An electrophoretic ZrO2 doped epoxy coating on a galvanized steel plate was prepared in a bath of pigment-free waterborne epoxy paint plus an appropriate amount of zirconium nitrate pentahydrate. The examination with FTIR revealed that the hydrolysis product of zirconium nitrate pentahydrate could be co-electrodeposited with epoxy paint and the resulted ZrO2 particles enriched at the interface between the coating and the substrate. Then the corrosion protectiveness of the coatings was characterized by means of immersion test in NaCl solution, electrochemical impedance spectroscopy and scanning electrochemical microscopy. The results indicated that the corrosion procetiveness of the electrophoretic epoxy coating was significantly improved by the doped ZrO2, which may be resulted from the fulfilling of micro-pores in the coating by ZrO2 component on one hand and the enhancement of adhesion provided by the enriched ZrO2 layer at the interface of coating/ substrate on the other hand.
采用硅藻土模拟法研究了Q235,A1和A2钢在模拟酸性土壤中的腐蚀行为,对比分析了材料的腐蚀失重,利用扫描电镜 (SEM) 和X射线衍射 (XRD) 等方法研究了材料的腐蚀形貌及腐蚀产物。结果表明,在模拟酸性土壤中,Q235,A1和A2钢周期360 h的腐蚀速率别为0.48,0.14和0.097 mm/a。碳层分析表明,降低碳含量有助于减少钢中的微电池腐蚀；Cr的加入可以提高基体的自腐蚀电位；腐蚀后内锈层位置Cr的富集可以提高锈层的致密性,并改变点蚀的扩展方式；3种材料主要腐蚀产物均为α-FeOOH,γ-FeOOH和Fe3O4,其中A1和A2钢内锈层腐蚀产物中α-FeOOH比例增大,其α /γ-FeOOH比值约为Q235的10倍,腐蚀产物保护性更优。
The corrosion behavior of a commercial carbon steel Q235, and two new steels A1 and A2 in an artificial soil, which consisted of diatomite and appropriate acid solution to simulate a typical acidic soil at Southern China was studied by mean of corrosion weight loss measurement, and then the corrosion morphology and products were characterized by SEM and XRD. The results showed that the corrosion rate of Q235, A1 and A2 steel in the simulated acidic soil was 0.48, 0.14 and 0.097 mm/a respectively after 300 h corrosion; the tendency to micro-cell corrosion of a steel can be lowered as the carbon content of the steel has been reduced; an appropriate addition of Cr can shift positively the corrosion potential of the matrix; the enrichment of Cr in the inner portion of the rust scale can improve its compactness, and change the propagation mode of corrosion pits; the corrosion products of Q235, A1 and A2 steel were mainly consisted of α-FeOOH, γ-FeOOH and Fe3O4, however, the corrosion products of A1 and A2 steels possess a ratio of α-FeOOH to γ-FeOOH ca 10 times higher than that of Q235 steel, which implying a better protectiveness of the rust layers for the two new steels.
应用动电位极化、Mott-Schottky曲线测试和XPS测试等方法研究了含0.05 mol/L Cl-,pH值为11的混凝土模拟孔隙液中常用缓蚀剂亚硝酸盐对Q235碳钢小孔腐蚀早期行为的影响。结果显示,NO2-对稳定孔蚀和亚稳态孔蚀均有很好的抑制作用,亚稳态孔蚀电位和稳定孔蚀电位均随着NO2-浓度的增加而增大,且影响趋势接近。NO2-浓度较低时,对孔蚀的抑制作用很明显,超过0.03 mol/L后抑制作用变化不大。这是因为,NO2-浓度增大,钝化膜中更多的Fe2+被氧化为Fe3+,膜中的氧空位缺陷浓度降低,因此小孔的形核受到抑制。
The Effect of NO2- on the early stages of pitting corrosion of Q235 carbon steel in a simulated concrete pore solution (pH=11) was studied by means of polarization curves, Mott-Schottky curves and XPS methods. It was found that, NO2- inhibits both the stable pitting corrosion and the metastable pitting corrosion. The metastable pitting corrosion potential and the stable pitting corrosion potential increase with the increase of NO2- concentration and follow the similar trend. The nucleation process of pits can apparently be inhibited by a low content of NO2-, however this effect increases only slightly as the NO2- content higher than a critical value about 0.03 mol/L. With the increase of NO2- concentration, more Fe2+ in the passive film can be oxidized into Fe3+ and thereby, the defect density related with oxygen vacancies decreases, so the nucleation process of pits may be inhibited.
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.
采用全浸失重实验、电化学实验对实验室炼制的Cu-Sb-Mo低合金钢,对比钢304不锈钢和Q235B钢的耐硫酸、盐酸腐蚀性能进行评估。并且使用电化学阻抗谱 (EIS)、扫描电镜 (SEM) 和X射线衍射 (XRD) 研究了试制钢在硫酸、盐酸中的耐蚀机理。结果表明：合金元素Cu,Sb和Mo的添加,可以同时抑制金属的阳极溶解反应和阴极析氢反应,降低腐蚀电流密度,增大金属的电荷转移电阻。合金元素的添加在金属表面形成了对应的氧化物、硫化物,它们在腐蚀介质中的稳定性比钢基体更高,从而抑制钢基体的进一步腐蚀。
Hot rolled plate of a new low alloy steel Cu-Sb-Mo was prepared and then its corrosion performance was evaluated in solutions of sulfuric acid and hydrochloric acid respectively by means of weight loss tests and electrochemical measurements in comparison with two commercial steels 304 stainless steel and Q235B steel. Then the corroded steel was examined by EIS, SEM and XRD. The results indicate that the formed scale consisted of oxides and sulfides of the alloying elements (Cu, Sb and Mo) can inhibit both the anodic dissolution and cathodic hydrogen evolution reaction of the steel, decrease the corrosion current density and raise the charge transfer resistance of the steel, thereby the steel may be protected from further corrosion.
采用氯化物溶液在430不锈钢表面电沉积Co-Mn合金,重点研究了镀液pH值和电流密度对镀层微观结构及成分的影响。结果表明：pH值为2.5~6.5、电流密度为125~225 mA/cm2时,镀层中的Mn含量随着pH值和电流密度的增大而增加；电流密度为125和175 mA/cm2时,pH值是决定合金成分的主要因素,电流密度达到225 mA/cm2时电流密度是影响合金成分的主要因素；电镀Co-Mn合金的优化工艺参数为pH值为4.5、电流密度为125 mA/cm2,此时镀层质量良好,Mn含量可达20%(原子分数) 以上；通过除氢处理及在800 ℃空气中的氧化处理,合金镀层转变为连续、与基体结合良好的MnCo2O4尖晶石涂层。
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.
采用电化学方法研究了浓度、温度、阴阳极面积比的变化对乙二醇水溶液中3A21铝合金/H62黄铜 (Al/Cu)、3A21铝合金/304不锈钢 (Al/SS) 两种电偶对的腐蚀行为的影响。通过扫描电子显微镜观察了电偶对中铝合金局部腐蚀形貌。结果表明：随着乙二醇浓度的升高,Al/Cu和Al/SS电偶对的平均电偶电流密度Ig下降。随着温度的升高或Sc/Sa比例的增大,Al/Cu和Al/SS电偶对的Ig增大；相同条件下,Al/Cu电偶对Ig均大于Al/SS电偶对,Al/Cu和Al/SS两种电偶对具有相似的电偶腐蚀规律。
The influence of the ethylene glycol concentration, temperature and the ratio of cathode-to-anode area on galvanic corrosion of two couples of 3A21 Al-alloy/H62 brass (Al/Cu) and 3A21 Al-alloy/304 stainless steel (Al/SS) was studied in ethylene glycol-water solutions by means of electrochemical methods. Then the localized corrosion morphology of 3A21 alloy, which was the anode in the two galvanic couples, was examined by scanning electron microscope (SEM). The results showed that the average galvanic current densities (Ig) of the two couples Al/Cu and Al/SS decreased with the increasing ethylene glycol concentration, but increased with the rising temperature and ratio of cathode-to-anode area. Although the galvanic couples of Al/Cu and Al/SS exhibited similar corrosion behavior, the ig of galvanic couple Al/Cu was greater than that of the couple Al/SS under the same test condition.
采用金相显微镜、扫描电镜 (SEM) 和X射线光电子能谱仪 (XPS) 对不同Cl-浓度酸洗液作用下304热轧不锈钢酸洗后表面残余氧化铁鳞的形貌、结构、组成进行了分析。结果表明：随着Cl-浓度的提高,有利于去除与304热轧不锈钢板表面紧密接触的致密氧化层。致密的氧化层主要是以Cr2O3为主,其次是Fe的氧化物 (Fe2O3,Fe3O4和FeO) 等；当Cl-浓度含量为145 mg/L时,可较彻底的清除304热轧不锈钢表面致密的氧化层,且该Cl-浓度酸洗后304不锈钢热轧板所对应的钝化处理后钝化膜厚、致密性好。
The composition and structure of the residual oxide scale on hot-rolled 304 stainless steel after pickling in a bath of acid solution with different concentrations of Cl- was characterized by means of optical microscope (OM), scanning electron microscope (SEM), and X-ray photoelectron spectroscopy (XPS). The result showed that the increase of Cl- concentration in the pickling liquor may facilitate the removal of the inner dense portion of the oxide scale, which consisted mainly of Cr2O3 and Fe oxides (Fe2O3, Fe3O4, FeO) and exhibited strongly adhesive strength to the steel; the pickling liquor with 145 mg/L of Cl- is the best for effectively removing the oxide scale on hot rolled steel, as a result which facilitated the formation of a dense and compact passive film on the steel by subsequent passivation treatment.
A nanocomposite coating was prepared with epoxy resin as film-forming agent,polysiloxane as coupling agent and with proper additives of pigments, fillers and nano silicon dioxide. The nanocomposite coating was applied on carbon steel Q235, and its corrosion performance, in comparison with a present used coating, was investigated by means of simulate acid rain test, immersion test and electrochemical impedance spectroscopy. Results showed corrosion resistance of the nanocomposite coating is better than that of the current coating, it is suitable especially for the protection of engineering steel components for electric power facilities.
基于再生水管网铁细菌 (IB) 与腐蚀控制,着重探讨了不同次氯酸钠 (NaClO) 初始投加量下IB控制效果随时间的变化规律,以及上述控制过程中NaClO初始投加量对金属腐蚀行为影响及其腐蚀产物。结果表明,NaClO对再生水中IB的控制效果显著；初始投加浓度越高,IB复活所需时间越长,IB数量控制的效果也越好。IB可明显加重碳钢的腐蚀,但随着时间的延长,生物膜生长又对碳钢腐蚀具有延缓作用,投加NaClO可有效缓解初期IB腐蚀。投加NaClO虽然对IB有一定的控制作用,但其本身也具有腐蚀性,且初始投加NaClO浓度越高,金属腐蚀速率越大。综合IB控制和腐蚀控制,确定NaClO的最佳投加量为7 mg/L。
The effect of the initial dose of NaClO on the bacteriostasis of iron bacteria and the corrosion behavior of the pipeline steel for water distribution network was studied in an urban reclaimed water, which was sampled from a water recycle work in North China. Results show that the iron bacteria can be effectively inhibited by the addition of NaClO; the higher the dose is the longer time needs for the resurrection of the iron bacteria, therefore the better bacteriostasis may be realized; the existence of iron bacteria can significantly promote the corrosion of carbon steel, but with the extension of time, the corrosion of the steel may be suppressed to certain extent due to the formation of biofilms on the steel surface; in fact the addition of NaClO in the initial stage can suppress the corrosion of carbon steel induced by iron bacteria, however NaClO itself is also a corrosive medium to the steel, thus in the meanwhile a higher initial dose of NaClO may enhance the corrosion rate of the steel. Finally an optimal dose of NaClO 7 mg/L is acquired in terms of a compromise between the bacteriostasis in the reclaim water and the corrosion control of the steel.
采用单因素实验和正交实验,以腐蚀深度量为评价指标,研究了污泥的pH值和含水率,以及腐蚀温度、腐蚀时间和污泥种类对干燥器用两种金属腐蚀行为的影响规律。采用极差和方差分析,给出了各因素影响的主次顺序和不同因素对金属腐蚀影响的显著性,最后通过SEM和EDX对腐蚀产物进行表征。结果表明：Q235碳钢的腐蚀深度量随着温度、污泥含水率和污泥酸度的增加而逐渐增加；各因素对金属腐蚀深度量的影响主次顺序为：钢材种类、温度、污泥pH值、时间t、污泥种类；最大腐蚀条件为：腐蚀温度为100 ℃、腐蚀时间为288 h、污泥pH值为4.9、污泥种类为市政污泥、金属材料为Q235碳钢；污泥pH值和温度引起的腐蚀为非均匀腐蚀,而污泥含水率引起的腐蚀为均匀腐蚀。
Taking the corrosion depth as the evaluation index, the influence of different factors such as pH value and moisture content of sludges, as well as corrosion temperature and time on corrosion behavior of two candidate material for dryers: Q235 carbon steel and 304 stainless steel is studied by single factor experiment and orthogonal experiment. The corrosion product is characterized by SEM and EDX at last. The results show that the corrosion depth of Q235 carbon steel increases with the increase of temperature, moisture content and acidity of the sludge. The effect of the influence of factors on the corrosion depth of steels may be ranked as a decreasing sequence as following: steel type, temperature, pH of sludge, time, and sludge type. The maximum corrosion of Q235 occurred in a metropolitan sludge with pH 4.9 at 100 ℃ for 288 h. The corrosion product on Q235 carbon steel is mainly brown loose substance, while that on 304 stainless steel is mainly light color strain-like one. The corrosion extent and the penetration of the aggressive elements for carbon steel is much deeper than those for stainless steel. The variation of temperature and pH value of the sludge may induce non-uniform corrosion of the steels, while the variation of the moisture content of the sludge may be responsible to uniform corrosion.
通过极化曲线,电化学阻抗谱,恒流放电曲线等方法研究了AZ31镁合金在1.16,1.74,2.30,2.90和3.50 mol/L 的Mg(ClO4)2溶液中的腐蚀行为和电化学性能以及放电行为。结果表明,AZ31镁合金在2.90 mol/L Mg(ClO4)2溶液中腐蚀电流密度最大,传递电阻最小,放电容量最大。AZ31镁合金在Mg(ClO4)2溶液放电过程中会生成致密腐蚀产物,阻塞放电。并对镁一次电池的发展方向进行了展望。
Corrosion behavior, electrochemical characters and discharge performance of AZ31 magnesium alloy in various Mg(ClO4)2 solutions were investigated by means of polarization curve, electrochemical impedance spectroscopy and constant current discharge. The result shows that in 2.90 mol/L Mg(ClO4)2 solution, the transfer resistance of the alloy is the smallest and thereby the discharge capacity is the highest. The dense layer of corrosion products formed during the discharge process in Mg(ClO4)2 solution, which could inhibit the discharge process by covering effect. Finally, this paper prospects the development direction of magnesium primary batteries.
Epoxy coatings with different additives of phytic acid were applied on rust and sand-blated Q235 carbon steels respectively. The adhesive strength and corrosion perfromance of these coatings were studied by means of adhesion measurement and electrochemical impedance spectroscopy (EIS). The results showed that the adhesive strength, corrosion resistance and the barrier effectiveness of the epoxy based coatings could be enhanced by the addition of phytic acid in the epoxy varnish. Moreover, phytic acid could inhibit the corrosion of the metal beneath the coating. The coating containing 3% phytic acid had the best corrosion perfromance.
在徐深气田的开发过程中,发现多起气井油管钢穿孔和管柱断裂事故,分析原因主要是由CO2局部腐蚀造成。为准确反映管柱穿孔失效的实际状况,开展了局部腐蚀敏感区间预测研究。通过模拟徐深气田典型井下腐蚀工况,对常用N80油管钢进行了高温高压腐蚀模拟实验,根据腐蚀形貌及局部腐蚀敏感性的分析,探索出环境因素 (温度和CO2分压) 对CO2局部腐蚀的影响,以及N80钢局部腐蚀的敏感温度-CO2分压组合区间,建立了CO2局部腐蚀敏感区间的预测模型。通过对比徐深气田实际失效油管与模拟实验试样腐蚀形貌,验证了N80钢CO2腐蚀类型和局部腐蚀敏感区间预测的准确性。
With the increasingly exploiting the gas field, several corrosion related failure cases, such as perforation and fracture of tubing steel did occurr in Xushen gas fields, which was thought to be the result of CO2 induced localized corrosion. In order to reveal the nature of those failure cases, the corrosion behavior of N80 steel a commonly used material for pipelines, in a high temperature and high pressure environment was studied, which arms to simulate the CO2 induced localized corrosion in the actual gas well processing practice, thereby to figure out the relation of the sensitivity to corrosion of the tubing steel with the relavant processing parameters. By characterizing the corrosion morphology and the sensitivity to localized corrosion and summing up the effect of environmental factors (temperature and CO2 partial pressure) on the CO2 induced localized corrosion of N80 steel, a corrosion map could be constructed to describe the relation of corrosion types of the N80 steel with the processing parameters temperature and CO2 partial pressure etc., thereafter, a prediction model for configuring a range of environment parameters, within which the N80 steel would be sensitive to the CO2 induced localized corrosion. Finally, it is noted that the prediction of corrosion types and the range of parameters responsible to the CO2 induced localized corrosion of N80 steel show a good agreement with the observation of the practical failure cases in Xushen gas fields.