<p>Stainless steel is created by adding elements (usually Chromium, but also Nickel) to steel. These added elements form an oxide layer with the outside air protecting the steel from corroding. </p>

<p>Whether stainless steel is magnetic or not depends on the added elements and the micro structure of the steel; some are and some aren't magnetic.</p>

<p>From <a href="https://www.physlink.com/Education/askexperts/ae546.cfm" rel="nofollow noreferrer">physlink</a>:</p>

<blockquote>
  <p>As for whether they (red. stainless steels) are magnetic, the answer is that it depends. There are several families of stainless steels with different physical properties. A basic stainless steel has a 'ferritic' structure and is magnetic. These are formed from the addition of chromium and can be hardened through the addition of carbon (making them 'martensitic') and are often used in cutlery. However, the most common stainless steels are 'austenitic' - these have a higher chromium content and nickel is also added. It is the nickel which modifies the physical structure of the steel and makes it non-magnetic.</p>
</blockquote>

<p>So the answer is that you cannot determine by testing for magnetic properties if the nozzle is stainless steel or not. But if it is not magnetic, it can be stainless steel. Note that discoloration is possible, this is the oxide layer.</p>

<p>To identify if the steel is stainless, you could without sacrificing the nozzle (according to <a href="https://www.hunker.com/13401485/how-to-tell-if-stainless-steel-is-real" rel="nofollow noreferrer">this reference</a>):</p>

<blockquote>
  <p><strong>Step 1</strong><br>
  Stick the magnet on the piece you are testing. If it holds firmly, the metal is possibly stainless steel. If not, it is (red. could be) another metal such as aluminum.</p>
  
  <p><strong>Step 2</strong><br>
  Pick a spot on the piece that you don't mind damaging a little.</p>
  
  <p><strong>Step 3</strong><br>
  Fill the eye dropper with <a href="https://en.wikipedia.org/wiki/Hydrochloric_acid" rel="nofollow noreferrer">muriatic acid</a>. Drop a small amount of the acid on the test spot. Wait half an hour.</p>
  
  <p><strong>Step 4</strong><br>
  Wipe the acid off the piece. Examine the test spot. If it is discolored, the piece is stainless steel.</p>
</blockquote>

<hr>

<p><sup>Note that the image you posted shows a Zinc plated steel screw, not a stainless steel screw.</sup></p>

CC BY-SA 4.0
2019-10-10T08:42:23.533Z
It seems to me that Step 1 reveals nothing according to previous quote "...that depends," which makes me doubt the muriatic acid (hydrochloric acid) test is valid, especially as it says nothing about the nature of the discolouration (I could be wrong). A better test might be to file a groove in the surface and immerse it in salty water overnight: if it goes rusty, it isn't stainless steel.
Andrew Morton
CC BY-SA 4.0
2019-10-10T09:44:56.697Z
@AndrewMorton I've left it as a quote of the complete steps, but indeed step 1 is not necessary considering the other quote. If I would have left out step one, I would have received comments about "where is step 1". Thanks for the comment, if you have a better reference, please feel free to alter the answer.
0scar
CC BY-SA 4.0
2023-01-14T15:55:31.027Z
Anecdotal note - In the late 1960s the USN machine shops I served in used a nitric acid test with instant results. Carbon steel stained black; monel (a salt-water resistant copper nickel alloy we used extensively) stained green; stainless steel didn't react at all.
allardjd
CC BY-SA 4.0
2019-10-09T06:07:47.900Z
2019-10-09T14:46:27.247Z
2019-10-09T14:46:27.247Z
0scar
<p>The other answers are good. For a more practical answer:</p>
<h2>Magnet test</h2>
<p>As answered by Trish, steel with an austenitic atom structure, which most stainless steels have, are not magnetic. So forget the magnets. Metallurgy is complicated.</p>
<p><a href="https://i.sstatic.net/ZqtU5.gif" rel="nofollow noreferrer"><img src="https://i.sstatic.net/ZqtU5.gif" alt="enter image description here" /></a></p>
<h2>Density test</h2>
<p>Brass has a density of 8.5 - 9, stainless steel is below 8. Depends on the alloy. Might be a bit tricky to detect such small differences.</p>
<h2>Hardness test</h2>
<p>Better to do a hardness test. Hammer a nail made of mild steel into the nozzle, if the nozzle is softer than the nail, it's brass. If it's harder, it's stainless steel.</p>
<p>There are also HRC hardness scratch tests for that, although more intended for testing hardened steel. Find a chunk of structural steel and scratch the nozzle into it. Stainless steel will scratch the structural steel, brass &amp; aluminium will scratch itself.</p>
<h2>Spark test</h2>
<p>Use an angle grinder or a dremel tool: if there are sparks, it's steel. This is probably the easiest method.</p>

CC BY-SA 4.0
2023-01-30T22:45:54.537Z
2023-01-30T22:45:54.537Z
AzulShiva
<p>Let's preface, that there are a LOT of metal identification methods. For example, I found <a href="http://fac.ksu.edu.sa/sites/default/files/Metal%20Identification%20Ready%20_unprotected.pdf" rel="nofollow noreferrer">this guide</a> helpful and I had been at the scrapyard lately, where I have been told that 90+% of the time, steel objects that are non-magnetic are the more valuable stainless steel. The kitchen sink I dropped off? Stainless, non-magnetic steel. That's because <a href="https://www.reliance-foundry.com/blog/does-stainless-steel-rust" rel="nofollow noreferrer">about 70% of the made stainless steel is Austenitic Steel</a>, <a href="https://www.thyssenkrupp-materials.co.uk/is-stainless-steel-magnetic" rel="nofollow noreferrer">which happens to be generally non-ferromagnetic</a>.</p>
<h2>Magnetic test</h2>
<p>A common test in scrapyards is, to check if an item is magnetic, as <a href="https://www.meadmetals.com/blog/why-is-stainless-steel-not-magnetic" rel="nofollow noreferrer">a lot of stainless steels are non-magnetic</a> and then prove to be iron metals with a short spark test (see below).</p>
<h2>Tempering/Annealing behavior</h2>
<p>The very fact that the nozzles do change color to a brassy color that is commonly called straw is proof that it is indeed steel: heating up a piece of steel does alter the steel and also alters the surface color in a process called <a href="https://en.wikipedia.org/wiki/Tempering_(metallurgy)" rel="nofollow noreferrer">tempering</a>. The color is only the surface, and the mild straw color would become orange-brown, purple, pale blue teal and yellow if you were to heat it higher. Take a look at the tempering colors of steel here:
<a href="https://i.sstatic.net/hY7Pp.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/hY7Pp.jpg" alt="Steel temper colors" /></a></p>
<p>In contrast, brass acts differently when heated and <a href="https://www.highettmetal.com.au/blog/brass/how-to-temper-brass" rel="nofollow noreferrer">tempering</a> is somewhat different. Subjecting the piece of brass to heat you will not temper but <a href="https://en.wikipedia.org/wiki/Annealing_(metallurgy)" rel="nofollow noreferrer">anneal</a> it and you get colors differently. Instead of becoming straw before blue, Brass becomes dark, starting with its pale gold to go over a dark &quot;antique&quot; look to before going green, teal, purple-blue, red and then losing its color like this piece of a polished brass plate shows:</p>
<p><a href="https://i.sstatic.net/zqtQT.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/zqtQT.jpg" alt="Brass, annealed" /></a></p>
<h2>Hardness/Chip</h2>
<p>Another test that would be easy to conduct is hardness. The base idea of hardness is: An item can scratch a piece of equal or lower hardness, but not of higher hardness. If you have a chisel handy, then you have a piece of steel at hand. Most chisels are rated as HRC 58-62 - which is the Rockwell hardness scale. Brass could be <a href="http://www.matweb.com/search/DataSheet.aspx?MatGUID=d3bd4617903543ada92f4c101c2a20e5&amp;ckck=1" rel="nofollow noreferrer">all over the place</a>, depending on work hardening. But the identification is not by the hardness but by how the chisel - or better a graver - cuts.</p>
<p>We expect Brass to get a smooth cut with saw tooth edges while stainless cuts smoothly and has sharp edges to the cut.</p>
<h2>Sparktest</h2>
<p>If you want to scrap one, get an angle grinder or another power tool to grind at the nozzle. <a href="https://youtu.be/D094eBa4S7c?t=150" rel="nofollow noreferrer">Steel sparks</a> red-orange to whitish and depend on the mix, Carbide sparks very short and orange. Stainless creates a HUGE shower of sparks, yellow-white and dense, no burstes and branching. Copper, aluminium and Brass <strong><a href="https://youtu.be/D094eBa4S7c?t=428" rel="nofollow noreferrer">do not spark</a></strong>. Titanium is very bright white. It can <a href="https://www.youtube.com/watch?v=D094eBa4S7c" rel="nofollow noreferrer">tell you what kind of steel you have</a>: Stainless steel typically has medium-to-long, non- to low-branching, non- or low-exploding sparks.</p>
<p><a href="https://i.sstatic.net/aEyq2.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/aEyq2.jpg" alt="Photos of a spark test" /></a>
<a href="https://i.sstatic.net/tE9qc.png" rel="nofollow noreferrer"><img src="https://i.sstatic.net/tE9qc.png" alt="a spark test pattern chart" /></a>
<a href="https://i.sstatic.net/eqzvT.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/eqzvT.jpg" alt="a different spark test pattern chart" /></a></p>
<h2>Drilltest</h2>
<p>As we are at destroying a pair of nozzles, why not drill them? we should have done that before subjecting it to heat treating and grinding, but alas... Basically, we clamp the piece down and take an HSS drill to drill out the center.</p>
<p>Brass needs a different drill type but can be drilled and machined without coolant. Typical HSS drills from the home depot have a positive rake, brass wants a neutral or negative rake to drill or machine smoothly. If the piece grabs, creates short spials and dusty small flakes with an unmodified, new drill (or under positive rake machining), it drills like brass, as you see here from a <a href="https://youtu.be/pAngKHIZgyA" rel="nofollow noreferrer">Clickspring video on drilling brass</a>:</p>
<p><a href="https://i.sstatic.net/CgVeN.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/CgVeN.jpg" alt="HSS on Steel, ft. Clickspring" /></a></p>
<p>In contrast, stainless steel doesn't want to be machined <strong>without cooling</strong> at all and using high speed creates smoke quickly and nearly no chips at all. A moment later your tool starts to glow and gets a dull edge. If your drilling experiment turns a new drill blunt on high speeds or uncooled, you have stainless at your hands. To get chips, you need to work <em>slow</em> and have some sort of cooling. It is still a painfully slow process that needs a lot of pressure, but it gets larger, nesting chips like seen here from a <a href="https://www.youtube.com/watch?v=FMzIHl1HMXc" rel="nofollow noreferrer">Wayne Canning steel drilling tutorial</a>:</p>
<p><a href="https://i.sstatic.net/a5VG2.jpg" rel="nofollow noreferrer"><img src="https://i.sstatic.net/a5VG2.jpg" alt="Drilling HSS in Stainless Steel" /></a></p>
<h2>Rust test</h2>
<p>If you have established it is an iron metal via spark testing, you also have an exposed surface. There are commonly <a href="https://www.assemblymag.com/articles/94878-corrosion-of-stainless-steel-test-methods-and-proper-expectations" rel="nofollow noreferrer">three tests</a> to see the quality of stainless steel, which will show only minimal rusting on such an exposed surface.</p>
<ul>
<li>Copper Sulfate Solution will react with most non-stainless steels or contaminated stainless steels quite aggressively, while stainless steels react only minimally.</li>
<li>A high-humidity warmed chamber at about 30 °C results in a dense rust layer within 24 hours on exposed steel. Just dumping into water will do so too, so into a bucket and wait a day. If it's all over rusted, it's not stainless.</li>
<li>Saltwater spray is very corrosive on non-stainless steels, resulting in accelerated rust. While this test typically is run as a stress test for days or weeks to test exposure to marine life, a few hours will rule out non-stainless steel.</li>
</ul>

CC BY-SA 4.0
2019-10-10T19:30:25.657Z
A Q&A answerer from the Amazon page that the OP linked to says that they have machined the nozzles and reckons that they are stainless steel, which goes along with the suggestions in your answer to try machining it and see what it's like.
Andrew Morton
CC BY-SA 4.0
2023-01-16T12:58:00.757Z
Good answer, but what about steel vs stainless teel?
FarO
CC BY-SA 4.0
2023-01-16T13:55:37.300Z
see the new spark-test picture @FarO
Trish
CC BY-SA 4.0
2019-10-09T12:52:46.410Z
2023-01-16T17:46:40.880Z
2023-01-16T17:46:40.880Z
Trish
<p>Normally stainless steel is magnetic. But whenever i order stainless steel nozzles from Amazon, they are not magnetic. This makes me think they could be brass coated in something like aluminum. However, there are many types of steel.</p>

<p>I've attached an image of someone who reviewed these nozzles. He says they are not stainless steel because they are not magnetic.</p>

<p><img src="https://i.sstatic.net/FYGZr.jpg" alt="enter image description here"></p>

<p>But whenever I order "stainless steel" nozzles, even from other sellers, they are not magnetic. i already returned one pack from another seller and just received a nonmagnetic one from a third seller.</p>

<p>So that's it? Amazon just sells junk now? Or is there a way I can easily tell whether these are something other than colored brass / good for abrasive or high temp printing. Here is the product that was reviewed: 
AUSTOR 13 Pieces Stainless Steel 3D Printer Nozzles 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm Extruder Nozzle Print Head for E3D Makerbot <a href="https://rads.stackoverflow.com/amzn/click/com/B07CHZMGRH" rel="nofollow noreferrer" rel="nofollow noreferrer">https://www.amazon.com/dp/B07CHZMGRH/ref=cm_sw_r_cp_apa_i_XtrNDbRMVH8SW</a></p>

CC BY-SA 4.0
2019-10-08T23:04:28.863Z
Stainless steel (at least the versions I've tried) are not magnetic, so I'm pretty sure that's *not* a way to tell.
Pᴀᴜʟsᴛᴇʀ2
CC BY-SA 4.0
2019-10-08T23:06:27.100Z
But a screw (like the reviewer includes in the photo) is stainless steel and is very magnetic. Still, your comment helps.... Does the nonmagnetic kind hold up better than brass?
K Mmmm
CC BY-SA 4.0
2019-10-08T23:14:23.713Z
That's not stainless ... it looks to be zinc plated. Stainless isn't shiny like that ... unless it's in silverware.
Pᴀᴜʟsᴛᴇʀ2
CC BY-SA 4.0
2019-10-08T23:40:32.353Z
[This bolt is stainless](https://images.homedepot-static.com/productImages/2cf72e85-cd5c-4198-9b3b-06f51bebf434/svn/robtec-hex-bolts-rti2322610-64_1000.jpg) ... [this bolt is zinc coated](https://sc01.alicdn.com/kf/HTB1amm9KFXXXXcKXVXXq6xXFXXXe/Grade-2-Zinc-Plated-Steel-Hex-Bolt.jpg).
Pᴀᴜʟsᴛᴇʀ2
CC BY-SA 4.0
2019-10-11T13:36:56.933Z
There's always the Archimedes test. Submerge an equivalent mass of known-real steel in a clear glass of water and note the displacement. Then submerge your hot end. If the displacements are similar, they are the same material. But for what it's worth, Amazon has *always* sold junk.
Joel Coehoorn
CC BY-SA 4.0
2019-10-12T17:23:31.397Z
@steveantwan Some stainless steel are magnetic, this depends on his grade. the main test is simple; just add water then keep it one or couple of day out side, then see results.
Fernando Baltazar
CC BY-SA 4.0
2023-01-16T12:54:59.473Z
The correct answer is the one about Archimede. It won't distinguish between steel and stainless steel, but it's a good step.
FarO
<metal-parts>
How to tell if a nozzle is truly stainless steel?
K Mmmm
# How to tell if a nozzle is truly stainless steel?

(Asked by: username_0 on 2019-10-08)

Normally stainless steel is magnetic. But whenever i order stainless steel nozzles from Amazon, they are not magnetic. This makes me think they could be brass coated in something like aluminum. However, there are many types of steel.

I've attached an image of someone who reviewed these nozzles. He says they are not stainless steel because they are not magnetic.

![enter image description here](https://i.sstatic.net/FYGZr.jpg)

But whenever I order "stainless steel" nozzles, even from other sellers, they are not magnetic. i already returned one pack from another seller and just received a nonmagnetic one from a third seller.

So that's it? Amazon just sells junk now? Or is there a way I can easily tell whether these are something other than colored brass / good for abrasive or high temp printing. Here is the product that was reviewed:
AUSTOR 13 Pieces Stainless Steel 3D Printer Nozzles 0.2 mm, 0.4 mm, 0.6 mm, 0.8 mm, 1.0 mm Extruder Nozzle Print Head for E3D Makerbot [https://www.amazon.com/dp/B07CHZMGRH/ref=cm\_sw\_r\_cp\_apa\_i\_XtrNDbRMVH8SW](https://rads.stackoverflow.com/amzn/click/com/B07CHZMGRH)

**Tags:** metal-parts

> **Comments:**
> **username_1**: Stainless steel (at least the versions I've tried) are not magnetic, so I'm pretty sure that's *not* a way to tell.  
> **username_0**: But a screw (like the reviewer includes in the photo) is stainless steel and is very magnetic. Still, your comment helps.... Does the nonmagnetic kind hold up better than brass?  
> **username_1**: That's not stainless ... it looks to be zinc plated. Stainless isn't shiny like that ... unless it's in silverware.  
> **username_1**: [This bolt is stainless](https://images.homedepot-static.com/productImages/2cf72e85-cd5c-4198-9b3b-06f51bebf434/svn/robtec-hex-bolts-rti2322610-64_1000.jpg) ... [this bolt is zinc coated](https://sc01.alicdn.com/kf/HTB1amm9KFXXXXcKXVXXq6xXFXXXe/Grade-2-Zinc-Plated-Steel-Hex-Bolt.jpg).  
> **username_2**: There's always the Archimedes test. Submerge an equivalent mass of known-real steel in a clear glass of water and note the displacement. Then submerge your hot end. If the displacements are similar, they are the same material. But for what it's worth, Amazon has *always* sold junk.  
> **username_3**: @steveantwan Some stainless steel are magnetic, this depends on his grade. the main test is simple; just add water then keep it one or couple of day out side, then see results.  
> **username_4**: The correct answer is the one about Archimede. It won't distinguish between steel and stainless steel, but it's a good step.  

---

## 3 answers

### Answer by username_9 on 2019-10-09. Score: 8 | Accepted answer

Let's preface, that there are a LOT of metal identification methods. For example, I found [this guide](http://fac.ksu.edu.sa/sites/default/files/Metal%20Identification%20Ready%20_unprotected.pdf) helpful and I had been at the scrapyard lately, where I have been told that 90+% of the time, steel objects that are non-magnetic are the more valuable stainless steel. The kitchen sink I dropped off? Stainless, non-magnetic steel. That's because [about 70% of the made stainless steel is Austenitic Steel](https://www.reliance-foundry.com/blog/does-stainless-steel-rust), [which happens to be generally non-ferromagnetic](https://www.thyssenkrupp-materials.co.uk/is-stainless-steel-magnetic).

## Magnetic test

A common test in scrapyards is, to check if an item is magnetic, as [a lot of stainless steels are non-magnetic](https://www.meadmetals.com/blog/why-is-stainless-steel-not-magnetic) and then prove to be iron metals with a short spark test (see below).

## Tempering/Annealing behavior

The very fact that the nozzles do change color to a brassy color that is commonly called straw is proof that it is indeed steel: heating up a piece of steel does alter the steel and also alters the surface color in a process called [tempering](https://en.wikipedia.org/wiki/Tempering_(metallurgy)). The color is only the surface, and the mild straw color would become orange-brown, purple, pale blue teal and yellow if you were to heat it higher. Take a look at the tempering colors of steel here:
[![Steel temper colors](https://i.sstatic.net/hY7Pp.jpg)](https://i.sstatic.net/hY7Pp.jpg)

In contrast, brass acts differently when heated and [tempering](https://www.highettmetal.com.au/blog/brass/how-to-temper-brass) is somewhat different. Subjecting the piece of brass to heat you will not temper but [anneal](https://en.wikipedia.org/wiki/Annealing_(metallurgy)) it and you get colors differently. Instead of becoming straw before blue, Brass becomes dark, starting with its pale gold to go over a dark "antique" look to before going green, teal, purple-blue, red and then losing its color like this piece of a polished brass plate shows:

[![Brass, annealed](https://i.sstatic.net/zqtQT.jpg)](https://i.sstatic.net/zqtQT.jpg)

## Hardness/Chip

Another test that would be easy to conduct is hardness. The base idea of hardness is: An item can scratch a piece of equal or lower hardness, but not of higher hardness. If you have a chisel handy, then you have a piece of steel at hand. Most chisels are rated as HRC 58-62 - which is the Rockwell hardness scale. Brass could be [all over the place](http://www.matweb.com/search/DataSheet.aspx?MatGUID=d3bd4617903543ada92f4c101c2a20e5&ckck=1), depending on work hardening. But the identification is not by the hardness but by how the chisel - or better a graver - cuts.

We expect Brass to get a smooth cut with saw tooth edges while stainless cuts smoothly and has sharp edges to the cut.

## Sparktest

If you want to scrap one, get an angle grinder or another power tool to grind at the nozzle. [Steel sparks](https://youtu.be/D094eBa4S7c?t=150) red-orange to whitish and depend on the mix, Carbide sparks very short and orange. Stainless creates a HUGE shower of sparks, yellow-white and dense, no burstes and branching. Copper, aluminium and Brass **[do not spark](https://youtu.be/D094eBa4S7c?t=428)**. Titanium is very bright white. It can [tell you what kind of steel you have](https://www.youtube.com/watch?v=D094eBa4S7c): Stainless steel typically has medium-to-long, non- to low-branching, non- or low-exploding sparks.

[![Photos of a spark test](https://i.sstatic.net/aEyq2.jpg)](https://i.sstatic.net/aEyq2.jpg)
[![a spark test pattern chart](https://i.sstatic.net/tE9qc.png)](https://i.sstatic.net/tE9qc.png)
[![a different spark test pattern chart](https://i.sstatic.net/eqzvT.jpg)](https://i.sstatic.net/eqzvT.jpg)

## Drilltest

As we are at destroying a pair of nozzles, why not drill them? we should have done that before subjecting it to heat treating and grinding, but alas... Basically, we clamp the piece down and take an HSS drill to drill out the center.

Brass needs a different drill type but can be drilled and machined without coolant. Typical HSS drills from the home depot have a positive rake, brass wants a neutral or negative rake to drill or machine smoothly. If the piece grabs, creates short spials and dusty small flakes with an unmodified, new drill (or under positive rake machining), it drills like brass, as you see here from a [Clickspring video on drilling brass](https://youtu.be/pAngKHIZgyA):

[![HSS on Steel, ft. Clickspring](https://i.sstatic.net/CgVeN.jpg)](https://i.sstatic.net/CgVeN.jpg)

In contrast, stainless steel doesn't want to be machined **without cooling** at all and using high speed creates smoke quickly and nearly no chips at all. A moment later your tool starts to glow and gets a dull edge. If your drilling experiment turns a new drill blunt on high speeds or uncooled, you have stainless at your hands. To get chips, you need to work *slow* and have some sort of cooling. It is still a painfully slow process that needs a lot of pressure, but it gets larger, nesting chips like seen here from a [Wayne Canning steel drilling tutorial](https://www.youtube.com/watch?v=FMzIHl1HMXc):

[![Drilling HSS in Stainless Steel](https://i.sstatic.net/a5VG2.jpg)](https://i.sstatic.net/a5VG2.jpg)

## Rust test

If you have established it is an iron metal via spark testing, you also have an exposed surface. There are commonly [three tests](https://www.assemblymag.com/articles/94878-corrosion-of-stainless-steel-test-methods-and-proper-expectations) to see the quality of stainless steel, which will show only minimal rusting on such an exposed surface.

* Copper Sulfate Solution will react with most non-stainless steels or contaminated stainless steels quite aggressively, while stainless steels react only minimally.
* A high-humidity warmed chamber at about 30 °C results in a dense rust layer within 24 hours on exposed steel. Just dumping into water will do so too, so into a bucket and wait a day. If it's all over rusted, it's not stainless.
* Saltwater spray is very corrosive on non-stainless steels, resulting in accelerated rust. While this test typically is run as a stress test for days or weeks to test exposure to marine life, a few hours will rule out non-stainless steel.

> **Comments:**
> **username_6**: A Q&A answerer from the Amazon page that the OP linked to says that they have machined the nozzles and reckons that they are stainless steel, which goes along with the suggestions in your answer to try machining it and see what it's like.  
> **username_4**: Good answer, but what about steel vs stainless teel?  
> **username_9**: see the new spark-test picture @username_4  

---

### Answer by username_5 on 2019-10-09. Score: 3

Stainless steel is created by adding elements (usually Chromium, but also Nickel) to steel. These added elements form an oxide layer with the outside air protecting the steel from corroding.

Whether stainless steel is magnetic or not depends on the added elements and the micro structure of the steel; some are and some aren't magnetic.

From [physlink](https://www.physlink.com/Education/askexperts/ae546.cfm):

> As for whether they (red. stainless steels) are magnetic, the answer is that it depends. There are several families of stainless steels with different physical properties. A basic stainless steel has a 'ferritic' structure and is magnetic. These are formed from the addition of chromium and can be hardened through the addition of carbon (making them 'martensitic') and are often used in cutlery. However, the most common stainless steels are 'austenitic' - these have a higher chromium content and nickel is also added. It is the nickel which modifies the physical structure of the steel and makes it non-magnetic.

So the answer is that you cannot determine by testing for magnetic properties if the nozzle is stainless steel or not. But if it is not magnetic, it can be stainless steel. Note that discoloration is possible, this is the oxide layer.

To identify if the steel is stainless, you could without sacrificing the nozzle (according to [this reference](https://www.hunker.com/13401485/how-to-tell-if-stainless-steel-is-real)):

> **Step 1**  
> Stick the magnet on the piece you are testing. If it holds firmly, the metal is possibly stainless steel. If not, it is (red. could be) another metal such as aluminum.
>
> **Step 2**  
> Pick a spot on the piece that you don't mind damaging a little.
>
> **Step 3**  
> Fill the eye dropper with [muriatic acid](https://en.wikipedia.org/wiki/Hydrochloric_acid). Drop a small amount of the acid on the test spot. Wait half an hour.
>
> **Step 4**  
> Wipe the acid off the piece. Examine the test spot. If it is discolored, the piece is stainless steel.

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Note that the image you posted shows a Zinc plated steel screw, not a stainless steel screw.

> **Comments:**
> **username_6**: It seems to me that Step 1 reveals nothing according to previous quote "...that depends," which makes me doubt the muriatic acid (hydrochloric acid) test is valid, especially as it says nothing about the nature of the discolouration (I could be wrong). A better test might be to file a groove in the surface and immerse it in salty water overnight: if it goes rusty, it isn't stainless steel.  
> **username_5**: @username_6 I've left it as a quote of the complete steps, but indeed step 1 is not necessary considering the other quote. If I would have left out step one, I would have received comments about "where is step 1". Thanks for the comment, if you have a better reference, please feel free to alter the answer.  
> **username_7**: Anecdotal note - In the late 1960s the USN machine shops I served in used a nitric acid test with instant results. Carbon steel stained black; monel (a salt-water resistant copper nickel alloy we used extensively) stained green; stainless steel didn't react at all.  

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### Answer by username_8 on 2023-01-30. Score: 0

The other answers are good. For a more practical answer:

## Magnet test

As answered by username_9, steel with an austenitic atom structure, which most stainless steels have, are not magnetic. So forget the magnets. Metallurgy is complicated.

[![enter image description here](https://i.sstatic.net/ZqtU5.gif)](https://i.sstatic.net/ZqtU5.gif)

## Density test

Brass has a density of 8.5 - 9, stainless steel is below 8. Depends on the alloy. Might be a bit tricky to detect such small differences.

## Hardness test

Better to do a hardness test. Hammer a nail made of mild steel into the nozzle, if the nozzle is softer than the nail, it's brass. If it's harder, it's stainless steel.

There are also HRC hardness scratch tests for that, although more intended for testing hardened steel. Find a chunk of structural steel and scratch the nozzle into it. Stainless steel will scratch the structural steel, brass & aluminium will scratch itself.

## Spark test

Use an angle grinder or a dremel tool: if there are sparks, it's steel. This is probably the easiest method.


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