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How safe is passivated 304 or 316 stainless for children?  

June 20, 2008

I've been reading Finishing.com now for about three hours and what a great education! However, I'm unable to put my finger on the answer to a couple questions.

I'm having alphabetic letters, laser cut out of either 304 or 316 stainless steel (.075"). The letters will be cut using nitrogen gas to avoid dark edges from the laser. The finished product will receive a brushed surface and eventually be passivated. Sorry, I don't have the passivation details at the moment. These letters are intended to spell my 1 year old daughters name.

Question one, once the letters are cut, I'd like to smooth the edges so they're not sharp. What can I use to smooth the edges so I do not introduce other metals (iron for example) into the stainless. I assume some sort of stone grinder would introduce iron and such? Scotch-Brite™ would not be strong enough to smooth the edges I don't believe.

Once the edges are smooth, I'm sending the letters back to the shop to be passivated. Question two, once passivated, how safe is the stainless for my daughter to handle? I assume this will be a liquid passivation of some sort and will be thoroughly rinsed, etc. I'm concerned because my daughter will likely be handling the letters and its inevitable they could end up in her mouth at some point. I guess another way to ask this question is how is stainless passivated for the food/flatware industry compared to my finished product of brushed 304 or 316 passivated stainless? I just want to be sure its safe.

Thank you for your time and consideration of this request.
Gunther

Gunther Miller
Hobbyist - Severn, MD, U.S.A

Hi, Gunther. Very Safe. Typical grinding and sanding tools can be used for stainless, proportional to the amount of removal needed and the final finish. I believe scotch-brite will work but that you probably need to use it on a power tool rather than by hand. You are correct that the tools must not be contaminated with iron. Most shops that offer passivation will have the ability to do this mechanical polishing for you if you want them to, and they will have the discipline of not mixing steel polishing tools with stainless, but if you want an exact brush finish you may need to do it yourself.

There is no secret to the removal of the passivation solution, just good rinsing. So, to feel good, rinse them well yourself before letting your child at them. You could perhaps have the letters electropolished rather than passivated if you wish. This achieves passivation, but also leaves the surface free of microscopically small burrs and clods, so it is the ultimate in clean and cleanable; but then you wouldn't have a brushed finish.

Regards,

Ted Mooney, P.E.  finishing.com Brick, New Jersey

No problem at all as surgical instruments are stainless and so are some parts of implants in the body.
If you are paranoid about it, just boil them in a Pyrex dish and distilled water for a couple of minutes and rinse with cold distilled water.

James Watts
- Navarre, Florida

Ted, James, your input is greatly appreciated. My concerns have been reduced and I'm comfortable proceeding.

I'll consider the electropolishing also over passivation, since clean is generally a good idea with small children.

Thanks again for taking the time to respond and looking after the little people in this fascinating industry.

Gunther

Gunther Miller
- Severn, MD, U.S.A

We are the little people :-)

Ted Mooney finishing.com Brick, New Jersey