UNS N08825: “UNS” stands for Unified Numbering System, which is a standardized system for identifying metals and alloys. “N08825” is the designation for a specific nickel-iron-chromium alloy known as Incoloy 825. This alloy offers excellent corrosion resistance in a wide range of corrosive environments, including those containing sulfuric acid, phosphoric acid, and seawater.

INCOLOY® alloy 825 (UNS N08825/W.Nr. 2.4858) is a nickel-iron-chromium alloy with additions of molybdenum, copper, and titanium. The alloy’s chemical composition, given in Table 1, is designed to provide exceptional resistance to many corrosive environments. The nickel content is sufficient for resistance to chloride-ion stress-corrosion cracking. The nickel, in conjunction with the molybdenum and copper, also gives outstanding resistance to reducing environments such as those containing sulfuric and phosphoric acids. The molybdenum also aids resistance to pitting and crevice corrosion. The alloy’s chromium content confers resistance to a variety of oxidizing substances such as nitric acid, nitrates and oxidizing salt. The titanium addition serves, with an appropriate heat treatment, to stabilize the alloy against sensitization to intergranular corrosion.