Corrosion mechanism and evaluation of anodized magnesium alloys

The corrosion of anodized Mg alloys is investigated by means of immersion, salt spray, polarization curve, AC electrochemical impedance spectroscopy (EIS), SEM and optical microscopy analyses. Based on the blocking, retarding and passivating effects of an anodized coating on corrosion of Mg alloys, a corrosion model is proposed to illustrate the corrosion reaction at the coating/substrate interface in coating through-pores. It is found that EIS can sensitively respond to the occurrence of corrosion in anodized Mg alloys and reflect the protection performance of anodized coatings, which may be used as an in situ method of monitoring corrosion for anodized Mg alloys

Low apparent valence of Mg during corrosion

Our recent data on Mg corrosion has been reanalysed because of the recent criticism that our previous data analysis was inadequate. Re-analysis leads to similar conclusions as previously. The apparent valence of Mg during corrosion was in each case less than 2.0, and in many cases less than 1.0. Moreover, these values were probably over-estimates. The low values were consistent with the evolving hydrogen gas acting as an insulator, so that the corrosion of parts of the specimen could occur isolated from the electrochemical measurement system

(E)-N′-(3,4-Dimethoxy­benzyl­idene)-2,4-dihydroxy­benzohydrazide methanol solvate

The title compound, C16H16N2O5·CH3OH, was obtained from a condensation reaction of 3,4-dimethoxy­benzaldehyde and 2,4-dihydroxy­benzohydrazide. The non-H atoms of the Schiff base mol­ecule are approximately coplanar (r.m.s. deviation = 0.043 Å) and the dihedral angle between the two benzene rings is 1.6 (1)°. The mol­ecule adopts an E configuration with respect to the C=N double bond. An intra­molecular O—H⋯O hydrogen bond is observed. The Schiff base and methanol mol­ecules are linked into a two-dimensional network parallel to (10) by inter­molecular N—H⋯O, O—H⋯N and O—H⋯O hydrogen bonds

Corrosion and passivation of magnesium alloys

This paper reviews and discusses the possibility of the production of a passive magnesium (Mg) alloy through metallurgical approaches, such as purification, alloying, heat-treatment, mechanical processing and non-equilibrium sputter deposition. High-purity Mg and all existing Mg alloys produced by traditional methods are found to be active in a chloride containing solution. Passivity in a Mg alloy might be produced through a non-equilibrium technique with a sufficiently-high concentration of a strong passivating element supersaturated in the matrix phase. This paper clarifies important concepts regarding the passivity of Mg alloys, and suggests possible approaches to develop a passive, corrosion-resistant Mg alloy

Bis(1,10-phenanthroline-5,6-dione-κ2 N,N′)silver(I) 2-hy­droxy-3,5-dinitro­benzoate

In the cation of the title salt, [Ag(C12H6N2O2)2](C7H3N2O7), the AgI atom is coordinated in a distorted tetra­hedral geometry by four N atoms from two 1,10-phenanthroline-5,6-dione ligands, while the 3,5-dinitro­salicylate anion has only a short contact [2.847 (6) Å] between one of its O atoms and the AgI atom. The dihedral angle between the two 1,10-phenanthroline-5,6-dione ligands is 58.4 (1)°. There is an intra­molecular O—H⋯O hydrogen bond in the 3,5-dinitro­salicylate anion

Influence of microstructure of carbon fibre reinforced polymer on the metal in contact

Abstract(#br)The influence of the microstructure of carbon fibre reinforced polymers (CFRPs) with epoxy matrix (E-CFRP) and nylon matrix (T-CFRP) on the galvanic behaviour of DP590 steel, 6022-aluminium alloy, 1040-steel and AZ31-magnesium alloy was investigated in the GMW14872 solution. The E-CFRP/metal couples were initially more galvanic corrosion resistant, but their galvanic corrosion gradually became more severe than the T-CFRP/metal couples. The effective micro-defects in the surface polymer layer of the CFRP samples critically determined the galvanic corrosion. A detailed surface layer model was proposed, the electrochemical processes through the surface polymer layers during galvanic corrosion were discussed. A better understanding on the microstructure of CFRP determined by composites manufacture process can be obtained

Clinical Study CEUS Helps to Rerate Small Breast Tumors of BI-RADS Category 3 and Category 4

. Purpose. The primary aim of this study was to explore if classification, whether using the BI-RADS categories based on CEUS or conventional ultrasound, was conducive to the identification of benign and malignant category 3 or 4 small breast lesions. Material and Methods. We evaluated 30 malignant and 77 benign small breast lesions using CEUS. The range of enhancement, type of enhancement strength, intensity of enhancement, and enhancement patterns were independent factors included to assess the BI-RADS categories. Results. Of the nonenhanced breast lesions, 97.8% (44/45) were malignant, while, of the hyperplasic nodules, 96.8% (30/31) showed no enhancement in our study. Category changes of the lesions were made according to the features determined using CEUS. The results showed that these features could improve diagnostic sensitivity (from 70.0 to 80.0, 80.0, 90.0, and 90.0%), reduce the negative likelihood ratio (from 0.33 to 0.22, 0.25, 0.11, and 0.12), and improve the NPV (from 88.8 to 92.2, 91.2, 96.2, and 95.5%). However, this was not conducive to improve diagnostic specificity or the PPV. Conclusion. The vast majority of nonenhanced small breast lesions were malignant and most of the hyperplasic nodules showed no contrast enhancement. As a reference, CEUS was helpful in identifying BI-RADS category 3 or 4 small breast lesions

Active corrosion protection by a smart coating based on a MgAl-layered double hydroxide on a cerium-modified plasma electrolytic oxidation coating on Mg alloy AZ31

A composite coating was produced via (i) plasma electrolytic oxidation (PEO) with Ce salt sealing, on which layered double hydroxides (LDHs) were deposited via a hydrothermal treatment, and (ii) then modified by phytic acid (PA) via an ion-exchange reaction. The final coating (characterized using XRD, XPS, FT-IR, SEM, EDS and GDOES) consisted of LDHs/Mg(OH)/CeO/Ce(OH) with a non-uniform Ce distribution. The corrosion protection and self-healing ability were investigated using polarization curves, EIS, immersion tests and SVET. The composite coating modified with PA showed the most superior corrosion protection and self-healing ability, attributed to the synergistic effect between Ce species and phosphate