Functional montmorillonite can be dispersed in polymer coatings and organic species and polymers can be intercalated into the interlayer space or grafted onto the surface of the functional montmorillonite. The addition of functional montmorillonite into polymer-based coatings can significantly improve anti-corrosion, refractory, super-hydrophobicity, antibacterial activity, and absorption of solar radiation by the resulting montmorillonite/polymer coatings. Montmorillonite can be functionalized for this purpose by ion exchange, intercalation, exfoliation, or combinations of these treatments. The rigid montmorillonite layers interspersed within the polymer matrix inhibit the penetration of corrosive substances, minimize the impact of high-temperature airflow, and thereby lead to strong resistance of the coating to corrosion and fire. The combination of polymers and dispersed montmorillonite nanolayers, which are modified by metal ions, metal oxides, and hydrophobic organic species, allows the resulting  composite coating to have quite a rough surface and a much smaller surface free energy so that the montmorillonite/polymer coating possesses superhydrophobicity. The interlayer space of functional montmorillonite can also host or encapsulate antibacterial substances, phase-change materials, and solar energy-absorbing materials. Moreover, it can act as a template to make these guest species exist in a more stable and ordered state. Literature surveys suggest that future work on the functional montmorillonite/polymer coatings should be targeted at the manufacture of functional montmorillonite nanolayers by finding more suitable modifiers and tuning the dispersion and funtionalities of montmorillonite in the coatings.

There is a significant interest in developing the corrosion-resistant magnesium (Mg) alloy as a degradable biomaterial. In this work, the magnesium–zirconium (Zr = 1 wt%)–strontium (Sr = 2 wt%)–cerium (Ce = 0, 0.5 wt%) alloy was developed using the casting process. Effects of Ce addition on alloy microstructure, corrosion behavior, and biocompatibility were systematically investigated. Detailed microstructural analysis indicated that 0.5 wt% Ce addition refined the second phase (Mg17Sr2) in the Mg–2Sr–1Zr alloy. Furthermore, phase analysis of corrosion product showed the formation of stable CeO2 oxide layer on the corroded surface of the Mg alloy. Both the precipitate refinement and stable CeO2 layer formation significantly contributed toward enhanced corrosion resistance of the Mg–Sr–Zr–Ce alloy, as determined by both electrochemical and immersion corrosion in phosphate-buffered saline. Significantly higher osteoblast-like cell (MG-63) proliferation was observed in Ce-containing Mg alloy at both day 1 and day 3. Overall, the results showed that Ce addition could modulate degradation behavior and biocompatibility of the ternary Mg alloy.

The study investigated novel wear and corrosion resistance of stainless steel and 316 stainless steel samples which were successfully prepared by laser melting deposition. Phase composition, microstructure, microhardness, wear resistance, and electrochemical corrosion resistance were studied. The experimental results showed that novel stainless steel was mainly composed of α-Fe and a few carbide phase (Cr, Fe)7C3. The microhardness of novel stainless steel was about 2.7 times greater than 316 stainless steel. Meanwhile, the specific wear rate of novel stainless steel and 316 stainless steel was 2.63 × 10−5 mm3/N m and 1.63 × 10−4 mm3/N m, respectively. The wear volume of 316 stainless steel was 6.19 times greater than novel stainless steel. The corrosion current and the corrosion potential of novel stainless steel and 316 stainless steel were 1.02 × 10−7 A/cm2 and 1.5 × 10−7 A/cm2, and −138.8 mV, −135.9 mV, respectively, in 3.5 wt% NaCl solution. Therefore, both microhardness and wear resistance of novel stainless steel were greatly improved, with high corrosion resistance.

Magnesium (Mg) alloys have received considerable attention as favorable orthopedic implant materials. However, their uncontrolled degradation in the physiological environment has led to premature implant failure. Thus, to address this problem, the present study was focused on developing protective monolayer coatings of fluorine-doped hydroxyapatite (FHA) and a bilayer coating of FHA and poly(lactic acid) (FHA–PLA) on AZ31 Mg. The synthesis involved microwave irradiation which helped in rapid synthesis of FHA coatings and spin coating for developing the PLA layer. Results revealed the formation of dense and defect-free FHA–PLA hybrid coatings. Importantly, they helped in significant reduction of galvanic–corrosion reactions of AZ31 in a physiological medium. The corrosion current density of FHA/PLA–coated samples was about two orders of magnitude lower than uncoated samples. Their lower weight losses further confirmed the coatings’ corrosion resistance. Combined, the as-synthesized FHA–PLA coatings can provide favorable corrosion protection to AZ31 Mg.

The current paper focuses on the issue associated with the biological response of medical grade cobalt chromium (Co–Cr) alloy treated with electrical discharge at different spark energy levels by a varying current, pulse on-time, and pause (off) time. Three types of electrodes, namely, graphite (C), tungsten (W), and copper tungsten (Cu–W) were utilized for treating Co–Cr substrates in two different dielectric media such as mineral oil and deionized water. Electrochemical potentiodynamic tests were performed to investigate the corrosion resistance of untreated and treated surfaces. Furthermore, in vitro hemocompatibility tests were executed on the superior corrosion resistance samples for scrutinizing the red blood cell lysis (human blood response). The study revealed a significant improvement in the corrosion resistivity (<80%) and biological response for the surface treated with W–Cu electrode at low pulse pause duration. X-ray diffraction verified the formation of oxides and phosphides on the treated surface that promotes the biocompatibility.

Iranian montmorillonite (MMT) was modified with hexadecyltrimethylammonium bromide (HDTB) and used as a nano-additive for the enhancement of the mechanical and anticorrosion properties of an epoxy coating. Infrared (IR) spectroscopy, thermo-gravimetric analysis (TGA), transmission electron microscopy (TEM) and X-ray diffraction (XRD) analysis indicated that HDTB reacted with MMT (with 97% yield) and increased the d001 spacing of MMT from 1.27 to 3.92 nm. Some 1, 3 and 5 wt.% of organically modified montmorillonite (OMMT) were added to the epoxy coating formulation. XRD and TEM/image processing analysis showed that the extent of intercalation/exfoliation of OMMT was substantially greater than that of MMT. Dynamic mechanical analysis showed that the glass transition temperature and storage modulus increased significantly with the addition of OMMT. Electrochemical impedance spectroscopy (EIS) and salt spray/image processing results revealed that addition of OMMT to the epoxy coating significantly increased the corrosion resistance of the coating compared to neat and MMT-containing epoxy coatings. The optimum concentration of OMMT was 3 wt.%. At this concentration, the mechanical and anticorrosion properties were greatly superior to those of neat and MMT-containing epoxy coatings.

The effect of aging time on the corrosion behavior of 6005 Al alloys has been investigated in aerated 3.5% NaCl aqueous solution. The corrosion resistance of the alloy with different aging times is analyzed by measuring potentiodynamic polarization, electrochemical impedance spectroscopy. The surface morphology is examined by scanning electron microscopy. The results demonstrated that the corrosion resistance of the alloy in the peak-aged condition is worse than the other conditions. Accordingly, corrosion rate and the corrosion current density of the alloy reach its maximum value. An Fe-rich phase is identified as the β-Al4.5FeSi phase by atomic-resolution high angle annular dark field scanning transmission electron microscopy and energy dispersive X-ray spectroscopy mapping analyses. The β-Al4.5FeSi is wrapped slowly by the precipitates of Mg2Si from the process of the peak-aged condition to the over-aged condition. It is hypothesized that the change of corrosion behavior of the alloy may be attributed to the β-Al4.5FeSi wrapped slowly by the precipitates of Mg2Si.

The effects of stress-aging processing on corrosion resistance of an Al–Zn–Mg–Cu alloy were investigated. It is found that the one-stage stress-aged alloy is strongly sensitive to the electrochemical corrosion. The poor corrosion resistance of the one-stage stress-aged alloy can be attributed to fine intragranular aging precipitates and continuous distribution of grain boundary precipitates. Meanwhile, the incomplete precipitation of solute atoms results in high electrochemical activity of aluminum matrix. However, when the alloy is two-stage stress-aged, the corrosion resistance is greatly improved. Furthermore, the corrosion resistance decreases firstly and then increases with increasing the first stage stress-aging temperature. Increasing external stress can enhance the corrosion resistance of the two-stage stress-aged alloy. These phenomena are mainly related to aging precipitates within grains and along grain boundaries. The coarse and relatively low-density intragranular aging precipitates, as well as the discontinuously distributed grain boundary precipitates can enhance the corrosion resistance of the stress-aged alloy.

The corrosion resistance behavior of age-treated at 250 °C, 150 °C and solution-treated at 540 °C Al–4.2 wt%Ag alloys were investigated in a 3.5 wt% NaCl solution using cyclic potentiodynamic polarization (CPP) and electrochemical impedance spectroscopy measurements. Furthermore, the Vickers microhardness, microstructure, and phase analysis were studied by Vickers microhardness test, scanning electron microscopy (SEM), and x-ray diffraction. The Vickers microhardness test indicated significant increase in the hardness of the aged samples due to precipitation formation in the Al matrix. SEM images of all samples after corrosion tests showed pitting corrosion. Furthermore, it is found that the presence of ageing precipitates (Ag2Al plates) in the age-treated samples created local galvanic cells and can led to the formation of the anodic and cathodic sites. Hence, the corrosion resistance decreased compared to the solution-treated sample without any precipitates. In addition, for more ageing temperature at 250 °C in comparison with 150 °C, was made more anodic and cathodic sites due to more Ag2Al precipitates formation, and decreased resistance to pitting corrosion. Besides, the aluminum and silver oxides were corrosion products. The major phase was aluminum oxide because the Al was the main element of the alloy.

In this study, the effects of Sm on the microstructure and corrosion resistance of hot-extruded AZ61 magnesium alloys were investigated by optical microscopy, scanning electron microscopy, and transmission electron microscopy. The results showed that uniformly dispersed Al2Sm particles with size of ∼2 μm were discovered in the hot-extruded AZ61 magnesium alloy sample modified with 1.0 wt% Sm, which promoted dynamic recrystallization grain growth during the hot-extruded process, gradually increasing the grain of the alloy as Sm content increased. The morphology of the corroded surface and the corrosion rate of the hot-extruded AZ61 magnesium alloy both were significantly improved after Sm addition. The alloy sample modified with 2.0 wt% Sm after immersion in 3.5 wt% NaCl solution for 12 h showed minimum corrosion rate value, 3.1 mg/cm2 day, which is only 3.7% of the corrosion rate of unmodified alloy (82 mg/cm2 day).

The alloyed layers were produced on Mg by heating the specimens in contact with pure Al powder or Al + Zn powder mixtures. The powder material acting as the source of diffusion elements was held under pressure during heating, and this led to the formation of thick, continuous layers in a short heating time (1 h). The layer formation process took place through partial melting at the substrate/powder interface. The Al-enriched layer was characterized by a eutectic structure composed of an Mg17Al12 intermetallic phase and a solid solution of Al in Mg. The Al/Zn-enriched layers produced from Al + 20% Zn and Al + 40% Zn powder mixtures consisted of Mg17(Al,Zn)12 and Mg5Al2Zn2 and a solid solution of Al and Zn in Mg. The alloyed layers had higher hardness and better wear resistance than the Mg substrate. The results of the polarization measurements show that the Al- and the Al/Zn-enriched layers provide a certain level of protection to Mg against corrosion.

The effects of the different shot peening parameters on the 6061 alloy specimens' surface have been investigated. It is found that the compressive residual stresses and the surface roughness of the surface layer for all shot-peened specimens are improved greatly. The maximum stress value and the maximum roughness are obtained by the shot flow rate of 5.5 lbs/min and air pressure of 20 psi. The microstructure observation results indicate that a nanostructured layer with an average grain size below 100 nm has been created on the top surface layer of each specimen. In the top surface nanostructured layer, the microhardness is enhanced. It is resulted from the grain refinement and the strain hardening. The results of electrochemical measurements, surface corrosion morphology observation, and EDS analysis indicate that the corrosion susceptibility of the 6061 alloy could be significantly enhanced by means of the shot-peening-induced surface nanocrystallization.

Duplex stainless steels are known to have a good resistance to localised corrosion,especially thanks to their quiet high level of chromium (and for some of them molybdenum),but also because of their very low level of sulphur. These very low levels of sulphur arealso useful to guaranty a good toughness and a good hot workability for these grades.Concerning long products like bars made in Duplex Stainless steels, one of their mostimportant property, after corrosion resistance, is their machinability. Unfortunately, oneof the most known way to improve the machinability of stainless steels is to increasetheir sulphur level, thus forming manganese sulphides in the stainless steels which inducebetter chip breaking and lubrication at the chip – cutting tool interface. So the questionis: can the sulphur well-known way to improve machinability of stainless steels be used onDuplex Stainless Steels, without inducing hot rolling difficulties and too important adecrease of their other main properties, i.e. localised corrosion resistance andtoughness? If not, are other ways possible?