Key takeaways
- A magnet can rule Inconel out but never confirm it, and clad pipe can fool it.
- A UNS marking with a matching certificate is the fastest evidence; confirm it with a reading.
- Weight, colour, sparks and spot tests cannot separate Inconel from 316 stainless.
- XRF confirms Inconel by high nickel and low iron, and iron, chromium, molybdenum and niobium name the grade.
If you are working out how to identify Inconel in a pile of scrap, start by being clear about the question. "Is it Inconel?" usually means "is this nickel alloy or stainless steel?", because the two look the same and are valued very differently. "Which Inconel?" is the second question, and it matters just as much, because 600, 625 and 718 are priced on different chemistry.
Field checks such as a magnet, markings and weight answer part of the first question. Only an instrument reading answers the second. This guide shows what each check can and cannot tell you, how to read markings, which look-alikes cause the mistakes, and what to do with pieces you cannot confirm.
Is It Inconel? A Quick Sorting Route
The quickest reliable route is a magnet first to remove carbon steel and duplex, markings next for a strong lead, and an XRF reading to confirm nickel-base chemistry and name the grade. Each step removes candidates. None of the early steps proves Inconel on its own.
- Does a magnet grip firmly?YesNot solid Inconel. Carbon steel, ferritic stainless, duplex, or a steel backing behind cladding
- Is there a legible UNS number such as N06625 or N07718?YesA strong lead. Match the heat number to a certificate, then confirm with a reading
- Does XRF show iron as the main element with 25% nickel or less?YesStainless steel such as 304, 316, 310S or 904L, not Inconel
- Does XRF show nickel above about 50%?YesA nickel-base alloy. Use the separating elements to tell Inconel from Hastelloy, Monel and Nimonic
- Nickel near 40% with high iron points to Incoloy 825 or 925, or Inconel 706. Read copper and molybdenum
Work through it in that order and you spend instrument time only on pieces that could be Inconel. Keep a separate box for anything that stops at the last line: those pieces need a closer look at the minor elements, not a guess.
Where Does Inconel Usually Turn Up in Scrap?
Where a piece came from is often the first useful clue to its grade. Inconel is chosen for heat or corrosion, so it turns up in predictable places, and knowing the source tells you which grade to expect before you take a reading.
- Furnaces and heat-treatment lines: muffles, retorts, radiant tubes and baskets point to 600 or 601, though 310S stainless is used for the same jobs.
- Offshore, subsea and pipe-spool fabrication: pipe offcuts, flanges and clad pipe point to 625.
- Aerospace and oilfield machining: chips, bar ends and forging trims point to 718.
- Steam generator replacements: tubing points to 690 or 600, traded only after radiological clearance.
Treat the source as a hypothesis to test, not a result. Plants mix alloys, and a furnace basket can as easily be stainless as Inconel.
What Do Markings on Inconel Tell You?
A legible marking is the fastest evidence there is. New Inconel pipe, plate and bar is stencilled or stamped with the product specification, the UNS number and a heat number, and fabrication offcuts often keep it.
ASTM B444product specification for 625 pipe and tubeN06625UNS number for Inconel 6252.4856European W.Nr. for the same alloy, where shownHeat no.links the piece to its 3.1 certificate| UNS | W.Nr. | Grade | Specifications you may see |
|---|---|---|---|
| N06600 | 2.4816 | Inconel 600 | ASTM B168, B163, B167, B166 |
| N06601 | 2.4851 | Inconel 601 | ASTM B168, B167, B166 |
| N06617 | 2.4663 | Inconel 617 | ASTM B168, B166, B167 |
| N06625 | 2.4856 | Inconel 625 | ASTM B443, B444, B446, B704, B705 |
| N06690 | 2.4642 | Inconel 690 | ASTM B163, B167, B166, B168 |
| N07718 | 2.4668 | Inconel 718 | ASTM B637, B670; AMS 5662, 5663, 5596 |
| N08825 | 2.4858 | Incoloy 825, often sold as "Inconel 825" | ASTM B424, B423, B425 |
Two cautions. A marking tells you what the piece was sold as, not what it is if it has been mixed up since, so confirm it with a reading. And on clad or overlaid pipe the stencil may describe the carbon steel base pipe, not the alloy layer. For more, see how UNS numbers work, ASTM B specifications for nickel alloys and reading a 3.1 mill certificate. The grade name converter translates between trade names, UNS and W.Nr.
What Can a Magnet Tell You About Inconel?
A magnet can rule Inconel out but never rule it in. Inconel alloys are non-magnetic at room temperature, so a magnet that grips firmly rules Inconel out. It cannot rule Inconel in, because 304 and 316 stainless, Hastelloy, Incoloy, titanium and most Nimonic and Haynes grades are non-magnetic too.
The case that costs Inconel sellers most is clad or weld-overlaid pipe: it grips the magnet on the outside because the backing is carbon steel, while the bore is genuine Inconel 625. Test the bore and the cut edge before you discard a piece. Cold work, Monel 400 and the other traps are covered in the magnet test for scrap sorting.
Can You Tell Inconel from Stainless Steel by Weight, Colour or Sparks?
Not reliably. These checks can make a piece worth testing, but none of them separates Inconel from austenitic stainless steel with confidence.
Weight. Inconel is a little denser than stainless: about 8.44 g/cm³ for 625 and 8.47 for 600, against about 8.0 for 316 and 7.93 for 304. That gap of 5–7% cannot be felt in the hand, and dimensional tolerance or wall loss can hide it. Inconel 718, at about 8.19, is closer still. If you know the dimensions, the scrap weight calculator shows whether a weighed piece fits one grade better than another, but treat the result as a hint.
Colour and surface. New Inconel is a plain grey, much like stainless. Service pieces from furnaces or turbines carry dark oxide or heat tint, which tells you where the piece has been, not what it is.
Sparks. Nickel alloys give short, dull spark streams that are hard to tell apart. A spark test separates carbon steel well; it does not name a nickel alloy, and it marks the piece.
Spot tests. Chemical spot tests show that an element such as nickel or molybdenum is present. Since 316 contains both, a positive result does not prove Inconel.
| Rules out carbon steel | Separates Inconel from 316 | Names the Inconel grade | Works on turnings | |
|---|---|---|---|---|
| Magnet | ● | ○ | ○ | ◐ |
| Marking and certificate | ◐ | ● | ● | ○ |
| Weight and density | ○ | ◐ | ○ | ○ |
| Spark test | ● | ○ | ○ | ○ |
| Chemical spot test | ◐ | ○ | ○ | ◐ |
| Handheld XRF | ● | ● | ● | ◐ |
| Spark OES | ● | ● | ● | ○ |
| Laboratory analysis | ● | ● | ● | ● |
● yes ◐ partly ○ no
How Do You Tell Inconel from Stainless Steel with XRF?
Look at nickel and iron. Inconel reads as a nickel-base alloy, mostly about 50–76% nickel with iron below about 20%, while 304 and 316 read as iron-base with about 9–11% nickel. One reading on a clean spot settles it.
The comparison shows the whole story. Inconel 625 is about 62% nickel and 4% iron, with about 9% molybdenum and 3.6% niobium; 316 is about 68% iron and 11% nickel, with about 2% molybdenum and no niobium. Inconel 706 is the one Inconel that reads iron-rich, at about 42% nickel and 37.5% iron, and it comes mainly from large land-based turbine forgings. For the family difference in general, see nickel alloy vs stainless steel.
How Do You Tell Inconel 625 from 718 and the Other Grades?
Use the elements that separate each pair, not just the analyser's grade call. Iron is the fastest single separator inside the Inconel family, with chromium, niobium and aluminium settling the rest.
| Pair | What separates them on XRF |
|---|---|
| Inconel 625 vs 718 | Iron about 4% against 18.5%; molybdenum about 9% against 3%; niobium 3.6% against 5.1% |
| Inconel 600 vs 690 | Chromium about 15.5% against 29% |
| Inconel 600 vs 601 | Chromium 15.5% against 23%, iron 8% against 14%; 601's 1.4% aluminium needs a light-element setup or OES |
| Inconel 625 vs Hastelloy C-276 | C-276 has about 16% molybdenum and 3.75% tungsten and no niobium |
| Inconel 718 vs Hastelloy X | Both about 18.5% iron; X has about 9% molybdenum and no niobium, 718 about 5% niobium |
| Inconel 718 vs 706 | 706 has about 37.5% iron and no molybdenum |
| Inconel 625 vs Incoloy 825 | 825 has about 30% iron and 2.25% copper |
An analyser's library is only as good as its entries and the test spot. Clean the spot, read for long enough to settle the minor elements, and check the separating elements yourself. Technique is covered in how handheld XRF sorts nickel alloys, and when a light-element method is needed in XRF, OES or lab analysis. You can also enter readings into the grade identifier to see the closest matches.
The simulated spectrum above is what an analyser sees on Inconel 718: a strong nickel peak, chromium and iron close behind, and niobium and molybdenum in the higher-energy range. Compare it with 625 and the iron peak is the giveaway.
Which Metals Get Mistaken for Inconel?
Austenitic stainless steels, Incoloy, Hastelloy, Monel and Nimonic all get mistaken for Inconel, because they share the look, the non-magnetic response and often the same plant. The table lists the usual suspects and the readings that separate them.
| Look-alike | Why it gets confused | What separates it |
|---|---|---|
| 304 and 316 stainless | Same appearance, non-magnetic when annealed | Iron-base, about 9–11% nickel |
| 310S stainless | Used beside 600 and 601 in furnaces | About 53% iron, 25% chromium, 20% nickel |
| 904L | Acid plant service, high nickel for a stainless | About 48% iron, 25% nickel, 1.5% copper |
| Incoloy 825 and 925 | Sold as "Inconel 825" and "Inconel 925" | About 28–30% iron and about 2% copper; see Inconel vs Incoloy |
| Hastelloy C-276, C-22 and X | Same plants and turbines as Inconel | Tungsten in the C grades; X has high iron and no niobium; see Inconel vs Hastelloy |
| Monel 400 | Nickel-base, used in marine and chemical service | About 31.5% copper and almost no chromium |
| Nimonic 75 and 80A | Nickel-chromium sheet and bar in turbines | About 20% chromium, low iron, titanium (and aluminium in 80A) |
Getting the look-alike right is worth as much as getting Inconel right. Hastelloy C-276 is not a lesser find than Inconel 625; it is a different one, priced on different elements.
Identifying Turnings, Wire, Coated and Cast Pieces
Awkward forms need adapted checks, because a single reading only describes the metal it touched.
- Turnings. Drain the oil, then read several samples from different depths in each drum. A buyer will often want a composite analysis as well.
- Wire. Read a cleaned length and check the spool label; welding wire is often a filler alloy close to, but not always the same as, the base metal.
- Coated, painted or oxidised pieces. Grind or file a small spot back to bright metal, because coatings and scale distort the reading.
- Cast pieces. Turbocharger wheels of Inconel 713C carry about 6% aluminium, which needs a light-element setup or OES to confirm.
What to Do with a Piece You Cannot Confirm
Keep it apart. A suspect piece dropped into the wrong bin can cost more than the piece is worth, because it makes the buyer recheck the whole lot. Label it as unconfirmed, photograph it with any markings, note where it came from, and get a reading before it joins a graded lot.
When you are ready to sell, the preparation and paperwork are covered in how to sell Inconel scrap. Mipra Steel buys and supplies nickel alloy scrap described by grade and asks sellers for readings, certificates and photographs; send us the details and photographs and we'll review your enquiry.
Submit a requirement with the grade, form, quantity and delivery location.
Source a GradeFAQ
Does Inconel rust?
Inconel does not form the flaky red rust you see on carbon steel, because its chromium and nickel protect the surface. Service pieces may carry dark oxide from high temperature, or brown staining from contact with carbon steel or process deposits. Stainless steel also resists rusting, so the absence of rust tells you the piece is not plain carbon steel, but it does not tell you the piece is Inconel.
Is Inconel 718 magnetic?
No. Inconel 718 is non-magnetic at room temperature, like the other common Inconel grades. A magnet will therefore not separate 718 from 625, 600, Hastelloy or 316 stainless. If a 718 piece seems to pull a magnet, look for carbon steel attachments, magnetic tooling debris or contamination on the surface, and confirm the grade with an XRF reading that shows iron near 18% and niobium near 5%.
What does N07718 on a part mean?
N07718 is the UNS number for Inconel 718. The N prefix marks a nickel alloy, and the five digits identify the specific alloy. On aerospace parts it may appear with an AMS specification such as AMS 5662 or 5663; on bar and forgings for other industries, with ASTM B637. The marking tells you what the part was made from, and a reading confirms that nothing has been mixed up since.
How accurate is a handheld XRF on Inconel?
On a clean, flat spot, handheld XRF reads the elements that separate Inconel grades well: nickel, chromium, iron, molybdenum, niobium, cobalt and tungsten. It cannot measure carbon, and it reads aluminium poorly without a light-element setup, which matters for 601 and cast grades such as 713C. Paint, scale and coatings distort results, so prepare the spot, and check element values rather than relying on the grade call alone.
Can I identify Inconel turnings without an analyser?
Only partly. A magnet removes carbon steel chips, and knowing which job and machine produced them is strong evidence of the grade. But stainless and Inconel chips look alike, and cold-worked stainless chips can be slightly magnetic. For sale, a buyer will normally want readings on several samples or a composite analysis. Keeping chips in labelled bins at each machine is the most reliable identification you can do.
Is Inconel 825 really Inconel?
No. The alloy traded as "Inconel 825" is Incoloy 825, UNS N08825, an iron-nickel-chromium alloy with about 42% nickel, 30% iron, 3% molybdenum and 2.25% copper. It is a useful corrosion alloy with its own scrap value, but it reads very differently from any Inconel on XRF. Describing it as Incoloy 825 avoids confusion and tells a buyer the rest of your description can be trusted.
My analyser says Inconel 625 but the seller says Hastelloy. Who is right?
Check the separating elements. Inconel 625 shows about 3.6% niobium, no tungsten and about 9% molybdenum. Hastelloy C-276 shows about 16% molybdenum and 3.75% tungsten with no niobium, and C-22 shows about 13% molybdenum and 22% chromium. If the readings match 625, the piece is 625 whatever the label says. If they sit between grades, clean the spot, reread, and consider OES or a laboratory check.
