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Derusting - revisited

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  • Derusting - revisited

    Rather than resurrect the "Project Finishes" thread, I'll start a new one.

    THANKS FRANZ - I'M IMPRESSED - Electrolytic derusting definitely works. The attached pic is of a cheap scissor type jack that my son found in the trunk of a car that he just "inherited" - after it was derusted. The spare well in the car had about two inches of water in it along with the jack and spare. The jack was almost 100% rusted and the threaded shaft would not budge at all. My son was going to pitch it in the trash and I "rescued" it to try out electrolytic desrusting. What an operation - the tank was an old cat litter box (the cat left about a year ago), I used two old lawn mower blades as the anodes and screwed a piece of copper wire to the jack for easier electrical connection, my trusty 6 amp battery charger and started out with a baking soda solution (since I didn't have any washing soda). I started it at 10 PM and was surprised to discover the next morning that the shaft was now starting to free up - I also had the most disgusting looking liquid I had ever seen, in the litter box. I stopped the process and cleaned the anodes (equally disgusting) and let things continue. A good part of the rust was gone from the jack and I let it run until supper time. I found washing soda at the store and since the solution was so disgusting and had so much sediment, I decided to change the solution. Washing soda seems to be more "active" (more bubbles) and overall seems to work better. After about 48 hours total, I stopped the process and pressure washed the jack (and my Jeep) and as Franz said, things will rerust in a hurry, so be prepared and work quick. I took some pics and finished the cleanup and started painting. Please don't get any ideas that I am now in the jack rescue business, but I was really amazed at how well this process works. I cold never have gotten the rust out of the nooks and crannies like this process did. I honestly thought this jack would end up in the trash, but with a good paint job and lubrication, it has been returned to service. Now about those rusty antique tools that I have been wondering what to do with - I think I found the answer. I should add that all of the remarks Franz has posted in this thread have been right on. Interesting process, if you haven't tried it, you might give it a try.

    Edit - the spots you see in the picture are paint that hadn't come off yet - not rust. I cleaned it up some more before painting.

    Allen T.
    Last edited by atucker; 05-17-2003, 09:02 PM.

  • #2
    Allen, glad something I did turned out right for somebody today.
    If I didn't put it in the original posting, things like the jack that have multiple parts that may not be electricly connected often require multiple connections for best electrolytic performence.

    Also, I don't get worried about the rust that forms on the surface as the item dries, I just let it form, and then treat with Phosphoric acid solution. After it drys, you have a nice chemicly bonded layer of Iron Phosphate, (FeO3) witch acts as an impervious coating to future rusting, and is an excellent enamel primer.
    NOW, if you just keep this process secret, you can haul home a lot of rusty clamps & tools friends are going to toss cause they've rusted beyond use, and have yourself a big box of lo cost tools to play with.


    • #3

      Give me some more specific instructions on how to do what you did with the rusted part.


      How do you use the phosphoric acid and where do you get it?
      Todd Eldridge
      [email protected]
      Newbie Hobby Welder


      • #4

        I am up for this information also. If the process and materials list could be reposted I would be grateful...
        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


        • #5
          It works well. I have a leg vise that had gone through a brush fire and sat outside for who knows how many years. The tank I used was an old trash can.


          THE POLARITY IS CRUCIAL!! The iron or stainless electrode is connected to the positive (red) terminal. The object being cleaned, to the negative(black). Submerge the object, making sure you have good contact, which can be difficult with heavily rusted objects.

          A couple of days latter I had clean parts that I could dissassemble and send though the derusting process again. As each part came out, it was rinsed and scrubbed then given a coat of rust converter in a spray can then a coat of paint.


          • #6
            Most of the info is in the "Project Finishes" thread HERE from about a week ago. One of the posts has a link to more info located HERE.

            Franz appears to be the "resident expert" - while doing a net search on "electrolytic derusting", he shows up other places too . My newly learned opinion is the process is very simple, VERY effective and is kinda messy (your family may think it's gross ). The process will probably give you a whole new outlook on derusting - it did me. Here's some observations I learned real quick - 1) If you don't have a sink in your work area, you'll wish you did - 2) Good electrical connections are crucial, clean the connection area if possible, I screwed lengths of copper wire to the various parts where possible - 3) WASHING SODA (grocery store item located with laundry supplies) seems to be more effective than baking soda 4) Watch the little bubbles, a good indication that it's working (no bubbles = poor connection) - 5) I'm sure I'll learn more as I use this process .

            The most amazing thing to me was that this process can free up a rusted, threaded device and remove rust in very obscure places. It is also "environmentally friendly" compared to other rust removal processes.

            Allen T.


            • #7
              Dang, sure sounds like you guys got the process understood, so I guess I can't make a fortune selling Uncle Franz's SECRET rust removal powder. Would anyone be interested in a solar powered laundry drier kit?

              Phosphoric Acid~ well, it's a real interesting acid, used in all sorts of things, from Coca Cola to Naval Jelly, and my favorite overpriced oversold product, POR 15.
              For converting rust to Iron Phosphate, the simplest method of use is to soak the rusty part in a 4% solution of phosphoric acid in water till the rust layer is fully wet. When the wet rust drys, you will have a very interesting looking layer of FeO3, basicly rust with an extra Oxygen molecule. FeO3 will chemicly bond to steel, and is impervious, so new rust won't form. That's the process being used on a lot of new guardrail and bridge steel that looks rusty when first erected.
              A version of Phosphating is called Parkerizing, where the steel is boiled in a solution of acid with zink and magnesium disolved in it. Parkerizing is used as a gun finish on military guns.
              One of the best things about phosphating steel is that you can then paint it with enamel, directly, without any primer. The FeO3 layer works better than primer because it is part of the steel, and not just sticking to the steel. I've done this with every trailer I built in the last 20 years, and have yet to need to repaint. The FeO3 layer also prevents rust pop under a paint job.
              ONE MAJOR drawback, you don't want to get Phosphoric acid on aluminum, it will disolve aluminum.
              You also want to use extreme caution if you opt to spray the acid solution. If you inhale this acid, it will feel like somebody is inside wirebrushing your lungs.
              I buy mine from a chemicle supply house at 85% concentration, but thanks to government intervention, that is getting harder to do. Home Depot sells a weaker acid in their paint department, and it's also sold by body shop suppliers, called metal prep.


              • #8
                What do you use for a power sorce, and what is the amprage.

                Ac or DC



                • #9

                  You got me interesing in the phosphoric acid. What is the mixing rate? acid to water?

                  Also, if I bead blast a piece and then stick it in the acid solution will that form the protective layer?
                  Todd Eldridge
                  [email protected]
                  Newbie Hobby Welder


                  • #10
                    Question A) DC polarity. A battery charger works very well, and amperage is governed entirely by the size of the object being derusted and the clean surface area on the anode.

                    Question B) In order for the Phosphating to work, you will need to let the object form a coating of surface rust before acid treating. The acid would only etch the metal if you put it on clean steel.
                    Acid concentration between 2 and 5% by volume of acid to water. Different concentrations work best on different alloys, and work at different speeds.


                    • #11
                      have you ever thought of using molasses for rust removal? yup molasses here are a couple of link to look at on it.

                      later jim
                      Dynasty 200 DX
                      Spectrum 300
                      MM 90
                      next up to buy MM251


                      • #12
                        The New and Improved Mark 7 Solar powered Laundry Drier kit, complete with instructions, is now available for sale.
                        For a limited time, I will be offering this kit, regularly $495.97, for $350.99, plus shipping and handling. For your convenience, I accept payment by PayPal.


                        • #13
                          Power source - I used a 6 amp Wal Mart cheapy battery charger. As Franz says, lots of things effect the amperage. On the jack I started out with one lawnmower blade (using baking soda) and at clean start I was drawing about 3 amps - the current goes down as the anodes get NASTY. When I changed the solution to washing soda (1 heaping TBSP/gal), I also added a second blade, the current started at 6 and would drop as the anodes got messed up and would come back up when I cleaned the anodes. Current draw is also a decent indication that your connections are good/bad (along with the bubbles). As I stated earlier, bolt/screw the connections, if possible, I started out with alligator clips and the battery charger clips and had trouble keeping connections - drilled, bolted and screwed things and took care of that problem.

                          Allen T.


                          • #14
                            If you treat the steel and then weld through the FeO2 are there any harmful effects? Looks like you would release the extra O2 with the heat. Will the steel need to be re-treated?


                            • #15
                              Duke, FeO3 is just another form of RUST, more correctly rust with an extra oxygen molecule.
                              Welding thru it is about like welding rusty iron, not the best way to make a weld, but it can be done.
                              It's also sort of a flexible coating, softer than rust, so scraping it off is fairly easy.
                              Now, I may be anticipating you here, so let me say I've never exposed it to the level of heat that will be inside that giant cooker you're making.