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> Does anyone know how I can blacken stainless steel? I can get some
> discolouration by heating it, but I'm after a even, deep black
First question, what grade stainless are you working with? I work
with type 316L stainless so these are my experiences, you may get
different results with different grades of stainless.
Heating the stainless will give you the most lasting darkness, abeit
its not a true black, but it is the SAFEST way to achieve a darker
color on stainless that is not an oxide coating. I will also say
that getting a true black on stainless is very difficult, its more
of a blue black/dark grey that is achieved.
Rio carries a product called *Black Max* this will oxidize stainless
but the coating will wear. Applying this to a heated piece makes for
a more durable oxide, but difficult to control the evenness of
color. This is good for surfaces that are below the main wear
Now if you want to get serious, hit up www.epi.com they carry
several products that work well. Both in a room temperature product
and a heat applied product.
I will prempt the usage of these products by saying that both of
these products should be taken very seriously in the personal health
department, these are industrial products and should used with
respect, so use adequate protection and ventilation, espeically if
you are dealing with the acids involved.
Insta-Blak SS-370 is one product i use, its room temperature
blackening agent and on type 316 stainless works well if applied
correctly. Once again this product produces results similar to the
Black Max and the oxide will wear. You will get more durable results
by heating the piece (or solution) prior to application, or by
cleaning the part in an acidic solution (muratic acid works
decently, this strips the chromium oxide off the part). USE ADEQUATE
VENTILATION and proper respitory devices with this product,
especially if you use the acid bath prior.
Ultra-Blak 407 is a heated solution that you immerse the stainless
into, you also have to prep the stainless with an acid solution
(muratic acid works in a pinch) prior to clean the surface and get
rid of the chromium oxide layer. this product works very well and
has a good resistance to wear. The down side to this products is you
really are dealing with some nasty chemicals that have a HUGE
potential for personal harm. Once again, this is a very industrial
product so use extreme caution.
With all these chemicals please consult EPI for proper
health/safety/hazzard/disposal related issues.
With all these solutions you will get a more even color by bead
blasting the part producing an even surface finish.
Now if your looking for a polished black on stainless, to date i
have found nothing that can achieve this in a small setting. PVD
coatings work well but are normally for large runs of product and
are not condusive for doing single parts. Black chrome plating is
another option that i have not yet done research on.
Other options are physical methods like powder coating, epoxies, or
similar coatings. Good luck and be safe if you try any of these