Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: The electrochemical behavior of three solvent- free epoxy coatings on Q345E carbon steel during corrosion-erosion induced by flowing slurry of simulated sea water with 1% (mass fraction) of sand at 60 ℃ was investigated by means of electrochemical impedance spectroscopy (EIS), scanning electron microscope (SEM) and confocal laser scanning microscopy (CLSM), respectively. The results showed that the flowing slurry induced erosion aggravated the deterioration of coatings. The amine-cured epoxy powder coating and phenolic aldehyde amine-cured liquid epoxy coating were cured with slow speed and thus much densified, accordingly, their deterioration process experienced three stages: firstly, the inward migration of corrosive medium; secondly, the corrosion initiation of the substrate metal; thirdly, the corrosion propagation of the substrate metal beneath the coating and finally the failure of coatings. On the contrary, the phenolic aldehyde-cured epoxy powder coating was cured with fast speed and thus much porous, its deterioration process experienced two stages with a shortened second stage. Therefore,the existence of pores in the coating is one of the important factors for inducing failure of coatings during corrosion-erosion.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: 316L stainless steel is widely used for enhancing the pitting resistance of pipelines in gas field. The corrosion environment is complex and diversified in different working districts of gas field. Therefore, it is necessary to develop a model for predicting the pitting resistance of pipelines serving in different corrosive environments. Critical pitting temperature (CPT) is considered as a criterion for evaluating the pitting resistance of stainless steel. Based on a survey on the operation situations of gas field, the relevant data of CPT for 316L stainless steel is acquired by potentiodynamic polarization method in solutions with various Cl- concentrations and pH values, which are selected to correspond with the real environments in operation. Then, an artificial neutral network (ANN) model is developed to predict the CPT, and therewith to compare with the measured data. The results show that the CPT decreases with the increase of Cl- concentration, but on which pH value has little influence. The developed ANN model has good ability to predict the CPT of 316L stainless steel, and can be used for the prediction of CPT in complex environments in gas field. It is also revealed that there is no interactive effect between Cl- concentration and pH value, and Cl- concentration was the main influencing factor on the CPT. Therefore, Cl- concentration will be peculiarly concerned with for the implementation of a corrosion control project in gas field.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: The debonding process of organic coatings with desired artificial defects in 3.5%NaCl solution was studied by means of wire beam electrode (WBE) method and electrochemical impedance spectroscopy (EIS) technique. The purpose was to reveal the relevant debonding mechanism of organic coatings in the area nearby water-line via analyzing the current distribution and the variation of impedance spectroscopy during the experiment. It was found that, either the artificial defect or inherent defect could accelerate cathodic debonding rate of the coating around the defects. Besides, due to the effect of waterline, a coating debonding, which initiated from one inherent defect will expand towards the waterline. The coating debonding occurred firstly on the area below the waterline, and then later above the waterline. The coating debonding rate on the area above waterline was controlled by the permeation rate of electrolyte through the coating.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: Pure Al plates were exposed in different atmospheres for 12 months at three typical test sites respectively: i.e. a rural site at Xishuangbanna of Yunnan province, an industrial site at Jiangjin of Sichuan province and a coastal site at Wanning of Hainan province. Then the corroded Al plates were characterized by means of EIS technique and SEM. The results indicate that the corrosion resistance of pure Al is the worst in the coastal atmosphere, the best in the rural atmosphere and the middle in the industrial atmosphere. Different thick layers of corrosion products were formed on Al surface in the rural and industrial atmosphere. In the contrast, a few corrosion products were formed dispersedly in the coastal atmosphere. The rate controlling step may be the diffusion of corrosive ions for the corrosion process in the coastal atmosphere, while the charge transfer for those in the rural and industrial atmospheres.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《中国腐蚀与防护学报》
Abstract: Atmospheric corrosion of carbon steel Q235 and 45#, and weathering steel Corten A was studied in three typical atmospheres at tropic rainforest-, marine- and industrial-exposure sites respectively. Results show that the carbon steels and the weathering steel exhibited more or less the same corrosion kinetics, the formation of rusts and their evolution for exposure in one test site. But they were significant different from those for exposure in other test sites. Finally, the influence factors on corrosion process and the corrosivity of the three atmospheres were also discussed.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Model for describing the high temperature corrosion behavior of binary A-B alloys induced by two oxidants X-Y in the presence of an external scale of a compoundAYn. Then a kinetic analysis is made according to the proposed corrosion model for the experimental results of corrosion of several binary alloys in oxygen-sulfur containing gas mixture at 800 ℃. It shows that the prediction of the proposed model is receivable. However, the practical diffusion path of the two oxidants X-Y in the alloys is rather complex and thus hard to fully foresee, which therefore may result in certain deviations between the experimental values of the thicknesses of the internal oxidation zone and those obtained by calculation.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Three kind of solvent- free epoxy coatings was prepared on 16Mn (Q345E) steel and then their degradation process in flowing artificial sea water 3.5%NaCl solution was investigated by means of gravimetric method, and the acquired weight gain curves were fitted by Fick model. The effect of the flow velocities on the degradation process of coatings was also studied by open circuit potential method (OCP) and electrochemical impedance spectroscopy (EIS). The results showed that, for the amine- cured epoxy powder coating and the phenolic aldehyde- cured epoxy powder coating within the scope of the test flow velocities and the phenolic aldehyde amine-cured liquid epoxy coating at lower flow velocities, the diffusion of water through the coatings by different flow velocities all agreed well with Fick II diffusion model. However, the phenolic aldehyde amine-cured liquid epoxy coating showed irregular regulation by flow velocity 4 m/s, which may be due to aggravated dissolution, thus the diffusion of water through the coating departed from Fick II diffusion model. As the flow velocity increased, the amount of saturated water uptake of the coatings and the water diffusion coefficient increased simultaneously. The degradation processes of the above mentioned three coatings within the scope of test flow velocities may be differentiated as a process of three stages. The increase of flow velocity could accelerate the degradation of the phe-nolic aldehyde -cured epoxy powder coating and the phenolic aldehyde amine-cured liquid epoxy coating, but had little influence on the amine-cured epoxy powder coating.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: The natural salt spray (NSS) induced corrosion of pure copper was investigated by weight loss measurement. The correlation of the indoor accelerated corrosion and the outdoor exposure was studied with Grey correlation method. The results show that the corrosion kinetics of pure copper in the two environments follows the exponential function. The corrosion kinetics of the indoor accelerated test does not agree with those in rural environment with low pollutants, however, it presents better relativity with those acquired from the marine and industrial atmospheres. Then a prediction model for the corrosion of outdoor exposure of pure copper in various atmospheres was established by Grey correlation method.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Effect of heat treatment on electrochemical corrosion behavior of Ni- base superalloy DZ125 laser recast layer in chemical milling solution was investigated in terms of characterizing the recast layer by means of electrochemical corrosion, scanning electron microscopy, as well as Xray diffraction of corrosion products and scanning corrosion surface. It was found that DZ125 alloy recast layer was mainly consisted of dendrite structure with less γ ' phase precipitate. However, there were lots of γ ' phases precipitating enough densely in recast layer after heat treatment. Heat treatment of the recast layer enhances its passivation. The as heat-treated samples were dissolved even slowly than those recast sample, as well as its corrosion tendency decreased. There fore, heat treatment can significantly improve corrosion resistance of laser recast layer in the chemical milling solution.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: none
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: none
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Effect of NaHSO3 coupled with NaCl on the corrosion of Q235 steel in an alternative dry/wet test environment, which aims to simulate atmosphere corrosion, was investigated by SEM, XRD, FTIR and mass loss analysis. The results show that the synergic effect of NaHSO3 and NaCl plays an important role in the corrosion process of Q235 steel. The mass losses are larger in the test environment with the simultaneous presence of NaHSO3 and NaCl rather than either of the two. The corrosivity of corrosive media could be ranked as follows: NaHSO3+NaCl>NaHSO3>NaCl. The presence of NaHSO3 in the test environment could facilitate the formation of corrosion product α-FeOOH, while NaCl could facilitate the formation of γ-Fe2O3 and Fe3O4.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: none
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: A weld ring with rim of 90/10 cupronickel for marine pipe combination was corroded after 3 years operation. The failure of the ring was analyzed by means of chemical composition analysis, visual examination, metallographic observation of the alloy, as well as characterization of corrosion morphology and corrosion product by SEM/EDS. Results showed that intergranular corrosion was prevalent on the bottom of corrosion pits, in the erosion-corrosion zones and in the thinned region around corrosion perforations. De- nickelification and dissolution occurred in grains which were surrounded by the preferentially attacked boundaries. It was supposed that selective dealloying and dissolution was related with the types of grain boundary and the grain orientations. Sulfide was detected on the surface of the corrosion product and on the facet of emerged grains on the erosion-corrosion zone. Therefore, the failure of the cupronickel ring was the result from the synergistic effect of intergranular corrosion, dealloying corrosion and erosion-corrosion in the sulfide-containing environment.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Research progress on corrosion of carbon steels induced by SRB is reviewed in terms of the formation mechanism of biofilm, the traditional corrosion mechanism of SRB, mechanism of biocatalysis cathodic sulfate reduction, and the corrosion of carbon steels under the deposit scale induced by SRB biomineralization. In addition, the paper focused on the key role of the theory of bioenergetics and bioelectrochemistry in understanding the mechanism of MIC induced by SRB. The novel technologies and methods for control of SRB biofilm which provide reference for control of SRB corrosion are introduced.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: A leakages related failure occurred of an electric water heater tank after 8 a service. The material of the specific area of that failed tanker was examined by means of macroscopic and the enamel coating of the inner side of the tanker and the Mg alloy sacrificial anode were also examined by electrochemical methods. The results indicated that the performance of enamel film decreased and the Mg sacrificial anode was significantly degraded after several years' service; while the open circuit potential of twisted area of steel substrate is much negative in comparison with that of ordinary area, so it is more likely that corrosion may preferentially occur at the twisted area and then the corrosion develops till leaking.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: Co-Mn alloy coatings can be prepared on 304 stainless steel with a chloride containing bath, while the effect of pH value of the electrolyte and the applied current density on the microstructure and composition of the coatings was investigated. The results indicated that the Mn content in the coatings increased with either increasing pH value or current density in a pH value range of 2.5 to 6.5 and a current density range of 125 to 225 mA/cm2 respectively. The pH value was the main factor determining the composition of Co-Mn alloys when the current density was of 125 and175 mA/cm2, while the current density turned to be the main factor when it reached up to 225 mA/cm2. A smooth, dense and uniform coating with Mn content above 20% (atomic fraction) could be obtained by pH value of 4.5 and current density of 125 mA/cm2. After a hydrogen-relief treatment and then an oxidation treatment at 800 ℃, the electroplated Co-Mn alloy coating might be transformed into a continuous MnCo2O4 spinel oxide film with a good compatibility to the substrate.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: A treatment process with a complex liquor containing phosphoric and tannic acid was used to pre-treat rusted structural steel so that to enhance the adhesion of applied organic coatings on the rusted structural steel. Adhesion test results showed that this treatment process enhanced the adhesion obviously of several organic coatings (epoxy, acrylic and fluorocarbon coatings) on the pre-treated rusted structural steel, therewith the adhesion of coatings could meet the requirements cited in the relevant coating standards for actual application. Further analysis revealed that the enhancement in adhesion might be attributed to the formation of a conversion film consisted of a dense inner potion and a micro-cracked outer portion instead of the original porous rust scale.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《腐蚀科学与防护技术》
Abstract: A δ-Ni2Al3-Cr2O3/Ni-Cr2O3 coating system was prepared by aluminizing partially a preelectrodeposited Ni-Cr2O3 film on pure Ni by means of a conventional pack cementation process at 620 ℃, during which a part of Cr2O3 particles reacted with Al to form more stable oxide of Al2O3. After oxidation at 1000 ℃ for 20 h, Cr2O3 particles in the aluminide coating and the rest electrodeposited composite film all transformed into Al2O3 particles, therewith at the interface aluminide/Ni, an Al2O3-rich layer might form and then act as a diffusion barrier to mitigate the inter diffusion between the aluminide coating and the Ni-substrate.
Subjects: Materials Science >> Materials Science (General) submitted time 2023-03-31 Cooperative journals: 《材料研究学报》
Abstract: The W fiber/Zr-based metallic glass composite was prepared by infiltration and rapid solidification. The effect of the ratios of length to diameter of fibers on the compressive properties of the composite was investigated in detail. The results show that the yield strength firstly decreases with the increase of the length to diameter ratio then reaches a stable value when the ratio is greater than 1. The plastic strain has no obvious change when the ratio is greater than or equal to 1.25, while the plastic strain is bigger than 50% when the ratio is smaller than 1.25. The reason for these phenomena is the comprehensive effect of the friction force between pressure head and the end of the compressive sample, the change of the length to diameter ratio of the metallic glass fibers between W fibers and the mismatching between metallic glass matrix and the W fiber during deformation.