Sound technical content, curated with aloha by
Ted Mooney, P.E. RET
Pine Beach, NJ
The authoritative public forum
for Metal Finishing since 1989
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Chemical and electrochemical etching of stainless steel
Q. I am facing problem in stainless steel etching process. What are the chemical to etching (fast) stainless steel and what is the process involved in it? I want to etch over stainless steel back of watch. How should I get print a design over it?
Manish Tyagi- India
2001
A. One of many chemicals to etch stainless steel is ferric chloride
⇦ this on
eBay or
Amazon [affil links] solution.
It can be brought as a solution or made from solid, if you make from solid take care as it generates a fair amount of heat on dissolution, about 30% by weight is a good enough etch.
It can be used cold and removes approx. 0.0003 inch in two minutes leaving a matte grey finish (on S80 stainless steel).
As to designs try a few paints and see how they respond to the solution.
A few years ago at school I made a PCB using a marker pen to draw where the tracks were on a copper board and used ferric chloride ⇦ this on eBay or Amazon [affil links] to remove the copper. Sorry but I can not remember what sort of marker it was - try some pens and see what happens.
Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England
2001
Q. Thank you Martin,
ferric chloride ⇦ this on eBay or Amazon [affil links] is very slow. Actually I am using 314SS. Can you suggest me any other chemical? What about Chemical Milling process?
Manish Tyagi [returning]- India
2001
A. Hi, Manish.
Letter 33699 suggests adding 20 g/l of HCl and provides references. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
2001
A. Dear Manish:
You can try with electrochemical reaction rather than the chemical alone. Apply a reverse voltage during immersion (part is the positive), graphite or platinum can serve as cathodes for extended periods and use the same ferric chloride ⇦ this on eBay or Amazon [affil links] solution, this will increase etch rate.
Guillermo MarrufoMonterrey, NL, Mexico
2001
Q. I would like to know the chemical mixture to etch the stainless steel metal for a certain dept.-- enough to fill it with paint. I know ferric chloride ⇦ this on eBay or Amazon [affil links] will etch the surface, just to remove the glossy surface and to result in grey finish. What I need is to etch it in certain depth. Thanking you in anticipation.
Jacob Berberian- Kuwait
2004
How does photochemical milling work?
I want to try and design belt buckles from aluminum and brass. I want to know if photochemical milling is easier than CNC milling for this process? Also how does photo chemical machining work? Where can I purchase the equipment for this process? What kind of equipment would I need in order to do this process and how much would that machinery cost? Any information on this subject would be greatly appreciated.
ErcanHobbyist - Southfield, Michigan, United States
2005
Its all horses for courses. If you have thousands of simple buckles to make that are little more than 2 dimensional, use electrochemical machining, but if you have to add one-off with intricate filligree on the surface you may prefer CNC. Electrochemical machining (aka electrochemical etching) is done by creating a pattern on the surface of the metal using photoresist. This is like a light sensitive paint that can be patterned by exposing to it the correct wavelength of light, but through a pattern, or mask. The unexposed resist is then dissolved away and the exposed metal is etched away by a suitable chemical. The favourite ones are ferric chloride ⇦ this on eBay or Amazon [affil links] and cuprous chloride. Both will have significant environmental impacts and high disposal costs. Capital investment in the etching unit, photoresist applicator and light box could be prohibitive.
Trevor Crichton
R&D practical scientist
Chesham, Bucks, UK
2005
Q. We are in the field of Medical industry. One of our products for which we require the chemical name and etching process, how we can etch on Stainless steel, magnetic and non-magnetic metal sheet as ruler marking with 0.01 to 0.03 deep etching.
Iqbal BhuttaManufacturer of Medical Devices - Sialkot, Punjab, Pakistan
2007
A. Hi, Jacob; hi, Iqbal. I'm not experienced in this, but letter 28409 suggests via photographs that you are in error in believing that ferric chloride ⇦ this on eBay or Amazon [affil links] can only remove glossy surfaces and not actually etch patterns into the metal. You may find it informative. Good luck.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. I want to fast etch SS so what can I use for more depth.
M Imtiaz- Sialkot, Pakistan
January 2, 2010
Q. I want to fast etch SS so what can I use for more depth.
PRASHANT KATHUMARIA- JHANSI,U.P., INDIA
January 28, 2011
Hi, cousins. Imtiaz's inquiry has been ignored by thousands of readers for over a year now, and Prashant's copy&paste probably will be too. The responders apparently don't like to simply repeat themselves. Please take a few seconds to read the previous entries on this thread and try to phrase your further questions in terms of what has already been said. Then, we will be able to keep the thread moving forward, rather than running it in circles, and I think everyone will happy. Thanks!
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
June 7, 2011
A. As an artist who routinely uses etching methods, here are my observations:
-The rough, sandblasted look in ferric chloride
⇦ this on
eBay or
Amazon [affil links] is often because salts have settled on the metal during the etching process and blocked the chemical from reaching the base evenly. Large open areas are more prone to uneven etching. Check these areas often (brush clean) to be sure they are free of any salt buildup.
-An absolutely clean and degreased surface is mandatory before you apply the resist and during handling. I usually use Bon Ami
⇦ this on
eBay
or
Amazon [affil links]
or Barkeepers Friend
⇦ this on
eBay
or
Amazon [affil links] .
with a Scotchbrite pad to polish the metal clean. Those cleaners don't have chlorine in them. (Comet has chlorine- which might cause problems). Be sure to rinse well and then don't touch the surface. Check to make sure that water sheets evenly over the surface. If it separates in an area - like rain on a waxed car- go back and clean that area again until the water sheets over it. This can't be stressed enough. Fine sandpaper can also be used as long as you are sure to clean away the residue.
- Oils from your fingers (or anything else) that gets on the surface may cause the resist to lift. This can cause anything from fuzzy lines to whole areas of resist lifting.
-If dirt or oils get into the open areas, it will create a weak resist that leads to an uneven etch.
-when etching in a bath of the ferric chloride
⇦ this on
eBay or
Amazon [affil links] , the surface should be faced downward so that the salts will fall to the bottom of your tank; if using a spray solution, keep the metal tilted slightly forward.
-Too deep an etch can cause undercutting of the lines. If you want to etch deeply, you may need to stop at some point and reinforce the lines with a stop-out varnish on the walls of the cut.
- I have found that a slower etch gives a cleaner bite.
Copper is easier to etch, and an Edinburgh Etch solution helps. www.lawrence.co.uk/fact_sheets/pdfs/Edinburgh%20Etch.pdf
I'm not a chemist, but the theory is that the citric acid
⇦ this on
eBay
or
Amazon [affil links] creates negative ions that wick the salts into suspension and help give a cleaner etch.
- Dayton, Tennessee
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Ed. note: Great response, Mary. Thank you!
Q. Dear sir/madam,
We are into chemical etching from past few years, we are able to etch copper, brass & nickel up to 1 mm thick, whereas we are finding very difficult in stainless steel 304, 301, 316. Even we are not able to etch 0.2 mm. The chemical we are using is ferric chloride
⇦ this on
eBay or
Amazon [affil links] at 40° C.
We are mixing 60 kgs of ferric chloride
⇦ this on
eBay or
Amazon [affil links] salt and 20 lts of HCl with water in our 200 lts tank, but still dry film is lifting from the material as it reaches the depth of 0.1 mm.
I have seen through etching done on 1.2 mm stainless steel.
Kindly let us know how can we reach that point.
- Bangalore, karanataka, India
April 4, 2012
Q. I want to know how to etch s.s.202. What chemical is used for chemical etching?
nilesh panchalmechanical industrial works - gujrat India
April 21, 2012
Q. I am using DHS-1 material [Ed. note: free machining ferritic stainless steel used for hard disk drives] for EN Plating Process at which the Ni Strike bath is involved (Current + Acid).
However, I am seeing pitting on the surface of the part.
It is common to have pitting on the surface and how to improve this condition.
- Malaysia
June 5, 2012
Q. Can we get precision etching using ferric chloride ⇦ this on eBay or Amazon [affil links] - say precise to the micron level?
Arvind Agarwal- Uttar Pradesh, India
August 27, 2012
A. The simplest way to etch Stainless Steel is to use Electricity (12 Volts DC) and plain old Table or Cooking Salt. Paint the surface of the item to etched with a quick drying but 'Sticky' paint. Off the 12 Volt Dc power supply use ANY type of piece of metal (a Stainless Steel Bolt about 1/2 inch diameter for jewellery or say a Knife ) and connect this to the NEGATIVE terminal of power supply, and the item to be etched to the POSITIVE terminal.
Saturate TAP WATER with Table Salt and immerse bolt and item to be etched in the Salt Solution. Bubbles will form on the BOLT showing that etching is taking place. KEEP THE TWO SUBMERGED items apart or if they touch then the FULL power supply voltage will flow and the Power Supply will blow a fuse or set on fire if it is not fused. Make sure that ALL surfaces that are not to be etched are painted or the WHOLE item will be dissolved.
Chemical etching is OK in some circumstances but ALWAYS messy and TOXIC to various degrees. I etch Copper clad PCB boards for circuitry and use the quicker and cleaner SODIUM PERSULPHATE and not the usual slower but less expensive ferric chloride ⇦ this on eBay or Amazon [affil links] . EXPERIMENT yourself with the Salt and Electric method and you will surprise yourself. Power Supply current? Around ONE AMP.
William JacksonHome DIY and Radio Ham. - Blackburn, Lancashire,England.UK.
March 6, 2014
Q. William, thank you for your response, it has been very helpful.
I have used the 12V power supply/salt water and found it provides an etch deep enough to significantly improve the adhesion of coatings on a high nickel steel.
Does anyone know what the by-products of this reaction are? What gas is in the bubbles? A brown solid "sludge" forms in the bath. Any information on what that might be (iron oxide)? I want to make sure this process is not creating a hazardous environment or waste.
- West Chester, Pennsylvania, USA
May 13, 2014
A. Hi Jim. Generally the gas released at the workpiece (cathode, positive side) is hydrogen. Gas released at the anode, if any, is oxygen. However, in an acidic solution with a lot of chloride (if you add any acid to the saltwater), it is possible to generate chlorine -- which is a poisonous gas. You will hopefully notice the bleach-y smell and see the faint yellow color before it is problematic.
Presumably you are a hobbyist? Because the thing is, if you are an industrialist you may be generating "hazardous waste" regardless of what is in it. Many industries are regulated by "categorical standards" which means that if a waste came from a particular type of process/operation, it is regulated regardless of its actual chemical analysis.
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 2014
September 10, 2014
A. Hello everyone,
I was in photolitography business for years and I might have the exact formula for you need.
I used 20% HCl solution and Hydrogen 90% to etch through various metals, including some types of stainless steel.
However, I have met some formulas of stainless steel that were completely resistant to almost any kind of electro/chemical stress.
To be direct: Mix One part hydrogen (90% pure) and three parts (HCl 20%) in a PLASTIC container. About 30 ml of solution "eats up" 10 mm x 20 mm 0.5 mm stainless steel plate in time of about 5 minutes.
Have a nice day and quick etching.
P.S.: The solution heats up like hell and boils often.
- Tuzla, Bosnia and Herzegovina
September 2014
? Hi Nermin. Thanks! But what do you mean by "hydrogen" -- hydrogen is a gas. Did you intend to say "hydrogen peroxide" (H2O2)?
Regards,
Ted Mooney, P.E.
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
Q. Dear Sir,
Thanks a lot for replies to people.
I want to make some Aluminum Auto parts with my own name and Brand (Reg) and my required design for stamping on parts is so Helical and Fine Finished. So please advise me that how can I etch so helical and Fine on this Stainless Steel Die.
- Pakistan Rawalpindi
October 20, 2015
Q. We are making PCBs, for that we need stainless steel' we are etching PCBs (copper) with ammonia ⇦ this on eBay or Amazon [affil links] . Can we use it for stainless steel too? Please reply.
Ketan SoniAnalog Technologies - Vadodara, Gujarat, India
September 16, 2017
A. Hi Ketan. Sorry, ammonia will not etch stainless steel.
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
September 2017
Precision Etching for 316L watch parts
August 16, 2018Q. My situation:
I work for a watch case manufacturer that currently outsources the acid etching of it's case backs and various parts. This is both costly and time consuming as the partner we do this with is across border. We are looking to integrate this process into our manufacturing process but since none of us is a chemist, we've met some road blocks and getting the correct information isn't easy.
First, here are the results we currently obtain from our supplier and are looking for:
i.) Clear, clean and well defined lettering and logos etched to a depth of 0.1 mm (0.08 - 0.12 is the range)
ii.) A homogeneous, light grey, etched surface (not dissimilar to a fine sandblast or microbead)
iii.) We will etch designs on a flat horizontal or slightly angled surface.
Second, a few comments on the supposed means our supplier arrives at these results and the solutions we would like to explore:
a.) We suppose that our current supplier is using a UV light/photosensitive resist setup to achieve current results.
b.) We purchased a conveyor style etching machine which sprays the etchant/acid on the parts as they run through the machine. The 4 inputs we have are: Acid strength/concentration, Conveyor speed (time), Spray strength and acid temperature.
Before going to the acid machine we spray the parts with a blue etch resist and cure for 30 minutes in an oven (parts are previously cleaned in trichlorethylene). We then laser engrave the design to reveal the steel where we want to etch. We want to do this instead of UV photoresist as we already have the laser machines in-house.
c.) We use ferric chloride
⇦ this on
eBay or
Amazon [affil links] (FeCl3) at 40% and 46%
d.) We've tried a 5 minute cycle time (longer and the resist is gone, less and the etch isn't deep).
e.) 45 - 49 °C acid temp
Finally, Our problems are as follows:
1.) We are unable to etch beyond 0.03-0.04mm in depth (46% allows for slightly deeper etches 0.04 instead of 0.03 after 5 minutes).
2.) The resist (we have tried numerous) is not well adapted as it either peels off during the process or cracks when we laser engrave.
3.) The etched surface is pitted and not homogenous.
4.) initial tests showed that FeCl3 worked well with 304L but it seems we are not able to replicate the same results with 316L (1.4404 and 1.4435).
Any help on this matter would be greatly appreciated.
Best,
Philippe
Director - Geneva, Switzerland
A. Hello, I am from Australia, We also bought a similar etcher many years back but it did not work out the way we wanted for the precision. In 2019 we bought nano etching technology from an Indian company [name deleted by ed. (Why?)]; you can take a semi-automatic setup -- will definitely serve your purpose
Best wishes
William
Lapel Pins - Melbourne Australia
March 25, 2020
May 26, 2019appended
Q. Hello,
Please can anyone Provide me with detailed information about chemical etching and electro etching.
Chemical Etching-( Deep Etching)
1.Chemicals to be used for 304SS . Plate size is 12"x 17" inches and 2 mm thick.
2.The volume of chemicals to be mixed.
3. Process, to keep still the plate or continuously move the plate. Or any other technique.
Electro etching-( Deep Etching)
1.Chemicals to be used for 304SS . Plate size is 12"x 17" inches and 2 mm thick.
2.The volume of chemicals to be mixed.
3. Process, to keep still the plate or continuously move the plate. Or any other technique.
4. Voltage and Current with which cathode to use.
- Pune, Maharashtra, India
A. Hi cousin Omkar. As you see, we added your questions to a thread where many of them are already answered.
Please try re-frame any open questions you still have, or inquire about anything you didn't understand, while trying to introduce your experience & knowledge of the topic because we find that your fellow readers rarely answer abstract questions :-(
We also have another half dozen threads about etching of stainless steel if you search the site with the term "etch stainless steel". Good luck!
Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com - Pine Beach, New Jersey
May 2019
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