Both Nickel 200 and 201 offer corrosion resistance in reducing and neutral media as well as in oxidizing atmospheres provided that the oxidizing media allows the formation of a passive oxide film. This oxide film accounts for the materials excellent resistance in caustic environments. Corrosion rates in both marine and rural atmospheres are very low. The resistance of Nickel 200/201 to corrosion by distilled and natural waters is excellent. Plus it also 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. In hot water systems where the steam contains carbon dioxide and air in certain proportions, corrosion rates will be initially high but will decrease with time if conditions favor the formation of a protective film.
Nickel 200 is normally limited to service at temperatures below 600° F. At higher temperatures Nickel 200 products can suffer from graphitization which can result in severely compromised properties. When operating temperatures are expected to exceed 600° F, carbon content becomes critical. The lower carbon content of Nickel 201 makes the material resistant to graphitization and therefore less subject to embrittlement. Nickel 200 & 201 are approved for construction of pressure vessels and components under ASME Boiler and Pressure Vessel Code Section VIII, Division 1. Nickel 200 is approved for service up to 600° F while Nickel 201 is approved for service up to 1230° F. Melting point is 2615-2635° F.