With the increasing requirements for automobile light mass, the R&D of the third generation of high strength automobile steel has attracted extensive attention. The progress and current status for the research of medium-Mn steel are summarized, including the influence of composition design and processing technology on the mechanical properties. In the field of hydrogen induced cracking (HIC), the mechanism of HIC susceptibility affected by the microstructure of medium-Mn steel is described, with a focus on the effect of transformation induced plasticizing (TRIP) on the HIC susceptibility. The research hotspots such as the influence of second phase precipitation and microstructure defects on HIC, are also discussed. Finally, challenges on mechanical properties and HIC susceptibility of medium-Mn steel is pointed out, and further research perspectives such as the precise control of microstructure and the technology related with direct detection of hydrogen in steels were also briefly addressed.
The galvanic corrosion behavior of a coupling of 907A steel, 921A steel and 980 steel, in artificial seawater at different temperatures within the range of 0-20 ℃ was assessed by electrochemical method, mass loss method and morphology observation techniques. The results showed that at different temperatures, 907A steel acted as anode in the coupling, while 921A steel and 980 steel acted as cathode. The galvanic corrosion coefficient of 907A steel increased with the increasing temperature. Besides, galvanic corrosion may emerge to certain extent, for galvanic pairs of metals with close open circuit potential (<60 mV). The galvanic corrosion effect changed the uniform corrosion of 907A steel into local pitting corrosion, which might increase the failure risk of marine facility. For the control of such corrosion, the combination of protective coating and cathodic protection may be a better option.
In order to search for new green and low-cost organic corrosion inhibitors, the fresh lotus leave was selected as raw material, and then lotus leaf extract (LLE) was obtained by simple ethanol reflux extraction. The LLE could produce orderly aggregation material in a mixture of THF/HCl (tetrahydrofuran/HCl) solution (1.0 mol/L HCl solution) at room temperature. The results of Fourier transform infrared spectroscopy (FT-IR) and X-ray photoelectron spectroscopy (XPS) showed that the LLE underwent chemisorption on the surface of Q235 steel, and further the LLE could be adsorbed on the surface of mild steel, which formed super hydrophobic organic adsorption film. Electrochemical test results showed that lotus leaf extract had good corrosion inhibition performance for carbon steel in HCl solution. The maximal corrosion inhibition efficiency of LLE reached 93.14% for Q235 steel in HCl solution of 0.4 g/L.
The composition of fouling organism's community was on-spot detected on several portions below waterline, including the bow, hull and stern rudder bay, of the so called “Seagull floating dock”, which has been in service for more than 5 years at Qingdao harbor. It is found that more than 30 species of eight types of organisms were detected, among which Mytilus galloprovincialis is the dominant species, and it is the first time that the Scrupocellaria species was discovered in this area. The ranking of species diversity is bow > stern rudder bay>hull. The most seriously fouling portion is the stern rudder bay, where the fouling organisms here overlap and attach to a thickness up to 15 cm, and the percentage of covered area of the hard-shelled fouling organisms reached 70%. The influence of seasonal factors, hull structure, sea current state and sunniness on the fouling organism's community was discussed. The on-the-spot classification method was proposed for the first time and applied in this study, the fouling organisms detected on the Seagull floating dock were classified into four categories: hard-shelled groups, crusting groups, uprighting groups, and algae groups. Then the biofouling distribution map of the floating dock was drawn according to the size of the attachment area of the hard-shelled groups. This can promote the communications between the non-biological professionals, the formulation of anti-fouling standards, and the mathematical modeling of fouling organisms.
The corrosion behavior of A517Gr. Q steel was studied by mass loss method, SEM, EDS, XRD, and FT-IR in a cyclic wet/dry testing chamber, which was specially designed to simulate the corrosion condition of marine splash zone i.e. cyclically wetting in 3.5%NaCl solution and drying in atmospheres with humidity of either (62±5)% or (83±5)%. The results show that A517 steel is suffered from serious corrosion in the simulated environments of marine splash zone. The corrosion mass loss increases with time, while the average corrosion rate increases first and then stabilizes. The corrosion products are all composed of γ-FeOOH, β-FeOOH, α-FeOOH and Fe3O4. In the condition when the chamber atmosphere with humidity of 62%RH, the electrolyte film formed on the steel surface after immersion can be maintained only for a shorter period, as a result, the steel surface undergoes distinct dry and wet changes, and the formed rust scale is porous with obviously high amount of β-FeOOH, which is of high cathode oxidation activity, thus the steel presents much severe non-uniform corrosion. On the other hand, when the chamber atmosphere with humidity of 83%RH, the corrosion products scale is much dense and uniform with higher amount of Fe3O4, therefore, exhibits a blocking effect on the attack of aggressive Cl- to certain extent.
The failure behavior of epoxy powder coating and solvent-free epoxy liquid coating in simulated ultra-deep-sea environment for 480 h was studied by means of EIS and LEIS, while by applied alternating pressures within ranges 0.1-20 and 0.1-30 MPa respectively. The effect of alternating pressure on the corrosion resistance of coatings in deep-sea was examined, and the surface morphology of the coating/Q345 steel interface after immersion was characterized by SEM. The results show that the failure process of the two coatings is obvious under the alternating pressure of 0.1-30 MPa. After 480 h of pressured immersion, the impedance value of the epoxy powder coating decreased by 2 and 1 orders of magnitude after 480 h immersion at 0.1-30 and 0.1-20 MPa alternating pressures, respectively, and the impedance value of the solvent-free epoxy liquid coating decreased by 3 and 2 orders of magnitude respectively after immersion in the same environment. It shows that the epoxy powder coating has better protection performance to the Q345 steel in the condition of alternating pressure, and the ability to block ion penetration is stronger. According to the LEIS results, the failure behavior of the coating gradually spreads from local sites to the whole area under the alternating pressure, and the greater the alternating pressure, the faster the spread rate of the localized damage of the coating.
Flos Sophorae Immaturus extract (FSIE) was acquired by ultrasonic extraction method with ethanol solution as extract agent. The corrosion inhibition of Al-plate in 1.0 mol/L HCl solution by FSIE was studied for the first time by means of mass loss measurement, electrochemical method and surface analysis (SEM and AFM). The functional groups of FSIE and the formed inhibition film on Al is characterized by FTIR. The results show that FSIE has a significant inhibition effect on Al in 1.0 mol/L HCl solution. The inhibition efficiency enhances with the increase of FSIE concentration, while decreases with the increasing temperature. The inhibition efficiency can reaches 83.2% for a dose of 500 mg/L FSIE at 20 ℃. The adsorption of FSIE on Al surface conforms to Langmuir adsorption isotherm, and the adsorption type is a mixture of physical and chemical adsorption while mainly the physical adsorption. Potentiodynamic polarization curves show that FSIE is a cathodic inhibitor that prominently inhibits the cathodic hydrogen evolution. The capacitive arc in Nyquist plot at high frequencies increases with the concentration of PSIE. The inhibited aluminum surface by FSIE exhibits low corrosion extent as well as low surface roughness. FTIR confirms that FSIE can efficiently adsorb on Al surface to from inhibition film.
The effect of dry-wet ratio of cyclically dry/wet testing, i.e. drying in atmosphere of (55±5)% humidity and wetting in 120 mmol/L NH4H2PO4 solution at an external temperature of (25±2) ℃, on the electrochemical corrosion behavior of 2Cr-1Ni-1.2Mo-0.2V and 2Cr-4Ni-0.4Mo-0.1V steels respectively were investigated by laser scanning confocal microscopy (CLSM), X-ray polycrystalline diffractometer (XRD), X-ray photoelectron spectroscope (XPS), open circuit potential and electrochemical impedance spectroscope. The results show that after tested for 21 d with dry/wet ratio of 0, 1/3, 1 and 3 respectively, uniform corrosion and pitting corrosion emerged for the two steels. With the increase of dry/wet ratio, the corrosion rate and the pitting degree of the two steels increased, but the corrosion resistance of 2Cr-1Ni-1.2Mo-0.2V steel was better than 2Cr-4Ni-0.4Mo-0.1V steel. The corrosion product film of the two steels composed mainly of Fe3(PO4)2, FePO4, Fe2O3, and FeOOH. However, with the increasing dry/wet ratio, the amount of Fe3(PO4)2 and FeOOH decreased, that of Fe2O3 increased in the corrosion product film. Meanwhile, the open circuit potential and charge-transfer resistance decreased, it is worth pointing out in particular that the corrosion rate of 2Cr-1Ni-1.2Mo-0.2V steel exhibited corrosion rate smaller than 2Cr-4Ni-0.4Mo-0.1V steel.
The corrosion fatigue crack growth (CFCG) of DH36 steel in artificial seawater was studied via a home-made test set, which can accurately control the load, stress ratio, frequency, temperature, flow rate, pH value, ion concentration, and other factors of the artificial seawater, meanwhile, electrochemical monitoring of the whole process could be applied. The results show that the higher the stress ratio R, the faster the CFCG rate. The average acceleration ratio of CFCG rate by R=0.3 and R=0.5 is 115% and 217% of that by R=0.1 respectively. On the other hand, the CFCG rate becomes faster with the increase of temperature. The average acceleration ratio at 30 ℃ is only 20% of that at 5 ℃. The CFCG rate turns to be faster with the increase of seawater flow rate. The average acceleration ratio by flow rate of 0.3, 1 and 3 L/min, is 19%, 34% and 50% of that in static seawater, respectively. There is no difference in the fatigue crack growth (FCG) rate in air by changing test frequencies, but there is a great difference in the CFCG rate in seawater, namely the lower the frequency, the faster the CFCG rate. By comparing the CFCG rate with the FCG rate by different frequencies, it shows that seawater corrosion can inhibit the crack growth to certain extent at 10 Hz, but accelerates the crack growth at 1 and 0.1 Hz with an average acceleration ratio of 47.8% and 261.8%. The acceleration effect of corrosion on fatigue crack growth can be quantified by in-situ monitoring the electrochemical corrosion behavior at the crack tip during CFCG.
Superamphiphobic surface film was prepared on 5083 Al-alloy substrate by using chemical etching and then finishing in an ethanol solution of perfluorodecyl triethoxysilane. Its microscopic morphology, chemical composition, superamphiphobicity and corrosion resistance were characterized by means of field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), contact angle measurements and electrochemical tests. The results showed that the contact angles of water and ethylene glycol on the surface were 158° and 154.3°, respectively, exhibiting good superamphiphobicity. In comparison with the bare alloy, the free corrosion potential of the 5083 Al-alloy with superamphiphobic surface film exhibited significantly positive shift, while the corrosion current decreased from 4.016×10-6 A·cm-2 to 1.531×10-7 A·cm-2; after immersing in 3.5% (mass fraction) NaCl solution for 5 d, the charge transfer resistance of the alloy with superamphiphobic surface film was still significantly higher than that of the bare alloy, it follows that the superamphiphobic surface finishing can enhance the corrosion resistance of 5083 Al-alloy substrate.
A kind of gradient structure on the surface of S31254 super austenitic stainless steel was prepared by surface mechanical attrition treatment (SMAT) technology. The gradient structure was characterized by microstructural analysis and electrochemical test, while the variation of corrosion characteristics along the depth of the gradient structure was also studied in 10%NaCl solution. The results show that after SMAT treatment, the surface of S31254 steel emerged a structure composed of two gradient layers, while a coarse-grained layer inserted in between the two layers. In the gradient layer, the density of the nanoscale deformation twins shows a gradient distribution along the depth direction. Through mechanically thinning the gradient structure layer by layer and followed by electrochemical detection in the NaCl solution, it is revealed that nearby the location at depth of 80 μm exhibits the best corrosion resistance, which may be ascribed to that the prepared surface was smoother with higher twin density.
Marine seawater pipeline and various fittings play an important role in cooling and firefighting, among which square elbow is widely used. However, it is found from daily maintenance that the square elbow is also the part mostly prone to leakage. In this paper, the effect of related parameters for pipe, such as diameter (A), inlet velocity (B), liquid flow direction (C), sand diameter (D) and sand mass flow (E) on the erosion-corrosion behavior of square elbow in the condition of liquid-solid two-phase flow was studied by means of orthogonal test and numerical simulation. The results show that the order of influence of different factors on erosion-corrosion of square elbow may be ranked as: B>A>E>C>D. The erosion rate of the square elbow reaches the maximum in case that B is 5 m/s, A is 30 mm, E is 0.03 kg/s, C is the flow direction horizontal and vertical upward, and D is 500 μm respectively. The area with large erosion rate is concentrated in the range between 60° and 90° of the axial angle of the elbow, whilst near 180° of the radial angle, i.e., where located on the outside of the elbow near the exit. The experimental results also verify that the corrosion rate on the outside of the elbow near the exit is higher in this working condition. At the same time, the results of tests by factors of optimal level also show that reducing the inlet velocity and increasing the pipe diameter can greatly reduce the erosion rate.
The effect of hydroxyethylidene diphosphonic acid (HEDP) on the corrosion behavior and biofilm properties of iron bacteria (IB) on carbon steel surface in the circulating cooling water system was investigated by means of corrosion mass loss method, electrochemical technology, scanning electron microscope (SEM), X-ray photoelectron spectroscopy (XPS), atomic force microscope (AFM), confocal laser microscope (CLSM) and biochemical technology. The results showed that in the presence of HEDP, the iron bacteria induced corrosion rate of carbon steel reduced by 68.72%, correspondingly the corrosion current density decreased by 56.93%, the corrosion potential shifted positively, and the increase in the slope of the cathode in the polarization curve was much higher than that of the anode. The cathodic reaction inhibited the corrosion of iron bacteria; at the same time, under the action of HEDP, iron bacteria increased by 0.3~1.0 orders of magnitude, the secretion amount of extracellular polymeric substance (EPS) increased by 23.91%, and the biofilm structure was IB-EPS-IB, which reflected that the presence of HEDP was able to stimulate the growth of iron bacteria and the secretion of EPS, resulting in the formation of a thin and compact biofilm. This study can provide support for the in-depth study of corrosion theory and control methods in circulating cooling water systems.
The oxidation behavior of two ternary alloys Co-20Ni-xAl (x=3, 5, mass fraction, %) was studied in 105 Pa O2 at 800-1000 ℃ for 20 h. After oxidation, the two alloys all formed double-layered external scales composed of an outer layer of CoO (with a small amount of NiO) and an inner layer of mixtures CoO and spinels, usually followed by a region of internal oxidation of Al. The oxidation rate of the alloys increases with the increasing temperature. When the increase of Al content from 3% to 5%, the oxidation rate of Co-Ni-Al alloys is reduced, however, the Al content of 5% is not yet sufficient to ensure the formation of a protective external alumina scale on the alloy. In fact, the experimental results may be well interpreted by the prediction according to the theoretical mode related to the reaction of binary alloy with single oxidant by simplifying the ternary Co-Ni-Al alloys as binary (Co-Ni)-Al alloys.
The corrosion behavior of high strength and high electrical conductivity Al-Mg-Si alloy wires used for long-distance overhead conductors was studied by means of immersion corrosion test and electrochemical tests. The results show that corrosion first started at the interface between Al-Fe-Si phase (or Si-rich phase) and α-matrix due to the micro-galvanic effect during the 20 d immersion corrosion in 3.5%NaCl solution. With the progress of corrosion process, Al-Fe-Si phase and Si-rich phase peeled off and corrosion pits formed. According to statistics, the sizes of Al-Fe-Si phase and Si-rich phase decrease gradually with the increasing area reduction of Al-Mg-Si alloy wire; accordingly, the extreme average depth of corrosion pits decreases gradually. This indicated that the size of Al-Fe-Si phase and Si-rich phase is the key factor dominating the pitting corrosion behavior of Al-Mg-Si alloy wire.
Due to the surface smoothness and chemical inertia of basalt flakes, the interfacial bond strength of basalt flake/epoxy resin is poor. In this paper, the basalt flakes were chemically modified by silane coupling agent (KH550) to prepare the modified basalt (MB) flakes. The bare and modified basalt flakes were characterized by FT-IR and SEM/EDS. The dispersibility and compatibility of MB flakes in epoxy resin were examined by sedimentation test and cross-sectional microstructure observation of the prepared flakes/epoxy coating. The adhesion and anti-corrosion properties of MB flakes/epoxy coating were investigated using adhesion test and EIS technology, respectively. The results show that the chemical modification makes the surface of basalt flakes being chemically bonded with KH550, and which is beneficial to the formation the chemical bond interface of MB flakes/epoxy coating, leading to improve the compatibility of MB flakes with epoxy resin, therewith increase the barrier performance and adhesion of the coating, as a result, enhance the anti-corrosion performance of the modified epoxy coating.
The galvanic corrosion behavior for the galvanic pair of AZ91D Mg-alloy/2002 Al-alloy in 0.5 mg/L NaCl solution was studied by means of electrochemical methods and surface analysis techniques. For the galvanic pair of AZ91D Mg-alloy/2002 Al-alloy in the NaCl solution, Mg-alloy always acted as anode, thus its corrosion potential positively shifted, while corrosion rate increased. This could be attributed to that the galvanic effect between the two alloys significantly accelerated its cathode process. On the other hand, Al-alloy, always acted as cathode, its corrosion potential also positively shifted, and the corrosion rate increased. This could be ascribed to that the galvanic effect between the two alloys inhibited the formation of the passivation film on its surface. With the extension of immersion time, the coupling potential of the two alloys shifted towards positive first and then gradually negative, and finally reached a relatively stable state. The galvanic current densities increased first and then decreased and increased gradually again, and finally reached a relatively stable state. The research results not only enriched the knowledge of galvanic corrosion, but also provided a theoretical basis for the selection and design of automotive engine materials and the inhibition of the galvanic corrosion of multi-metal pairs.
In order to study the effect of the precipitated phase on the corrosion resistance of duplex stainless steel, surfacing layers of 00Cr21NiMn5Mo2N duplex stainless steel were prepared on Q235 via tungsten inert gas (TIG) powder surfacing. The surfacing layered samples were solid-solution treated at 1170 ℃, then sensitized at 800 ℃ for 0.5, 1, 2 and 4 h respectively, and then the effect of sensitization time on the microstructure and corrosion resistance of the surfacing layer was assessed. The results showed that the microstructures of the duplex stainless steel surface layers after solution treatment were mainly composed of ferrite phase and austenite phase. After sensitization, the precipitated phase dispersed along phase boundaries, while the content of the precipitated phase gradually increased with the sensitization time. The corrosion resistance of the samples decreased when the sensitization time increased from 0.5 h to 2 h. However, the corrosion resistance of the samples sensitized for 4 h increased significantly. The pitting potential of the sample sensitized for 4 h was 668 mV higher than that of the sample sensitized for 2 h. In addition, the morphology of samples after pitting also reflected the change of pitting resistance of the samples.
The use of micro-arc oxidation (MAO) coating is a promising approach for controlling corrosion for Mg alloys. However, MAO coating and the underneath Mg-alloy substrate are constantly threatened by pitting corrosion. In order to reveal the relevant mechanism, the pitting corrosion behavior of AZ91 Mg alloy without and with MAO coating was studied via cyclic potentiodynamic polarization (CPDP) test. Meanwhile, the pitting corrosion morphology and corrosion products at different CPDP stages were characterized by means of optical microscope (OM), scanning electron microscope (SEM) and energy dispersive X-ray (EDS) spectroscope. Results show that pits initiate on α-Mg phase rather than on β phase for AZ91 Mg alloy, however, they initiate around pores and cracks on MAO-coating. The initial pits show a volcano-like morphology for both the alloy and the coating. Moreover, inside the pits on the alloy there is a corrosion products film, which act as protective barrier for the substrate, as a result, pits on the alloy widened with time. By comparison, corrosion products of poor protectiveness exfoliate and dissolve inside the pits on the MAO coating, thus, where pits grow deeper with time. The morphology evolution of pits validates the positive hysteresis loops that exist on CPDP curves for both the alloy and coating, and can also explain the larger area of the positive hysteresis loop on the MAO coating. Overall, the MAO-coated alloy might fail without proper post-treatments due to the severe pitting corrosion, therefore, it is necessary to conduct pore sealing treatment for MAO coating to provide a promising corrosion protectiveness for Mg alloys.
The corrosion rate of L80, L80Cr13, 22Cr and 25Cr in CO2-H2S-Cl--containing artificial stratum waters in a high temperature and high pressure autoclave equipped with electromagnetic drive shaft was evaluated by means of mass loss method. The surface morphology and element distributions of corrosion product films were analyzed by SEM, EDS and XRD. The roughness and the pitting morphology of the material surface after corrosion was characterized by means of AFM and CLSM respectively. The results suggested that the corrosion rates of L80Cr13, L80, 22Cr and 25Cr decreased sequentially in the artificial stratum water with 0.12 MPa CO2 0.003 MPa H2S, 150.8 g/L Cl- at 80 ℃ for samples with rotating speed of 100 r/min. The corrosion product film on the surface of L80Cr13 was mainly composed of Cr2O3 and Cr(OH)3, which was locally damaged under the action of Cl-, thereby, severe pitting corrosion emerged; the corrosion product film on the surface of L80 was mainly composed of FeS and FeCO3, which has certain protective effect for the steel,thus the steel suffered from slight pitting corrosion. There is a passivation film formed only on the surface of steels 22Cr and 25Cr, while little pitting was detected.
The influence of temperature on the microbial induced corrosion (uniform corrosion rate and local corrosion rate) of the tank bottom for crude oil storage was assessed by means of 16S rRNA gene sequencing, as well as scanning electron microscope and laser confocal microscope in terms of the characteristics of microbial populations, and the morphology of the microbial film, and the characteristics of pitting. The results showed that the water microorganisms on the tank bottom composed of mesophilic and thermophilic sulfate-reducing bacteria (SRB), and saprophytic bacteria (TGB). The uniform corrosion rate of the Q235A steel plate reached a peak at 65 ℃, however, the overall corrosion rate was slight. The pitting corrosion rate peaked at 35 ℃, reaching 0.8 mm/a, and the pitting corrosion rate decreased significantly at temperatures below 25 ℃ and over 85 ℃. The influence of temperature on the microbial induced corrosion of the Q235A steel plate of tank floor is related to the temperature tolerance of microbial species. The temperature range between 30 and 70 ℃ is the sensitive temperature range of pitting corrosion. The emerge of corrosion pits are related to the growth of colony clusters, while microbes first form clusters on the metal surface. Therefore,during the process of metabolism, the metal beneath the colonies was rapidly corroded.
A three-dimensional metal organic frame material (MOF-5) was synthesized by hydrothermal method, and then, the corrosion inhibitor benzotriazole (BTA) molecule was loaded into MOF-5 to form corrosion inhibitor capsules. The structures and corrosion inhibition properties of the prepared BTA@MOF-5 was characterized by means of TEM, SEM, FT-IR, XRD and electrochemical testing techniques. The results show that the prepared MOF-5 can be an ideal candidate as an inhibitor carrier, while the BTA molecules were successfully loaded into MOF-5. Furthermore, the acquired BTA@MOF-5 had the characteristics of slow release for corrosion inhibitor benzotriazole, which could provide corrosion protection for copper.
The corrosion behavior of 1050 Al-alloy under current-carrying condition was studied by means of salt spray test, electrochemical measurement, scanning electron microscope (SEM) and X-ray diffraction (XRD). The results showed that the current condition had a significant effect on the corrosion of 1050 Al-alloy. Both of the corrosion current density and mass loss rate of the sample increased gradually with the increment of applied current density.The corrosion behavior of 1050 Al-alloy in marine atmosphere was characterized in simulated electrification condition through the analysis of the structure and morphology of corrosion products.
In order to solve the difficulty related to the prediction for the aging behavior of composites in natural environment with the complexity of environmental factors, polyethylene was chosen as composite matrix, and subjected to natural exposure test in the marine atmospheric environment of Qingdao area for 3, 6, 9, 12, 15, 18 and 24 months. Thereafter, based on the evolution of tensile and bending mechanical properties of the exposed polyethylene, by taking the consideration of the comprehensive influence of environmental factors into consideration, the natural weathering model with the radiation quantity as independent variable and the multi-factor superposition model with aging time as independent variable were established respectively. The results show that the tensile mechanical properties and bending mechanical properties of polyethylene both decreased with aging time and total solar irradiation in the marine atmospheric environment of Qingdao area. After exposure for 24 months, damages with micro-cracks occurred on the surface. The prediction error of natural weathering model for tensile and bending mechanical properties of polyethylene was less than 11.20%, while that of multi-factor superposition model was less than 3.07%. Therefore, the multi-factor superposition model had a better prediction precision.
The corrosion behavior of 10CrNi3MoV steel was investigated, by means of morphologies observation, mass-loss calculation, pitting depth measurement and products composition analysis, after field exposure tests in different depths in western Pacific deep-sea environment. The main corrosion morphology of 10CrNi3MoV steel was pitting, and the growths of pitting density and pitting depth were observed as the test depth increased. The corrosion rate firstly decreased, and then slightly increased, in accordance with the variation of the dissolved oxygen concentration with depths. Due to the addition of alloying elements, the corrosion resistance of 10CrNi3MoV steel was inferior to that of ordinary carbon steel. γ-FeOOH was the main component in corrosion products, however, of which the amount of crystalline ones reduced with the increasing test depth.
The possible causes for the microbial contamination of aircraft fuel during the process of manufacturing, transportation, storage, and daily use and maintenance of aircraft are summarized and analyzed by taking the prerequisite for microbial growth and reproduction, namely water, nutrients, temperature, and pH etc. into consideration. The effect of the existing microorganisms on the fuel performance, fuel tank structure, fuel pump/oil filter, and non-metallic materials are also summarized in terms of the growth and reproduction characteristics of microorganisms in the fuel system. In addition, we comparatively analyzed the existing methods and standards related with the detection of microorganisms for the aircraft fuel systems. Finally, the prevention methods and processes against microbes are also analyzed. This review will provide a theoretical basis and research direction for the detection and prevention in microbial contamination in aircraft fuel system, while play a guiding role for engineering application.
