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

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

The Corrosion Behavior of Mg5Y in Nominally Distilled Water

This paper studies the macro and micro corrosion of Mg5Y in nominally distilled water. The Y-containing corrosion product film formed on the alloy surface provides some protection for the Mg matrix to the galvanic corrosion caused by Y-containing second-phase particles. In some cases, there is no corrosion of the matrix surrounding most of the second phase particles. However, about 2% of the second-phase particles in the as-cast Mg5Y causes micro-galvanic corrosion, resulting in 'bump' or 'volcano' shaped corrosion product deposit. These 'active particles' cannot be significantly reduced by solution-heat-treatment

The inhibitive effect of artificial seawater on magnesium corrosion

The corrosion behavior of pure magnesium (Mg) immersed in 3.5 wt% NaCl and artificial seawater is evaluated by immersion test, electrochemical impedance spectroscopy (EIS), polarization curve, scanning electrochemical microscopy (SECM), and corrosion morphology analysis. The results show that the corrosion rate of the pure Mg in the artificial seawater is nearly a half of that in the 3.5 wt% NaCl, and the serious localized corrosion of Mg in the NaCl is inhibited in the artificial seawater. The main constituents MgCl and NaSO in artificial seawater are found to be inhibitive for the corrosion of Mg. The presence of Mg ions could facilitate the formation of Mg(OH) film and thus to some extent retard the dissolution of Mg. The SO ions in the artificial seawater might be absorbed competitively against Cl on the Mg surface to retard the corrosion of Mg. The corrosive and inhibitive effects of other anions and cations on Mg dissolution in the artificial seawater were also briefly analyzed

Influence of casting porosity on the corrosion behaviour of Mg0.1Si

The influence of casting porosity on the corrosion behaviour of Mg0.1Si was investigated for immersion in 3.5% NaCl solution saturated with Mg(OH)(2). The corrosion behaviour was characterised using (i) hydrogen evolution, (ii) weight loss, (iii) cathodic polarisation curves, (iv) electrochemical impedance spectroscopy (EIS), and (v) an examination of the corroded surfaces. Specimens with porosity had higher corrosion rates attributed to the corrosion associated with the pores activating significant corrosion over the whole specimen surface, wherein important aspects were (i) the breakdown of a partly protective surface film, and (ii) micro-galvanic acceleration of the corrosion by Fe-rich particles. (C) 2015 Elsevier Ltd. All rights reserved

Influence of hot rolling on the corrosion behavior of several Mg-X alloys

The influence of hot rolling on the corrosion of Mg-X alloys (X = Gd, Ca, Al, Mn, Sn, Sr, Nd, La, Ce, Zr or Si) was investigated by immersion tests in 3.5% NaCl solution saturated with Mg(OH)(2). The corrosion rates for all Mg-X alloys (except Mg0.1Zr and Mg0.3Si) decreased after hot rolling, attributed to fine-grained alloys having a more homogeneous microstructure, and fewer, smaller second-phase particles. For Mg0.1Zr and Mg0.3Si, the corrosion rate increased after hot rolling. There were a number of possible reasons, one of which was a greater sensitivity to the precipitation of deleterious Fe-rich particles. (C) 2014 Elsevier Ltd. All rights reserved

Long-term exposure to low-dose Di(2-ethylhexyl) phthalate aggravated high fat diet-induced obesity in female mice

The potential obesogenic roles of di(2-ethylhexyl) phthalate (DEHP) have attracted great attention. The current study aimed to evaluate the combined effects of chronic low-dose DEHP (0.05 mg/kg BW) and a high-fat diet (HFD) on obesity in female mice and explore the underlying mechanisms. We found that low-dose DEHP challenge for 29 weeks increased fat accumulation both in CD- and HFD-fed mice and significantly accelerated the weight gain without affecting food intake in HFD-fed mice. DEHP exposure reduced the energy metabolism, down-regulated the uncoupling protein 1 (UCP1) and total oxidative phosphorylation (OXPHOS) proteins expression in the brown adipose tissue, and up-regulated the PPARγ expression and its phosphorylation at Ser273 in white adipose tissue (WAT). Besides, the combination of DEHP and HFD drove the remodeling of gut microbiota of mice, characterized by the reduced richness and diversity and the elevated Firmicutes to Bacteroidetes (F/B) ratio. Short-chain fatty acids (SCFAs) analysis revealed that DEHP and HFD cotreatment led to a decrease in levels of acetic acid, butyric acid, and pentanoic acid. Interestingly, sodium butyrate (NaB) significantly inhibited the adipogenesis and lipid accumulation of NIH/3T3 mouse embryonic fibroblasts (PPARγ2 overexpression) and the PPARγ phosphorylation at Ser273 induced by DEHP or MEHP. These findings demonstrate that chronic low-dose DEHP challenge could prompt fat accumulation by increasing PPARγ phosphorylation at Ser273 and decreasing thermogenesis in BAT, which might be associated with the SCFAs reduction

Review of recent developments in the field of magnesium corrosion

This paper provides a review of recent developments in the field of Mg corrosion and puts those into context. This includes considerations of corrosion manifestations, material influences, surface treatment, anodization, coatings, inhibition, biodegradable medical applications, stress corrosion cracking, flammability, corrosion mechanisms for HP Mg, critical evaluation of corrosion mechanisms, and concluding remarks. There has been much research recently, and much research continues in this area. This is expected to produce significantly better, more-corrosion-resistant Mg alloys