Corrosion Grade Research Articles

Effect of nano-TiC/TiB2 and final thermo-mechanical treatment on microstructure and properties of 7185 alloy

In this study, a new generation of ultra-high strength 7185 aluminum alloy and nano-sized TiC+TiB2 particles reinforced 7185 alloy matrix composites (PRAMCs) were prepared, and its thermos-mechanical treatment (TMT) was studied. The electron probe microanalyzer, electron back scattered diffraction, and transmission electron microscope are used to study microstructure evolution. Tensile tests are used to investigate the mechanical properties of composite materials. The results showed that the grain can be refined significantly by adding particles. The grain size of the quenched state is very fine. The strength and plasticity of the alloy are significantly improved. After the final TMT, many dislocations were introduced, and the precipitation phase and dislocation intertwined with each other during the aging process. This increased the dislocation density and promoted the precipitation process. Thus, the strength and corrosion resistance are improved, but the plasticity is reduced. The yield strength, tensile strength, and elongation of the PRAMCs designed in this study after final TMT are 483.6 MPa, 520.4 MPa, and 9.1 %, respectively. The inter-granular corrosion layer depth is 47.2 μm. The grade of exfoliation corrosion for 6 h and 24 h is PC, and EA, respectively. This study can provide strategies for the performance optimization of PRAMCs.

Effect of pre-recovery solid solution treatment on microstructure and comprehensive properties of Al-11.0Zn-3.0Mg-1.0Cu-0.2Zr-0.16Ti-0.15Er-0.15La alloy

ABSTRACT In this paper, the microstructure and comprehensive properties of Al-11.0Zn-3.0Mg-1.0Cu-0.2Zr-0.16Ti-0.15Er-0.15La aluminium alloy with two solid solution regimes of G1 and G2 were investigated. The microstructure of the alloy was characterised using an optical microscope (OM) and a scanning electron microscope (SEM). The phases were analysed using an X-ray diffraction (XRD). The grains were measured using an electron backscatter diffraction (EBSD). The hardness and tensile properties of the alloy were investigated using a Vickers hardness tester and a tensile testing machine, respectively. The results showed that the best property of the alloys was obtained after pre-recovery solid solution treatment of G2. The grain size of the alloy was significantly refined, and the tensile strength and elongation at break of the alloy after G2 solid solution treatment were increased by 10.4% and 6.9% compared to those of G1, respectively. The G2 alloy possessed good resistance to intergranular corrosion, exfoliation corrosion and electrochemical corrosion. The maximum corrosion depth of its intergranular corrosion was decreased by 34.7% and the grade of exfoliation corrosion was PB. The electrochemical corrosion current density and corrosion potential of G2 alloy were 5.421 × 10−5A/cm2 and −0.978 V, respectively.

A new method for preparing Mg-Al-layered double hydroxides coating using supercritical CO2 fluid

A new method for preparing Mg-Al-layered double hydroxides (Mg-Al-LDHs) coating using supercritical CO2 fluid was developed. The morphologies, structures, compositions, and corrosion resistances of the surface coatings were investigated. Unlike traditional methods, the method using supercritical CO2 fluid generated ultrafine nanocrystal coatings with an average size of 30 nm, and a thickness of ca. ∼ 11 μm. The Mg-Al-LDHs coating was mainly composed of C, O, Mg, and Al. Corrosion resistance measurements show that the amount of hydrogen evolution for the nanocrystal LDHs coating was only 0.133 mL·cm−2, the polarisation resistance was 3174.9 Ω·cm2, and the immersion test corrosion grade of 7G. Finally, the formation mechanism of the Mg-Al-LDHs coating under supercritical CO2 fluid was proposed.

Corrosion characteristics and evaluation of galvanized high-strength steel wire for bridge cables based on 3D laser scanning and image recognition

The study investigates the corrosion behavior of galvanized high-strength steel wire, which significantly affects the bearing capacity and residual fatigue life of cables in cable-supported bridges. Through standardized salt spray accelerated corrosion tests, steel wires with varying corrosion degrees are obtained. Three-dimensional laser scanning technology reconstructs the corroded wire surface, while image recognition techniques extract geometric characteristics of corrosion pits. Fitting expressions are established to correlate the minimum cross-sectional area, maximum pit depth and dip angle, and mass loss ratio of the wire. Statistical analysis reveals log-normal distributions for the lengths of major and minor axes of corrosion pits over time. Fitting curves for elongation after fracture, nominal yield strength, and nominal ultimate strength, along with elastic modulus distribution, are derived for different mass loss ratios. Comparing corrosion grading criteria, the study quantitatively describes corrosion characteristic parameters for distinct corrosion grades. These insights enhance understanding of corrosion behavior and mechanical property degradation in high-strength steel wires, offering a quantitative framework for assessing and classifying corrosion extent based on measurable parameters.

Evaluating trunnionosis in modular anatomic shoulder arthroplasties: a retrieval study.

Shoulder arthroplasty procedures are widely indicated, and the number of shoulder arthroplasty procedures has drastically increased over the years. Rapid expansion of the utilization of reverse total shoulder arthroplasty has outpaced the more modest growth of anatomic total shoulder arthroplasty (aTSA) while shoulder hemiarthroplasty (HA) has trended down. Recently, shoulder prostheses have transitioned to increasingly modular systems offering more individualized options with the potential for decreased pain and increased range of motion. However, increased primary procedures has resulted in increased revision surgeries, with one potential cause being fretting and corrosion damage within these modular systems. Following institutional review board approval, 130 retrieved aTSA and 135 HA explants were identified through database query. Humeral stem and head components were included in all 265 explants, whereas 108 included polyethylene glenoid liner components. All explanted components were macroscopically evaluated for standard damage modes, and taper junctions were microscopically examined for fretting/corrosion using a modified Goldberg-Cusick classification system that was 4-quadrant graded for both the male and female component. Medical records were reviewed for patient demographics and surgical information. In this series, 158 of explants were from female patients (male=107), and 162 explants were from the right shoulder. Average age at implantation was 61 years (range: 24-83), average age at explanation was 66 years (range, 32-90), and average duration of implantation was 61.4 months (range, 0.5-240). Scratching, edge deformation, and burnishing were the most commonly observed standard damage modes. Of the 265 explants, 146 had a male stem component vs. 118 with a female stem component. Average summed fretting grades on male and female stem components were 8.3 and 5.9, respectively (P<.001). Average summed corrosion grades for male and female stem components were 8.2 and 6.2, respectively (P<.001). Wider male tapers (>11 mm) showed significantly less fretting and corrosion (P<.001). Lastly, mismatched metal compositions between the head and stem components showed greater fretting and corrosion damage (P=.002). In this series of 265 aTSA and HA explants, there was substantial damage present on the explanted components. All components demonstrated macroscopic damage. In this retrieval study, small-tapered male stems with small, thin female heads and mismatched metal composition between components were risk factors for increased implant wear. As shoulder arthroplasty volume increases, optimizing design is paramount for long-term success. Additional work could determine the clinical significance of these findings.

Investigation of the Quenching Sensitivity of the Mechanical and Corrosion Properties of 7475 Aluminum Alloy

Based on end-quenching experiments combined with conductivity, hardness testing, and microstructural characterization, the quenching sensitivity of the mechanical and corrosion properties of 7475 aluminum alloy was investigated. The study revealed that as the quenching rate decreased, both the mechanical properties and exfoliation corrosion resistance exhibited increased quenching sensitivity. With the quenching rate decreasing from 31.9 °C/s to 2.5 °C/s, the conductivity increased by 4.1%IACS, the hardness decreased by 31%, the exfoliation corrosion grade transitioned from EC to ED, and the maximum exfoliation corrosion depth increased from 237 μm to 508 μm. As the quenching rate decreased, the η phase sequentially precipitated at recrystallized grain boundaries (RGBs), E phase particles, and subgrain boundaries (SGBs), while the T phase primarily precipitated on E phase particles. Furthermore, the significant precipitation of η and T phases led to a notable reduction in the quantity of age-precipitated phases, an increase in their size, and poor coherency with the matrix, resulting in decreased mechanical properties and a higher quenching sensitivity of the mechanical performance. Meanwhile, with the reduction in quenching rate, the size and spacing of grain boundary precipitated phases increased, the Zn and Mg contents of grain boundary precipitated phases increased, and the Precipitation Free Zone (PFZ) widened, leading to decreased exfoliation corrosion resistance and higher quenching sensitivity of the exfoliation corrosion performance.

Investigations on the historical Széchenyi chain bridge

AbstractThe Széchenyi chain bridge is an almost 170‐year‐old historical structure located in the downtown of Budapest, which has been reconstructed between 2020‐2022. The chain system of the bridge is more than 100 years old, and the rotational capacity of the pins is questionable due to corrosion and friction. This phenomenon significantly influences the static behavior of the chain elements and the entire suspending system. Therefore, connected to the renewal process, the Budapest University of Technology and Economics, Department of Structural Engineering investigated the rotational capacity of the pins of the chain elements, and the corrosion grade of the chain bars. To investigate these two issues, three on‐site measurements are executed: (i) loading test to measure the bending moments in the chains and checking the rotation of the pins, (ii) one‐year‐long monitoring system operating during the renewal process and checking the internal force distribution of the structure during the reconstruction phases, and (iii) corrosion measurements on the chain bars. The paper introduces the measurement results, the main conclusions, and their practical application possibilities in the renewal process.

Efficient removal of alkali and alkaline earth metals from biodiesel using Ion-exchange resin: Performance and mechanism

Raw materials, production process, and other factors cause several metal ions to exist in biodiesel. Furthermore, the existence of alkali and alkaline earth metals seriously affects the quality and performance of biodiesel. To improve fuel quality, a 732 ion-exchange resin was used to reduce the contents of alkali and alkaline earth metal ions in Jatropha biodiesel. The adsorption efficiency of the ion-exchange resin for alkali and alkaline earth metal ions in biodiesel was evaluated using ion chromatography, while the adsorption mechanism of ion change resin on alkali and alkaline earth metal ions in biodiesel was elucidated via FTIR and XPS. In addition, the effects of ion-exchange resin on several key physiochemical properties of biodiesel, including oxidation stability, corrosivity, heat value and kinematic viscosity, were also explored. The results showed that the total content of alkali and alkaline earth metal ions in biodiesel was reduced by 88.19%, and the K+, Na+, Mg2+, and Ca2+ contents were reduced to 0.11 mg/kg, 0.89 mg/kg, 0.53 mg/kg, and 0.78 mg/kg, respectively, after removing the ion-exchange resin. In the removal process, the hydroxyl group of sulfonic acid group on the ion-exchange resin is broken, and the substitution adsorption reaction between H+ and the alkali and alkaline earth metal ions in biodiesel is carried out. Moreover, the oxidation induction period of biodiesel was prolonged by 40.8% owing to the reduction in the content of alkali and alkaline earth metal ions, which significantly blocked the decomposition pathways of unstable oxidation intermediates in biodiesel. The degree of copper corrosion in biodiesel did not change significantly before and after ion-exchange resin adsorption during short-term corrosion (3 h); however, the copper corrosion grade decreased from 2c to 1b after ion-exchange resin adsorption during long term corrosion (240 h). Nevertheless, the heat value and kinematic viscosity of biodiesel were observed to be independent of the ionic metal content.

Study on intermediate annealing process of thermal mechanical treatment of 7185 alloy with two stage deformation

This study investigated the effect of intermediate annealing (IA) during a special thermo-mechanical treatment on the microstructure and properties of 7185 Al alloy. The results show that after IA, many sub-structures are formed in the alloy and many particles are precipitated. The particle size increases and the width of the dislocation wall becomes narrower with increasing IA time and temperature. After the second stage of deformation, the dislocations are ordered again and generate micro shear bands (MSBs). The final T6 treated alloy under IA2 process (holding time for 40 min at 400 °C) has good plasticity and corrosion resistance. The tensile strength is 523 MPa, the yield strength is 458 MPa, the elongation is 17.6%, the depth of intergranular corrosion layer is 15.6 μm, and the corrosion grade after 6 and 12 h exfoliation corrosion is N, PC.

Effect of variable rate non-isothermal aging on microstructure and properties of Al-Zn-Mg-Cu alloy

Variable rate non-isothermal aging (VR-NIA) treatment by changing the heating and cooling rates is proposed and applied to 7055 aluminum alloy to optimize the mechanical properties and corrosion resistance. The investigated 7055 aluminum alloy undergone two-stage solid solution is heated from 100 °C to 160 °C at a rate of 20 °C/h, then heated to 210 °C at a rate of 60 °C/h, and finally cooled to 100 °C according to the symmetrical temperature route, the hardness and tensile strength can reach 173.3 HV and 654.6 MPa, respectively, and the electrical conductivity is able to reach 38.6 %IACS. At the same time, improved corrosion resistance is obtained, the maximum depth of intergranular corrosion (IGC) is 29.4 μm, the 48 h exfoliation corrosion (EXCO) grade is EA, and the stress corrosion sensitivity index (ISSRT) is 1.8%. The results of electrochemical tests show that the open circuit potential (OCP) of VR-NIA alloy is −764.2 mV, the corrosion potential (Ecorr) is −715.3 mV, and the corrosion current density (Icorr) is 4.6 × 10−8 A/cm2. Microstructure observation shows that GPI zones, GPII zones and a small number of η’ phases are formed during the heating process of 100 → 160 °C, which enhances the mechanical properties of the alloy; in the process of 160 → 210 → 160 °C, small-sized precipitates dissolve back, and part of the large-sized η’ phases grow and transform into η phases. At the same time, the grain boundary precipitates (GBPs) change from continuous to discontinuous distribution, forming a precipitation-free zone (PFZ) with a suitable width, which greatly improves the electrical conductivity and corrosion resistance of the alloy. In the process of 160 → 100 °C, the GPI zones are re-precipitated, and more η phases are formed from the η’ phases without remarkable coarsening. Enhanced performance can be achieved in a relatively shorter time through VR-NIA, behaving with greater advantage over constant-rate non-isothermal aging.

Larger-Diameter Trunnions and Bolt-Reinforced Taper Junctions are Associated with Less Tribocorrosion in Reverse Total Shoulder Arthroplasty.

Morse taper junction tribocorrosion is recognized as an important failure mode in total hip arthroplasty (THA). While taper junctions are used in almost all shoulder arthroplasty systems currently available in the United States, with large variation in designs, limited literature has described comparable analyses of taper damage in these implants. In this study, taper junction damage in retrieved reverse total shoulder arthroplasty (RTSA) implants was assessed and analyzed. Fifty-seven retrieved RTSAs with paired baseplate and glenosphere components with Morse taper junctions were identified via database query; 19 of these also included paired humeral stems and trays or spacers with taper junctions. Components were graded for standard damage modes and for fretting corrosion with a modified Goldberg-Cusick classification system. Medical records and preoperative radiographs were reviewed. Comparative analyses were performed assessing the impact of various implant, radiographic, and patient factors on taper damage. Standard damage modes were commonly found on the evaluated trunnion junctions, with scratching and edge deformation damage on 76% and 46% of all components, respectively. Fretting and corrosion damage was also common, observed on 86% and 72% of baseplates and on 23% and 40% of glenospheres, respectively. Baseplates showed greater moderate-to-severe (grades≥3) fretting (43%) and corrosion (27%) damage than matched glenospheres (fretting, 9%; corrosion, 13%). Humeral stems showed moderate-to-severe fretting and corrosion on 28% and 30% of implants, respectively; matched humeral trays/spacers showed both less fretting (14%) and corrosion (17%). In subgroup analysis, on glenospheres, large-tapered implants had significantly lower summed fretting and corrosion grades than small-tapered implants (both p≤0.001); paired baseplate corrosion grades were also significantly lower (p=0.031) on large-tapered implants. Factorial analysis showed bolt-reinforcement of the taper junction was also associated with less fretting corrosion damage on both baseplates and glenospheres. Summed fretting and corrosion grades on glenospheres with trunnions (male) were significantly greater than glenospheres with bores (female) (both p≤0.001). Damage to the taper junction is commonly found in retrieved RTSAs and can occur after only months of being implanted. In this study, tribocorrosion predominantly occurred on the taper surface of the baseplate (vs. glenosphere) and on the humeral stem (vs. tray/spacer), which may relate to the flexural rigidity difference between the titanium and the cobalt-chrome components. Bolt-reinforcement and use of large-diameter trunnions led to less tribocorrosion of the taper junction. The findings of this study provide evidence for the improved design of RTSA prostheses to decrease tribocorrosion.

Influence of Relative Humidity and Oxygen Concentration on Corrosion Behaviour of Copper in H2S-Containing Liquid Petroleum Gas

In this paper, the influences of relative humidity (RH) and concentration of O2 on copper corrosion in H2S-containing LPG (liquid petroleum gas) were studied. The corrosion products obtained in different environments were also analysed by scanning electron microscopy (SEM), energy dispersive spectrometry (EDS), grazing incidence X-ray diffraction (GIXRD), X-ray photoelectron spectroscopy (XPS) and Fourier transform infrared spectroscopy (FTIR). In H2S-containing LPG, RH has pronounced influence on the corrosion grade of copper. The variation in the critical point (CP) with the RH of LPG is a linear relationship. The presence of O2 in dry H2S has limited influence on the corrosion of copper. In the presence of different RHs, the CP always follows a negative exponential function with O2 concentration. The analysis of different corrosion products implies different corrosion behaviours and mechanisms, which are dependent on the presence or absence of water vapour. The corrosion mechanisms obtained in four different environments were also proposed.

Combined effect of the exposure angle and face orientation on the atmospheric corrosion behavior of low carbon steel

Tropical atmospheric corrosion in Central America and The Caribbean has been studied preferentially in coastal areas, using samples placed at 30° angles and under ISO 9223 and ISO 8407 standards. Recent studies have shown that the variation of the exposure angle influences the grade of corrosion between both sides of the sample; the side facing up (skyward) and the side facing down (groundward). An evaluation of the annual corrosion at different angles with respect to the horizontal in the San Jose Valley in Costa Rica was carried out, to consider this. The results were analyzed by classical methodologies (gravimetric methods, thickness measurement, XRD and SEM), as well as by electrochemical methods (LPR, EIS and EFM). The values obtained show a decrease in corrosion with increasing angle, as well as differences in corrosion levels between faces. Electrochemical measurements were consistent with each other and with those obtained using classical measurements.

Failure analysis of the leakage in girth weld of bimetal composite pipe

A bimetal mechanically-composite pipe leaked at the entrance of processing station. The failure location was the 6o'clock direction of the girth weld connecting the gathering pipe and pipe in the station. In order to figure out the root cause of the failure, a series of experiments were carried out. The macroscopic analysis and metallographic test results show that the leakage point is located at the 6o'clock direction of the girth weld, the root welding and the base pipe of the bimetallic composite pipe are corroded, resulting in perforation. The end of the bimetallic composite pipe is not seal-welded, the girth weld has misalignment and at 6o'clock, the root weld was concave, and the wall thickness of the root weld and the lining is<1.5 mm. The FeCl3 pitting corrosion test results of the girth weld show that the pitting corrosion resistance of the root weld is lower than that of the liner and pure stainless-steel pipe. The galvanic corrosion test shows that the galvanic corrosion grades of weld-pure material, weld-liner, carbon steel-weld, carbon steel-liner are all severe corrosion, and the galvanic corrosion of carbon steel-weld is the most serious. The root cause of the failure of girth weld puncture leakage: the end of the bimetallic composite pipe is not seal-welded. At 6o’clock, the girth weld has misalignment, and the root weld is concave, resulting in that the thickness connecting the root weld and the liner being small. In the medium environment containing Cl- and CO2, local corrosion occurs, and then the medium enters the base pipe and the liner interlayer, and the galvanic corrosion aggravates the corrosion of the base pipe. To avoid the reoccurrence of such failure, the mitigation measures were proposed.

The effect of trunnionosis on the risk of re-revision following femoral head exchange in hip arthroplasty.

Fretting corrosion at modular junctions contributes to arthroplasty failure. Currently, no evidence-based guidelines are available regarding the acceptable level of trunnion corrosion that can occur in vivo. We aimed to examine the relationship between trunnion corrosion and risk of re-revision to assist surgeons with intraoperative decision making. Grading by 3 independent examiners of revised and re-revised head components was performed using a modified Goldberg corrosion scale. Samples were separated into low-grade (LG) and high-grade (HG) corrosion. Mechanical testing determined the relationship between corrosion severity and pull-off strength at the head-stem junction. 529 retrieved femoral heads were analysed. A positive association was detected between males and HG corrosion (OR 2.07; 95% CI, 1.45-2.94; p < 0.001). No difference between the survivorship of LG and HG heads was detected (p-value = 0.247). In the re-revised sample, the first implant had a time in situ that was on average 7.97 years longer (95% CI, 5.4-10.6) than that of the subsequent re-revised femoral head. Severe corrosion on the first head was associated with a 37.5 (95% CI, 4.00-1944) fold increase of HG on the subsequent head (p < 0.001). Femoral disassembly force had a positive correlation with stem taper corrosion grade (p = 0.001). A well-fixed stem with corrosion may remain in situ.

Experimental Research on the Apparent Corrosion Law of a Suspension Bridge’s Main Cable Steel Wire under Status of Holding Force

Regarding the corrosion law of a suspension bridge’s main cable steel wire under the status of holding force, a set of electrolytic-accelerated corrosion test devices with preload was designed. The electrolytic-accelerated corrosion test of the main cable steel wire of a suspension bridge under the status of holding force was carried out. A total of 60 steel wires with diameter 5.25 mm were selected under four working conditions of 0, 1,000, 2,000, and 3,000 μϵ. The quality and diameter of steel wire after 0–4 days of electrolytic-accelerated corrosion were measured. Additionally, the change law of the average mass loss rate and cross-sectional loss rate of the main cable steel wire with strain and time growth were discussed. The results of the tests showed that with the increase of strain level and corrosion time, the corrosion of steel wire under the stress state is more obvious, the fluctuation of local characterization is more intense, and the corrosion presents a nonlinear growth trend. The mass loss of the steel wire with 3,000 μϵ after four days of accelerated electrolytic corrosion is similar to the 420-day test result of natural corrosion, and the change trend is consistent. Under accelerated corrosion conditions, the average mass loss rate of a steel wire with 3,000 μϵ after four days of accelerated electrolytic corrosion is 6.40 times that of one day. At the same time, the average mass loss rate of steel wire with 3,000 μϵ after one to four days of accelerated electrolytic corrosion are 1.17 times, 1.22 times, 2.27 times, and 3.02 times than 2,000 μϵ respectively. The maximum section loss rate increases with the increase of strain and time, and it has a good correlation with the two variables. Therefore, the maximum section loss rate can be considered as the core intermediate variable to measure the corrosion grade of main cable steel wire.

Influence of Air Pollution Factors on Corrosion of Metal Equipment in Transmission and Transformation Power Stations

In this paper, the atmospheric environmental corrosion grade of substations in 11 prefecture level cities in Shanxi Province is evaluated through a metal hanging sheet experiment. Combined with the main environmental factors, such as temperature, relative humidity, and the concentration of main pollution factors, such as SO2, Cl−, dust, etc., the influence of various factors on the corrosion of transmission and transformation equipment is analyzed, and the corresponding anti-corrosion measures are put forward.

Corrosion grade recognition for weathering steel plate based on a convolutional neural network

For the maintenance of weathering steel structure facilities, it is necessary to evaluate the corrosion grade of the rust layer on the surface regularly. At present, corrosion grade classification of weathering steel is mainly based on visual inspection with the human eye. In this paper, a deep learning method using a convolutional neural network (CNN) to evaluate the corrosion grade of weathering steel is proposed to save time and manpower. Firstly, the image dataset of the corrosion steel plate was established using salt spray tests. Then, a CNN architecture named VGG-Corrosion was designed to evaluate the corrosion grade of the corroded steel plate. The effects of the learning rate, transfer learning, and batch size were also investigated to clarify the best hyperparameter configurations to train a powerful corrosion grade classification model. Under the best combination of considered hyperparameters, the mean average accuracy for the corrosion grade evaluation of the test results is 90.96%. The test results indicated that the CNN-based corrosion grade recognition for weathering steel plate is prospective, which would be helpful for safety evaluation of steel structures.

Tribological properties of borate ionic liquids with low corrosion grade and excellent thermal stability in 500 N base oil

AbstractTwo borate ionic liquids 1‐Butyl‐3‐(2‐methoxy‐2‐oxoethyl)‐imidazole bis(mandelato)‐borate [MABIM][BMB]) and 1,3‐Dioctylbenzotriazole bis(mandelato)‐borate ([DOBI][BMB]) were synthesised and utilised as the lubricating additives. Their corrosion degrees were measured and the results show that [DOBI][BMB] and [MABIM][BMB] exhibit remarkable anti‐corrosion properties ([DOBI][BMB]: 1a, [MABIM][BMB]: 1b). The 4‐ball machine was employed to evaluate their tribological properties in 500 N base oil. When [DOBI][BMB] and [MABIM][BMB] were added at the concentration of 3.0 wt%, the friction coefficient of 500 N was reduced by 37.5% and 29.5%. It can be concluded from the results of XPS and SEM that a lubricating film containing iron oxide, B2O3 and organic N‐containing compounds have formed. And a model is proposed so as to describe the lubricating mechanism.

Improvements in Fire Resistance, Decay Resistance, Anti-Mold Property and Bonding Performance in Plywood Treated with Manganese Chloride, Phosphoric Acid, Boric Acid and Ammonium Chloride

(1) A compound protectant was prepared using manganese chloride, phosphoric acid, boric acid and ammonium chloride, and then a veneer was immersed in the prepared protectant to prepare plywood in this paper. Great attention was paid to discussing influences of such protectant on fire resistance, decay resistance, anti-mold property and bonding performance of plywood. Results demonstrated that after protectant treatment, the plywood showed not only good fire resistance and smoke inhibition, but also strong char-formation ability, slow flame spreading, long time to ignition, small fire risk and high safety level. (2) The mass loss rates of plywood with protectant treatment after infection and erosion in wood-destroying Coriolus versicolor and Gloeophyllum trabeum were 19.73% and 17.27%, reaching the II-level corrosion grade. (3) There is not a significant difference with Aspergillus niger V.; however, it was possible to observe a strong difference with Trichoderma viride Pers. ex Fr., indicating that the protectant acted as a good anti-mold product for plywood. (4) The protectant influenced the bonding interface of wood and bonding conditions of the adhesive. The bonding strength of plywood was weakened, but it still met the requirements on bonding strength of GB/T 9846-2015. (5) The protectant changed the thermal decomposition and thermal degradation of plywood, inhibiting the generation of inflammable goods, blocking transmission of heats and lowering the thermal decomposition temperature of plywood. These promoted dehydrations and charring of wood and the generated carbon had a high thermal stability. (6) Compared with untreated plywood, the prepared protectant treatment significantly enhanced the fire resistance of plywood, reduced its biodegradability by wood-decaying fungi and showed good mold resistance.