite grains in the steel, at grain boundaries between ferrite grains with different crystallographic orientations and at pearlite grains (intergrown cementite (Fe3C) and ferrite), which are readily found in 1018 carbon steel. Here we hypothesize and show experimentally that accelerated biocorrosion in 1018 carbon steel finds its roots in the electrochemical potential difference (micro galvanic cells) generated between the unstrained ferrite iron (α - Fe) and the lattice defects, dislocations and mismatches found at interfaces formed between α - Fe?and secondary phases i.e. MnS inclusions, cementite lamellar structures and grain boundaries distributed throughout the 3D network of the carbon steel. This hypothesis is supported by results from multiple micro- and nanoscale imaging and analytical methods obtained from field emission scanning electron microscopy, energy dispersive spectroscopy, electron backscattered diffraction and Auger nanoprobe electron spectroscopy. The morphology and composition of grains in the steel coupons were characterized before and after exposure to suboxic and sulfidogenic environments dominated by aerobic and anaerobic marine organisms. Corrosion processes are demonstrated to initiate in localized areas of high residual strain.展开更多
This paper examines the metallic rare earth element (REE) formations that grow on ion exchange/chelating resins. Formation of these stabilized metallic structures leads to composite particle destruction and appears to...This paper examines the metallic rare earth element (REE) formations that grow on ion exchange/chelating resins. Formation of these stabilized metallic structures leads to composite particle destruction and appears to be the result of the dynamic environment of the batch experimentation. Polymeric structure, electron availability, pH, kinetic factors, and the REE f-orbitals play significant roles in the formation of the organometallic framework. f-orbitals are largely still not understood to a great extent but this work serves to elucidate the larger role they may play in ligand interactions. Molecular modeling was utilized as a secondary component in investigating rare earth element (REE) deposition onto ion exchange/chelating resins. Modeling of the f-orbital frontier regions and the application of the HOMO-LUMO transition’s effect on molecular transfer and stability is discussed. Advanced metallic loading, in the manner of an organometallic structure, shows short-term stability resulting in particle destruction as increased REE is adsorbed.展开更多
The present research brings new insights on the role of admixed corrosion inhibitors in the processes of cement hydration and rebar corrosion. The admixing of NaCl and the corrosion inhibitors in fresh mortar was foun...The present research brings new insights on the role of admixed corrosion inhibitors in the processes of cement hydration and rebar corrosion. The admixing of NaCl and the corrosion inhibitors in fresh mortar was found to alter the morphology and microstructure of the hardened mortar at the steel-mortar interfacial region. The admixing of the inhibitors increased the risk of carbonation of cement hydrates at the steel-mortar interfacial region, but partially displaced chloride ions. Chloride and the admixed inhibitors facilitated the formation of different cement hydrates and affected chloride binding at the steel-mortar interfacial region. The admixing of all three inhibitors was found to increase the polarization resistance of steel, indicating reduced corrosion rate of the steel over 48-day exposures to salt ponding.展开更多
文摘Localized residual strain develops within the metallurgical texture of 1018 carbon steel from metallurgical processes, such as fabrication, annealing, and shaping. This residual strain results in accelerated localized pitting due to the formation of anodic sites at these locations. Once initiated, micron-sized corrosion pits can coalesce to form sites of potential catastrophic failure. In this contribution, we focus on the localized biocorrosion which initiates and grows in areas of localized strain such as the interfaces between manganese sulfide (MnS) inclusions and ferrite grains in the steel, at grain boundaries between ferrite grains with different crystallographic orientations and at pearlite grains (intergrown cementite (Fe3C) and ferrite), which are readily found in 1018 carbon steel. Here we hypothesize and show experimentally that accelerated biocorrosion in 1018 carbon steel finds its roots in the electrochemical potential difference (micro galvanic cells) generated between the unstrained ferrite iron (α - Fe) and the lattice defects, dislocations and mismatches found at interfaces formed between α - Fe?and secondary phases i.e. MnS inclusions, cementite lamellar structures and grain boundaries distributed throughout the 3D network of the carbon steel. This hypothesis is supported by results from multiple micro- and nanoscale imaging and analytical methods obtained from field emission scanning electron microscopy, energy dispersive spectroscopy, electron backscattered diffraction and Auger nanoprobe electron spectroscopy. The morphology and composition of grains in the steel coupons were characterized before and after exposure to suboxic and sulfidogenic environments dominated by aerobic and anaerobic marine organisms. Corrosion processes are demonstrated to initiate in localized areas of high residual strain.
文摘This paper examines the metallic rare earth element (REE) formations that grow on ion exchange/chelating resins. Formation of these stabilized metallic structures leads to composite particle destruction and appears to be the result of the dynamic environment of the batch experimentation. Polymeric structure, electron availability, pH, kinetic factors, and the REE f-orbitals play significant roles in the formation of the organometallic framework. f-orbitals are largely still not understood to a great extent but this work serves to elucidate the larger role they may play in ligand interactions. Molecular modeling was utilized as a secondary component in investigating rare earth element (REE) deposition onto ion exchange/chelating resins. Modeling of the f-orbital frontier regions and the application of the HOMO-LUMO transition’s effect on molecular transfer and stability is discussed. Advanced metallic loading, in the manner of an organometallic structure, shows short-term stability resulting in particle destruction as increased REE is adsorbed.
基金Supported by the Research and Innovative Technology Administration under the U.S. Department of Transportation through the University Transportation Center
文摘The present research brings new insights on the role of admixed corrosion inhibitors in the processes of cement hydration and rebar corrosion. The admixing of NaCl and the corrosion inhibitors in fresh mortar was found to alter the morphology and microstructure of the hardened mortar at the steel-mortar interfacial region. The admixing of the inhibitors increased the risk of carbonation of cement hydrates at the steel-mortar interfacial region, but partially displaced chloride ions. Chloride and the admixed inhibitors facilitated the formation of different cement hydrates and affected chloride binding at the steel-mortar interfacial region. The admixing of all three inhibitors was found to increase the polarization resistance of steel, indicating reduced corrosion rate of the steel over 48-day exposures to salt ponding.
