The Potential of the Superhydrophobic State to Protect Magnesium Alloy against Corrosion

We describe the technologically simple route for the fabrication of the superhydrophobic coatings on top of wrought magnesium alloy MA8 based on nanosecond laser processing followed by the chemical vapor deposition of fluorosilane. The chemical and phase composition, surface morphologies, and variation of the coating wettability during prolonged contact with 0.5 NaCl solution or with salt aerosol were characterized using X-ray diffraction, FT-IR spectroscopy, scanning electron microscopy measurements, and the wettability analysis. The as-prepared coatings demonstrate corrosion current of more than eight orders of magnitude lower, while after 30 days of sample immersion into corrosive solution, the current was four orders of magnitude lower than that obtained for a polished sample which was for only 2 h in contact with electrolyte. The mechanisms of the protective activity of fabricated coatings were discussed.

Peculiarities of stress corrosion fracture of sensitized and neutron irradiated chromium-nickel austenitic steel

The results of SEM studies of fracture surfaces for the 12Cr18Ni9 austenitic steel ruptured under a fixedtensile load in FeCl3 water solutionand in air are presented. The samples of austenized, sensitized at 650° and irradiated with neutrons (to 1020n/cm2) steel were examined. It was shown thatirradiation hardening and sensitizing annealing increased the susceptibility of steel to intergranular cracking in corrosive solution. Structural features of formation of the strain-induced α’-martensite and its reinforcing effect on fracture in various environments are discussed.

Laser Additively Manufactured Iron-Based Biocomposite: Microstructure, Degradation, and In Vitro Cell Behavior

A too slow degradation of iron (Fe) limits its orthopedic application. In this study, calcium chloride (CaCl2) was incorporated into a Fe-based biocomposite fabricated by laser additive manufacturing, with an aim to accelerate the degradation. It was found that CaCl2 with strong water absorptivity improved the hydrophilicity of the Fe matrix and thereby promoted the invasion of corrosive solution. On the other hand, CaCl2 could rapidly dissolve once contacting the solution and release massive chloride ion. Interestingly, the local high concentration of chloride ion effectively destroyed the corrosion product layer due to its strong erosion ability. As a result, the corrosion product layer covered on the Fe/CaCl2 matrix exhibited an extremely porous structure, thus exhibiting a significantly reduced corrosion resistance. Besides, in vivo cell testing proved that the Fe/CaCl2 biocomposite also showed favorable cytocompatibility.

Effect on Current Density on Zero Charge Corrosion Protection of Pure Mg in 3.5% NaCl Solution

The cathodic protection uses two-electrode polarization, which requires large currents and substantial voltages. Efforts are being made to identify possibilities for improvements by developing zero-charge corrosion protection techniques. Studies were performed to determine the zero-charges potential effect by analyzing corrosion signs on reactive metal samples such as pure Mg. Mg samples were fed by current/ voltage pulses for 120 hours, with specified pulse parameters and varied Ecorr- offsets, ranging from +2 to -218 mV. The volumetric hydrogen gas collection technique is used to determine the hydrogen evolution rate. Surface observation is carried out by stereomicroscope to determine the presence of corrosion signs on the sample surface. Overall, all current densities and hydrogen evolution rates had very low readings on the studied Ecor offset parameters. Mg samples fed with pulses at -1800 and -1900 mV vs SCE revealed zero charge potential effects since their surface was clean and showed no indications of corrosion even after being exposed to the corrosive solution for 120 hours. Thus, corrosion protection is successfully done and meets the Epzc condition.

Prediction of Sulfate Attack Products in Portland-Limestone Cements: The Effect of Cation Type and Concentration

Portland-limestone cement materials are susceptible to sulfate attack at low temperature and high humidity, because such conditions facilitate the formation of thaumasite, detriment to the structural integrity of calcium silicate hydrates (C─S─H). In this work, the effect of the cation associated with sulfates, concentration of sulfate solution, and limestone content in cement, were thermodynamically simulated. MgSO4 solution is of higher risk, degrading extensively the structural integrity of C─S─H. Although this phase is partially preserved under the effect of Na2SO4 and K2SO4 solutions, extensive expansion and thaumasite formation occur. The sulfate content of the corrosive solution and the limestone content in cement are the factors mostly intensifying the attack caused by MgSO4 and Na2SO4/K2SO4 solutions, respectively.

Titanium Dioxide and Its Applications in Mechanical, Electrical, Optical, and Biomedical Fields

Titanium dioxide (TiO2), owing to its non-toxicity, chemical stability, and low cost, is one of the most valuable ceramic materials. TiO2 derived coatings not only act like a ceramic protective shield for the metallic substrate but also provide cathodic protection to the metals against the corrosive solution under Ultraviolet (UV) illumination. Being biocompatible, TiO2 coatings are widely used as an implant material. The acid treatment of TiO2 promotes the attachment of cells and bone tissue integration with the implant. In this chapter, the applications of TiO2 as a corrosion inhibitor and bioactive material are briefly discussed. The semiconducting nature and high refractive index of TiO2 conferred UV shielding properties, allowing it to absorb or reflect UV rays. Several studies showed that a high ultraviolet protection factor (UPF) was achieved by incorporating TiO2 in the sunscreens (to protect the human skin) and textile fibers (to minimize its photochemical degradation). The rutile phase of TiO2 offers high whiteness, and opacity owing to its tendency to scatter light. These properties enable TiO2 to be used as a pigment a brief review of which is also addressed in this chapter. Since TiO2 exhibits high hardness and fracture toughness, the wear rate of composite is considerably reduced by adding TiO2. On interacting with gases like hydrogen at elevated temperatures, the electrical resistance of TiO2 changes to some different value. The change in resistance can be utilized in detecting various gases that enables TiO2 to be used as a gas sensor for monitoring different gases. This chapter attempts to provide a comprehensive review of applications of TiO2 as an anti-corrosion, wear-resistant material in the mechanical field, a UV absorber, pigment in the optical sector, a bioactive material in the biomedical field, and a gas sensor in the electrical domain.

In Vitro Ion Release of Wires in Removable Orthodontic Appliances

Various orthodontic wire compositions and configurations are present on the market for removable appliances; however, there have still been only few studies focusing on the effect of resin color and additives such as glitter on corrosion of metallic wires under different conditions. Thus, the aim of the study was to compare concentrations of released ions (aluminium, chromium, nickel) in a corrosive medium under three different conditions: non-loaded wires, loaded wires, and non-loaded wires treated with Kukis® cleaning tablets. Six different wires made of three types of steel alloy were embedded in PMMA resin leaving one centimetre of each wire emerging from the resin to come into contact with the corrosive medium. Glitter particles were added to half of the produced test specimens. For the unloaded test series, five specimens of each group were covered in a petri dish with 50 mL of corrosive medium (pH 2.3) following EN-ISO 10271 for seven days at 37 °C. The wires for the mechanically loaded test specimens overlapped the resin by 5 cm and were clamped into a time-switched electric drive for a defined period of time before the samples were taken after a testing time of 7 days. In the third group, unloaded test specimens were transferred from their petri dishes into the prepared Kukis® solution every 24 h before being stored in the corrosive medium. Inductively coupled plasma mass spectrometry (ICP-MS) was used to quantify the specific ions in the corrosive solution. Statistical analysis showed that the mechanical loading of all wires could significantly raise the diffusion of ions into the corrosive medium. The colour of the resin did not affect the concentration of the released ions. The Kukis® cleaning tabs could not lower the corrosion of the tested metals, as some of the wires were corroded even more using the brace cleanser. Glitter-containing test specimens showed significantly higher amounts of aluminium. Mechanical loading as well as the presence of glitter particles in the resin significantly affected ion concentrations.

DNA Inhibition of Hydrogen Ion-Induced Corrosion of Mild Steel Used for Pipelines in Oil and Gas Industries

Corrosion of mild steel via chemical reaction in a corrosive environment is a problematic occurrence that is very common in oil and gas industries. Corrosion constitutes a huge part of the total costs in the production of oil and gas. Corrosion inhibitors have found interest in the scientific domain because they are mainly understood by their chemical complexes and formulations. Their utilization in small amount on metal surface used in oil and gas industries can help shield the metal from corrosion devoid of any significant alteration in the concentration of the corrosive media in the environment. An effort was made to study the possibility of using calf thymus gland DNA (CTGDNA) inhibitor in chlorine induced mild steel for possible usage in piping in oil and gas industry. The SEM micrograph shows that the adsorption of the CTGDNA biomacromolecules coat on the mild steel surfaces functions as a protection against HCl corrosive solution. Electrochemical study and weight loss analysis showed that the inhibitor efficiency (70.48 and 72%, respectively) of the tested DNA (CTGDNA) in HCl acidic corrosion environment for the mild steel was high at 1.5 M of HCl. The inhibitor efficiency decreased with increasing HCl concentrations. The open circuit potential (OPC) revealed that the mild steels got corroded until the end of the immersion. The intensities of XRD peak substantiate the existence of corrosion products of FeCl2.

Corrosion Rate of Black Chromium Coating Result of Electroplating on Copper

The problem faced is that the white chromium coating has a low selling value or aesthetic value than the black chromium layer which is more in demand, especially by the younger generation who prioritizes aesthetics. The purpose of the corrosion test was to determine the corrosion resistance ability of the black chromium coating resulting from the electroplating process on the relationship between the solution temperature and the immersion time of copper in a corrosive solution. Corrosion test methods include literature studies, field observations, weighing specimens, immersing specimens in corrosive solutions, weighing specimens, calculating corrosion rates, and data analyzing. Corrosion test results show that the higher the temperature of the solution and the longer the immersion time, the smaller the corrosion rate for the lowest conditions at 30oC and a duration of 5 minutes with a corrosion rate of 0.2004 mm/year and the highest conditions at a temperature of 50oC and a duration of 9 minutes at a rate of corrosion of 0.0108 mm/year.

Ability to use of Robinia pseudoacania L fruit extract as a natural corrosion inhibitor in the protection of historical bronze objects

Background: The phenomenon of bronze disease is considered as the most important factor in the destruction of bronze objects. Different methods have been proposed to cope with it. The most important inhibitors used in this regard are BTA and AMT(5-ami- no-2-mercapto-1,3,4-thiadiazole). While these inhibitors control the corrosion, they are toxic and cancerous. In the ideal conditions, these inhibitors are able to slow down the activity of chlorine ion, but they leave some side effects after a period of treatment. Today, plant extracts are used for this purpose. In this study, Robinia pseudoacania L extract was selected for this purpose.Material and methods: Natural inhibitor of Robinia fruit at concentrations of 200 ppm to 1800 ppm was evaluated in a corrosive solution of sodium chloride 0.5 M on a bronze alloy with a percentage similar to ancient alloys (Cu-10Sn) using potentiostat, weight loss method, and humidifier area.Results: Given the data derived from potentiostate device showed that Robinia pseudoacania L Inhibitory power at 1000 ppm with corrosion rate of 12.78% is 55% and the classic method of weight loss inhibitory power after four week at 1800 ppm Robinia pseudoacania L in contrast a corrosive solution of sodium chloride 0.5 M is 92% for bronze alloy (Cu-10Sn). In addition, SEM images suggest that the formation of film on the coupon has been flacked. While the results of the analyses suggest the inhibitory power of Robinia pseudoacania L, granular corrosion is evident on the coupons surfaces in SEM-EDX(Scanning Electron Microscope-Energy Dispersive X-rays) images and analysis.Conclusion: According to the SEM-EDX method, the acetate potential device and the classical weight loss method on bronze (Cu-10sn), the results show that the corrosion rate in the acetate potential method is 55%, while in the classical method the reduction is shown. The weight of this figure reaches 92%. It is important to note that the SEM images show a kind of grain boundary separation on the coupons of this alloy, which is due to the presence of this substance in the corrosive solution of sodium chloride.