通过腐蚀失重比较了4种不同Cr含量的Q420钢在模拟的高盐度工业大气环境下的耐蚀性能,研究了Cr对Q420钢锈层结构与组成的影响及其作用机理。结果表明,含Cr钢的耐蚀性能优于Q420钢,且9% (质量分数) Cr钢的腐蚀速率最低,耐蚀性最好;Q420钢的腐蚀速率保持稳定,含Cr钢的腐蚀速率先增大后减小,这是因为含Cr钢的锈层随着腐蚀的进行会由初期的不稳定状态转变为稳定状态,耐蚀性得到增强;Cr促进了内锈层中稳定相
Effect of Cr on the corrosion resistance of Q420 steels with different Cr content (2%, 5% and 9% mass fraction) in atmosphere with high salinity was investigated by means of weight loss test, XRD and SEM. The results show that corrosion resistance of Cr modified Q420 steels is higher than that of simple Q420 steel. Among others the Q420 steel with 9%Cr shows the lowest corrosion rate and the highest corrosion resistance. The curve of corrosion rate versus time of the simple Q420 steel kept stable within a high level. While the corrosion rate of Cr modified steels increases in the initial stage and then increases, which indicates that the rust scale became compact and stable in the later stage. It was revealed that Cr can promote the formation of
本实验材料为Q420钢及3种分别添加2.0%、5.0%及9.0%Cr合金化后的实验钢。基材Q420的主要化学成分 (质量分数,%) 为：C 0.160,Cr 0.038,Mn 1.46,P 0.010,S 0.001,Si 0.25,Ni 0.03,Cu 0.04,Ti 0.015,Fe余量。
采用1.0% (质量分数) NaCl+0.1%NaHSO3的混合溶液作为实验溶液模拟沿海地区的高盐度工业大气环境。腐蚀失重实验试样尺寸为30 mm×25 mm×3 mm,每组3个平行试样。干湿循环周期为60 min,浸润于混合溶液时间为12 min,溶液温度为45 ℃,干燥时间为48 min,试样表面温度为 (70±10) ℃,溶液每3 d更换一次。加速腐蚀实验周期分为4组,分别为72,144,240和360 h。
利用扫描电镜 (SEM,Hitachi S-3400N)、X射线衍射仪 (XRD,D8 Advance) 对试样表面锈层的形貌与组成进行观察和分析。用于微观形貌观察的试样尺寸为20 mm×15 mm×3 mm,实验周期取72和360 h。用于锈层检测的试样尺寸为15 mm×15 mm×3 mm,实验周期取360 h。
综合式 (1) 和 (2) 得到周浸腐蚀试样的单位面积平均腐蚀减薄量计算公式为：
The authors have declared that no competing interests exist.
This paper investigates the impact of additional nitrate sources on mild steel coupon corrosion in a seawater/sediment system. The results show that addition of 5mM of nitrate sources significantly increased the weight loss of coupons after 20weeks. SEM results indicate increase in microbial populations and corrosive products in the non-autoclaved and the nitrate-treated environments. EDX analyses revealed an increase in contents of carbon, calcium, magnesium, phosphorus and sodium with the exception of iron with an increase in incubation time.
Fabrication of a newly nanocrystalline Al and two of its alloys, namely Al–10%Cu; and Al–10%Cu–5%Ti has been carried out using mechanical alloying (MA) technique. The corrosion behavior of these materials in aerated stagnant Arabian Gulf seawater (AGSW) at room temperature has been reported. Cyclic potentiodynamic polarization (CPP), chronoamperometric current-time (CCT) and electrochemical impedance spectroscopy (EIS) measurements along with scanning electron microscopy (SEM) and X-ray energy dispersive (EDX) investigations were employed to report the corrosion behavior of the fabricated materials. All results indicated that Al suffers both uniform and localized corrosion in the AGSW test solution. The presence of 10%Cu decreases the corrosion current density, the anodic and cathodic currents and corrosion rate and increases the corrosion resistance of Al. The addition of 5%Ti to the Al–10%Cu alloy produced further decreases in the corrosion parameters. Measurements together confirmed that the corrosion of the fabricated materials in AGSW decreases in the order Al>Al–10%Cu>Al–10%Cu–5%Ti.
61Corrosion of a low nickel SS in carbonated alkali activated fly ash mortars.61Severe conditions are induced by chloride penetration.61Very good corrosion performance of this steel during a 650 day exposure.61The corrosion performance of this steel is slightly worse than that of AISI 304.61Higher protection against pitting attack offered by fly ash vs OPC mortars.
The Mo-N surface modified layer on Ti6Al4V alloy was obtained by the plasma surface alloying technique.The structure and composition of the Mo-N modified Ti6Al4V alloy were investigated by X-ray diffraction(XRD)and glow discharge optical emission spectroscopy(GDOES).The Mo-N modified layer contains Mo-N coating on subsurface and diffusion layers between the subsurface and substrate.The X-ray diffraction analysis of the Mo-N modified Ti6Al4V alloy reveals that the outmost surface of the Mo-N modified Ti6Al4V alloy is composed of phase Mo 2 N(fcc)and Mo 2 N(tetr).The electrochemical corrosion performance of the Mo-N modified Ti6Al4V alloy in 0.5 mol/L HCl solution was investigated and compared with that of Ti6Al4V alloy.The chemical corrosion performance of the Mo-N modified Ti6Al4V alloy in boiling 37%HCl solution was investigated and compared with that of Ti6Al4V alloy.Results indicate that self-corroding electric potentials and corrosion-rate of the Mo-N modified Ti6Al4V alloy are higher than that of Ti6Al4V alloy in 0.5 mol/L HCl solution.The corrosion-rate of the Mo-N modified Ti6Al4V alloy is lower than that of Ti6Al4V alloy in boiling 37%HCl solution.
An investigation was carried out, through laboratory experiments, into the corrosion behaviour of stainless steels immersed in natural and sterile sea-water to determine whether the observed ennoble ment of the free corrosion potentials in sea-immersed stainless steels can be explained as due to the settlement of living microbiological slime on the metal surface. Experiments corroborated the fact that in natural environments, metal surface colonization by bacterial and algal populations alters the cathodic oxygen reduction process, presumably as a result of enzymic catalysis. This phenomenon not only facilitates the initiation of localized attack, but also heightens their progress and extension, thus justifying the greater aggressivity of natural, as compared with sterile, environments with equal salt content.
This work aims at studying the electrochemical behavior, by Electrochemical Impedance Spectroscopy (EIS), of austenitic (AISI 304 and AISI 316) and duplex (SAF 2205 and SAF 2304) stainless steels, when embedded in concrete specimens. Concrete specimens were exposed to chloride containing solutions simulating the aggressive conditions found in sweater environments. Samples were fully immersed and submitted to periodic immersion/emersion cycles. EIS and open circuit potential (OCP) were monitored in a monthly basis. Samples containing carbon steel (C-steel) rebars were also prepared for comparison of the corrosion rates between the different materials. The results showed that the austenitic and duplex SAF 2205 stainless steels were passive for all the testing period, due to the formation of protective oxide layer, with the AISI 316 presenting the higher corrosion resistance value. The EIS results suggest an increase of more than one order of magnitude in the corrosion resistance of the duplex steels and AISI 316 comparatively to C-steel rebars.
目的：研究304不锈钢在模拟深海和浅海中的应力腐蚀开裂( SCC)行为。方法通过控制不同环境因素模拟南海某海域环境，利用动电位扫描、交流阻抗谱、慢应变速率拉伸( SSRT)及SEM表面分析等手段进行研究。结果304不锈钢在模拟海水溶液中呈现钝化状态，出现应力腐蚀敏感性，且裂纹扩展方式为穿晶开裂。在深海中的SCC机制为氢致开裂，浅海中的SCC机制主要为阳极溶解。结论304不锈钢在深海与浅海中的SCC机制不同，但两者的SCC敏感性相近且相对较低，在模拟海水环境中的应用不受海水深度限制。
ABSTRACT Bulk glassy Fe60-xCrxMo15C15B10 (x = 0, 7.5, 15, 22.5 and 30 at%) alloys with high thermal stability were synthesized and the effects of chromium on the glass formation and corrosion behavior were clarified. The maximum diameter for glass formation is 2-2.5 mm for the 7.5 and 15 at%Cr alloys and 1 mm for the other alloys. In the present glassy alloy system, the temperature interval of the supercooled liquid region (DeltaT(x)) changed with chromium and was enlarged from around 70 K at x = 0, 22.5 and 30 at% to over 80 K at x = 7.5 and 15 at%. Both corrosion rate and anodic current density by potentiodynamic polarization in HCl solutions decreased with an increase of chromium content in the alloys. For the Cr-free alloy, molybdenum was significantly concentrated in the surface film after immersion in 1N HCl solution. The bulk glassy alloys containing chromium was immune to corrosion by the formation of protective passive film enriched with chromium during immersion in the solution.
The corrosion behaviour of 316L stainless steel was studied in the concentrated artificial seawater at 7202°C, i.e., the simulated low temperature-multi effect distillation environments, by using electrochemical measurement techniques. The corrosion state changes from spontaneous passivation to pitting after about 115002h of immersion. Pitting corrosion is under mixed control of charge transfer and diffusion processes in the long-term immersion. The salt deposits retard the diffusion of oxygen to the metal surface. The pit depth only reaches about 3802μm after one year of immersion due to the alloying effect of Mo, low dissolved oxygen levels and weak occlusion states.
AbstractWastage as a result of the combined effects of wear and corrosion occurs in many environments, ranging from offshore to the healthcare industries. In such cases, the degradation is dependent on a wide range of parameters relating to the materials in contact and the nature of the corrosive environments. Defining conditions in which the wastage is minimised is critically important for engineers charged with monitoring such processes. The nature of the tribological contact plays a critical role in determining the effect of corrosion on the wastage rate. In some cases, as in sliding wear, frictional heating may arise at high velocities and applied loads, leading to oxide film formation, even at room temperatures. In other cases, as in solid particle erosion, frictional heating may play a significant role only at very high fluxes of particle impact. The action of a corrosive medium, either in gaseous or in liquid form, thus may have very different effects on such diverse tribological processes. The int...
The formation of corrosion products during atmospheric corrosion on open and confined surfaces of electrogalvanized steel exposed to periodic wet/dry conditions was studied. The composition of the corrosion products was determined using Fourier transform infrared spectroscopy (FTIR) and extra information about the phases present was obtained by x-ray diffraction (XRD). Corrosion products that formed consisted mainly of different amounts of zinc oxide (ZnO), hydrozincite (Zn
The processes of atmospheric corrosion of iron and steel and the properties of corrosion products (rusts) are modeled based on a quantitative evaluation of the chemical reactions pertaining to corrosion to elucidate the conditions with which corrosion-protective rust films form. Based on the model, it is suggested that in the initial stage of corrosion, in the rusts, the pH of the aquatic system is maintained at 9.31 owing to an equilibrium with iron(II) hydroxide and the rate of air-oxidation at this pH is very fast, and that dense, self-repairing rust films form, protecting the underlying iron and steel. However, after corrosion stops, the rust film deteriorates due to the dissolution and shrinkage by aging, and the deteriorated rust film separates the anode and cathode reaction products (Fe and OH ions) to cause crevice corrosion. The air-oxidation of iron(II) in anode channels without the presence of OH ions results in strongly acidic solutions (pH 1.41), causing acid-corrosion. It is proposed that good catalysts (e.g. copper(II) and phosphate ions) accelerate the air-oxidation at low pH, delaying the crevice- and acid-corrosion stages. Further, it is argued that iron compounds with negative charges due to the non-stoichiometric proportions of the lattice oxide ions and metal ions (solid oxoanions of iron) exhibit stable cation-selective permeability even with a drop in pH. Rust films including such compounds would stop the passage of aggressive anions and act to protect iron and steel.