Summary for smooth chemical etching Discussion
smooth chemical etching is the core issue here: the questioner wants a formula that will etch 431 stainless steel and PH 17-4 stainless steel evenly, without the inconsistent attack and roughness they have seen from several other solutions. The thread’s main practical guidance is that nitric-hydrofluoric acid solutions are generally considered the best chemical etchants for stainless steel, but the excerpt also warns strongly that hydrofluoric acid is hazardous and should never be used without proper training and calcium gluconate antidote gel on hand, as emphasized in the safety note attributed to Ted Mooney, P.E. An additional option mentioned is electropolishing in salts, which can produce a smooth surface but requires special equipment. The overall takeaway is that a smooth finish is possible, but the process choice must balance surface quality, safety, and equipment availability.
Q. I want to get a hold of a formula for a smooth chemical etching of 431 stainless steel and ph 17-4 stainless steel. I have tried several different solutions however their attack is not consistent and leave an uneven surface. I need to have a smooth finish. It doesn’t have to be bright, just smooth.
Hydrofluoric acid burns
Never use HF anywhere unless trained!
If you do, you MUST have the antidote gel on hand for instant use!
Calcium Gluconate
for HF acid burns
on Amazon or
(affil link)
Jeffrey Jones
– San Diego, California
2001
A. Normally a Nitric acid / hydrofluoric acid is best.
About 30 to 40% nitric by volume and 3 to 4% Hydrofluoric acid remainder water.
Fume extraction is required and great precautions in the handling of HF. Breathing fumes is very toxic and the acid must be treated with great care.
Should give you a smooth surface if etch is restricted to say 5 minutes
Bernard Irving
– United Kingdom
2001
Q. Hi Bernard, how are you?
I used HF and nitric mixture, but at 10 percent the HF was super fast cutting and in lower it was very slow. Is there a catch in this that we have to wait for nitric and HF to react then put in the pieces?
Shobhit
– Delhi, India
December 26, 2024
This is a meeting place for camaraderie & sharing, not a free consultancy. So some readers don’t engage with anonymous posters.
A. Hi Shobhit,
Bernard’s posting was from decades ago. We’ll try to reach him and request a reply but it’s not likely.
The two acids certainly must mix before you put the metal in, but I may be misunderstanding your question.
Luck & Regards,
Ted Mooney, P.E. RET
Striving to live Aloha
finishing.com – Pine Beach, New Jersey
Need quick confidential answers? $25
Need project assistance? $100/hr.
adv.
There is another option: electropolishing in salts, but special equipment is required.
Anna Berkovich
Russamer Lab – Pittsburgh, Pennsylvania
(ed. update July, 2025: sorry, Anna has retired)