LIPID METABOLISM DYNAMICS IN TEST-SUBJECTS OF A 5-DAY DRY IMMERSION EXPERIMENT

Blood samples from six 25–40 y.o. male subjects in a 5-d dry immersion (DI) experiment were analyzed for cholesterol, cholesterol of high- (HDLP), low- (LDLP) and very low density lipoproteins, triglycerides, apolipoproteins А1 (аpoА1) and apolipoproteins В (аpоВ), non-esterified (free) fatty acids (NEFA), β-hydroxibutyrate and phospholipids. Atherogenic indices were calculated, as well as the ratios of cholesterol, аpоВ/аpоА1 and cholesterol/phospholipids. No significant changes in cholesterol or lipoprotein fractions were determined. Increases in the triglyceride level and apoB/apoA1 ratio as harbingers of incipient atherogenesis showed up on the final day in DI and disappeared two days later. The process of readaptation to normal conditions is accompanied by the development of a stress reaction characterized by increased use of lipid substrates (phospholipids, β-hydroxybutyrate, NEFA) for energy synthesis.

The mechanical properties and corrosion resistance of selective laser melting 30CrMnSiA steel

Purpose The purpose of this paper is to study the mechanical and corrosion behaviors of selective laser melting (SLM) 30CrMnSiA steel. Design/methodology/approach The microstructure, mechanical behavior and corrosion resistance of SLM 30CrMnSiA steel were studied by electrochemical test and immersion experiment. Findings The results showed that the microstructure of SLM 30CrMnSiA steel contained equiaxed fine (25.0 µm) ferrite and lamellar pearlite. The tensile strength of SLM 30CrMnSiA steel under the process parameters is 1,447 MPa and the elongation is 7.5%. As the immersion/salt spray test time increased to 15 days/48 h, corrosion mainly occurred in the local position of the sample and corrosion resistance decreased. When the immersion/salt spray test time increased to 30 days/168 h, the corrosion production covered the surface of the samples and the corrosion resistance increased. Originality/value The paper can guide the application and in situ repair for low-alloy steel by additive manufacturing.

Influence of Acetic Acid on the Integrity and Protectiveness by an Iron Carbonate (FeCO3) Corrosion Product Layer

ABSTRACT The effect of undissociated acetic acid on the integrity of iron carbonate (FeCO3) layer formed on platinum and X65 steel substrates is investigated. Experiments were conducted using buffered solutions with 0.8 - 5 mM undissociated acetic acid. For the platinum substrates, changes in the FeCO3 layer were monitored via in-situ electrochemical quartz crystal microbalance (EQCM) measurements. This investigation was supported by performing electrochemical experiments, under comparable conditions, on the X65 steel specimens, linking the integrity of FeCO3 layer to its corrosion protection effect. The EQCM measurements revealed that the addition of acetic acid, at all concentrations tested here, caused partial dissolution of the FeCO3 layer. The dissolution occurred selectively, with the outer layer dissolving first, leaving behind an inner FeCO3 layer at the end of the immersion experiment. The electrochemical results revealed that introducing the acetic acid caused a sudden increase in the corrosion rate, which over time returned to a lower value similar in magnitude to that seen before addition of the acetic acid. This was attributed to the protection provided by the inner FeCO3 layer, which was only mildly affected by the addition of acetic acid and was able to repair over time. It was proven that the dissolution of the protective FeCO3 layer in the presence of acetic acid was not due to a small pH change but rather due to the formation of ferrous acetate complexes and changes in ionic strength, which decreases the FeCO3 saturation values.

Marine Biofouling Communities of Manila South Harbor, Philippines

An immersion experiment was conducted in the Manila South Harbor to document the development of sessile biofouling communities. Test panels were submerged below the sea surface in April 2012 for short- (one and three months) and long-term (one year) exposures in seawater, then foauling types and occurrences were scored based on digital images of panel surfaces. The short-term immersed panels were found with significant cover of soft fouling (undet.), slime, and the invasive Balanus (=Amphibalanus) amphitrite. These also filled the long-term immersed panels, although some fell off due to mortality from crude oil smothering. Perna viridis, native but also invasive, successfully established and then dominated the fouling cover by the 12th month (April 2013). Oysters, bryozoans (Watersipora sp.), colonial tunicates, polychaetes (Hydroides sp.), and green algae contributed minor to fouling cover. These fouling communities in the Manila South Harbor consisted of organisms that were cosmopolitan in port waters of SE Asia. A similar study must be carried out in other major ports of the country and then compared.

Effect of Ultrasonic Surface Rolling Treatment on Corrosion Behavior of Alloy 690

The nanograins (NG) on the top surface layer of alloy 690 were successfully prepared by ultrasonic surface rolling treatment (USRT). The average grain size of NG alloy 690 was 55 nm, and the thickness of the NG surface layer was about 1 μm. Meanwhile, the surface roughness was significantly reduced after surface nanocrystalliztion. The corrosion behavior of alloy 690 before and after USRT was studied in a secondary side environment containing chloride. Electrochemical corrosion experiments demonstrated that the passive film generated by USRT was denser than that formed on coarse-grained (CG) alloy 690. Pitting corrosion was prone to occur in grain boundaries of CG alloy 690, and the pits on the surface of NG alloy 690 were smaller than those generated on CG alloy 690 after 1000 h of an immersion experiment.

Preparation and Corrosion Behavior in Marine Environment of MAO Coatings on Magnesium Alloy

To improve the corrosion performance of magnesium alloys in the marine environment, the MAO, MAO–Cu2CO3(OH)2·H2O and MAO–Cu2P2O7 ceramic coatings were deposited on AZ91D magnesium alloys in basic electrolyte and the discoloration mechanism of the Cu-doped MAO coatings and the corrosion behavior of the three MAO coatings in the artificial seawater solution were investigated by SEM, EDS and XPS. The results indicated that the formation and discoloration mechanism of the brown MAO ceramic coatings were attributable to the formation of Cu2O in the coatings. Though the three MAO coatings had a certain protective effect against the corrosion of AZ91D substrate in the artificial seawater, the distinctive stratification phenomenon was found on the MAO–Cu2P2O7 coated sample and the corrosion model of the MAO–Cu2P2O7 coatings in the immersion experiment was established. Therefore, the brown Cu-doped MAO coatings were speculated to significantly reduce the risk of the magnesium parts in marine environments.

Sources of metasilicate in mineral water of Jingyu County, northeastern China

The source of metasilicate in mineral water of Jingyu County. located in Changbai Mountains of northeastern China, was analysed through two groups of water-rock interaction experiments. One is a hydrolysis immersion experiment using basalt and the other is an immersion experiment utilizing a mixture of soil, scoria, and clastic basalt under the same conditions. Results indicate that the metasilicate in mineral water is mainly derived from the hydrolysis of silicates and silica in the basalt, scoria, and soil. In the first immersion experiment, the release of metasilicate is linear, with dissolved metasilicate increasing continuously through time at a stable release rate of about 0.01 mg/(kg·day). The second experiment indicates that the contribution of soil and scoria to metasilicate in mineral water is higher than that of clastic basalt under the same conditions.

Induced-Pitting Behaviors of MnS Inclusions in Steel

This paper investigated the effects of MnS inclusions on inducing pitting in steel. Three different cooling methods were used to control the morphology, size, and distribution of MnS inclusions. AC (alternating current) impedance spectroscopy experiments and potentiodynamic polarization experiments were carried out for different sizes of MnS inclusions. The corrosion immersion experiment was conducted to study the pitting corrosion process in different morphologies of MnS inclusions. The experiment results showed that pitting corrosion occurred around MnS inclusions and pitting was induced along the junction of MnS inclusions and their surrounding steel matrix. Also, the sensitivity of inducing-pitting of MnS inclusions was changed with the change of the average size of MnS in steel and it had a critical size of MnS. The deeper the MnS inclusions were buried in steel matrix, the more difficult it was for it to dissolve and fall off. Herein, it would cause greater damage.

Improvement of Corrosion Resistance of Hastelloy-N Alloy in LiF-NaF-KF Molten Salt by Laser Cladding Pure Metallic Coatings

The corrosion protection of Hastelloy-N alloy in LiF-NaF-KF (commonly referred to as FLiNaK) molten salt has been developed by pure Ni and Co coatings using the laser cladding technique. An immersion experiment with samples was performed in molten FLiNaK salt at 900 °C for 100 h. It was found that the corrosion rates of the pure Ni-coated specimen and the pure Co-coated specimen are 39.9% and 35.7% of that of Hastelloy-N alloy, respectively. A careful microstructural characterization indicates that a selective dissolution of the elemental Cr occurred in the surface of bare Hastelloy-N alloy, showing a severe intergranular corrosion. For pure metal-coated specimens, in contrast, only metal oxide formed during the laser cladding process dissolved into the molten fluoride salt. The dense pure metal (Ni or Co) coatings exhibit a slightly general corrosion and protect the Hastelloy-N substrate effectively. The possible corrosion mechanism for both coated and uncoated Hastelloy-N under the current experimental condition are discussed in this work.

On mechanical properties and bioactivity of PVDF-BCP composites

A ceramic/polymer biocomposite with high potential for multifunctional practical applications in bone tissue engineering was synthesized by using a well-known piezoelectric polymer, polyvinylidene fluoride (PVDF), and a high bioactive biphasic calcium phosphate (BCP) ceramic obtained from recycled fish bones. High-bioactivity was observed for the PVDF-BCP composite when it was subjected to conditions that simulate the animal body once a very thick apatite layer (9 μm) was grown on its surface in an immersion experiment (7 days) in simulated body fluid. The structural characteristics of the PVDF-BCP composite showed similarities with highly bioactive young animal bones, overlapped with PVDF polymorphic phases. Mechanical tests revealed properties very similar to those of the human bone tissue with a resistance strength reaching 80 MPa. Together, all these factors indicated a very promising material for application in osseous implants/replacement with postoperative recovery controlled/accelerated by external stimuli.