Electrochemical behavior of organic and inorganic zinc-rich coatings in 3.5% NaCl solution

1　INTRODUCTIONZinc richcoatings (ZRP)havebeenusedformanyyearsinordertoprotectsteeleffectivelyinag gressiveatmospheres ,mainlyinmarineandindustrialenvironments,againstcorrosion .ItiscommonlyacceptedthattwofundamentalprotectionmechanismsoperateinZRP[13] :1)thegalvanicprotectionstage ,whichrequires goodelectricalcontactamongthezincparticlesthemselvesaswellasbetweenthemandthesteelsubstrate ;2 )thebarrier likebehaviorstage ,whichisreinforcedbytheamountandnatureofzinccorrosionproductslead ing…     

富锌漆研究进展

综述了70年来富锌漆的研究与应用的若干进展。对富锌漆的分类、防蚀机理、耐久性、性能特点以及存在的问题和补救措施等，进行了比较全面的评价．简单介绍了用于富锌漆的锌粉的分类和性能特点，此外，还介绍了有关富锌涂层电化学研究的一些进展．     

硅烷偶联剂处理对富锌涂层行为的影响

 采用测量涂层的腐蚀电位和电化学阻抗谱(EIS)等方法研究了硅烷偶联剂处理(钢铁表面的硅烷偶联剂预处理和富锌漆中掺入硅烷偶联剂)对富锌涂层在3.5mass%NaCl溶液中腐蚀行为的影响.结果表明，两种硅烷处理方式均明显延长了富锌涂层的阴极保护期.钢铁表面硅烷处理减弱了无机富锌涂层的阴极保护作用.      

The corrosion behavior of zinc-rich paints on steel: Influence of simulated salts deposition in an offshore atmosphere at the steel/paint interface

The corrosion behavior of an epoxy zinc-rich paint on interface-contaminated carbon manganese-silicon steel was studied. SEM observation on the cross-section of the paint indicates that the zinc corrosion products grew from the surface to the inner of the paint and salts contamination promoted the growth at locations close to the steel/paint interface. The results of electrochemical impedance spectroscopy show that the corrosion resistance of the contaminated paint was significantly influenced by diffusion of zinc corrosion products during the initial stage of immersion, and diffusion of iron corrosion products at the end of immersion. Three transmission line models were applied to account for the corrosion process of the uncontaminated and contaminated zinc-rich paints.     

Effects of surface modification on electrochemical performance of MnO2

The MnO2 samples coated with Ca（OH）2 were prepared by a liquid-phase surface treatment method. The physical properties of the samples were examined by SEM, EDAX and chemical analysis, and their electrochemical performances were investigated by means of galvanostatic charge-discharge, cyclic voltammetry and electrochemical impedance spectroscopy （EIS）. The SEM results show that the samples coated with Ca（OH）2 display a porous surface structure. The electrochemical experiments indicate that the surface modification decreases the polarization of MnO2 electrodes and improves their discharge potentials and discharge capacities.     

Corrosion protection of cold-rolled steel by zinc-rich epoxy paint coatings loaded with nano-size alumina supported polypyrrole

High porosity and intense galvanic function related low electrolytic barrier profile and fast delamination of zinc-rich paints (ZRPs) are addressed by the utilisation of intimately structured, highly dispersed, polypyrrole (PPy) deposited alumina particles (PDAPs) embedded zinc-rich hybrid paints. The more globular but less-packed structure type PPy-contained water-solvent-prepared PDAPs-composited hybrids comprising spherical zinc pigment at 70 wt.%, provided moderate galvanic function with enhanced electrolytic barrier properties. In addition, the less globular structured but well-packed PPy-comprised aqueous ethanol-solvent-prepared PDAPs-composited hybrid coatings indicated highly efficient suppressed galvanic function and improved barrier properties, realising solid performance improvement over conventional ZRPs in immersion and salt-spray chamber tests. Furthermore, the application of highly dispersed PDAPs at a content of 3.2 wt.% while PPy incorporated into zinc-rich hybrids at 0.16 wt.% is proposed to result in emerging additional functionalities increasing long-term anticorrosive performance of ZRPs by inhibiting sacrificial and self-corrosion of zinc and scavenging oxidative radicals thereby hindering oxidative degradation of the organic binder.     

基体表面粗糙度对镀硬铬层零件镜面抛光的影响

机械电解镜面抛磨镀硬铬层轴类零件时，通常从电、液参数以及工件、工具转速等着手，优选出最佳参数。但从实验中发现，零件基体表面粗糙度对抛光效果有着非常重要的影响，甚至决定抛光的成败。通过大量的对比试验和观察发现：零件基体表面粗糙度越小，抛光效果越好；反之，则差。     

涂料中含铬量对烧结式富锌涂层性能的影响

以片状锌粉和铝粉为原材料 ,研究了涂料中铬酐含量对烧结式富锌涂层性能的影响。结果表明 :涂料中的铬酐含量决定涂层中金属粉的粘结情况 ,铬酐含量过高 ,涂层局部爆皮 ;铬酐含量过低 ,涂层粉化。在得到粘结性好的涂层范围内 ,铬含量越高 ,涂层耐蚀性越好。     

Influence of the Pigment Shape on the Electrochemical Behaviors of Zinc—Rich Paint Coatings in 3.5% NaCl Solution

针对粘合剂种类、Zn粒形状和涂层厚度的协同作用，采用电化学阻抗谱(EIS)研究了富Zn涂层在3．5％NaCl溶液中的电化学行为．富Zn涂层的EIS谱有两个时间常数，其中，锌的电子转移反应发生在低频段，而高频段则体现聚合物和Zn表面氧化层的介电性质．根据等效电路及其元件参数解释了钢铁／富Zn涂层／盐水体系的EIS测量结果．实验结果表明，鳞片锌消耗速度太快以至于鳞片富Zn涂层在相对较短的时间内就失去了阴极保护作用，随后形成了稍微致密的屏蔽阻挡层。     

轴承钢试样表面粗糙度对氧含量检测的影响

利用氧氮分析仪、粗糙度轮廓仪对不同表面粗糙度的试样进行试验对比分析,探讨轴承钢试样表面粗糙度对其氧含量测定的影响。结果表明：GCr15轴承钢试样在去除表面氧化层后,表面粗糙度为0.4 μm＜Ra＜1 μm时,会影响氧含量检测结果。但当试样表面粗糙度Ra＜0.1 μm时,表面粗糙度对氧含量检测结果基本没有影响,且结果稳定接近生产设定值。     

表面粗糙度对磁控溅射纯Cu靶材刻蚀区表面形貌及溅射性能的影响

通过将不同粗糙度的纯Cu试样安装在组合靶中以保证相同试验条件,采用白光干涉仪、离子镀膜机、电子分析天平和扫描电镜等方法研究了表面粗糙度对磁控溅射金属靶刻蚀区表面形貌及溅射性能的影响。结果表明,不同粗糙度的试样严重影响其溅射后的表面形貌,在靶材刻蚀最深区域出现凹坑和连续凸起分布的形貌,而在刻蚀较浅的区域出现了溅射蚀坑和不完全刻蚀的晶粒所形成的“亮点”;取向不同的晶粒内部和晶粒边界刻蚀后均出现台阶状形貌,但晶粒内部台阶高度和宽度远远小于晶粒边界,这是由于晶界刻蚀速率较晶粒内部快;表面初始粗糙度越大的试样溅射10 h后,其刻蚀最深区域的表面粗糙度越大;试样溅射过程的前10 h,初始表面粗糙度最小的试样其溅射产额最大。因此,可通过降低靶材表面粗糙度来增加薄膜沉积速率和溅射过程的稳定性。     

Novel zinc‐rich epoxy paint coatings with hydrated alumina and carbon nanotubes supported polypyrrole for corrosion protection of low carbon steel: Part II: Corrosion prevention behavior of the hybrid paint coatings

Utilization of various types of multi‐walled carbon nanotubes (MWCNTs) in zinc‐rich paints (ZRPs) is presented addressing percolation and porosity related phenomena of traditional ZRPs. Hybrid paint coatings were formulated with 3.21 wt% polypyrrole (PPy) deposited alumina‐MWCNT inhibitor particles (PDAMIPs) and 70 wt% zinc contents. Corrosion protection behavior of the hybrid coatings was investigated by electrochemical impedance spectroscopy (EIS), glow‐discharge optical emission spectroscopy (GD OES), X‐ray photoelectron spectroscopy (XPS), and FT‐Raman spectroscopy. Immersion and salt‐spray chamber tests gave evidence of improved galvanic protection and barrier nature of the hybrid coatings over the conventional ZRPs, whereas inhibited zinc corrosion and ignorable steel corrosion took place besides lower degradation of the binder. Zinc‐rich hybrid paints with either high relative amount of polyelectrolyte‐modified or low proportion of functionalized MWCNTs afforded enhanced corrosion prevention. This result is partly attributed to the nanotube volume fractions around the threshold of infinite cluster formation contributing to electrical percolation and galvanic action of the hybrids. Experimental results are discussed in a broader context on the basis of structure related findings of the PDAMIPs (described in Part I) and in the light of recent literature data. From the newly developed inhibitor particles, some of them are respected as worthy additives for application in hybrid coatings featuring high performance corrosion prevention functionality.     

高速铣削表面粗糙度的研究

通过在HSM－700型高速铣床上的正交铣削试验，联系平时实际的生产加工情况，分析高速铣削的切削加工参数对零件表面粗糙度的影响。通过分析不同铣削参数下的零件表面粗糙度和切屑变形，为高速加工切削参数的选择和表面质量的控制提供依据。     

Effect of substrate surface roughness on the adherence of NiCrAlY thermal spray coatings

The adherence of plasma sprayed NiCrAlY bond coats can be improved by an appropriate substrate surface finish. The interface fracture energy for crack propagation along the coating/substrate interface has been measured for different surface roughness by means of a specially designed four-point bending test. An increase of the interface fracture energy of about 15% was observed for a three times higher surface roughness. In addition, four-point bending tests with the coating on the side face of bending specimens were performed to analyze the fracture and spalling behavior of the coatings both under large tensile and compressive substrate deformations.     

Investigation on the effect of various surface preparations on corrosion performance of powder coated steel by EIS

Powder coating systems have been considered for different purposes since they have many advantages in use. The performance of the different powder coating systems needs to be examined by various methods. In this paper, a polyester powder coating was applied on various pretreated mild steel panels. Electrochemical Impedance Spectroscopy (EIS) measurements were used to study the durability of the coating on pretreated mild steels upon immersion in 3.5% w/w NaCl solution at ambient temperature for 7 and 50 days. Various elements of the equivalent circuit are proposed for the different metal/coating systems. The lowest coating and double layer capacitances were measured for acid pickled followed by phosphating pretreated steel panel while the coating and charge transfer resistance were the highest for this system. It revealed an improvement of coating durability on the substrate by phosphating pretreatment. This can be attributed to decreasing ingress of water, dissolved oxygen and ions into the coating.     

NiCrAlY涂层的表面状态对高温氧化行为的影响

将原始喷涂态和表面抛光的NiCrAlY涂层在1050℃恒温氧化300h，利用XRD、SEM，EDS方法，测定涂层的氧化物及其相转变，分析表面氧化膜的生长破坏行为，结果表明：两种涂层在1050℃保温，在150h以内均能生成α-Al2O3氧化膜，150h后，抛光态涂层保护性氧化膜被破坏，抗氧化能力下降，喷涂态涂层表面粗糙，连续Al2O3保护膜的形成较晚，氧化早期氧化膜中存在微裂纹，可释放应力，有利于氧化膜与涂层的结合。氧化动力学曲线符合抛物线规律，氧化至300h，表面氧化膜只有少量微裂纹，无剥落，说明喷涂涂层的长期恒温抗氧化能力比抛光态涂层强。     

Ga和Bi对Al-Zn-Sn牺牲阳极电化学性能的影响(英文)

通过光学显微镜(OM)、扫描电镜(SEM)、能谱分析(EDAX)和电化学性能测试等方法,研究了Ga和Bi对Al-7Zn-0.1Sn(质量分数,%)牺牲阳极微观组织和电化学性能的影响。Al-Zn-Sn合金加入Ga和Bi元素后,合金组织由粗大枝晶转变为等轴晶,仅剩下少量枝晶。Al-7Zn-0.1Sn-0.015Ga-0.1Bi合金具有高的电流效率(97%)和均匀的腐蚀形貌,表明添加适量的Ga和Bi元素能有效改善Al-Zn-Sn合金的组织和电化学性能。     

Influence of surface roughness of PVD coatings on tribological performance in sliding contacts

The influence of surface roughness on the tribological performance, i.e. friction, wear and material pick-up tendency, of two different commercial PVD coatings, TiN and WC/C, in sliding contact with ball bearing steel has been evaluated using two different types of sliding wear laboratory tests. Post-test characterisation using SEM/EDS, AES, ToF-SIMS and XPS was used to evaluate the prevailing friction and wear. The results show that the surface roughness of the coating is of importance in order to control the initial material pick-up tendency and thus the friction characteristics in a sliding contact. Once initiated, the material pick-up tendency will increase, generating a tribofilm at the sliding interface. For steel-TiN sliding couples a FeO-based tribofilm is generated on the two surfaces and FeO/FeO becomes the sliding interface (interfilm sliding) resulting in a high friction coefficient. For steel-WC/C sliding couples the WC/C displays a pronounced running-in behaviour which generates a WO₃-based tribofilm on the steel surface while a carbon rich surface layer is formed on the WC/C surface, i.e. WO₃/C becomes the sliding interface (interface sliding) resulting in a low friction coefficient.