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  • Acid Etch Test Question

    I have no formal welding insruction, but have been MIG & stick welding for a while. I've always checked for welding penetration by cutting a test weld on a coupon in half, sanding it smooth, polishing it and looking at the penetration with a magnifying glass. Or just try to break the test pieces with a BFH !!

    I'd never used the acid etch test before reading about it on this forum, so on my last test, I put a few drops of Muriatic acid, which the label says contains Hydrochloric acid, on the cut & polished end on the coupon and let it sit. After the acid dried, I don't see ANY difference in coloration between the base metal (1/8" CRS) and the weld (MIG). Is this acid too weak or am I doing something wrong?
    -Bob (JalopyBldr)

    HH187
    13" SBL

  • #2
    See if you can buy some ammonium persulfate. It should have better contrast between base and weld metal and is safer to use. Dilute [5-10%] nitric acid in alcohol should also work.
    Last edited by Benesesso; 06-30-2007, 12:56 PM. Reason: Spelling Correction
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    • #3
      I on't let the acid dry. I let it sit for two or three minutes and then rinse the coupon with plenty of fresh water. I've used muriatic, but nitric seems to work better.

      There is not a major difference in coloration, but the fusion line is much more clear, which is what you are trying to see. A bead "layed on top" will show a distinct dark line between the bead and the weld metal, indicating lack of fusion.

      Hank
      ...from the Gadget Garage
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      • #4
        NItric acid nasty stuff!!!

        What concentration do you use it in?

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        • #5
          I use muratic acid in a 50/50 consentration and leave it in about 30 seconds.
          Regards, George

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          • #6
            Hmmmm......danged if I can see any distinction to show weld / base metal separation. I'll try it again, guys.
            Thanks for your responses.
            -Bob
            -Bob (JalopyBldr)

            HH187
            13" SBL

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            • #7
              I've been using Naval Jelly. Let it sit three or four minutes, rinse off and you will see the penetration.
              Don


              Go Spurs Go!!!!!!

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              • #8
                Originally posted by PeteZ28 View Post
                NItric acid nasty stuff!!!

                What concentration do you use it in?
                Pete,

                I'm not sure, since I don't have any right now, but I use it right out of the container it comes in. I'm sure it's weak - but I'll find out and let you know.

                Hank
                ...from the Gadget Garage
                MM 210 w/3035, BWE
                HH 210 w/DP 3035
                TA185TSW
                Victor O/A "J" series, SuperRange
                Avatar courtesy of Bob Sigmon...

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                • #9
                  Originally posted by dda52 View Post
                  I've been using Naval Jelly. Let it sit three or four minutes, rinse off and you will see the penetration.
                  Dosen't the BB lint that comes in that stuff get in the way
                  Regards, George

                  Hobart Handler 210 w/DP3035 - Great 240V small Mig
                  Hobart Handler 140 - Great 120V Mig
                  Hobart Handler EZ125 - IMO the best 120V Flux Core only machine

                  Miller Dynasty 200DX with cooler of my design, works for me
                  Miller Spectrum 375 - Nice Cutter

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                  • #10
                    Originally posted by PeteZ28 View Post
                    NItric acid nasty stuff!!!

                    What concentration do you use it in?
                    I dissolve about 1cc of concentrated in about 20cc of denatured alcohol for this. Metal wants to be warm, not hot (80F or so). A couple miinutes, then rinse. I have concentrated at work (job 1) for an assortment of uses. Etch solution doesn't even show on the log sheet. For more info, look up 'Nitol'... (http://list.uvm.edu/cgi-bin/wa?A2=in...safety&P=17877 , for one)
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                    • #11
                      Originally posted by Sundown View Post
                      Dosen't the BB lint that comes in that stuff get in the way


                      I haven't had a problem with it.


                      Don


                      Go Spurs Go!!!!!!

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