Inhibiting Corrosion of Mg Alloy AZ31B-H24 Sheet Metal with Lithium Carbonate

CORROSION ◽  
10.5006/3625 ◽  
2020 ◽  
Author(s):  
Basem Zaghloul ◽  
Carol Glover ◽  
John Scully ◽  
Joey Kish
Keyword(s):  
Sheet Metal ◽  
Anodic Dissolution ◽  
Surface Film ◽  
Lithium Carbonate ◽  
H2 Evolution ◽  
X Ray ◽  
Corrosion Rates ◽  
Macro Scale ◽  
Corrosion Mode ◽  
Electrode Technique

The objective of this work was to determine the effectiveness of dissolved Li2CO3 as a corrosion inhibitor for AZ31B-H24 sheet metal when immersed in NaCl (aq) at ambient temperature. Corrosion rates were determined by gravimetric mass loss and volumetric H2 evolution measurements and the observed inhibition was investigated further using potentiodynamic polarization, scanning vibrating electrode technique and X-ray photoelectron surface analytical measurements. We show that dissolved Li2CO3 significantly inhibits corrosion as it reduces the corrosion rate by a factor of 10. The manner in which inhibition is achieved is rationalized by the role played by the surface film produced during corrosion in inhibiting both the anode (anodic dissolution) and cathode (H2 evolution) kinetics. Inhibition involves the suppression of the filament-like corrosion mode, albeit on the macro-scale, and associated cathodic activation. By process of elimination, we propose that the Li+ cations play a key role in inhibiting the anodic dissolution and associated cathodic activation that is required to drive the filament-like corrosion.

scholarly journals Towards a Physical Description of the Role of Germanium in Moderating Cathodic Activation of Magnesium

CORROSION ◽  
10.5006/3624 ◽  
2020 ◽  
Author(s):  
Carol Glover ◽  
Ruiliang Liu ◽  
Beth McNally ◽  
Shooka Mahboubi ◽  
Joseph McDermid ◽  
...  
Keyword(s):  
Anodic Dissolution ◽  
Anodic Polarization ◽  
Film Formation ◽  
Surface Film ◽  
H2 Evolution ◽  
Physical Description ◽  
Alloying Additions ◽  
Testing Condition ◽  
Electrode Technique

The role played by surface film formation in moderating cathodic activation (i.e. H2 evolution associated with anodic dissolution in NaCl (aq)) was determined for an Mg-0.3Ge (wt%) alloy and contrasted with this process in pure Mg. Cathodic activation was not detected using the scanning vibrating electrode technique (SVET) during anodic dissolution of the Mg-0.3Ge alloy under either freely corroding or anodic polarization conditions. Filament tracks that initiated under the more aggressive testing condition remained electrochemically inert. However, volumetric H2 evolution measurements revealed that Ge alloying additions ‘switch off’ the remote cathodes observed on previously corroded pure Mg surfaces, while Ge additions did not eliminate the “local” cathode at the principal sites of anodic activity (which cannot be detected by SVET). As such, the quantity of H2 measured on the corroding Mg-0.3Ge alloy arises exclusively from cathodic H2 evolution at the anodic sites. Moderation of sustained cathodic activation by alloying with Ge was associated with the incorporation of Ge into the inner MgO/Mg(OH)2 layer during anodic dissolution of Mg. It is possible that entrapped Ge particles or GeO2 serve as an effective poison for H recombination in the overall H2 evolution reaction that would otherwise readily occur on freshly formed Mg(OH)2 at anodic dissolution sites.

Localized Corrosion of Binary Mg-Nd Alloys in Chloride-Containing Electrolyte Using a Scanning Vibrating Electrode Technique

CORROSION ◽  
2012 ◽  
Vol 68 (6) ◽  
pp. 489-498 ◽  
Author(s):  
G. Williams ◽  
K. Gusieva ◽  
N. Birbilis
Keyword(s):  
Localized Corrosion ◽  
Radial Expansion ◽  
Alloying Additions ◽  
Corrosion Rates ◽  
Surface Breakdown ◽  
Density Values ◽  
Intact Surface ◽  
Mean Current ◽  
Electrode Technique

The influence of neodymium (Nd) alloying additions in the 0.47 wt% to 3.53 wt% range on the localized corrosion behavior of Mg, when freely corroding in aqueous sodium chloride (NaCl) electrolyte, is investigated using an in situ scanning vibrating electrode technique (SVET). For all samples, the point of surface breakdown is an intense focal anode that expands radially with respect to time, revealing a cathodically activated interior, which is galvanically coupled with the local anode at the perimeter. However, for Nd compositions of ≤0.74%, radial expansion ceases within ca. 2 h of initiation, whereupon dark filiform-like corrosion features are observed, which traverse over the exposed Mg surface. For Nd additions of ≥1.25%, the radial expansion continues with time up to a point where the entire intact surface becomes consumed. The intensity of the local anode ring of circular corroded regions is seen to increase as more cathodically activated corroded surface becomes exposed. Mean current density values measured within these corroded areas increase progressively with Nd content, leading to a progressive rise in localized corrosion rates. The cathodic activation of corroded regions is proposed to derive from an enrichment of noble, Nd-rich intermetallic grains caused as the alpha-Mg phase becomes attacked at local anode sites.

scholarly journals Surface film X-ray microanalysis

Scanning ◽  
1990 ◽  
Vol 12 (4) ◽  
pp. 212-224 ◽  
Author(s):  
J. L. Pouchou ◽  
F. Pichoir
Keyword(s):  
Surface Film ◽  
X Ray

Analysis of Wet-Process Phosphoric Acid and By-Product Filter Cake by X-ray Spectrometry

1984 ◽  
Vol 28 ◽  
pp. 221-226
Author(s):  
Wendell D. Wilhide ◽  
Doris H. Ash
Keyword(s):  
Phosphoric Acid ◽  
Calcium Sulfate ◽  
Filter Cake ◽  
Lithium Carbonate ◽  
Chemical Analyses ◽  
Element Analysis ◽  
X Ray ◽  
Wet Process ◽  
Control Precision ◽  
Preparation Techniques

AbstractRapid X-ray fluorescence (XRF) analytical methods have been developed for analyzing wet-process phosphoric acid liquid samples and by-product calcium sulfate filter-cake solids. Liquid acid samples are neutralized by lithium carbonate and pressed-pellet, dry sample wafers are prepared for a nine-element analysis. Filter-cake solids are dehydrated to anhydrous calcium sulfate for a ten-element analysis. Hovel sample preparation techniques are described which permit maximum use of the automated XRF system for process control. Precision obtained for typical materials is compared with results of conventional chemical analyses.

scholarly journals An Operando X-ray Absorption Spectroscopy Study of a NiCu−TiO2 Photocatalyst for H2 Evolution

ACS Catalysis ◽  
2020 ◽  
Vol 10 (15) ◽  
pp. 8293-8302 ◽  
Author(s):  
Davide Spanu ◽  
Alessandro Minguzzi ◽  
Sandro Recchia ◽  
Fahimeh Shahvardanfard ◽  
Ondřej Tomanec ◽  
...  
Keyword(s):  
Absorption Spectroscopy ◽  
Spectroscopy Study ◽  
Tio2 Photocatalyst ◽  
H2 Evolution ◽  
X Ray ◽  
X Ray Absorption

scholarly journals Micro- and macro-scale water retention properties of granular soils: contribution of the X-Ray CT-based voxel percolation method

Soil Research ◽  
2019 ◽  
Vol 57 (6) ◽  
pp. 575
Author(s):  
Erika Shiota ◽  
Toshifumi Mukunoki ◽  
Laurent Oxarango ◽  
Anne-Julie Tinet ◽  
Fabrice Golfier
Keyword(s):  
Water Retention ◽  
Drainage Water ◽  
Transport Processes ◽  
Water Retention Curve ◽  
Granular Soils ◽  
Pore Scale ◽  
Micro Computed Tomography ◽  
X Ray ◽  
Percolation Method ◽  
Macro Scale

Water retention in granular soils is a key mechanism for understanding transport processes in the vadose zone for various applications from agronomy to hydrological and environmental sciences. The macroscopic pattern of water entrapment is mainly driven by the pore-scale morphology and capillary and gravity forces. In the present study, the drainage water retention curve (WRC) was measured for three different granular materials using a miniaturised hanging column apparatus. The samples were scanned using X-ray micro-computed tomography during the experiment. A segmentation procedure was applied to identify air, water and solid phases in 3D at the pore-scale. A representative elementary volume analysis based on volume and surface properties validated the experimental setup size. A morphological approach, the voxel percolation method (VPM) was used to model the drainage experiment under the assumption of capillary-dominated quasi-static flow. At the macro-scale, the VPM showed a good capability to predict the WRC when compared with direct experimental measurements. An in-depth comparison with image data also revealed a satisfactory agreement concerning both the average volumetric distributions and the pore-scale local topology. Image voxelisation and the quasi-static assumption of VPM are likely to explain minor discrepancies observed at low suctions and for coarser materials.

scholarly journals Understanding H2 Evolution from the Decomposition of Dibutylmagnesium Isomers Using in-Situ X-ray Diffraction Coupled with Mass Spectroscopy

2019 ◽  
Vol 2 (7) ◽  
pp. 5272-5278 ◽  
Author(s):  
Jian Liu ◽  
H. Todd Schaef ◽  
Paul F. Martin ◽  
B. Pete McGrail ◽  
Leonard S. Fifield
Keyword(s):  
Mass Spectroscopy ◽  
H2 Evolution ◽  
X Ray Diffraction ◽  
X Ray

scholarly journals Hydrothermal Synthesis of rGO/PbTiO3 Photocatalyst and Its Photocatalytic H2 Evolution Activity

2019 ◽  
Vol 2019 ◽  
pp. 1-9 ◽  
Author(s):  
Chunyan Wang ◽  
Lianwei Shan ◽  
Dongyuan Song ◽  
Yanwei Xiao ◽  
Jagadeesh Suriyaprakash
Keyword(s):  
Photocatalytic Performance ◽  
H2 Evolution ◽  
X Ray Diffraction ◽  
Hydrothermal Route ◽  
X Ray ◽  
Transmission Electron ◽  
Reduced Graphene ◽  
Efficient Charge ◽  
One Step ◽  
Photocatalytic H2 Evolution

In this letter, we investigated the photocatalytic activity of the newly formed rGO/PbTiO3 composites, which are synthesized by a one-step hydrothermal route. By adjusting the amount of reduced graphene oxide (rGO) (0, 0.15, 0.30, 0.60, and 1.20 wt%) with the PbTiO3, we constructed various photocatalysts for this investigation. The crystal structure and morphology of the various composites were studied by powder X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HRTEM). Photoelectron spectroscopic study revealed that the band structure of the newly formed composites and efficient charge separation can be obtained by the interfaces of various rGO content. In addition, the photocatalytic performance of the synthesized composites was explored by H2 evolution and rhodamine blue (RhB) degradation. The obtained results indicated that the addition of the appropriate amount of rGO could improve the activity of pure PbTiO3, significantly.

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