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The biodegradation rate of Mg alloy medical devices, such as screws and plates for temporary bone fracture fixation or coronary angioplasty stents, is an increasingly important area of study. In vitro models of the corrosion behavior of these devices use revised simulated body fluid (m-SBF) based on a healthy individual’s blood chemistry. Therefore, model outputs have limited application to patients with altered blood plasma glucose or protein concentrations. This work studies the biodegradation behavior of Mg alloy WE43 in m-SBF modified with varying concentrations of glucose and bovine serum albumin (BSA) to (1) mimic a range of disease states and (2) determine the contributions of each biomolecule to corrosion. Measurements include the Mg ion release rate, electrolyte pH, the extent of hydrogen evolution (as a proxy for corrosion rate), surface morphology, and corrosion product composition and effects. BSA (0.1 g l–1) suppresses the rate of hydrogen evolution (about 30%) after 24 h and—to a lesser degree—Mg2+ release in both the presence and absence of glucose. This effect gets more pronounced with time, possibly due to BSA adsorption on the Mg surface. Electrochemical studies confirm that adding glucose (2 g l–1) to the solution containing BSA (0.1 g l–1) caused a decrease in corrosion resistance (by around 40%), and concomitant increase in the hydrogen evolution rate (from 10.32 to 11.04 mg cm–2 d–1) to levels far beyond the tolerance limits of live tissues.

The consequence of exposure to the dual environment of seawater sea sand concrete (SWSSC) on the inner surface and seawater (SW) on the outer surface on the durability of fibre reinforced plastic (FRP) confining tubes has received very limited research attention. The durability of FRPs fabricated with different fibre types was investigated for the application of SWSSC filled tubes and SWSSC-filled double-skin tubes exposed to the external environment of SW. The colour and shininess of carbon-fibre-reinforced polymer (CFRP) surfaces generally stayed unchanged even after 6 months of exposure to the dual environment, whereas basalt-fibre-reinforced polymer (BFRP) and glass-fibre-reinforced polymer (GFRP) tubes suffered degradation. The degradation led to a ~20–30% increase in pH; however, the pH increase in the external SW was more pronounced when the internal solution was SWSSC. The extent of degradation was greater in BFRP that in GFRP. The investigation also included a specialised investigation of the degradation at the fibre–matrix interface by fracturing specimens in liquid nitrogen.

The steel making processes involves extreme and harsh operating conditions; hence, the production hardware is exposed to degradation mechanisms under high temperature oxidation, erosion, wear, impact, and corrosive environments. These adverse factors affect the product quality and efficiency of the steel making industry, which contributes to production downtime and maintenance costs. Thermal spray technologies that circumvent surface degradation mechanisms are also attractive for their environmental safety, effectiveness and ease of use. The need of thermal spray coatings and advancement in terms of materials and spray processes are reviewed in this article. Application and development of thermal spray coatings for steel making hardware from the molten metal processing stages such as electric arc and basic oxygen furnaces, through to continuous casting, annealing, and the galvanizing line; to the final shaping process such as cold and hot rolling of the steel strips are highlighted. Specifically, thermal spray feedstock materials and processes that have potential to replace hazardous hard chrome plating are discussed. It is projected that novel coating solutions will be incorporated as awareness and acceptance of thermal spray technology grows in the steel making sectors, which will improve the productivity of the industry.

Mild steel continues to be the most extensively used construction material in several industries and constructions. However, corrosion of mild steel in aggressive environments is a major concern. Under the tremendously increasing demand for improving the coatings strategies because of the environmental concerns due to some of the traditional coatings, silane pre-treatments have been emerging as one of the effective solutions, among other strategies. Different approaches, such as adding particles of metal oxide (such as SiO2, ZrO2, Al2O3, TiO2 and CeO2), incorporating plant extracts and impregnating 2D materials into the coatings, have been employed for durable corrosion resistance, including for mitigating enhanced corrosion due to the presence of bacteria. This review discusses the critical mechanistic features of silane coatings such as the role of hydrolysis and condensation in the bonding of silanes with metal surfaces. The factors that influence the performance of the silane coatings for corrosion resistance of mild steel are discussed. In particular, this review provides insight into silane coatings for mitigating microbiologically influenced corrosion (MIC) of mild steel.

Graphene coatings have been reported to suppress corrosion of various metal substrates due to their chemical inertness. However, the extent of protection offered depends on the uniformity and defect density of the graphene layers developed on the metallic substrates. Among the various synthesis methods, chemical vapour deposition (CVD) is one of the most promising ones to produce graphene coating on a variety of metal substrates. However, achieving controlled CVD growth of large area, uniform and less defective graphene coating is still challenging. This study investigates the influence of various CVD growth parameters during the graphene synthesis, such as hydrogen flow, carbon precursor flow, growth temperature and cooling rate used on the uniformity of the resultant graphene coating and its corrosion resistance. The barrier properties of graphene-coated Cu substrates were evaluated using potentiodynamic polarisation and electrochemical impedance spectroscopy (EIS) in 0.1 M NaCl for 1008 h. High graphene growth temperature (1060 ºC) and low hydrocarbon flow rate (1 sccm) in the absence of H2 flow were identified to synthesize a uniform graphene coating, which showed durable barrier performance. During the initial hours of immersion, the graphene coated copper (Cu) specimens showed about one and half order of magnitude improvement in corrosion resistance in 0.1 M NaCl and even after 1008 h, the corrosion resistance provided by the graphene coating was almost five times more than that of bare Cu. The optimized CVD graphene parameters reported here can provide a new direction to achieve long-term durable graphene coating.

Microstructurally different regions (namely the weld metal, heat affected zone (HAZ), and base metal) were characterised in weldments of 9Cr-1Mo steel, and composite specimens comprising the three regions were oxidised in air at 923 K. As measured by surface profilometry, the weld metal region was found to form a thicker oxide scale than the other regions of the weldment. The difference in thickness between the scales over the weld and adjoining H AZ regions was found to be ∼ 5 μm after 4 h but had increased to ∼ 100, μm in 100 h. Difference in thickness between the scales was also confirmed by a few examinations using scanning electron microscopy (SEM); this method also described the difference in morphology of the scales developed over the three regions. Secondary ion mass spectroscopy (SIMS) depth profiles of iron and chromium in scales developed over the different regions of the weldments have suggested a considerably higher chromium content of the inner scales on the H AZ and base metal than ...

Microstructural degradations in the base metal adjacent to the weld pool, i.e., the heat-affected zone (HAZ), caused during welding of 2.25Cr-1Mo steel, were characterized by electron and optical microscopy of different regions of the weldments. In order to study the influence of the microstructural degradations on scaling kinetics in steam and the resulting subscale features, samples of the base metal, the HAZ, and weld metal specimens were extracted from the weldment and oxidized in an environment of 35 pct steam+nitrogen at 873 K for 10 hours. Oxide scales formed in the three regions and the underlying subscales were characterized using scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Influence of the “free” chromium content in the three weldment regions on protective scale formation and on the subscale features has been investigated. As the principal achievement, this study has clearly shown the occurrence of oxidation-induced void formation in the subscale zone and grain boundary cavitation in the neighboring area during steam oxidation of the HAZ. This article also discusses the possible role of oxidation-induced void formation and grain boundary cavitation in the inferior service life of welds in 2.25Cr-1Mo steel components.

In order to study the influence of microstructural variation on the oxidation of the weldment of 2.25Cr-1Mo steel, regions with different microstructures were identified by optical microscopy. The weld metal, the base metal, and the heat-affected zone (HAZ), as well as the subzones within the HAZ, i.e., the intercritical (ICR), the fine-grain bainite (FGB), and the coarse-grain bainite (CGB) regions were separated from the weldment by precise steps of metallography. Transmission electron microscopic examinations for the identification of the secondary phases in microstructurally different regions and subzones have suggested that M23C6 and M7C3 pre-cipitates form predominantly in the subzones of HAZ, whereas the Mo2C type of carbide forms exclusively in the weld-metal and base-metal regions of the weldment. However, population and distribution of the secondary phases were different in the three subzones of the HAZ. In order to understand the influence of these microstructural variations on the oxidation behavior, the various regions and subzones were oxidized at 773 and 873 K. The HAZ and its constituents were found to oxidize at much higher rates than the weld metal and the base metal. Relative compositions and morphologies of the scales were compared by scanning electron microscopy with energy-dispersive analyses of X-rays (SEM/EDX), and secondary ion mass spectrometry (SIMS). Scale formed over the weld metal shows a greater tendency for spallation, as suggested by tests monitoring acoustic emission. X-ray diffraction (XRD) patterns of the scales over these specimens were taken. Results of the SEM/EDX, SIMS, and XRD investigations suggest for-mation of inner scales with less Cr(i.e., less protective) over the HAZ than over the weld-metal and the base-metal regions. Variation in the Cr contents of the scales formed over the various regions is proposed to arise from the difference in microstructural features in different regions of the weldments.

Two 9Cr–1Mo steels containing 0·26 and 0·75 wt-%Si were subjected to different annealing treatments to vary the prior austenite grain size. When oxidised in air at 973 K, the grain boundaries oxidise at higher rates than the areas within the grains, and thus develop oxide ridges. In addition to this morphological difference these grain boundary ridges also show compositional dissimilarities from the oxides formed within the grains, as suggested by the results from analyses using scanning electron microscopy and secondary ion mass spectrometry (SIMS) at these locations. Both energy dispersive X-ray analysis and secondary ion imaging confirm the high Si content of the oxides in the ridges. Oxide ridges and the scales within the grains of the oxidised alloys having different grain sizes and Si contents have been extensively characterised by obtaining depth profiles for different elements using SIMS. An important observation is that there is a synergistic influence of the grain size and the Si content...

This paper presents the characterization results of nanocrystalline Zinc Oxide with different crystallite sizes prepared by mechanochemical synthesis. Nano ZnO particles of different crystallite size were synthesized by high energy milling of precursor powders for various periods of time. Diluents were added to the precursor powders to reduce the agglomeration of product phase and to avoid the spontaneous reaction of precursor powders. After the milling process, diluents were selectively leached out using distilled water. X‐ray Diffraction data was used to analyze the crystallite size of the nanoparticles and also to analyze the progress of the chemical reaction during milling process. Crystallite sizes were calculated from the XRD peak broadening using the Sherrer’s formula. Crystallite sizes were seen to increase at a faster rate after 5h of milling where as bellow 5h of milling, little increase was observed. This increase in crystallite size at higher milling time could be attributed to cold welding and solid state diffusion of the nano particles as a result of high energy impacts from ball to powder collision. Scanning Electron Microscope was employed to analyze the particle morphology and size distribution of the nano ZnO powders. Ultraviolet ‐Visible (Uv‐Vis) spectroscope was employed to analyze the optical absorption of the ZnO nano particles.

Normalized 2¼Cr-1Mo steel was isothermally oxidized at 973 K in air to develop an oxide scale of about 40μm thickness. The pre-oxidized specimens were then subjected to thermal cycling between 973 ...

Accelerated Rupture Testing is used to aid in assessing the remaining life for components such as pipes and tubes used in high temperature plants. Due to the high temperature nature of the test, oxide growth plays a role in affecting the test by enhancing the stress. This paper includes the study of oxide-scale growth and metal loss kinetics during air oxidation of three Cr-Mo steels used in the manufacturing of boiler tubing. These tests were carried out using cylindrical specimens similar to creep test pieces at 700°C for times up to 600 h. 1.25Cr-0.5Mo and 2.25Cr-1Mo steels showed a similar oxidation behavior, however, the 9Cr-1Mo was much higher in oxidation resistance in air. Multilayer oxide formation was observed to occur in 1.25Cr-0.5Mo and 2.25Cr-1Mo steels, involving oxides with various compositions. This paper also explains the ongoing investigations at Monash University regarding the high temperature oxidation of Cr-Mo steels and the role of oxidation in affecting the accelerated creep tests.

A laser Raman microscope was used to collect spectra from individual phase regions visible in a polished cross-section of a thick oxide scale grown on a steel at high temperature. The technique was shown to be capable of unambiguously distinguishing the three iron oxides, FeO, Fe3O4,and Fe2O3. The standard spectra were then used to analyse the phases within thin (