Nickel alloys chromate

Method No 308. Delay Powder, Non-Gaseous (Zirconium-Nickel Alloy Type) Type I (delay 2-sec) - Ba chromate 60.0, 70/30 Zr-Ni alloy 26.0 8t K perchlorate 14.0% ... 

Zinc—Cobalt. Alloys of Zn—Co usually contain 0.3—0.8% cobalt. Higher cobalt alloys, from 4—8%, have shown better salt spray resistance (156), but the commonly plated alloy is 0.3—0.8%. One automotive company specifies 0.3—1.0%. Cobalt is expensive, and economics favor the lower alloys. Costs have been quoted for zinc—cobalt at 1.2 times the cost of chloride zinc, with zinc—nickel alloys at 1.5—1.6 times the chloride zinc. Deposits can be very bright, but the improved corrosion resistance advantage requires yellow or bronze chromates. Alkaline baths give fewer problems in plating components with lapped, spot-welded seams. 

Type I zirconium-nickel alloy delay compn having a formulation 60/14/26 BaCr04/KClC>4/ 70-30 Zr-Ni was used for these expts. Two different radioactive tracers, 27-day chromium-51 and 2.1-year cesium-134, were employed. The first was added to the compn in the form of BaslCr04 as a fractional percentage of total barium chromate, and the second tracer was included as 134CsQ in ppm concn of the total mixt... 

They are effective inhibitors for iron and a number of metals in a wide variety of waters. Like chromates, nitrites are anodic inhibitors and they inhibit the system by forming a passive film with ferric oxide. These are environmentally-ffiendly inhibitors. Besides steel, nitrites also inhibit the corrosion of copper, tin and nickel alloys at pH levels 9-10. Chromate is an extremely effective inhibitor for corrosion prevention of aluminum alloys. Nitrites should not be used in open systems as they would oxidize to nitrates in the presence of oxygen. 

Electrolytic zinc or zinc-nickel alloy (10-14% Ni) coating followed by chromate passivation and an organic topcoat... 

Both potassium nitrate (0.5%) and potassium chromate (0.2%) are very effective in carbon dioxide systems, but not with hydrogen sulfide. Use of metavanadate in hot carbonate systems can passivate steel in a carbonate solution only when the bicarbonate content is low. The addition of oxygen to the system increases passivation of mUd steel, but increases corrosion of copper-nickel alloys. 

Rubidium metal alloys with the other alkaU metals, the alkaline-earth metals, antimony, bismuth, gold, and mercury. Rubidium forms double haUde salts with antimony, bismuth, cadmium, cobalt, copper, iron, lead, manganese, mercury, nickel, thorium, and 2iac. These complexes are generally water iasoluble and not hygroscopic. The soluble mbidium compounds are acetate, bromide, carbonate, chloride, chromate, fluoride, formate, hydroxide, iodide. 

Zinc—Nickel. Steel has the best salt spray resistance when the nickel is 12—13% of the alloy. At increasing nickel contents, the deposit becomes more difficult to chromate and more noble, eventually becoming cathodic to steel. At those levels and above, corrosion resistance usually decreases and is dependent on a complete lack of porosity for protection of the steel. In efforts to replace cadmium and nickel—ca dmium diffused coatings in the aircraft industry, 2inc—nickel has insufficient wear properties for some appHcation, but is under study as an undercoat to various electroless nickel top coats (153). 

Low-carbon and chromium-nickel steels, certain copper, nickel and aluminium alloys (which are all widely used in marine and offshore engineering) are liable to exhibit stress-corrosion cracking whilst in service in specific environments, where combinations of perhaps relatively modest stress levels in material exposed to environments which are wet, damp or humid, and in the presence of certain gases or ions such as oxygen, chlorides, nitrates, hydroxides, chromates, nitrates, sulphides, sulphates, etc. 

Nickel catalysts, 77 94, 99, 109 precipitated, 77 121-122 Nickel-catalyzed dinitrotoluene hydrogenation, 25 194 Nickel chelates, 77 117 Nickel chloride hexahydrate, 77 109, 110 Nickel chromate, molecular formula, properties, and uses, 6 562t Nickel-chromium alloy 600, in galvanic series, 7 805t... 

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. 

Studies of chromate production workers, who are exposed to a variety of chromium compounds both hexavalent and trivalent, and chromate pigment industries, where exposure is mainly to chromium(VI), have consistently demonstrated an association with respiratory system cancer. Studies in chrome platers, who are exposed to chromium(VI) and other agents, including nickel, generally support the conclusion that certain chromium(VI) compounds are carcinogenic. Studies in stainless steel welders exposed to chromium(VI) and other chemicals, and in ferrochromium alloy workers, who are exposed mainly to chromium(O) and chromium(III), but also to some chromium(VI), were inconclusive. Studies in leather tanners, who are exposed to chromium(III), were consistently negative. 

USE In man Ilf of chrome-steel or chrome-nickel-steel alloys (stainless steel) for greatly increasing resistance and durability Of metals for chromeplating of other metals. The man-made slCr isotopa as tracer in various blood diseases and in the determination of blood volume (as the chloride or is Na chromate). 

Potassium or sodium-potassium alloy mixed with ammonium nitrate and ammonium sulfate results in explosion (NFPA 1986). Violent reactions may occur when a metal such as aluminum, magnesium, copper, cadmium, zinc, cobalt, nickel, lead, chromium, bismuth, or antimony in powdered form is mixed with fused ammonium nitrate. An explosion may occur when the mixture above is subjected to shock. A mixture with white phosphorus or sulfur explodes by percussion or shock. It explodes when heated with carbon. Mixture with concentrated acetic acid ignites on warming. Many metal salts, especially the chromates, dichromates, and chlorides, can lower the decomposition temperature of ammonium nitrate. For example, presence of 0.1% CaCb, NH4CI, AICI3, or FeCb can cause explosive decomposition at 175°C (347°F). Also, the presence of acid can further catalyze the decomposition of ammonium nitrate in presence of metal sulfides. 

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