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Up Topic Welding Industry / General Welding Discussion / Acid etching of HSLA material
- - By bd1017 Date 08-24-2005 15:05
What would be the best method and What type of etching solution
Parent - - By SWP (**) Date 08-24-2005 21:59
I'm no expert on metallography, but as I recall a simple 10% Nital solution applied to the polished surface via cotton swabs (with forceps and gloves) should work well. 10% Nital is a mixture containing 90% Alcohol and 10% Nitric Acid.
Parent - - By LindsayWeldTeam Date 09-12-2005 20:18
where do you purchase Nitric Acid?
Parent - By tjbutler (*) Date 09-12-2005 20:42
I bought some at the local jewelry supply house. It was about $4 for a pint. It was labled as 63% Nitric acid.
Parent - By MBSims (****) Date 09-13-2005 03:41
We order ours from Fisher Scientific. You can buy either reagent grade (70%) nitric and mix your own if you know how (always add acid to solvent, never solvent to acid!), or buy it already mixed. Here's the premixed 10% nital:

https://www1.fishersci.com/Coupon?catnum=NC9304999

Here's the reagent grade nitric acid and ethanol:

https://www1.fishersci.com/Coupon?catnum=AC424005001
https://www1.fishersci.com/Coupon?cid=1336&gid=22209

Parent - - By - Date 09-13-2005 12:41
While we're on this subject, I have a question. Since I have been dealing only in stainless steel for the last 35 years, my knowledge is limited on the cleaning of carbon steels. Avesta is supplying a large amount of stainless steel pickling solutions to a customer for cleaning and passivating SS, but he also has a lot of carbon steel components (regular mild steel) coming off of the SS fabrications. He asked me if there is a solution for cleaning the rust off of the CS surfaces. Is that what the Nital is used for, or is it only for etching polished surfaces? Thanks for your help.

Chuck
Parent - - By jon20013 (*****) Date 09-13-2005 15:31
If you can lay your hands on an ASME Section IX, there are formuli for etching under paragraph QW-472. Personally, I normally just use 1 part nitric acid mixed into 3 parts water. This works good for most ferritic materials, however there are several other choices offered in QW-472.
Parent - - By - Date 09-13-2005 18:10
Thanks, Jon...
Parent - - By jwright650 (*****) Date 09-13-2005 20:08
If you are using the same Nitric solution as I have, it(carbon steel) will rust almost instantly after washing the acid off. I had been spraying a clear enamel over my macro etches to save it.
John Wright
Parent - - By jon20013 (*****) Date 09-13-2005 20:23
John; the exact same stuff! It buffs off very easy though (when fresh) and the enamel does work well! A funny (not really) story of when I was a young pup of an inspector, my very first acid etch on my own (inside the shop) and with BRAND NEW linoleum in the test area, I couldn't find anything to put the mix in so finally found an old tin can! Oh, my goodness, you never saw someone run so fast! Grabbed the can with a pair of old plyers and flung it off the loading dock! A good lesson; never mix acid into anything but glass or plastic containers! And, of course, never mix water into acid!!!!
Parent - - By jwright650 (*****) Date 09-13-2005 20:45
Jon,
Somehow I can vividly see a guy running with a can of that fuming acid, when I read your post:) I've heard of horror stories when mixing acids and I don't want to experience that first hand.
John Wright
Parent - By jerrykroll (**) Date 09-13-2005 22:50
I always water wash nitric acid etches thoroughly, then dip or flush with acetone. Clear acrylic spray or lacquer can then be applied almost immediately. The very best etch (speed and clarity) I have ever used is a Nitric acid with ferric chloride solution.

I always keep others away from the area when applying an etch - the fumes can easily creep up on you without warning !
Parent - By jerrykroll (**) Date 09-13-2005 22:56
Also in response to above -
an easy resource for prepping and cleaning steel can be found at most auto body repair material suppliers. I don't recall the name, but I believe there is a water based solution or concentrate that is sold to prep auto body panels before painting to thoroughly remove light rust.

I am certain it to be much safer and reliable than woking with "concentrated" acids.
Parent - - By jwright650 (*****) Date 09-14-2005 00:05
http://aws.org/cgi-bin/mwf/topic_show.pl?id=7233

Check out this link to an earlier discussion.
John Wright
Parent - By Northweldor (***) Date 09-14-2005 12:05
But Brande never did get an answer on ammonium persulphate? (Couldn't find it with search all forums.) I assume this is a rust converter like Loctite's "EXTEND".
Parent - - By jwright650 (*****) Date 09-14-2005 12:18
http://www.aws.org/cgi-bin/mwf/topic_show.pl?id=5668#26144

Another thread from the archives....
John Wright
Parent - - By cfrancis (**) Date 09-29-2005 20:07
FeC13-6H20- 200 grams
HNO3 conc- 300 ml
H20- 100 ml


Above is a great recipe for etching Carbon steel. It etches dark in several seconds.
I get this mixed for me at the local Pharmacy.
Parent - By cfrancis (**) Date 09-29-2005 20:09
10 ml HNO3
20ml HCL
30 ml water

Here is a great and VERY fast etch for SS. I also get it mixed at the local drug store.
Up Topic Welding Industry / General Welding Discussion / Acid etching of HSLA material

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