Corrosion of carbon steel during cyclical exposure to wet elemental sulphur and the atmosphere

The corrosion of carbon steel during cyclical exposure to wet elemental sulphur (four days) and the atmosphere (six days) has been investigated. The integral corrosion rate is found to decrease with successive cycles, thereby demonstrating that oxidation of the sulphide film confers protection to the underlying steel.     

Corrosion of plastics and composites in chemical environments

The degradation of polymeric materials with chemical reaction in which the molecular chains is cut is called corrosion. In this paper the behavior, the forms and mechanisms of corrosion of resins and GFRP (glass fiber reinforced plastics) under several aqueous solutions are reviewed based on our experiments. Three types of corrosion exist: the surface reaction type, the corroded layer forming type and the penetration type. Each form was determined by the chemical structures of the resin, the reactivity between resins and environments, and also the diffusivity of environmental media into the resins. The concept of the corrosion rate of metals could be applied even in plastics and fiber reinforced plastics for each corrosion form.     

Corrosion control of galvanized steel using a phosphate/calcium ion inhibitor mixture

The corrosion inhibition of galvanized steel was studied in artificial acid rain solution using extracts of pigments normally used in organic coatings for corrosion control. It was established that a combination of zinc phosphate/molybdate and calcium ion exchange silica has a significant synergetic anticorrosion effect in the acid rain solution compared to the pigments used alone. Further, the charge transfer resistance of galvanized steel in acid rain solution saturated by the above pigment blend approaches that of strontium chromate in artificial acid rain solution. Use of the pigment blend was found to lead to development of a protective film, which is thought to be a complex mixture of calcium phosphates and zinc phosphate.     

Hydrogen permeation behavior in pure nickel implanted with phosphorus, sulphur and their mixture

The entry and transport of hydrogen in phosphorus (P)-, sulphur (S)- and their mixture (P + S)-implanted nickel specimens with a fluence range of 1 × 10¹⁵ to 1 × 10¹⁷/cm² have been investigated using an electrochemical permeation technique and etching treatment (0.2% HF solution). From the hydrogen permeation transients obtained, the effective hydrogen concentration (C_H), apparent hydrogen diffusion coefficient (D_lag) and breakthrough time (t_lag) were estimated by using the time lag method in addition to the steady state permeation current density (P_∞). It was found that at a fluence of less than 1 × 10¹⁶/cm² almost all hydrogen permeation transients of the implanted nickel specimens were affected by the defects (vacancy, compressive stress and so on) generated during ion implantation process. At a high fluence of 1 × 10¹⁷/cm² the hydrogen permeation transient had a specific behavior because of the formation of amorphous phase for P, the structure change from fcc-structure to bcc-structure for S and both of them for the mixture (P and S). However, a synergistic effect of P and S was not observed on the hydrogen permeation transient. The behavior of these parameters depending on fluence and implanting element was discussed in terms of an amount of hydrogen entry site, the degree of defects, the properties of amorphous phase and structure and so on.     

Corrosion of bronze by acetic and formic acid vapours,sulphur dioxide and sodium chloride particles

This paper studies the corrosion of patinated and unpatinated bronze by acetic and formic acid vapours, sulphur dioxide and sodium chloride salt particles, at 100% relative humidity. Weight loss, X-ray diffraction, infrared and scanning electron microscopy were the techniques used. Acetic and formic acid vapours, sulphur dioxide and sodium chloride produce a high corrosion rate on bronze. In general, no protective effect was found by the patina on bronze. The principal compounds identified were Cu₂O, Cu₂S, Cu₅(SO₄)₂(OH)₆ · 5H₂O, Cu(CH₃CO₂)₂ · XH₂O and Cu(HCO₂)2.     

镁合金表面电弧喷涂铝涂层在氯离子中的腐蚀行为

采用电弧喷涂技术在镁合金AZ91基材表面制备铝涂层.通过5(质量分数,%)NaCl溶液浸泡试验和盐雾试验,考察了镁合金表面铝涂层在氯离子中的耐蚀性能及其腐蚀行为.利用光学显微镜、扫描电子显微镜(SEM)和X射线衍射仪(XRD)分析技术对涂层形貌、显微组织结构和相组成进行了研究.结果表明,封孔处理后的试样耐蚀性能有较大提高,未封孔的涂层试样腐蚀比原始镁合金更严重.     

Cu-Cr合金在H_2-H_2S混合气中的腐蚀行为

研究了Cu Cr合金及纯铜、纯铬在 5 0 0～ 60 0℃ ,硫分压为 10 -5Pa时的硫化腐蚀。两种Cu Cr合金的腐蚀速度均介于两种纯金属之间 ,并随温度的升高而增大 ,但在两种Cu Cr合金的表面均形成了复杂的腐蚀产物膜 ,外层为Cu2 S层 ,有时不连续甚至剥落 ,中间层为二元Cu Cr硫化物CuCrS2 ,内层为二元Cu Cr硫化物Cu Cr2 S4和CrS的混合物 ,有时也包含未被腐蚀的金属铬颗粒。在腐蚀区以下的合金基体中没有铬的贫化现象发生。这种腐蚀膜结构的形成是合金中存在两相的结果     

Ultra-fast sulphur grain boundary segregation during hot deformation of nickel

Sulphur grain boundary segregation during hot-compression of nickel (5.4 wt. ppm S) is monitored using Auger electron spectroscopy and wavelength dispersive X-ray spectroscopy. The deformation conditions (temperature/deformation rate) investigated are: 550 °C/0, 550 °C/3 × 10^?5 s^?1, 550 °C/3 × 10^?4 s^?1 and 450 °C/3 × 10^?5 s^?1. It is shown that plastic deformation accelerates the kinetics of sulphur grain boundary segregation by a factor of ～10³ to a few 10⁵, depending on the deformation conditions. Very high levels of segregation (～0.8 monolayer of sulphur) are obtained after very low deformation (～5%). In addition a linear dependence of the segregation level with time and deformation is demonstrated. The segregation kinetics during plastic deformation is proportional to the deformation rate and almost independent of temperature. Several metallurgical mechanisms are discussed and confronted with the experimental results: dislocations dragging, pipe diffusion, dislocation collection/diffusion and acceleration by excess vacancies. It appears that the models developed in this work on the basis of the two latter mechanisms (dislocation collection/diffusion and acceleration by excess vacancies) predict the experimental data correctly.     

城市污泥焚烧过程中重金属形态与分布的热力学平衡分析

采用化学热力学平衡分析方法,应用污泥实测数据预测4种不同来源的污泥焚烧过程中重金属Pb、Ni、Mn、Cr、Zn和Cu的迁移和转化规律。结果表明:重金属Ni、Mn和Zn在低温条件下受矿物质Al2O3、CaO、SiO2和Fe2O3的影响较大,易形成稳定的固体而存在于炉渣中;Cr易形成氧化物而基本不受矿物质的影响,Pb的形态转化受多种因素的制约且易于挥发;随着焚烧温度的升高,重金属Pb、Cu和Zn从对应的金属固态盐类或氧化物逐渐转化为气态的金属氯化物、氧化物,再到气态单质进入灰飞或大气中;Mn、Ni和Cr易形成不易挥发的稳定固体而存在炉渣中;焚烧体系中S能与Ni、Cu和Pb结合形成硫酸盐,而对Mn、Cr和Zn的形态转化影响较小;焚烧体系中Cl对Pb的挥发影响最大,其次为Cu和Zn,影响较小或者不受影响的金属是Ni、Cr和Mn。     

一种聚合咪唑啉缓蚀剂的合成及其缓蚀性能

以蓖麻油酸为原料,合成多羟基聚蓖麻油酸,再与有机胺合成聚合咪唑啉缓蚀剂。采用动态挂片法和电化学方法评价了合成的缓蚀剂的缓蚀性能,并采用扫描电子显微镜(SEM)对N80试片表面的腐蚀形貌进行了观察。结果表明,该咪唑啉缓蚀剂在60℃,8 MPa中低温高压二氧化碳体系中对N80钢具有良好的缓蚀作用,加入量为30mg/L时,试片的腐蚀速率小于0.076mm/a。对该聚合咪唑啉缓蚀剂在钢片表面的吸附模型进行计算,发现该吸附遵循Langmuir等温吸附模型。     

Hydrogen embrittlement during the corrosion of steel by wet elemental sulphur

A solid state hydrogen sensor has been used to confirm that hydrogen is liberated and diffuses into the steel during corrosion in sulphur-water mixtures. Slow strain rate mechanical tests and fractography show that this hydrogen causes embrittlement of the steel.     

含氯低pH值溶液中BDT自组装膜对铜电极的缓蚀行为

采用分子自组装技术,在铜电极表面形成一层1, 3-二巯基硫醇(BDT)单分子自组装膜.通过交流阻抗、极化曲线和循环伏安等电化学方法探讨该自组装膜在3%NaCl溶液中对铜电极的缓蚀作用.实验表明:BDT能够有效地组装到铜的表面形成单分子自组装膜,BDT自组装膜能有效地抑制铜基底在3%NaCl腐蚀介质以及酸性NaCl溶液中的腐蚀行为;缓蚀效率随组装时间的延长逐渐升高并趋于稳定,在pH值较低的溶液中仍具有较好的缓蚀效果;当BDT浓度为1.0×10-2 mol/L、组装时间为40 h时,铜电极的腐蚀电流最小,缓蚀效率最好.     

Cu—Cr合金在H2—H2S混合气中的腐蚀行为

研究了Cu-Cr合金及纯铜、纯铬在500－600℃,硫分压为10^-5Pa时的硫化腐蚀。两种Cu-Cr合金的腐蚀速度均介于两种纯金属之间,并随温度的升高而增大,但在两种Cu-Cr合金的表面均形成了复杂的腐蚀产物膜,外层为Cu2S层,有时不连续甚至剥落,中间层为二元Cu-Cr硫化物CuCrS2,内层为二元Cu-Cr硫化物CuCr2S4和CrS的混合物,有时也包含未被腐蚀的金属铬颗粒。在腐蚀区以下的合金基体中没有铬的贫化现象发生。这种腐蚀膜结构的形成是合金中存在两相的结果。     

镀锌紧固件在储存过程中的锈蚀原因分析

防抱死制动系统(ABS:Anti-lock Braking System)的镀锌紧固件在存储过程中发生锈蚀。分别从大气腐蚀影响因素、腐蚀形貌及能谱分析(EDS)等方面分析了镀锌紧固件的锈蚀原因,并提出合理化建议,避免再次发生类似的锈蚀问题。     

Characteristics of a spindle bearing system with a gear located on the bearing span

The spindle bearing system is the main source of the total cutting point compliance of machine tool structures. In this work, the static and dynamic characteristics of a spindle bearing system driven by a gear located on the bearing span were investigated using the analytical and finite element methods. Based on the calculated results, a prototype spindle bearing system was manufactured and its static and dynamic characteristics were measured. From the comparison of the experimental results with the calculated results, it was found that the finite element method predicted well the static and dynamic characteristics of the spindle bearing system.     

汽车强化腐蚀试验中典型腐蚀问题分析

汽车腐蚀不仅影响车辆美观,还会造成车辆安全性能下降。本文主要介绍了整车强化腐蚀试验的试验方法,并对整车60循环试验后常见的腐蚀问题及腐蚀原因进行了分析,提出了改进措施及建议。