The Weathering of Nickel/Chromium Electrodeposits

The atmospheric corrosion of nickel foils, both wrought and electro-deposited, proceeds by pitting leading to perforation. This result, coupled with earlier tests showing that “porosity-test” reagents can produce pores during porosity tests, suggests that properly produced nickel electrodeposits may be far less porous than has been thought.

A chromium film on top of nickel is helpful in the early stages of industrial atmosphere exposure but may accelerate pitting in the later stages owing to the galvanic action of the nickel/chromium couple.

The number per unit area, size and shape of the pits vary widely. Factors influencing the type of pitting are the chemical composition and microstructure of the metal and its residual stresses.     

高耐蚀缎面装饰性双层镀铬工艺

介绍双层镀铬工艺过程,并讨论影响工艺的主要因素,验证了双层镀铬层的高耐蚀性能。     

Corrosion Resistance of Nickel+Chromium Deposits: Influence of Insoluble Non-Metallic Additives in Nickel Solutions

Recent research has shown that substantial improvements in the corrosion resistance of nickel+chromium coatings on steel and zinc-base alloy die castings can be obtained by the use of multiple deposits of these metals, plated under differing conditions. Certain decorative nickel deposits produced by codepositing various very fine, bath-insoluble non-metallic particles in the plate obtained from semi-bright and bright nickel electroplating solutions have also been found to lead to improved corrosion resistance, when they are used as the top plate in multiple-layer systems before the final chromium is applied. Accelerated and outdoor exposure tests are described and the theoretical basis of the results obtained is discussed.     

稀土对低镍铬合金铸铁耐烧碱腐蚀性能的影响

采用电化学和动态失重法测定稀土低镍铬铸铁在高温烧碱中的阳极极化曲线和腐蚀速度 ,借助显微镜和扫描电镜观察显微组织和腐蚀形貌 ,结果表明 ,加入稀土可细化低镍铬铸铁组织并改变石墨形态 ,提高耐高温烧碱腐蚀性能。其中DNJ3(0 0 4 6 %RE)腐蚀速度最小 ,维钝电流低 ,钝化区间长 ,是一种优良的耐碱蚀材料。     

Advances in Decorative Chromium Plating for Corrosion Protection of Zinc Die Castings

Crack-free chromium (0–025 or 0–05 mil thick) deposited at relatively high temperature provided excellent protection at static sites, but was only slightly better than ordinary chromium (0–01 mil) in mobile tests. Panels plated with duplex nickel (0–8 or 1–2 mil) plus ordinary or crack-free chromium suffered considerable basis-metal corrosion within two years on truck-trailers in the Michigan-Ohio area. Microcracked chromium with 1400 to 1800 cracks/in prevented basis-metal corrosion for 3½ years at all sites. Corrosion was faster on New York Harbour tugboats, but microcracked remained superior to crack-free chromium. Its superiority is attributed in part to its ability to resist damage by mechanical force.     

The Corrosion Resistance of Chromium Electroplated from Trivalent and Hexavalent Chromium Plating Solutions

A comparison has been made of the long term stability and corrosion resistance of trivalent chromium deposited from a chloride based solution and hexavalent chromium deposited from a sulphate based solution. The work showed a difference in corrosion resistance between the two systems and has revealed the corrosion mechanism that caused the failure of the plated films. All the work was carried out on a brass substrate overplated with bright nickel to provide a substrate for the chromium deposit.     

The Resistance of Electrodeposits to Corrosion,with Special Reference to Cadmium and Zinc

This paper describes measurements which have been made of the diffusion of hydrogen through mild steel and through steel to composition DTD4A during cathodic treatment in various sulphuric acid and sodium hydroxide electrolytes. The apparent hydrogen diffusion varies over wide limits between various electrolytes. For mild steel, the effect of cold work on diffusion rate differs between acid and alkaline electrolytes. The variations in diffusion rate are ascribed to the formation of cathodic films which affect the rate of transfer of hydrogen atoms into the metal lattice.

The quantity of hydrogen required to cause embrittlement of steel is very much less than that required to saturate the steel.     

Plastic-Fatigue and Corrosion-Mechanical Resistance of Multilayer Bellows of Chromium–Nickel Steels

The effect of the metal chemical composition on its resistance to repeated loading, and that of corrosive environment, including chlorides, on the corrosion and stress-corrosion cracking resistance of a strain-hardened metal in the initial condition and upon long-term service heating (resulting in the formation of second phases) is considered as applied to multilayer bellows.     

Importance of the Texture Index for Nickel Electrodeposits

Investigations of the properties of electrodeposited Ni-Mn-S layers are reported. The correlation between the texture, the texture index, and three groups of interactions, incorporated impurities, structural characteristics and mechanical properties, is described. It can be seen that the microhardness and ductility as well as the crystallite size and microdeformation correspond clearly to the texture index, whereas the impurities have no big influence on the texture development.

These results show that the texture index of the electroplated layers is not only an X-ray diffraction parameter, but it can very well describe the macroscopic materials properties.     

节镍型不锈钢的耐腐蚀性能比较

通过3.5%NaCl溶液中动电位极化曲线测定和中性盐雾试验,对200系列奥氏体不锈钢和400系列铁素体不锈钢两类节镍型不锈钢与304不锈钢的耐腐蚀性能进行了对比研究。结果显示,400系列铁素体不锈钢的耐点蚀性能优于200系列奥氏体不锈钢,两种节镍型不锈钢的耐点蚀性能均不如304不锈钢好;200系列奥氏体不锈钢的耐均匀腐蚀性能最差,443不锈钢耐均匀腐蚀性能与304不锈钢相当,439不锈钢比304不锈钢耐均匀腐蚀性能稍差。201、202、304、439和443不锈钢在3.5%NaCl溶液中的点蚀电位分别为(vs.SCE)-32 mV、-22 mV、312mV、165 mV和227 mV,腐蚀速率分别为0.0071 mm/a、0.0062 mm/a、0.0026 mm/a、0.0038 mm/a和0.0024mm/a。     

两种镍镀层耐蚀性能的研究

本试验着重研究了瓦特和半光亮两种镍镀层在400、600、800℃的高温氧化行为,并对其在常温5%NaCl+O.5%H2O2溶液中的腐蚀进行了比较:研究表明:两种镍镀层的高温氧化规律基本一致:在盐水溶液中,半光亮镀层表现出较好的耐蚀性能:能谱分析则证实:在高温氧化过程中,明显存在铜向镍镀层中的扩散,这可能有利于增强镀层与基底之间的结合.     

A New Method of Ductility Testing of Nickel Electrodeposits

A simple tensile test which can be used to evaluate the ductility of a nickel electrodeposit is described. A short account of its development and subsequent use in the control and assessment of both experimental and production solutions is given and the relationship between the results obtained using it and those obtained from simple bending tests investigated and discussed.     

The Structure and Protective Properties of Zinc and Nickel Alternate Electrodeposits

A NEW TYPE of coatings consisting of a large numberof laminar deposits has been the keen subject of muchresearch,because these layered-structure coatingspossess improved properties or novel phenomenon suchas increased mechanical strength,micro-hardness,giantmagnetoresistance and corrosion resistance[1"6'.Thesecoating systems with individual layers making upoverall structure are also called compositionallymodulated multilayer(CMM)coatings'3"5'.In view ofthe plating historical use of surface…     

含稀土镀液电沉积镍镀层耐蚀性的研究

借用扫描电镜、电化学分析和腐蚀失重实验方法研究了镀液中添加RE经直流和单向脉冲电沉积方法制备的镍镀层的耐蚀性。结果表明：单向脉冲法制备的镍镀层抗腐蚀能力优于直流法制备的镍镀层抗腐蚀能力，其原因主要归于单向脉冲镀层结晶比较细小致密，直流镀层结晶较粗大且致密性差。     

火焰喷塑涂层的防腐性能研究

作者利用FSP—2型火焰喷塑枪在A3钢基体上喷涂了高压低密的聚乙烯粉末涂层和环氧树脂粉末涂层，对涂层表面的通针孔进行了检测，并对这两种涂层进行了1032h的中性盐雾试验研究。这些试验的结果表明：火焰喷涂的聚乙烯和环氧树脂粉末涂层致密性较高，对基体有很好的保护作用，并且其防腐效果随着预处理工艺和喷涂厚度的不同而有较大的不同。     

镀锌层三价铬黑色钝化膜的耐蚀性能

制备了一种环保、不含六价铬的三价铬黑色钝化液,选择适当的封闭剂,研究其在镀锌层表面钝化后的耐腐蚀性能。通过醋酸铅点滴试验、塔菲尔极化曲线测试、电化学阻抗测试检测钝化膜的耐蚀性及采用扫描电子显微镜观察其表面形貌。结果表明:镀锌层表面经三价铬黑色钝化后再进行封闭处理,弥补了Cr3+钝化后无自愈能力的缺点,显著提高了镀锌层钝化膜的耐腐蚀性能,而且达到了Cr6+黑色钝化的外观效果。     

镍、铬对硬质合金酸性盐雾腐蚀性能的影响

本文采用传统粉末冶金工艺制备了WC-8%Co、WC-6%Co-2%Ni-0.4%Cr3C2、WC-8%Ni-0.4%Cr3C2硬质合金样品,利用酸性盐雾试验、极化曲线测试、扫描电镜观察和能谱分析等手段,研究了添加Ni、Cr等元素对硬质合金酸性盐雾环境中腐蚀行为的影响。试验结果表明:WC-Co硬质合金在酸性盐雾环境下由于粘结相标准还原电极电位低,更容易发生电化学腐蚀,造成粘结相流失;添加Ni和Cr,可以提高WC-Co硬质合金的电极电位,降低极化电流密度,提高其在酸性盐雾溶液中的抗腐蚀能力;扫描电镜和能谱分析结果表明添加Ni和Cr,可以降低硬质合金在酸性盐雾溶液中粘结相的流失。     

二种组合镀层汇流环盐雾及硫化腐蚀试验

报道了滑环摩擦副电镀Pd -Ni/Rh/Au和电镀Pd -Ni/Au的汇流环试验情况 :电图象法测孔隙率 ;在 5± 1 %NaCl溶液、 35± 2℃下连续喷雾 48h进行盐雾试验 ;在SO2 7×1 0 - 4 % (V/V) ,H2 S 1× 1 0 - 4 % (V/V) ,32～ 35℃下进行 2 4h静态硫化试验。结果表明 ,汇流环整体上基本无腐蚀现象 ,即镀层基本上无孔隙 ,可满足产品作业时耐环境腐蚀的要求     

Ni对Cr2O3涂层孔隙率及耐蚀性的影响

分别以纯Cr2O3陶瓷粉末、Ni粉和Cr2O3粉的混合粉末作为喷涂粉末,采用等离子喷涂技术在45钢表面喷涂Cr2O3涂层和Ni-Cr2O3涂层.通过X射线衍射、金相显微分析、扫描电镜分析、EDS成分分析、盐雾试验、电化学试验等方法,研究了Ni-Cr2O3和Cr2O3涂层的相组成、组织形貌、孔隙率以及耐蚀性.结果表明:由...