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Up Topic Welding Industry / General Welding Discussion / Hacked ways of macro etching mild steel?
- - By defaced (**) Date 05-02-2007 16:33
I'm looking for some easy to obtain ways to macro etch some welds (subarc 70s-6 on A36) I have.  I usually have access to a lab, but that's not an option right now.  Anything that uses common household chemicals would be ace.  All I really need is to be able to make out the fusion zone. 
Parent - - By jwright650 (*****) Date 05-02-2007 16:42
Battery acid works great. Saw it, polish the area to be etched, add the acid to that area, spray it off with water after it has had time to etch(don't wipe with a rag, you'll wipe off your etching).

http://aws.org/cgi-bin/mwf/topic_show.pl?pid=61008;hl=#pid61008
Parent - By defaced (**) Date 05-02-2007 23:31
Excellent.  Thank you very much. 
Parent - - By bellaru (*) Date 05-04-2007 06:08
john , i bought some battery acid but it was already mixed with water and it didn't do much,,,,,,too week...........am i supposed to use pure sulphuric acid.....?

i saw the pics you posted , and the stuff was bubbling,,,,,,,,,mine barely worked........
Parent - - By jwright650 (*****) Date 05-04-2007 10:29
Yeah, the last time that I bought battery acid from an auto parts place, the acid was not mixed. You had to add water to the battery after you filled the battery with acid to top it off. Sorry, I didn't realize they have started premixing it. You know the last lawn mower battery I bought, you had to add the acid and it wasn't diluted...hmm.

I used in the pics was red fuming nitric acid(%? not sure but it is strong)....melts the nose hairs out if you catch a whiff...LOL
Parent - By MDG Custom Weld (***) Date 05-04-2007 12:09
You can go to any hardware or big box store and buy muratic acid.  Use it straight, it will smoke some and burn nose hairs if you take a good whiff.
Parent - - By Joseph P. Kane (****) Date 05-04-2007 12:33
John,

Battery Acid is Sulphuric Acid.  If you used Nitric Acid in the photos, perhaps you could clarify, so everyone doesn't go out and buy $35.00 worth of battery acid?!?!?  The last time I tried battery acid as an etchant, it did not work.

Not everyone can go out and purchase Nitric Acid.  Businesses can, but usually they have to buy so much, that storage and disposal becomes a costly problem.

If you have Nitric Acid, there is mixing information in the back of the Lincoln Welding Handbook and in  the Howard Cary Hobart Welding Handbook, for mixing, and formulae for the diferent etchants.  You can tailor your mix for better results.   The best etchant information is in the ASM International Metallography Handbook.

I seldom use the NITAL (Nitric Acid and Alcohol) mixes, because I am always travelling, and these mixtures are flammable.  (I find that the pure alcohol is harder to get than the Nitric Acid!  You need a special ATF license and a State Liquor License to sell it!) I carry a small amount of (64% Nitric Acid), in case I have to mix a NITAL solution on the site, and I have pipettes so I can mix 1 CC or smaller amounts.  I used to carry straight Hydrofluoric acid, but that stuff is so dangerous, that now I only carry special mixtures for  Aluminum etching.   I use Marbles Etch for austenitic Stainless Steel.
Parent - - By jwright650 (*****) Date 05-04-2007 12:58
Good Morning Joe,
I've used battery acid before and it does work well, you get a very defined etch. As for the acid that was used in the pics, I mentioned in the text above the pics that I was using Nitric Acid...but the battery acid worked well for me, took a bit longer, but it gave a defined etch.
Does the battery acid cost $35 now?....geez, that stuff has really gone up, I don't remember it costing anywhere near that. 

Ok, I just called Fisher Auto Parts and they have a 1.5 gallon container of undilluted battery for $13, and $20-something for a 5 gallon bucket. This is the same stuff that comes with a new "dry" battery and you add to it to get the battery going. Same stuff that I've used before and it works. It has to be strong enough to eat lead so that the battery will work as a battery and not a door stop.

I certainly don't want to mis-lead anyone...it has worked for me.
Parent - By Joseph P. Kane (****) Date 05-04-2007 16:28
John  I'm Sorry!

I didn't mean to BARK at you with my reply to your post.  My experience with battery acid "From a Battery" took in excess of 10 minutes to begin to develop any type of indication, and then it browned out before it ever showed any micro-structure, phase change or depth of fusion.  I have Amonium Persulfate, and it was much faster, although still too slow, unless the part was slightly heated.  I tried the Sulphuric Acid that is died purple for use in Cesspools on Long Island, and it instantly stained darker than it already was, and still never seemed to give me a microstructure definition.  I never tried undiluted clear Sulphuric  Acid.

I had seen your original photo and I knew right away that Sulphuric Acid does not react that way on polished steel.
Parent - By Mwccwi (***) Date 05-12-2007 04:16
I get my nitric acid from the e-coat paint lines the techs use ic to clean thier systems with, they get 55gal drums of 42%. I take a small plastic droper bottle 150 ml and ask for some (with an explanation of why most of the time they have no problem with giving me such a small quantity) sometimes the want to see the finished etch, the 150 ml mixes with distiled water last a lot of etches. I dilute it down to between 7% to 15% with distilled water "in a beaker I fill 100ml of water finish filling to 120ml with the 42% nitric acid, I add to polished weld area, just enough to cover what I'm targeting. Works much faster than Amonium Persulfate. see photo (note: the photo is to diplay the quality of the etch - the lines that are annotated in, didn't grow equally with the picture when I enlarged it) how I done that I pasted the photo to excell sheet mark with drawing and text bow function grouped copied and pasted bak in to the picture file as paste as new picture.
Attachment: NewPicture1.png (184k)
Parent - - By waynekoe (**) Date 05-09-2007 16:15
I went down to the auto parts/paint supply place and bought thei stuff called "IRON ETCH". Think it about 20 bucks for a quart. Anyhow, the stuff worked great. only takes a couple minutes to come up,  and as the picture shows, it works pretty good.

[IMG]http://i100.photobucket.com/albums/m8/wayneko_2006/HPIM0088.jpg[/IMG]
Parent - By thirdeye (***) Date 05-12-2007 00:41
Would you mind posting a picture of the label or the Mfg information?

~thirdeye~
Up Topic Welding Industry / General Welding Discussion / Hacked ways of macro etching mild steel?

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