Commercially pure nickel

The standard quality of commercially pure nickel (nickel 99% minimum, carbon 0.15% maximum nickel 200/201) can be readily welded and fabricated in all wrought forms and as castings. However, it is restricted to... 

Nickel is usually alloyed with elements including copper, chromium, molybdenum and then for strengthening and to improve corrosion resistance for specific applications. Nickel-copper alloys (and copper-nickel alloys see Section 53.5.4) are widely used for handling water. Pumps and valve bodies for fresh water, seawater and mildly acidic alkaline conditions are made from cast Ni-30% Cu type alloys. The wrought material is used for shafts and stems. In seawater contaminated with sulfide, these alloys are subject to pitting and corrosion fatigue. Ammonia contamination creates corrosion problems as for commercially pure nickel. 

Based on the chemical composition, corrosion-resistant nickel-based alloys consist of commercially pure nickel. Ni-Cu alloys, Ni-Mo alloys, Ni-Cr-Mo alloys, and Ni-Cr-Fe alloys.63 The cast versions of the nickel-based alloys do not have the same corrosion resistance as the corresponding wrought products, mainly due to the higher carbon and silicon contents and the anisotropic microstructure of the cast products. (Rebak)5... 

Shortening units are constructed of carbon steel. The water phase in margarine is corrosive, and sanitation procedures require that all of the equipment used to manufacture it must be chemically cleaned. Margarine processing units contain chromium-plated commercially pure nickel heat transfer tubes and stainless steel for all product-contacted metal surfaces. 

Commercially pure nickel cathode is produced by electrowiiming in either sulfate or chloride electrolyte, or a combination of both. Chloride based electrolyte systems generate chlorine gas at the anode The nickel industry to developed anode bag technology in order to capture chlorine gas at the source. Not only is the chlorine gas collected and removed from the operating environment in the cellhouse using anode bags, it is also returned upstream as an oxidant in the matte leaching process step. 

Cupronickels (Ni-Cu) In this category the most common cupronickel alloys are the Monel 400 and Monel K-500. The Ni-Cu alloys differ from nickel 200 and 201 because their strength and hardness can be increased by age hardening. Ni-Cu alloys exhibit higher corrosion resistance than commercially pure nickel, especially to sulfuric and hydrofluoric acids, and chloride brines. Handling of waters, including seawater and brackish water, is the major application of these two alloys in the CPI (e.g., desaUnation plants). In addition, Monel 400 and K-500 are immune to chloride-ion stress-corrosion cracking, which is often considered in their selection. 

Commercially pure nickel contains at least 99% Ni (Table 2-1). Nickel is more noble than iron but less noble than copper (Pourbaix, 1974). Thermodynamically (Pourbaix diagram), nickel is shown to dissolve as Ni " at pH <9, to form nickel (II) oxide (NiO) at pH 9-12, and to dissolve as HNiOj at pH >12. Nickel (II) oxide is shown to be stable approximately between -0.5 and -1-0.3 V on the normal hydrogen scale (NHE). In practice it is found that nickel has good corrosion resistance in environments such as cold and hot aqueous caustic solutions. Nickel is also highly tolerant of... 

The widest industrial application of commercially pure nickel is in the handling of cold and hot caustic solutions. Table 2-2 lists the comparative general rates of corrosion of nickel and nickel alloys in caustic... 

Commercially pure nickel is not susceptible to stress-corrosion cracking except under heavily cold-worked conditions in concentrated caustic solutions at high temperature (>250 °C). Commercial nickel is not susceptible to hydrogen embrittlement... 

This family is represented by nickel alloys 200 (N0220) and 201 (N02201). The chemical composition is shown in Table 15.1. Commercially pure nickel is a white magnetic metal very similar to copper in its other physical and mechanical properties. 

The 1983 ASME Section VIII Code, VUI-l, lists five nonferrous alloys for code construction aluminum, copper, nickel, titanium, and zirconium. These alloys are normally used in corrosive environment or elevated temperatures where ferrous alloys are unsuitable. Nonferrous alloys are nonmagnetic except for commercially pure nickel which is slightly magnetic. 

Its chromium content gives the alloy resistance to sulfur compounds and various oxidizing environments. The chromimn content of the alloy makes it superior to commercially pure nickel under oxidizing conditions. In strong oxidizing solutions hke hot, concentrated nitric acid, 600 has poor resistance. Alloy 600 is relatively unattacked by the majority of neutral and alkaline salt solutions and is used in some caustic environments. The alloy resists steam and mixtures of steam, air, and carbon dioxide. 

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