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Etching s/s

2005

SIR,

AS A HOBBY I HOT FOIL ON PLASTIC FOR LEPAL BADGES I HAVE BEEN ASKED TO MAKE BADGES IN STAINLESS STEEL WITH A PAINT FILL CHECKING THE INTERNET I HAVE FOUND DIFFERENT SOLUTIONS TO USE.

WHICH ONE IS THE BEST TO GIVE THE FINEST DETAIL?

I AM USING A PHOTO RESIST AND POSITIVES FOR MY ART WORK.

LISTED BELOW ARE THE SOLUTIONS I HAVE BEEN GIVEN

1) 150cc HYDROCHLORIC ACID

50cc NITRIC ACID

1lt WATER

2) 35% --40% FERIC CLORIDE

3) FERIC CLORIDE

NITRIC ACID

4) 300cc Hydrochloric ACID

200cc SULFURIC ACID

1 lt WATER

5) 30cc HYDROFLORIC ACID

100cc NITRIC ACID

       50 grms NH2HF (I cannot find out what this is)

THANKING YOU

NOLAN MEYER
- South Africa

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2005

Those are some pretty nasty chemicals to be playing with, especially as a hobbyist. I would have serious concerns in using some of those mixtures in even the most controlled environments. Certainly playing with HF is to be avoided at all costs and ammonium bifluoride (NH2HF)isn't much better.

Of all of your mixtures I would suggest you use ferric chloride ⇦ this on eBay or Amazon [affil links] , but take care this substance is extremely corrosive and canbe highly reactive when initially added to water.

Definitely try not to use the acids, even the skilled professionals handle these with extreme care!

Brian Terry
Aerospace - Yeovil, Somerset, UK

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First of two simultaneous responses --

Firstly, I would suggest you use a 200 or 300 series stainless steel, preferably 304, 316 etc. Using some of the more esoteric ones may cause problems; also do not use heat treatable ones as you can get problems with fine line definition. As fra as acids are cocnerned, I would dtrongly advise you avoid the hydrofluoric acid one; it is extremely toxic, very dangerous and will give you nasty burns. You will also have environmental and waste problems. The other ones based on hydochloric acid and nitric acid are not so bad, but hydrochloric acid fumes a lot and is very pungent. Personally I would opt for the 35-40% ferric chloride ⇦ this on eBay or Amazon [affil links] bath as this is the simplest to control. However, be warned it is a very evasive liquid and will creep everywhere. It is also very corrosive, as they all are, and will stain things brown.

Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2005

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Second of two simultaneous responses --

My advise would be to stay away from hydrofluoric acid. It is so eager for human tissue that even if quickly washed after contact, it may continue it's path through flesh to end up eating the bone away and turning it into something like tooth paste. Many cases of repetitive plastic surgery, amputation or death are owed to it. Nitric and sulfuric acids are still dangerous but far from that. ferric chloride ⇦ this on eBay or Amazon [affil links] and hydrochloric acid pose relatively minor danger. A technique using reverse current attack might work for you and it requires less potent mixtures. In any case, the Material Safety Data Sheets (MSDS) must be read and followed and disposal done according to local regulations for every chemical substance.

Guillermo Marrufo
Monterrey, NL, Mexico
2005