• Corrosion Science and Technology
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• v.12 no.1
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• pp.40-49
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• 2013

Effects of magnesium and pH on corrosion of aluminum galvanically coupled to iron have studied by using potentio- dynamic and static tests for polarization curves, Mott-Schottky test for analysis of semiconductor property, and GD-AES and XPS for film analysis. Pitting potential was sensitive to magnesium as an alloying element but not to pH, while passive current was sensitive to pH but not to magnesium. It was explained with, instead of point defect model (PDM), surface charge model describing that the ingression of chloride depends on the state of surface charge and passive film at film/solution interface is affected by pH. In addition, galvanic current of aluminum electrically coupled to iron was not affected by magnesium in pH 8.4, 0.2M citrate solution but was increased by magnesium at the solution of pH 9.1. The galvanic current at pH 9.1 increased with time at the initial stage and after the exposure of about 200 minute, decreased and stabilized. The behavior of the galvanic current was related with the concentration of magnesium at the surface. It agreed with the depletion of magnesium at the oxide surface by using glow discharge atomic emission spectroscopy (GD-AES). In addition, pitting potential of pure aluminum was reduced in neutral pH solution where chloride ion maybe are competitively adsorbed on pure aluminum. It was confirmed by the exponential decrease of pitting potential with log of [$Cl^-$] around 0.025 M of [$Cl^-$] and linear decrease of the pitting potential. From the above results, unlike magnesium, alloying elements with higher electron negativity, lowering isoelectric point (ISE), are recommended to be added to improve pitting corrosion resistance of aluminum and its alloys in neutral solutions as well as their galvanic corrosion resistance in weakly basic solutions.

• Journal of the Korean Ceramic Society
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• v.55 no.5
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• pp.446-451
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• 2018

In this study, different formulations of magnesium oxide and various modifiers (phosphoric acid, ferrous sulfate, pure acrylic emulsion, silicone acrylic emulsion, glass fiber, and polypropylene fiber) were used to prepare magnesium oxychloride cement composites. The compressive strength of the magnesium oxychloride cement was tested, and the softening coefficients of the composites after soaking in water were also calculated. The results showed that a magnesium oxychloride cement sample could not be coagulated when the MgO activity was 24.3%, but the coagulation effect of the magnesium oxide cement sample was excellent when the MgO activity was 69.5%. While pure acrylic emulsion, silicon-acrylic emulsion, and glass fiber showed insignificant modification effects on the magnesium oxychloride cement, ferrous sulfate heptahydrate, phosphoric acid, and polypropylene fiber could effectively improve its water resistance and compressive strength. When the phosphoric acid, ferrous sulfate heptahydrate, and polypropylene fiber contents were 0.47%, 0.73%, and 0.25%, respectively, the softening coefficient of a composite soaked in water reached 0.93 after 7 days, and the compressive strength reached 64.3 MPa.

• Journal of the Korean Society of Marine Environment & Safety
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• v.17 no.2
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• pp.155-160
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• 2011

In these days, there are increasing demands for weight reduction in many industrial fields including marine industries. Therefore, magnesium thin films for lightweight materials were prepared on magnesium alloy substrate. The influence of gas pressure and substrate bias voltages on the crystal orientation and morphology of the films was determined by using X-ray diffraction and FE-SEM, respectively. And the effect of crystal orientation and morphology of the magnesium thin films on corrosion behavior was estimated by measuring electro-chemical anodic polarization curves in deaerated 3% NaCl solution. From the results, corrosion resistance of Mg thin films was improved by controlling the crystal orientation and morphology of the films with effective use of plasma ion plating technique.

• Journal of the Korean institute of surface engineering
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• v.52 no.2
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• pp.96-102
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• 2019

Magnesium and its alloys are prone to be corroded, thus surface treatments improving corrosion resistance are always required for practical applications. As a surface treatment of magnesium alloys, plasma electrolytic oxidation (PEO), creating porous stable oxide layer by a high voltage discharge in electrolyte, enhances the corrosion resistance. However, due to superhydrophilicity of the porous oxide layer, which easily allow the penetration of corrosive media toward magnesium alloys substrate, post-treatments inhibiting the transfer of corrosive media in porous oxide layer are required. In this work, we employed a hydrophobizing method to enhance the corrosion resistance of PEO treated Mg alloy. Three types of hydrophobizing techniques were used for PEO layer. Thin Teflon coating with solvent evaporation, self-assembled monolayer (SAM) coating of octadecyltrichlorosilane (OTS) based on solution method and SAM coating of perfluorodecyltrichlorosilane (FDTS) based on vacuum method significantly enhances corrosion resistance of PEO treated Mg alloy with reducing the contact of water on the surface. In particular, the vacuum based FDTS coating on PEO layer shows the most effective hydrophobicity with the highest corrosion resistance.

• Journal of Korean Society of Environmental Engineers
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• v.33 no.4
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• pp.231-236
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• 2011

The effects of magnesium and calcium ions on phosphorus removal by aluminium coagulation were investigated with various jar tests using settled raw sewage. Maximum TP (total phosphate) removal occurred at pH around 5~6 with aluminium coagulation, and it decreased above pH 6. TP and $H_nPO_4^{n-3}$ removal efficiencies, however, were kept above 95% at pH above 6 by adding the divalent metallic ions like magnesium or calcium ions on aluminium coagulation process. At molar ratio of Al/P ($Al^{3+}/H_nPO_4^{n-3}$) above 3, TP removal efficiency was as high as 80%, and residual TP less than 0.2 mg/L occurred at Al/P ratio above 6. TP removal efficiency was improved by adding magnesium or calcium ions and the optimum $Al^{3+}/Mg^{2+}$ and $Al^{3+}/Ca^{2+}$ ratios were about 2. The required dose of aluminium coagulant was reduced for equivalent amount of TP removal by adding magnesium or calcium ions, as a result sludge generation was also reduced.

• The Korean Journal of Ecology
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• v.19 no.3
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• pp.193-199
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• 1996

Alleviation of Al toxicity by Ca and Mg was studied with seedings of Pinus densiflora, P. rigida and P. thunbergii under the solution culture. The seedlings were cultivated in the enriched Can and Mg nutrient solution with 2, 000 ${\mu}M$ Al for three weeks. The hightest total root lengths of P. densiflora, P. rigida and P. thunbergii increased by 21, 33 and 133% in Ca enriched solution, and 23, 44 and 107% in Mg enriched solution, respectively. Ratios of lateral root to main root length increased significantly in Mg enriched solution, and redution of Al toxicity was more affected by enriched Mg than by enriched Ca. Al content in tissue was reduced by enriched Ca and Mg.

• Environmental Mutagens and Carcinogens
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• v.19 no.1
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• pp.20-27
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• 1999

In order to know the inhibitory effect of magnesium carbonate(MgCO3) on cytotoxicity, DNA damage, mutagenicity, and cell transforming ability of nickel subsulfide, the inhibition of cell proliferation, DNA-protein crosslinks formation (DPC), HGPRT point mutation, and cell transformation were evaluated. Nickel subsulfide(Ni3S2) and magnesium carbonate as insoluble compounds were used for this study. BALB/3T3 cell, CHO-K1 cell, and C3H10T1/2 cell were used in this experiment. Exposure concentration of nickel subsulfide was 1 $\mu\textrm{g}$/ml. The concentrations of magnesium carbonate in this study were 0.6 $\mu\textrm{g}$/ml, 1.2 $\mu\textrm{g}$/ml, 2.4 $\mu\textrm{g}$/ml and the molar ratio of magnesium to nickel when exposed simultanously were 0.5, 1.0 and 2.0 respectively. The results were as follows; 1. Magnesium carbonate reduced the inhibitory effect of nickel subsulfide on cell proliferation. 2. Magnesium carbonate also reduced the effect of nickel subsulfide on DNA-protein crosslinks formation. 3. HGPRT point mutagenicity of nickel subsulfide was reduced when magnesium carbonate treated simultaneously. 4. Magnesium carbonate reduced cell transforming ability of nickel subsulfide. Conclusively, nickel subsulfide showed cytotoxicity, cell transforming ability, and mutagenicity strongly and magnesium carbonate may have protective roles in these nickel effects.

• Journal of Nutrition and Health
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• v.26 no.9
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• pp.1118-1128
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• 1993

This study was undertaken to investigate the acute effect of caffeine consumption on the change of mineral concentration in serum and urinary mineral excretion in healthy young females. On two separate mornings at one week intervals, each subject drank a coffee which contained no caffeine and 3mg/kg body weight caffeine. To obviate dietary effects on mineral concentration in serum and urine, each subject fasted at least ten hours before consuming the test beverage. At one, two, three and four hours, serum and urine production collected seperately for measurement of sodium, potassium, calcium, phosphorus and magnesium concentration. The results were as following : 1) Mean age of subjects was 20.6$\pm$0.32, Mean body mass index of subjects was 21.64$\pm$0.89, which was within $\pm$10% of ideal body weight. 2) Total urine volume of caffein groups for 4 hour after caffeine consumption was higher than that of decaffeine one, but urine pH was unchanged after caffeine consumption. Total urinary four hour excretion of creatinine was not affected by caffeine consumption and creatinine clearance also was not different from the control value. 3) In serum, mean three hour content of sodium(p<0.01) and phosphorus was higher in the subject given the caffeine. Mean serum magnesium and calcium contents were lower in caffeine group than that of decaffeine one. Mean serum magnesium content for three hour after caffeine ingestion was affected by caffeine consumption(p<0.001). Mean serum content of potassium was unaffected by caffeine consumption. 4) Total urinary four hour excretion of sodium, increased significantly after caffeine consumption(p<0.05), while total urinary four hour excretion of potassium, calcium, phosphorus and magnesium was unchanged after caffeine intake. Urinary excretion of Na, Ca, P and Mg was greatest at one hour after caffeine consumption, especially urinary sodium and potassium excretion was significantly high(p<0.05, p<0.01). The above results show that only 3mg caffeine per kg body weight increase the urinary macro mineral excretion in healthy young females.

• Journal of the Korean Crystal Growth and Crystal Technology
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• v.19 no.6
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• pp.324-327
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• 2009

In the present study, the effect of Ca additions on the ignition and combustion behaviors of Mg alloys has been investigated. Cracks and inclusions were observed at the free surface and interior in as-cast pure magnesium but not in Ca-bearing Mg alloys. There was a tendency that ignition temperature rapidly increased with increasing Ca content in Mg-Ca alloy. Saturated composition for increasing of ignition temperature was related with solid solubility of Ca in Ca-bearing Mg alloys. The protective oxide layers, MgO, could also be found on the combustion surface of Ca-bearing magnesium alloy.

• The Journal of Advanced Prosthodontics
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• v.5 no.4
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• pp.402-408
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• 2013

PURPOSE. The aim of this study was to evaluate the surface properties and in vitro bioactivity to osteoblasts of magnesium and magnesium-hydroxyapatite coated titanium. MATERIALS AND METHODS. Themagnesium (Mg) and magnesium-hydroxyapatite (Mg-HA) coatings on titanium (Ti) substrates were prepared by radio frequency (RF) and direct current (DC) magnetron sputtering.The samples were divided into non-coated smooth Ti (Ti-S group), Mg coatinggroup (Ti-Mg group), and Mg-HA coating group (Ti-MgHA group).The surface properties were evaluated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). The surface roughness was evaluated by atomic force microscopy (AFM). Cell adhesion, cell proliferation and alkaline phosphatase (ALP) activity were evaluated using MC3T3-E1 cells. Reverse transcription polymerase chain reaction (RT-PCR) analysis was performed. RESULTS. Cross-sectional SEM images showed that Mg and Mg-HA depositionson titanium substrates were performed successfully. The surface roughness appeared to be similaramong the three groups. Ti-MgHA and Ti-Mg group had improved cellular responses with regard to the proliferation, alkaline phosphatase (ALP) activity, and bone-associated markers, such as bone sialoprotein (BSP) and osteocalcin (OCN) mRNA compared to those of Ti-S group. However, the differences between Ti-Mg group and Ti-MgHA group were not significant, in spite of the tendency of higher proliferation, ALP activity and BSP expression in Ti-MgHA group. CONCLUSION. Mg and Mg-HAcoatings could stimulate the differentiation into osteoblastic MC3T3-E1 cells, potentially contributing to rapid osseointegration.