Nickel

Commercially pure or low-alloy nickel has characteristics that are useful in several fields, notably chemical processing and electronics. Nickel is highly resistant to various reducing chemicals and is unexcelled in resistance to caustic alkalies. Compared with nickel alloys, commercially pure nickel has high electrical and thermal conductivity. It also has a high Curie temperature and good magnetostrictive properties. Annealed nickel has a low hardness and good ductility and malleability. Those attributes, combined with good weldability, make the metal highly fabricable. Nickel has a relatively low work-hardening rate, but it can be cold worked to moderately high strength levels while maintaining ductility.

Nickel 200 (UNS N02200/W.Nr. 2.4060 & 2.4066) is commercially pure (99.6%) wrought nickel. It has good mechanical properties and excellent resistance to many corrosive environments. Other useful features of the alloy are its magnetic and magnetostrictive properties, high thermal and electrical conductivities, low gas content and low vapor pressure. The corrosion resistance of Nickel 200 makes it particularly useful for maintaining product purity in the handling of foods, synthetic fibers, and caustic alkalies; and also in structural applications where resistance to corrosion is a prime consideration. Other applications include chemical shipping drums, electrical and electronic parts, aerospace and missile components.

Nickel 200 is highly resistant to many corrosive media. Although most useful in reducing environments, it can be used also under oxidizing conditions that cause the development of a passive oxide film. The outstanding resistance of Nickel 200 to caustics is based on this type of protection.

In all environments, when temperatures above 600°F (315°C) are involved, the preferred material is Nickel 201.

Nickel 200 normally remains bright in indoor atmospheres. Outdoors, the rate of attack is slow because of the formation of a thin protective film, usually a sulfate. This rate increases with increases in the sulfur dioxide content of the atmosphere (such as might occur in industrial areas). Corrosion rates in both marine and rural atmospheres are very low.

Nickel 200 gives excellent service in flowing sea water even at high velocity, but in stagnant or very low-velocity sea water severe local attack may occur under fouling organisms or other deposits.

Nickel 200 can be used with sulfuric acid at low or moderate temperatures. Both aeration and increasing temperatures increase corrosion rates so that the principal use of Nickel 200 in sulfuric acid is in nonaerated solutions near room temperature. The presence of oxidizing salts will also accelerate corrosion.

According to the data available, Nickel 200 may be used in hydrochloric acid in concentrations up to 30%, either aerated or unaerated, at room temperature. An important reason for its success is that its corrosion product – nickel chloride – has a relatively low solubility in this range of concentration. Because of this reason, the material should be used only with caution when solutions are at high velocity. Also, both increasing temperature and aeration will accelerate corrosion. Its use in air-saturated hydrochloric acid above room temperature is usually limited to concentrations of less than 3-4%, but completely airsaturated solutions are not commonly used in industry. If oxidizing salts are present in any but very small amounts, corrosion will be increased.

Nickel 200

Nickel 200 has excellent resistance to anhydrous hydrofluoric acid even at elevated temperatures. In aqueous solutions, however, service is usually limited to below 180°F (80°C). Even at room temperature, 60-65% commercial-grade acid has been found to severely corrode Nickel 200.

In general, Nickel 200 has excellent resistance to organic acids of all concentrations if aeration is not high. It has useful resistance to fatty acids such as stearic and oleic.

The outstanding corrosion resistance characteristic of Nickel 200 is its resistance to caustic soda and other alkalies. (Ammonium hydroxide is an exception. Nickel 200 is not attacked by anhydrous ammonia or ammonium hydroxide in concentrations of 1%. Stronger concentrations can cause rapid attack.) There is a wide range of proven industrial applications for this material in plant processes involving alkalies.

In caustic soda, Nickel 200 has excellent resistance to all concentrations up to and including the molten state. Below 50%, rates are negligible, even in boiling solutions. As concentration and temperature increase, corrosion rates increase very slowly.

The chief factor contributing to the outstanding performance of Nickel 200 in highly concentrated caustic soda is a black protective film that forms during exposure. This film – nickel oxide – results in a marked decrease in corrosion rates over long exposure under most conditions.

Because the presence of chlorates in caustic increases corrosion rates significantly, every effort should be made to remove as much of them as possible. Oxidizable sulfur compounds also tend to increase the corrosivity of caustic to Nickel 200. Adding sufficient sodium peroxide to oxidize these sulfur compounds to sulfates will counteract this condition.

Nickel 201

Nickel 201 (UNS N02201/W.Nr. 2.4061 and 2.4068) is the low-carbon version of Nickel 200. Typical applications are caustic evaporators, combustion boats, plater bars, and electronic components.

Nickel 201 is very widely used to handle caustic soda. At only above 75% caustic concentration and near the boiling point, did the corrosion rate start to go above 1 mpy (0.025 mm/a).

Like Nickel 200, Nickel 201 forms an oxide film that protects it in caustic. For example, specimens in a caustic solution (2 kg technical-grade flake caustic in 500 cc water) at 790°-830°F (420°-445°C) corroded 21 mpy (0.53 mm/a) in 24 hr. By that time they had developed an oxide coating. At the end of a week, corrosion rate dropped to 2.8 mpy (0.07 mm/a) for an additional week when the test was concluded.

Chlorates in caustic will accelerate corrosion and as much of them as possible should be removed. Oxidizable sulfur compounds are also harmful, but, by adding sodium peroxide to change them to sulfates, their effect can be minimized. In certain high-temperature caustic applications where sulfur is present, INCONEL alloy 600 is used rather than Nickel 201 because of its greater resistance to sulfur embrittlement.

In comparison with other commercial metals and alloys, Nickel 201 has outstanding resistance to dry fluorine.

Nickel 201 and INCONEL alloy 600 are the most practical alloys for service in chlorine or hydrogen chloride at elevated temperatures.Temperatures at which various corrosion rates were exceeded and a suggested upper temperature limit for continuous service. These limits are believed to be conservative since longer testing times will show the effect of a protective chloride developed. For instance, in a 500-hr laboratory corrosion test in anhydrous hydrochloric acid gas at 930°F (500°C), Nickel 201 corroded only 3 mpy (0.08 mm/a).

Studies have shown the effect of 0.25% moisture in hydrogen chloride on corrosion of Nickel 201 at 1000°F (540°C).

Nickel 201 has been successfully used for chlorination equipment at temperatures up to 1000°F (540°C) and for cylindrical retorts for the sublimation of zirconium chloride at temperatures of 800° to 1000°F (425° to 540°C).

Nickel 201 can be used effectively in hydrofluoric acid provided there are no conditions of flowing under which its protective fluoride film would be removed. Aeration or the presence of oxidizing chemicals will also increase corrosion rates. As an example of its performance, corrosion rate in anhydrous hydrogen fluoride (hydrofluoric acid gas) at temperatures of 930°-1100°F (500°-595°C) was 36 mpy (0.91 mm/a).

Nickel 200 Wire 1.0mm	Twill Weave Nickel 200 80mesh 0.12mm	Twill Weave Nickel 200 80mesh 0.12mm-02

Twill Weave Nickel 200 200mesh 0.05mm	Twill Weave Nickel 200 200mesh 0.05mm-02