Black Finish Suggestions on 301 SS

[hendersdc]

I have a few small sheet metal flat springs made from 301 SS. In this case small means around 0.5 mm thick and about 25 mm longest dimension. I need the parts to have a black finish to reduce reflected light. These parts are going inside a device with light sensitive components. Abrasion resistance is also a concern. Can anyone suggest finishes that might work for this application?

 

[drawoh]

hendersdc,

You can apply a black zinc plate, but as far as I know, it is shiny. Why do you need 301SS? If you make the springs out of aluminium, you can apply matte black anodize. If you use black delrin, you can apply rough, machined finish, perhaps 250/500[μ]in RMS.

--
JHG

 

[hendersdc]

drawoh, that was my concern about black zinc as well. I am really not comfortable with aluminum springs, I don't trust it to not take a set over time. I don't know if we have room for plastic, I'll see if I can make that work.

Do you know if 301 SS can have black oxide applied?

 

[drawoh]

hendersdc,

If you know how the springs are being bent, you should be able to do the structural analysis. I do this all the time. Stainless steel and aluminium are not particularly good spring materials, as they do not tolerate a lot of deflection. Delrin usually is better. If you need a lot of force, look into beryllium copper, or titanium.

Can you paint this thing?

--
JHG

 

[Sparweb]

Spring steel (such as AISI 1095) is normally carburized because it softens the surface, slightly. The side effect is blackening of the steel, which may be the appearance you're looking for, in the BEST metal for most spring applications.
See attached.


STF

 

[Nescius]

How about Cerakote thin film ceramic/polymer or similar?

 

[IRstuff]

Have you considered bluing? Bluing will reduce the reflectivity, although one might consider light shielding as a separate thing. It's better to keep the light from getting in at all than trying to kill reflections after the fact.

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[NBrink]

I know I've seen black stainless fasteners before. Google tells me MIL-DTL-13924D calls out an "Alkaline oxidizing process" for abrasion resistant black finishes on 300 series stainless. Might be worth asking around if anyone can do a MIL-DTL-13924D class 4 black oxide coating...



Nathan Brink

 

[tbuelna]

There are many durable proprietary black optical coatings that can be applied to a 301 cres material surface. You'll have to check on the price though.

http://www.acktar.com/category/Technology

 

[hendersdc]

Thanks for all the suggestions everyone! I'll look into all this and let you know where we land.

 

[sreid]

http://www.ssina.com/publications/spe_fin.html

 

[DanStro]

You can take a look at Black Nitride, it's reasonably dull. In the past when I had similar applications we'd bead blast or thread the surface and then paint it.

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