湿热环境中碱性泥浆附着下镀锌钢板的腐蚀行为

通过在湿热环境中进行高温高湿条件下进行腐蚀实验,研究了在泥浆附着条件下汽车用热浸镀锌钢板的腐蚀行为,观察了腐蚀的发展过程,并利用SEM和XRD等手段对腐蚀产物进行了观察和分析.结果表明,镀锌板的泥浆腐蚀过程可分为形成白锈的镀锌层腐蚀以及形成红锈和黑锈的基体腐蚀2个阶段.基体腐蚀产物中γ-FeOOH含量较高,而且泥浆中Cl-的富集对腐蚀产物的保护性具有加速破坏作用.在较低温度时,腐蚀失重率逐渐降低;而在较高的温度下,腐蚀失重率则出现先降后增的转折点,主要原因是温度升高导致腐蚀界面反应加速.在腐蚀过程中,腐蚀电位会发生从低至高的跃迁,分别对应着镀锌层和钢基体的腐蚀过程.环境温度提高,将导致电位跃迁提前.     

热镀锌板在不同地区的大气腐蚀

对热镀锌板在上海、天津进行大气暴晒试验,利用MINITAB统计软件建立时间和腐蚀量的数学模型,计算出热镀锌板的腐蚀率,从而预测热镀锌扳的使用寿命。     

汽车用热镀锌板连续退火工艺

从汽车用热镀锌原板的生产工艺、典型的退火制度、退火炉的直接加热法与间接加热法诸方面比较,论述了汽车用热镀锌原板的退火工艺;并对锌层合金化退火工艺进行了阐述。     

浦项大力增加汽车用热镀锌板的生产能力

POSCO于2 0 0 4年1月6日宣称在光阳厂扩建连续镀锌线。这条线是POSCO的6#CGL ,设计为汽车专用镀锌板生产线,将使POSCO每年新增40万t的镀锌板。6#CGL计划于2 0 0 4年1 1月开工,2 0 0 6年6月投入运转。估计产线耗资达2 0 0 0亿韩元(合1 . 6835亿美元)。6#CGL将集中生产汽车外板用     

热镀锌退火炉技术在汽车板生产中的应用

总结了近年来热镀锌退火炉开发、应用的合理张力分布、带钢质量控制、烧嘴及余热回收等主要技术,并对热镀锌退火炉新技术的发展进行了展望。     

热镀锌汽车板表面黑色污点缺陷研究

研究了热镀锌汽车板表面黑色污点的产生机理,提出了对应的整改措施。研究表明,黑色污点产生于镀锌之前,机组喷溅含碳化物的混合液到带钢表面,经过退火炉高温烧烤和辊系碾压黏附在带钢表面。实际生产中,建立生产机组清理制度,可有效减轻该缺陷。     

碱性硫化物环境中建筑用钢的应力腐蚀行为研究

通过模拟碱性硫化物土壤环境,研究了X70钢的应力腐蚀行为。结果表明,高应变速率下,剪切断裂组织的SCC敏感性较高,微观组织未出现二次裂纹,断裂机理以氢脆断裂为主;应变速率较低时,X70钢的断口出现以脆性解理为主的大腐蚀坑,断裂机理以阳极溶解断裂为主。     

pH值对热镀锌汽车板和IF钢基板在NaCl溶液中电化学行为的影响

通过电化学阻抗谱(EIS)和极化曲线测量,研究了pH值对热镀锌汽车板和IF钢(无间隙原子钢)基板在5%NaCl溶液中电化学腐蚀行为的影响。结果表明:在三种不同pH值的溶液中,镀锌板的腐蚀过程主要受电荷传递过程控制,而基板的腐蚀过程受氧和氢离子的扩散过程控制。虽然镀锌板的腐蚀速度比基板的腐蚀速度快,但腐蚀过程都呈现了相似的变化趋势,都是随着pH值的增大,电荷转移电阻逐渐增大,腐蚀电流密度依次减小,即腐蚀速度依次减小。     

我国超宽幅汽车板热镀锌生产线的分析

介绍了国内武钢、邯宝和京唐2 080 mm超宽幅汽车板热镀锌机组的产品方案、主要技术参数、机组特点、以及主要工艺装备,并针对未来汽车用钢的发展趋势,对今后国内新建宽幅汽车板热镀锌机组的建设和发展进行了展望。     

Growth and corrosion behavior of rare earth film on hot-dip galvanized steel

1Introduction For a long time,chromate compounds Cr(VI)have been used as effective and inexpensive corrosion inhibitors for zinc and zinc coating.However,with the advent of increasing environmental awareness,the toxicity and carcinogenic nature of Cr(VI)b…     

热镀锌钢表面铈转化膜的表征与腐蚀电化学行为

将热镀锌钢在20 g/L Ce(NO3)·6H2O溶液(pH=4,25℃)中处理10s~24 h,获得铈转化膜试样.应用极化曲线和电化学交流阻抗谱(EIS)研究铈转化膜试样和空白热镀锌试样在5%NaCl溶液中的耐蚀性能.利用扫描电镜(SEM)和X射线光电子能谱(XPS)研究转化膜的形貌和组分.结果表明:经硝酸铈溶液处理后的镀锌钢板,其腐蚀电流密度下降,极化电阻升高,同时,锌腐蚀过程中的阳极和阴极反应受到抑制,腐蚀保护效率显著提高;低频阻抗值随成膜时间的增加而先增大后减小,表明腐蚀电解质在转化膜层孔隙中扩散的难易程度先增加后下降;当成膜时间在30 min～1 h之间时,所得转化膜的阻抗值最大可达8~9 kΩ·cm2,耐蚀性最佳.铈转化膜随处理时间的增加首先在锌晶粒晶界附近发生开裂,逐渐形成"干涸的河床"样形貌.铈转化膜含铈、锌、氧等元素,主要由CeO2、Ce(OH)4(或CeO2·2H2O)、ZnO和少量Ce2O3、Ce(OH)3(或Ce2O3·2H2O)等混合组成.     

A corrosion study of hot-dip galvanized steel sheet pre-treated with γ-mercaptopropyltrimethoxysilane

In the present work an organofunctional silane, γ-mercaptopropyltrimethoxysilane (γ-MPS), has been deposited on hot-dip galvanized cold rolled steel from different silane solution concentrations. Painted and unpainted silane treated samples were corrosion tested and painted samples were adhesion tested. The surface chemistry of the unpainted silane treated samples was investigated with AES, ToF-SIMS and EDS and the surface morphology was studied with SEM.The results show that the silane film thickness is dependent on the silane concentration in the silane solution and a higher silane concentration gives a thicker film. Moreover, thicker films tend to give films with a pronounced crack pattern and even detachment of film debris. Corrosion tests of unpainted samples show that γ-MPS can not work as a passivation treatment but gives a very good adhesion to the paint.     

Growth and corrosion resistance of molybdate modified zinc phosphate conversion coatings on hot-dip galvanized steel

The modified zinc phosphate conversion coatings（ZPC） were formed on hot-dip galvanized（HDG） steel when 1.0 g/L sodium molybdate were added in a traditional zinc phosphate solution. The growth performance and corrosion resistance of the modified ZPC were investigated by SEM, open circuit potential（OCP）, mass gain, potentiodynamic polarization and electrochemical impedance spectroscopy（EIS） measurements and compared with those of the traditional ZPC. The results show that if sodium molybdate is added in a traditional zinc phosphate solution, the nucleation of zinc phosphate crystals is increased obviously; zinc phosphate crystals are changed from bulky acicular to fine flake and a more compact ZPC is obtained. Moreover, the mass gain and coverage of the modified ZPC are also boosted. The corrosion resistance of ZPC is increased with an increase in coverage, and thus the corrosion protection ability of the modified ZPC for HDG steel is more outstanding than that of the traditional ZPC.     

Effect of molybdate post-sealing on the corrosion resistance of zinc phosphate coatings on hot-dip galvanized steel

The technique of post-sealing the phosphated hot-dip galvanized (HDG) steel with molybdate solution was addressed. The composition and corrosion resistance of the improved phosphate coatings were investigated by SEM, EDS, potentiodynamic polarization and electrochemical impedance spectroscopy (EIS) measurements, and neutral salt spray (NSS) test. The results showed that molybdate films were formed in the pores of phosphate coatings, and the compact and complete composite coatings composed of phosphate coatings and molybdate films were formed on the zinc surface, resulting in that both the anodic and cathodic processes of zinc corrosion were inhibited remarkably; the corrosion protection efficiency values were increased; and the electrochemical impedance values were enhanced at least one order of magnitude. The low frequency impedance values for the composite coatings were increased at the initial stages of immersion in 5% sodium chloride solution, indicating the self-repairing activity of the composite coatings.     

高耐蚀性热镀锌板的钝化处理工艺探讨

介绍了热镀锌板钝化膜的形成机理 ;针对攀钢热镀锌板出现白锈、黑斑等问题 ,分析了钝化液pH值、添加剂及操作条件对钝化膜质量的影响 ,同时提出了改进热镀锌板耐蚀性能的措施     

磷化处理对无铬钝化热镀锌板耐蚀性能的影响

研究了磷化处理工艺对无铬钝化热镀锌板耐腐蚀性能和表面形貌的影响。采用扫描电镜对其表面形貌进行分析，同时与未经过磷化处理的钝化板表面形貌进行对比；采用电化学阳极极化曲线方法和电化学阻抗法对磷化处理后钝化板的耐腐蚀性能进行了研究。在钝化板膜重为0.8 g/m²的情况下，经磷化处理的钝化板表面钝化膜完好，没有发现锈蚀或钝化膜剥落现象；经磷化处理的钝化板自腐蚀电位和阳极电流密度不变，阴极电流密度和自腐蚀电流密度有所提高；Nyquist图的高频部分在磷化处理前为容抗弧，磷化处理后出现具有Warburg阻抗的直线，说明磷化处理后钝化膜表面出现扩散过程。 研究表明，钝化板经过磷化处理后表面未形成磷化膜，耐腐蚀性能仍来自原钝化膜，经磷化处理的钝化板的耐腐蚀性能有所降低。因此，现有常规的磷化处理并没有增加钝化板的耐腐蚀性能，如果有需要提高钝化板耐腐蚀性能的要求，必须针对无铬钝化板研制专用的磷化液和磷化工艺。     

高强度热镀锌结构钢SGC570的退火工艺

针对高强度热镀锌结构钢SGC570产品的技术要求,选择C-Mn化学成分体系、热连轧+冷轧+连续退火热镀锌的工艺路线对其连续退火工艺进行了研究。实验室通过热模拟退火试验、拉伸试验、硬度试验和显微组织观察等手段,得出高强度热镀锌结构钢SGC570产品的再结晶温度为550 ℃,为了提升屈服强度,选择在530~540 ℃之间进行不完全再结晶退火;在工业化小批量试制阶段,通过分析退火温度与产品组织性能的关系对连续退火工艺进行了研究,总结出工业化生产最佳退火温度为530 ℃。     

Growth and corrosion behavior of molybdate passivation film on hot dip galvanized steel

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An evaluation of the corrosion resistance and adhesion properties of an epoxy-nanocomposite on a hot-dip galvanized steel (HDG) treated by different kinds of conversion coatings

Hot-dip galvanized steel (HDG) samples were chemically treated by Cr(III), Cr(VI), Cr(III)-Co(II) and Cr(III)-Ni(II) conversion coatings. Epoxy nanocomposites were prepared using 2 wt.%, 3.5 wt.%, 5 wt.% and 6.5 wt.% nano-ZnO. Electrochemical impedance spectroscopy (EIS), pull-off adhesion tester and scanning electron microscope (SEM) were utilized to evaluate epoxy coatings properties on the surface of pre-treated HDG samples. Results showed that addition of nano-ZnO particles (specially 3.5 wt.%) can significantly improve the corrosion resistance of the epoxy coating on HDG. Decrease of contact angle (φ) and increase of surface roughness (Ra) of the pre-treated HDG samples were obtained. Decrease of the value of φ was more pronounced when the Cr(III) pre-treated samples were post-treated by Cr(III)-Co(II) and Cr(III)-Ni(II) conversion coatings (CCs). The dry and wet adhesion strengths of the epoxy coating to HDG were significantly increased after the surface treatment of the samples. Increase of the adhesion strength and decrease of the adhesion loss were more pronounced on Cr(III)-Co(II) and Cr(III)-Ni(II) post-treated samples. The corrosion resistance of epoxy coating was also increased on the surface of pre-treated HDG samples. Increase of the corrosion resistance of the Cr(III) pre-treated HDG samples was more pronounced on the samples which were post-treated by Co(II) and Ni(II).