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Problem etching stainless steel with Ferric Chloride - Pitted Finish


Hello, we are a sign manufacturer. On a regular basis we use 45 Baume Ferric Chloride to etch 304 stainless .007 to .015 inches deep. This is done at 47 °C. Sometimes however I get a very bumpy etch in wide areas. It almost looks like part of the stainless composition is breaking down faster than others but that is my guess.

I've documented this problem with photos and detailed information. These are all examples of 304 stainless steel panels etched with 45 Baume ferric chloride (FeCl3) in a spray nozzle conveyor system. The ferric chloride is heated to 45° C and has less than 3% hydrochloric acid as content when it is received.

Example of Smooth Etching (Acceptable)

Example of Reverse Etched Problem - small pits (Unacceptable)

Example of Reverse Etched Stainless -- Small raised areas within smooth etched area (Unacceptable)

Example of Reverse Etched Area that is smooth near the shoulders but bumpy in the wide open areas (Unacceptable)

Extreme Example of Shot Blast Look in Etched Area. I believe this was done with 30 Baume ferric chloride.

I appreciate any assistance that can be given! Unfortunately we are not chemists and only have a few basic measuring instruments -- i.e. Hydrometer and Thermometer. Thank you.

Jon Lorber
Architectural Signage Shop - Amityville, New York, United States


I was trying to get etching on stainless steel plate by Ferric nitrate solution plus small amount of nitric acid. It is not working. I don't know the reason. It works when I use ferric chloride plus nitric acid. I wanted chloride ion free stainless steel plate, so I am using ferric nitrate. can you give some solutions.

Arunabha Kundu
Yonsei University - Seoul, Korea

April 23, 2008

How Many Tablespoons of Ferric Nitrate in a Quart Of Water? Hello, I'm Doug Mosley; an artist from Portland, Oregon.
I use antique steel and iron farm tools and machine parts to create abstract sculptures. I have been using ferric nitrate in a very undisciplined fashion. I would like to know how much chemical to add to a quart of water to achieve a standardized concentration. I realize the found steel and iron objects I use in my work are inconsistently alloyed - this is why I need to standardize my ferric nitrate solution. Also, I have found that misting a treated surface with water will speed up the appearance of bright orange rust. Is it safe to seal this without further rinsing? I am trying to achieve a lighter color finish when sealed. I have been getting a brown or black color only.

Doug Mosley
Metal Sculptor - Portland, Or, USA

January 18, 2013

Q. Can anyone recommend a good resist stencil film that will adhere well to 304 Stainless for etching in Ferric Chloride. I have tried Oramask 813 but it just lifts right off.


Jared Smith
- Carbondale, Illinois, USA

Ed. note: We would prefer generic responses to brand name responses, readers. We're confident that the problem revolves more around either the best techniques for adhering stencil films, or the best materials for stencil films for etching with ferric chloride, rather than that some manufacturers' stencils are better than others.

June 8, 2013

A. We use liquid photo resist and this does not come out even when we go 1 mm deep.
its ready to use, just spray and bake it at 80 degree for 20 minutes.
Hope this helps.

Mukesh Gupta
- Delhi, India

February 14, 2014

Gupta Gi, which type of liquid resist do you use?

muneeb anwar
- sharjah uae

Ed. note: We'd prefer that people not ask for specific brand recommendations because it so often leads to phony testimonials from people with vested interests, pretending to be satisfied customers. Please appreciate what we've learned from 19 years of running the site -- if you provide an opportunity for commercial benefit from postings, few can resist, and we're soon drowning in spam :-)

May 6, 2015

Q. Jon, I use etching machine with spray nozzles and conveyor also and am presently having a similar issue after putting in fresh acid. please let me know if you find an answer.

kevin payseur
- cramerton North Carolina

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