Fringe LAB Experiment - "Burnt" Stainless

[FringeXVO]

As a couple of you may already be aware, I design and build various things of an electro-mechanical nature. I've recently produced a few limited sets of exhaust tips for the HKS resonated systems, and one request I've gotten several times over (for other tips as well) is the burnt look. Being a scientist/engineer, I've decided to tackle the issue and share my progress with you here.

First a little background on the phenomenon, since without understanding what we are doing when we do it, we have no hope of acquiring any semblance of control over the results.

All metals oxidize...except gold. In the cases of Ti or stainless alloys, the layer of oxidation that develops is invisible to the human eye. The reason we perceive color when the material is exposed to high levels of heat is because the heat causes a chemical reaction between the oxygen in the atmosphere and the resulting layer of oxidation has a thickness that interferes with certain wavelengths of light as they reflect off of the material. This is the same effect that makes certain insects appear to look like they have a metallic green, blue, purple, or pink hue to their shells or wings and why a super thin film of oil on water creates the rainbow affect in a puddle of water on the street. Depending on the thickness (measured in nanometers...just like wavelengths of light in the visible spectrum) different colors are either blocked or reflected.

So heating stainless to a specific temp will force it to develop a certain thickness of its oxidation layer, which will result in a specific color being "produced".

Using some spare parts from my previous GTR Afterburner tips, I have begun experimenting with the specific methods, techniques, times, and temperatures in order to develop a variable recipe that will allow me to make sets of burnt tips with beautiful, vibrant, and uniform colors. I'm going to use different heating methods along with different techniques for material preparation in order to generate a wide variety of results and narrow down which methods produce what I consider to be the "best" results. Varying the time will yield lighter or darker colors.


Experiment 1: What affect does the material roughness have on the color?

Initially I used one formed outer tip and prepared the fins 4 different ways. I left several raw, I used a grinder with a flap disk on 3 fins, I used a brass wire wheel on 3 fins, and I used an orbital sander on 3 fins. I then took a handheld Propane/Mapp gas (yellow bottle) torch and proceeded to hand-heat steel.

RAW


FLAP DISK


WIRE WHEEL


ORBITAL SANDER



I discovered immediately that without implementing some sort of mechanical control of the tip, getting any semblance of even heating on each fin is quite difficult...especially when you have standards as high as mine. I have a solution for this already, I believe.

Another experiment was to heat the edges of the tip using an electric stove burner. While this worked and did yield more even results, it was painstaking and time consuming. The burner being a coil worked against being able to heat the fins perfectly evenly.



I have ordered some polishing supplies for stainless steel from Eastwood and will be experimenting to see how bright I can get the stainless oxidation layers. I am sure it will never be as bright as the effect is when done on titanium, but I should be able to get some decent results. Over the next week or two I will be furthering this and I will share most of everything I learn. I might have to keep a secret or two for myself, however. You understand.

-Chad K

[wheee!]

hmmmm...

what if the tips were mounted on a lathe and rotated to a constant speed and the heat was applied to the tips at a constant and even rate. Then enclose the lathe area in an small enough area to add a small amount of the mineral corundum in a powdered aerosol or other form to bond with the tips at the molecular level during the heating process. This may produce a deeper bluing effect (depending on the variant of corundum). Corundum is a durable oxide mineral with a mohs hardness value of 9. Just a thought....

geeks continue reading below...

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Corundum - Wikipedia, the free encyclopedia

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http://www.mtc.edu.eg/ASAT13/pdf/MS15.pdf

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The effect of bond coat on mechanical properties of plasma-sprayed Al2O3 and Al2O3?13wt% TiO2 coatings on AISI 316L stainless steel

[FringeXVO]

I put another spare tip in a small wood lathe and fired it up. It will take a slower speed or hotter flame or a LOT longer time with this particular setup. I ended up slowly rotating the tip by hand.

The surface finish was done a long time ago and this whole tip was surfaced with an orbital sander.







Here are a few shots of the color progression:










This is what I've got so far with just spinning and heating a sanded surface, then quenching.






I'm going to get a hold of some Corundum as suggested and possibly start varying the oxygen content.

-Chad

[wheee!]

Cool work Chad! I like the way you think....

[Scone]

This is truly a cool thing to be able to do. I saw a few threads awhile back and we tried it on my roommate's Skyline. Took awhile before I finally got the hang of it but I like the outcome.

[Cbtech]

Ummm....

[Alstann]

I'm glad to see this working along Chad! I'm confident you can produce the result I desire.

[FringeXVO]

I started off by having these media blasted by Chris of Enigma Motorsports, then used a stainless polishing kit from Eastwood and followed the 3 step process. I then cleaned them, put them on a lathe, and have started building the oxide layers...and that means fire.

I'm gonna do this in stages and see what I can do with different looks. I like the relatively high gloss base material and I think it shows promise. I'm gonna run the gamut with the temps and see what else I can come up with.

Polished:



I must say I feel it was difficult to get my phone to capture the gold well, but these pictures are close enough for now.






I went a little longer to darken the gold a bit.

[wheee!]

I wonder if the polishing compounds are affecting the colour of the burn??

[FringeXVO]

Between cleaning the mechanically polished tips with brake cleaner and soap and water, there should be no compounds left on the surface.

[FringeXVO]

Update:

I did burn the rest of it, but it honestly looks a lot like the previous versions, just shinier. It's still not even enough. I have acquired several components of an oxy acetylene setup and once I have the rest I will try again with a MUCH hotter flame.

[Zbrah]

Originally Posted by Scone

This is truly a cool thing to be able to do. I saw a few threads awhile back and we tried it on my roommate's Skyline. Took awhile before I finally got the hang of it but I like the outcome.

Serious? please post pics of your result

[wheee!]

Hey Chad! Clean out your inbox!! lol

Can't PM you....

[FringeXVO]

Sorry all, I got fed up with Wells Fargo and moved my accounts. Working on getting updated info so I'll be blue again. Give it a day or two. Anyone can email me at chad.kassem@fringexvo.com if they need to get a hold of me.