nickel alloy UNS N06600 at a Glance
nickel alloy UNS N06600 pipe, designated UNS N06600, exhibits excellent corrosion resistance, particularly in oxidizing environments, high-temperature gases, and alkaline solutions. Its high nickel content provides strong resistance to chloride stress-corrosion cracking and allows it to withstand dry chlorine and hydrogen chloride environments up to 650°C. While generally very robust and durable, its corrosion resistance can be limited in certain reducing environments with high chloride-ion concentrations, so the specific service chemistry should always be checked.
Chemical Composition
The composition below follows SAE AMS 5540P-2017, the aerospace specification cited in the source article.
| Element | Composition (%) |
|---|---|
| Nickel (Ni) | 72.00 min |
| Chromium (Cr) | 14.0-17.0 |
| Iron (Fe) | 6.0-10.0 |
| Carbon (C) | 0.15 max |
| Manganese (Mn) | 1.00 max |
| Silicon (Si) | 0.50 max |
| Phosphorus (P) | 0.04 max |
| Sulfur (S) | 0.015 max |
| Copper (Cu) | 0.50 max |
| Titanium (Ti) | 0.50 max |
| Aluminum (Al) | 1.00 max |
| Niobium (Nb) | 0.35 max |
| Tantalum (Ta) | 1.00 max |
| Cobalt (Co) | 0.05 max |
Oxidation, Acid, and Alkali Resistance
Under oxidizing conditions, the chromium content of nickel alloy UNS N06600 pipe gives it superior corrosion resistance compared with commercially pure Nickel 200 grades. Chromium forms a stable and dense chromium oxide layer in high-temperature oxidizing atmospheres that effectively protects the alloy matrix from further oxidation and corrosion. This protection is maintained even at temperatures up to 1150°C in common industrial atmospheres containing oxygen, carbon dioxide, and sulfides, which is why 600 remains a workhorse for hot gas and furnace service despite being a relatively simple nickel-chromium-iron alloy.
nickel alloy UNS N06600 shows good corrosion resistance in a wide range of acidic media, including nitric acid, formic acid, acetic acid, acetic anhydride, hydrofluoric acid, oxalic acid, phosphoric acid, sulfuric acid, and stearic acid. In a 10% nitric acid solution its corrosion rate is less than 0.1 mm/year, which makes it highly suitable for chemical industry applications involving acidic media. The high nickel and chromium contents form a stable protective surface layer that prevents acid attack and ensures long-term stability.
In alkaline environments the alloy performs exceptionally well, resisting corrosion from sodium hydroxide, potassium hydroxide, sodium carbonate, and calcium hydroxide. This is the basis of its widespread use in caustic service and related industries.
Chloride SCC Resistance and Atmospheric Performance
nickel alloy UNS N06600 tubing is particularly renowned for resisting corrosion from dry chlorine and hydrogen chloride at temperatures up to 650°C, and it is virtually immune to chloride-induced stress-corrosion cracking. Chloride ions cause SCC in many alloys, but the high nickel content of 600 makes it a superior material for marine environments, chemical processes, and chloride-containing media. In addition, the alloy exhibits good corrosion resistance in reducing atmospheres, nitriding atmospheres, ammonia atmospheres, carburizing atmospheres, and high-temperature, high-pressure service.
Service Limits and Selection Notes
The practical selection questions are where 600 is the right answer and where it is not. Choose nickel alloy UNS N06600 when the risk is chloride stress-corrosion cracking, hot chlorine or hydrogen chloride service up to 650°C, oxidizing high-temperature atmospheres, or caustic and alkaline media. Consider alternatives when the service is strongly reducing with high chloride concentration, where molybdenum-bearing grades such as Alloy 625 or C-276 provide the reducing-acid resistance that 600 lacks, or where maximum high-temperature strength is required, where age-hardened grades such as 718 are more appropriate.
Frequently Asked Questions
Will nickel alloy UNS N06600 rust? No. The high nickel content makes nickel alloy UNS N06600 resistant to corrosion from a wide variety of organic and inorganic compounds, and it is virtually free from chloride stress-corrosion cracking, so it does not rust or corrode in the way carbon steel does.
How does nickel alloy UNS N06600 perform in acids? It resists nitric, formic, acetic, acetic anhydride, hydrofluoric, oxalic, phosphoric, sulfuric, and stearic acids, with a corrosion rate below 0.1 mm/year in 10% nitric acid solution, making it well suited to chemical industry acidic media.
What is the SCC resistance of nickel alloy UNS N06600? nickel alloy UNS N06600 is virtually immune to chloride-induced stress-corrosion cracking thanks to its high nickel content, and it resists dry chlorine and hydrogen chloride service up to 650°C.
Up to what temperature can nickel alloy UNS N06600 handle oxidizing atmospheres? Its stable chromium oxide layer protects the alloy at temperatures up to about 1150°C in common industrial atmospheres containing oxygen, carbon dioxide, and sulfides.
What are the limits of nickel alloy UNS N06600's corrosion resistance? In certain reducing environments with high chloride-ion concentrations, its resistance can be limited. For strongly reducing acid service, molybdenum-bearing nickel alloys such as 625 or C-276 are more appropriate.
What is the composition of nickel alloy UNS N06600? Per SAE AMS 5540P-2017: nickel 72% minimum, chromium 14-17%, iron 6-10%, with small limits on carbon, manganese, silicon, phosphorus, sulfur, copper, titanium, aluminum, niobium, tantalum, and cobalt.
