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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


A. One of many chemicals to etch stainless steel is ferric chloride 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 to remove the copper. Sorry but I can not remember what sort of marker it was - try some pens and see what happens.

Ferric Chloride


Martin Trigg-Hogarth
surface treatment shop - Stroud, Glos, England




Q.

Thank you Martin,

Ferric chloride is very slow. Actually I am using 314SS. Can you suggest me any other chemical? What about Chemical Milling process?

Manish Tyagi (returning)
- India


A. Hi, Manish.

Letter 33699 suggests adding 20 g/l of HCl and provides references. Good luck.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

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 solution, this will increase etch rate.

Guillermo Marrufo
Monterrey, NL, Mexico

 

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 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


+++++++

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 Bhutta
Manufacturer of Medical Devices - Sialkot, Punjab, Pakistan


 

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 can only remove glossy surfaces and not actually etch patterns into the metal. You may find it informative. Good luck.

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey

January 2, 2010

Q. I want to fast etch SS so what can I use for more depth.

M Imtiaz
- Sialkot, Pakistan


January 28, 2011

Q. I want to fast etch SS so what can I use for more depth.

PRASHANT KATHUMARIA
- JHANSI,U.P., INDIA

January 31, 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, as we are able to keep the thread moving forward, rather than running it in circles, I think everyone will happy. Thanks!

Regards,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
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 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 or Barkeepers Friend =>

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.

Bon Ami

Barkeeper's Friend

- 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, 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 creates negative ions that wick the salts into suspension and help give a cleaner etch.

M

Mary Whittle
- Dayton, Tennessee

----
Ed. note: Great response, Mary. Thank you!



April 4, 2012

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 at 40° C.
We are mixing 60 kgs of ferric chloride 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.

kishore chowdary
- bangalore, karanataka, india


April 21, 2012

Q. I want to know how to etch s.s.202. What chemical is used for chemical etching?

nilesh panchal
mechanical industrial works - gujrat india


June 5, 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.

H Hussain
- Malaysia

August 27, 2012

Q. Can we get precision etching using ferric chloride - say precise to the micron level?

Arvind Agarwal
- Uttar Pradesh, India


March 6, 2014

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. EXPERIMENT yourself with the Salt and Electric method and you will surprise yourself. Power Supply current? Around ONE AMP.

William Jackson
Home DIY and Radio Ham. - Blackburn, Lancashire,England.UK.



May 13, 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.

Jim Sloan
- West Chester, Pennsylvania, USA


May 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,

pic of Ted Mooney Teds signature
Ted Mooney, P.E. RET
finishing.com
Pine Beach, New Jersey
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