Some materials are versatile; Monel 400 is a specialist, and its specialty is the acid nothing else survives. Metinox Overseas supplies Monel 400 pipes and tubes to ASTM B165 seamless and B725 welded, UNS N04400, made to order with 100 percent PMI and 3.1 certification, serving refining, chemical and marine buyers across India, the USA, the Middle East and Africa. It is a nickel-copper alloy, roughly two-thirds nickel and one-third copper, and where hydrofluoric acid or fluoride chemistry rules, Monel 400 is frequently the only sensible pipe on the plant. The wider nickel range sits at Special Alloys Pipes & Tubes.
Its family ties run two ways. On the copper side it shares behaviour with the cupronickels on our Copper Pipes & Tubes page, and on the nickel side it sits below the chromium-bearing Hastelloy Pipes & Tubes grades, which take over where oxidizing conditions defeat Monel. Knowing that boundary is most of specifying it correctly.
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Table of content
- The One Job Nothing Else Does: Hydrofluoric Acid
- The Reducing-Conditions Rule for Monel 400
- Monel 400 Chemistry & Mechanical Properties
- Alloy 400 Standards, Sizes & Forms
- Monel 400 Applications
- Monel 400 Testing, PMI & Export to USA, Middle East & Africa
- Explore Related Grades
- Monel 400 Pipes & Tubes: Frequently Asked Questions
The One Job Nothing Else Does: Hydrofluoric Acid
Hydrofluoric acid destroys titanium, attacks most stainless quickly, and generates enough trouble from trace fluorides to end lesser materials, but Monel 400 handles it. HF alkylation units in refineries run on Monel for exactly this reason, and where a stream carries HF or free fluorides, the material conversation usually starts and ends here. The nickel-copper chemistry also gives excellent resistance to hydrochloric and sulphuric acids under reducing conditions, to neutral and alkaline salts, and to flowing seawater, where it resists the erosion and cavitation that trouble copper alloys. That last property makes it a marine material as well as a chemical one.
Monel 400 Chemistry & Mechanical Properties
| Element / Property | UNS N04400 |
|---|---|
| Nickel | 63.0% min |
| Copper | 28.0 – 34.0% |
| Iron | 2.5% max |
| Manganese | 2.0% max |
| Tensile Strength | 480 MPa (70 ksi) min |
| Yield Strength | 195 MPa (28 ksi) min |
| Elongation | 35% min |
Limits per ASTM B165. Monel is not hardenable by heat treatment; it strengthens by cold work, and it stays tough to cryogenic temperatures.
The Reducing-Conditions Rule for Monel 400
Here is the honest constraint that mirrors the Hastelloy B-series trap, and it is worth stating plainly. Monel 400 has no chromium, so it depends on reducing conditions and performs best when oxygen and oxidizing salts are absent. In aerated or oxidizing environments its corrosion resistance falls, and oxidizing acids such as nitric attack it. The practical rule: Monel is superb in de-aerated hydrofluoric, hydrochloric and sulphuric acid, and the wrong choice the moment the stream turns oxidizing. Where oxidizing conditions are present, the Hastelloy C grades or Inconel 625 take over. Tell us whether the stream is aerated when you enquire; it changes the answer.
Types of Monel 400 Pipes & Tubes
Coiled & Capillary Tube
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Heat Exchanger Tubes (ASTM B163)
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Seamless Pipes & Tubes (ASTM B165)
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Welded & ERW Pipes (ASTM B725)
Monel 400 Applications
- Refining, HF Alkylation: the flagship duty, acid piping and equipment in alkylation units across Gulf and Indian refineries.
- Chemical Processing: hydrofluoric, hydrochloric and sulphuric acid systems under reducing conditions.
- Marine & Offshore: seawater piping, pump and valve trim, where erosion resistance in flowing seawater pays.
- Oil & Gas: sour service components and wellhead hardware.
- Salt Production & Heat Exchangers: brine and neutral salt duty.
Monel 400 Testing, PMI & Export to USA, Middle East & Africa
Material is supplied to B165 or B725 with examination per the standard, 100 percent PMI attached to the EN 10204 3.1 certificate, 3.2 through BV, SGS or TUV at order stage. Metinox Overseas is ISO 9001 and PED certified; see Quality Policy. Supply is made to order; typical delivery runs 4 to 8 weeks, shipped from Mumbai with alloy-segregated packing per Packing and Dispatch, to the USA, the Middle East and Africa, where refinery HF units are the busiest lane.
Explore Related Grades
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Monel 400 Pipes & Tubes: Frequently Asked Questions
Because almost nothing else survives it. Hydrofluoric acid destroys titanium and attacks most stainless steels rapidly, while the nickel-copper chemistry of Monel 400 resists it, which is why refinery HF alkylation units are built around the alloy. Where a stream carries HF or free fluorides, Monel is usually the material the specification names.
Monel has no chromium, so it relies on reducing conditions and performs best when oxygen and oxidizing salts are absent. It is excellent in de-aerated hydrofluoric, hydrochloric and sulphuric acids, and the wrong choice in aerated or oxidizing streams, including nitric acid. Whether the stream is aerated decides whether Monel or a chromium-bearing alloy is correct.
Yes, particularly in flowing seawater, where it resists the erosion and cavitation that trouble copper alloys, which is why it appears in marine pump and valve trim and seawater piping. In stagnant or sulphide-polluted seawater its performance drops, as with the copper-nickel family it is related to.
Yes. UNS N04400 is the brand-neutral designation for the alloy sold as Monel 400, also W.Nr. 2.4360. Monel is a registered trademark of Special Metals Corporation, so ordering by UNS N04400 to ASTM B165 keeps specifications and quotations comparable across mills.
Yes, made to order with 100 percent PMI and 3.1 documentation. Refinery HF alkylation work in the USA and the Gulf, and marine and chemical duty across the region, are the regular lanes, shipped alloy-segregated and labelled from Mumbai.
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