Nickel-plated zinc

In many cases there will be a need to test metal-coated specimens, e.g. galvanised steel, tin-plated copper, nickel-plated zinc, etc. It will then be necessary to test specimens in the completely coated condition and also with the coating damaged so that the basis metal is exposed. The latter condition will provide the conditions for galvanic action between the coating and the basis metal. With sheet specimens this condition is most readily achieved by leaving cut edges exposed to the test environment. 

In developing a dual-fuel engine—to use alcohol as an alternative to gasoline—researchers in Brazil have found that nickel-plated zinc is a reliable material for the carburetor, resisting the ethanol fuel. Knowledge of this property opens the way for possible use of the ZA alloys. 

Cost savings of 50% to the end user have been achieved by replacing the nickel-plated zinc die-cast diode receptacle for fibre optics with LCP material. Critical dimensions must be held within a 0 009 mm tolerance, as indicated in Fig. 9.4. 

Aqueous Electrodeposition. The theory of electro deposition is well known (see Electroplating). Of the numerous metals used in electro deposition, only 10 have been reduced to large-scale commercial practice. The most commonly plated metals are chromium, nickel, copper, zinc, rhodium, silver, cadmium, tin, and gold, followed by the less frequendy plated metals iron, cesium, platinum, and palladium, and the infrequendy plated metals indium, mthenium, and rhenium. Of these, only platinum, rhodium, iddium, and rhenium are refractory. 

Fig. 12.4 Corrosion diagram for a zinc diecasting in a nickel plating bath, pH 2-2. There are two possible cathodic reactions, hydrogen evolution (H) and nickel ion reduction (AO. The corrosion current is the sum of the partial cathode currents. Even with live entry the potential is still too high to suppress corrosion, though the rate is reduced to...

Dry Copper, brass, aluminum, magnesium, magnesium-aluminum alloy, stainless steel, mild steel, mild steel coated with acid-proof black paint and mild steel plated with copper, cadmium, nickel or zinc are not affected... 

Chemical precipitation. Chemical precipitation followed by solids separation is particularly useful for separating heavy metals. The heavy metals of particular concern in the treatment of wastewaters include cadmium, chromium, copper, lead, mercury, nickel and zinc. This is a particular problem in the manufacture of dyes and textiles and in metal processes such as pickling, galvanizing and plating. 

Copper(l) cyanide is used in copper plating of nickel, chromium, zinc alloys, steel, and other metals or alloys. Such copper plating imparts brightness, smoothness, hardness, and strength. The cyanide solution employed for copper electroplating consists of copper cyanide and sodium cyanide. Other apph-cations of this compound are as an insecticide, a catalyst in polmerization, and as an antifouling agent in marine paints. 

The massive zinc (rod or plate) reacts spontaneously with activated bromides provided the preliminary electroreduction of a catalytic amount of zinc salt (ZnBr2 or ZnCl2) occurs. Reactions are carried out in nitrile solvents (CH3CN, PhCN,. ..) or their mixture with dichloromethane. An undivided cell fitted with a zinc anode and an indifferent cathode (gold, nickel, carbon, zinc,. ..) is used. As observed with benzylic bromides, the activation leads to an organozinc compound able to react with either the nitrile solvent or an electrophile reagent. The process is depicted in equation 12. 

Combines plastics with chrome, nickel and other metals analogous to chrome plated zinc die cast parts Combines some of the best characteristics of plastics and metals. 

A. Spent Nickel Plating Bath (Hard Disk Manufacturer) - contains cobalt, nickel and zinc. 

Zinc Alloys. There has been considerable worldwide activity in the area of plating zinc alloys. This interest results from efforts to improve the corrosion resistance of automobiles and automotive components without using cadmium (150). The use of zinc—alloy plated coil for automotive body steel originated in Japan, has spread through Europe, and more recendy has come to the United States. Three zinc alloys dominate the interest zinc—nickel, zinc—iron, and zinc—cobalt. Europe produces predominantly zinc—nickel. In Japan, zinc—nickel and zinc—iron are more popular (151). The annual worldwide nickel consumption for zinc—nickel alloy plating has been estimated at 2700—3175 metric tons (152). In the United States, consumption is estimated at about 225 metric tons for this purpose. Alloys are generally 6—12% nickel. Usage is expected to increase. 

Post-Treatments. Although many post-treatments have been used over plated metals, chromate conversion coatings remain as the most popular. Chromates are used to improve corrosion resistance, provide good paint and adhesive base properties, or to produce brighter or colored finishes. Formulations are usually proprietary, and variations are marketed for use on zinc, zinc alloys, cadmium, copper and copper alloys, and silver (157). Chromates are also used on aluminum and magnesium alloys (158,159). More recently, chromate passivation has been used to extend salt spray resistance of autocatalytic nickel plated parts. 

The metals recommended for use with ethanol include carbon steel, stainless steel, and bronze [3.10]. Like methanol, metals such as magnesium, zinc castings, brass, and copper are not recommended. Aluminum can be used if the ethanol is very pure, otherwise it should be nickel-plated or suitably protected from corrosion by another means. The metals compatible with ethanol represent a much wider range than those for methanol and represent most of the metals currently used in fuel systems, so few changes would be anticipated when using ethanol. 

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