Anodizing can be a really cool way of getting interesting colors on metal, and can sometimes be used as a way to make the metal more durable.
Can stainless steel be anodized? Stainless steel cannot be anodized in the true sense of the word unless a hot caustic solution is used. There are, however, a few alternative ways to achieve some similarish results to anodizing, like what you would expect with titanium and aluminum.
If you’re just wanting your stainless to turn a different color, then you’re probably thinking of heat coloring. Some people call this “heat anodizing”, which is a totally incorrect term and has nothing to do with anodizing.
Ok, so anodizing probably isn’t what you want, but there are a few other things that might match what you’re looking for. Let me explain why this is, a couple of alternative options, and how you can belligerently “anodize” it anyway.
What is Anodizing?
Anodizing is a process that forms an oxide layer on metal. It’s an electrolytic process, which means that it uses a DC current to create a chemical reaction. In this case, it’s oxidation.
The workpiece becomes an anode, which is the electrode where the electricity enters the circuit. This is where the term “anodizing” comes from – you’re turning that metal object into an anode, thereby anodizing it. Sorta like when you’re in the act of destroying something, you’re destroyitizing it.
The result is that any kind of oxidizing environment is made a million (rough guesstimate on my part) times stronger when you add this electrical current properly. Essentially, you’re making the metal oxidize super fast.
Ok, that was pretty boring. But it’s important to understand the rough idea if you want to understand why you probably don’t want to do a true anodizing on stainless.
How Does Anodizing Change the Color of Metal?
Two ways, depending on the material:
For aluminum, it makes the surface porous. On its own, anodized aluminum just becomes a kind of duller grey. But there’s a perk of this dull, porous surface.
Usually, aluminum is super smooth and it’s next to impossible to make any kind of coating stick to it. When you give it that porous anodized surface, though, this changes. These pores make it really easy for dyes to “seep in” to the surface and color the top layer of the aluminum. This also allows you to get nearly any color imaginable.
So anodizing itself doesn’t give you those bright, vibrant colors, but it does make them possible through additional processes.
If you want to know more about anodizing aluminum, check out this article about how to anodize aluminum at home.
Another alternative to dying is through powder coating or painting. Since the surface is now porous, coatings can really bite in to the surface of the aluminum.
Titanium colors for a totally different reason. You don’t need any dye, paint or otherwise. This is because the oxide layer on titanium, when uniform, can cause diffraction.
Diffraction messes with light waves. The oxide layer on titanium (also niobium and tantalum, but those are way less common) creates a surface that will break up all but one size of light wave, which will correspond to a particular color. The distance between the high spots on this textured surface will determine which color this is. You are comparatively more limited on colors for titanium.
I don’t want to get too off track with science here, but the point is that anodizing titanium gives it an oxide layer that messes with light waves, making it appear to change color without needing to add any coating or coloring to the metal. Different voltages will give different surface conditions, resulting in different colors. Whew.
Why Anodizing Stainless Doesn’t Work
Technically, anything can be anodized. You can throw your neighbor’s annoying, yowling cat into a bucket of water and wire it up. If the cat is on the receiving end of the electrons, you’ve got yourself an anodized cat.
So really, you can anodize stainless, but it’s definitely not a project worth your time. Aluminum and titanium, yes. Stainless, no.
Apparently some guys have been able to anodize stainless is by using a hot caustic solution. This is the kind of stuff that people do in a lab. Usually they wear massive goggles and hazmat suits, and it’s generally not very practical for most real-life situations. Keep it out of your garage.
Even still, there’s not a lot of public information on the process or how well it works.
Most professional companies that specialize in treating stainless won’t call their coloring process “anodizing”. They’ll simply refer to it as “stainless coloring”, and their processes are, for the most part, extremely proprietary.
So what happens when you try to anodize stainless?
Since stainless doesn’t corrode, it just dissolves. That’s not to say that you’ll get an instant bucket of sludge. But that outer surface would just get gradually eaten away. You won’t get that oxide layer.
If anything, the surface of the stainless will just get etched.
Other Viable Options
So now that your dreams of anodized stainless are thoroughly demolished, let’s go over a few options that might be able to get the results your looking for.
“Flame Anodizing” or Heat Coloring
This goes by a few different names – temper coloring, heat coloring, heat anodizing, flame coloring… you get the idea.
The process has pros and cons. The general idea is that at certain temperatures, the surface of the metal will change texture and diffract the light waves. This results in essentially the same thing as anodizing titanium, but it is not an anodizing process. There’s no electricity used.
The advantage of this is that it’s super easy. Just get a torch and heat it up until it’s the color you want. Now depending on the grade of stainless, the temperatures will correspond differently to the colors you get. That said, the color gradients are the same, you just might need to go a bit hotter or a bit cooler to get them.
Here’s a little chart on the temps you need to color 304 stainless (one of the most common types out there):
|Pale Yellow||550 F|
|Straw Yellow||640 F|
|Dark Yellow||700 F|
|Purple Brown||790 F|
|Dark Purple||840 F|
|Dark Blue||1110 F|
So if you have, for example, 309 or 316 stainless, those temps will be off a bit, but the color progression will be the same.
Coloring stainless consistently in a controlled kiln or heat treating oven, but it can definitely be done by hand. It just takes a bit more skill and practice, especially when it comes to keeping the heat even.
Pro Tip: If you’re coloring it with a torch or some other manual method, heat the center of the metal first and let the heat work its way outward.
The cons? The coloring scratches and wears off super easy. Like you could softly scrape your car keys across the colored surface and it’d come right off. So if you want this to last somewhat longer, you might want to consider using some kind of clear coat.
If this is the route you want to take, I’d recommend you pick up some of this clear coat.
Hard Coating (Ceramic, etc)
This is my preferred way to color stainless steel. There are a lot of options and great products out there, but (in my opinion) the most tried-and-true solution is Cerakote. It’s what people commonly use to finish their firearms and other related gear.
Cerakote is great because it’s insanely hard and it seriously can take some abuse. Plus it’s easy to apply (usually you’ll need an airbrush) and it’s really not expensive at all. Here’s a link for you to check it out for yourself.
There are a few alternate brands out there, but they’re not much cheaper and this one is the original. Might as well stick with what works.
Seriously, though, if you want to put some color on stainless, this is the best way to do it.
This is the “economy” way of coloring stainless. While there are some expensive paints out there, the large majority are uncomfortably budget friendly with performance to match.
I’ve honestly not had terrific experiences with just a basic paint, but sometimes it really doesn’t matter. If you just want to spray it and don’t care about whether it can take abuse (i.e. wall art) then just pick up a spray can of Rustoleum and go to town on it.
Ok, maybe I was a little hard on this option. There are some applications that totally call for a can of Rustoleum. But seriously, for a bit more money, Cerakote is going to perform way better.
Usually this is a process done to regular steel to make it more corrosion resistance, but you can also do it to stainless. This is definitely a possibility if you’re just wanting to make the stainless black.
You can buy kits online, but they’re usually a little harder to find. The large majority of the kits out there will not work on stainless. If you find something that looks like it might work, talk to customer service to make sure it’ll suit your application.
Anyway, that’s an outline of your options for “anodizing” stainless steel. Hopefully you’re now inspired to make something wonderful.
If you’re looking at different ways to treat metals, here are a few more posts that you might be interested in: