Announcement

Collapse
No announcement yet.

Does acid need air to remove rust

Collapse
X
 
  • Filter
  • Time
  • Show
Clear All
new posts

  • Does acid need air to remove rust

    I have an old vise that I have soaking in some vinegar and muriatic acid compound. It's in a container that has a lid
    that I can snap on to make it air tight, but didn't know if that would hinder the process.
    John Titor, when are you.

  • #2
    No, it doesn't need air. I like to use straight vinegar and let the item sit for a few weeks depending. The muriatic acid is a bit too aggressive for me. Be sure to scrub the piece off thoroughly with baking soda in hot water to kill the acid.

    Comment


    • #3
      Thanks for that, with the lid cracked it stank pretty good. Some of the pieces of the vise are as big as my head, and I put them in a 5gal pail.
      I didn't want to use that much Muriatic so I googled it and found they play nicely together. So it's a compromise between the two.
      John Titor, when are you.

      Comment


      • #4
        Are you trying to remove rust or destroy the vise?
        Your acid compound will certainly destroy the vise in a few hours.

        The process is called Graphitic softening.. There is no recovery from Graphitic softening unless you're making a display piece.

        Comment


        • #5
          Dunno about the softening from de-rusting, but it looks like it takes time, and a fair bit of corrosive compound to do it.

          I like to get stuff done quick. Not much bad happens in a few minutes soaking in phosphoric, and it should not take much more than 30 min to get rid of most rust on anything that has a chance of being usable again.
          1601

          Keep eye on ball.
          Hashim Khan

          Comment


          • #6
            I won't have hydrochloric acid (muriatic) anywhere near my shop. The chlorine ions are extremely difficult to get off steel and the part will be prone to rusting after. Just the chlorine gas seeping out of closed bottles will rust everything it touches. Baking soda isn't going to do it. I have a bunch of steel from a guy that got caught the way. I always turn it off to a fresh surface.

            Oh... I use it... to instantly take galv off steel, but it's stored outside away from the shop.

            Comment


            • #7
              Originally posted by J Tiers View Post
              Dunno about the softening from de-rusting, but it looks like it takes time, and a fair bit of corrosive compound to do it.

              I like to get stuff done quick. Not much bad happens in a few minutes soaking in phosphoric, and it should not take much more than 30 min to get rid of most rust on anything that has a chance of being usable again.
              I'm willing to bet you've never worked on a cast iron vinegar generator. Vinegar is Acetic acid and nasty. It loves eating Iron atoms for breakfast, lunch, dinner and bedtime snack. You pull the iron out of cast and you have a fairly representative structure of what the casting or steel was, that when viewed under magnification looks like coral. I watched a 1000 pound anchor pulled out of Sewer Ontario 30 years ago that had been submerged 100 years and was still stable and easy to identify missing only the wood arm. A person with Degrees in Chemistry made the decision to soak the rust off with Vinegar. A week into soak the attaching clevis was sufficiently weakened it fell to the bottom of the tank to finish dissolving. The "chemist" decided to leave the anchor in the tank. After 3 weeks the Chemist was so certain the anchor had been stolen he called in Police. We found enough of the hub still in the tank after killing the acid and dumping it to prove the Chemist should be employed asking "would you like me to supersize that"

              Neither Acedic or Muriatic that have entered the open spaces in cast iron or steel can be neutralized with baking or washing soda, you may have luck in a heated caustic tank.

              Phosphoric is probably the best, since it will either remove the rust, or convert the rust to Iron Phosphate which is ideal for coating adhesion. 5%± converts, 60% removes rust. Phosphoric stops acting when it reaches good iron..

              Don't like that process, go to Citric or Oxalic acids. Both work, both are gentle. Another is Tannic, very similar to phosphoric in mechanism but slower.. Advantage you can make your own from used teabags.

              On the other side of the street, you can chelate rust. That's what the overpriced slop called Evaporust does, for about 10 times the money cow molasses does the job. BTW, Evaporust is an off label of an Aluminum cleaner made by the truckload in Georgia if memory serves. The maker will sell you all you want for about 2 bucks a gallon + container.
              Chelating works by robbing the Oxygen atom from the rust molecule leaving the iron to fall away. Something very similar happens to rust in a hot caustic tank, but you gotta be nuts to play that game.

              As I've said before, you'll encounter additional difficulty if the rust formed in a salt environment.

              If you screwed up and dissolved the iron out of your future museum display it can still be saved for display by evacuation down to about 29.5" and injecting epoxy resin that has been thinned and slowed in lockup time.

              There are many ways to deal with rust, none are fast and non-harmful to the iron. Entropy is Mother Natures baseline, and all iron and steel will eventually return to being iron ore.

              Comment


              • #8
                Originally posted by Franz© View Post

                ........
                Phosphoric is probably the best, since it will either remove the rust, or convert the rust to Iron Phosphate which is ideal for coating adhesion. 5%± converts, 60% removes rust. Phosphoric stops acting when it reaches good iron..

                .........
                There are many ways to deal with rust, none are fast and non-harmful to the iron. Entropy is Mother Natures baseline, and all iron and steel will eventually return to being iron ore.
                Even phosphoric is not "perfect". Don't count on ANYTHING "stopping at good iron" if certain parts are left in a long time.

                If you leave stressed steel in it (or in anything else, even Evaporust) too long, it will be eaten. My favorite (not) example is the bow spring from a pair of dividers. Did not take it off the dividers, and put it in with it "sprung" still holding the divider legs. Left it too long, which was 2 or 3 hours, and the spring had been eaten partly through by "stress corrosion". I have also seen the surface of case hardened steel attacked in a pattern very much like what you see in color case hardening.

                Even material which is normally non-aggressive will eat steel in a stress corrosion situation.

                But it takes several hours with phosphoric, which is far longer than de-rusting should take.
                1601

                Keep eye on ball.
                Hashim Khan

                Comment


                • #9
                  Ok franz, Definitely sounds like you know what you are talking about so will take your warnings seriously.

                  But in my defense, I have heard of using vinegar for years to remove ruse, and this is the first time I am
                  hearing of this, but better late than never.

                  The vise is huge and the exact replacement for the one my granddaughter broke. She was squishing a piece of wood
                  and I was teaching her the power of leverage and told her to put this 3ft long piece of pipe on the handle and give er hell.

                  SNAP !!!! right in two … and .. bent the lead screw.


                  John Titor, when are you.

                  Comment


                  • #10
                    I've been using vinegar to derust various items, most recently a bunch of rusty drills. I dilute it with about half water and let it soak for a couple days. It helps to agitate the solution, and also to scrub the parts with a bristle brush. It leaves a grey-black coating which seems to be friendly to a coating of oil for future preservation. The solution turns brown and seems to bubble a bit. The reaction probably stops eventually as the acid gets depleted.

                    I've posted before the results I had for an old micrometer I treated with a vinegar soak:





                    I haven't tried it yet, but many people have reported good results using electrolysis:

                    https://hackaday.com/2014/05/15/elec...-shiny-as-new/

                    https://www.wwgoa.com/article/removi...electrolysis/#

                    http://pauleschoen.com/pix/PM08_P76_P54.png
                    Paul , P S Technology, Inc. and MrTibbs
                    USA Maryland 21030

                    Comment


                    • #11
                      Just to get it out of the way, I already covered the process MISNAMED "electrolysis" 8 ways to sunday in another thread, and have no intention of revisiting it here. It's a completely different process with the only relationship being rust goes byeby. Commingling the processes does no good.

                      As to me having an idea what I'm doing there are legions on both sides of that question. I'll just say I been at this rust thing since about 67 when I got into Phosphoric via Naval Jelly. I also have delivery receipts for 80,000 pounds of blast media ranging from soda to steel shot including corncob, wheat hull and walnut shell in between.. I've also bought a few barrels of acid. Also as I said in the other thread, there are a multitude of approaches.. I'll further state I have a very low tolerance for people who misrepresent processes and products to make a buck pasting labels and shipping product. Anybody wants to call me opinionated can save the keystrokes, I am, and I earned my opinions by doing, not dreaming. I'll even tell you if you got a fiberglass car or bathtub that needs scrubbing the best material to scrub with is Bread Flour on a damp cotton rag. Works well and don't scratch.

                      BTW, before you get worked up over the NEW Lazer, remember it's only a remake of the 1940s vintage O/A descaling torch using entrapped water in the rust to blow the rust away.

                      I'll also stick with Phosphoric doesn't attack good iron and steel.
                      Bear in mind, steel is NOT a solid polished surface under the rust, and it wasn't the day it left the mill or shop. Iron & steel are both loaded with porosity and microporosity where rust lives. It becomes very evident when you blast steel to "gray iron" and come back the next morning to find flash rust all over the gray. Blasting peens rust in the pores. Those seeds get air and water and they grow like grass after a rain.

                      As to phosphoric or any process eating springs and causing cracking, did you inspect the steel with a microscope prior to removing the rust? The cracks were there, and the rust was both expanding them and filling them. If you scrape the rust layer off and do Magneflux you'll see the cracks. I know it's easier to blame the rust removal process. Remember, rust is very powerful, look what it does to concrete bridge decks and parking structure decks when salt water helps Re-Bar rust. It's a little slower than busting concrete with Quick Lime but rist busts concrete. Sorry part is all that rusting Re-Bar can be protected from rusting with electricity, but politicians won't let it be done.

                      Graphitic softening is probably a poor name as well, but that's the name that was assigned 100 years ago when books were written on the subject..

                      Vinegar is probably one of the worst ways to remove rust deposits, and Muriatic is a poor way to clean toilet bowls. Yes they both work, but neither works well. If you want to use either, feel free, ain't my money yer throwing away, and I ain't got time to fight about it.

                      Also if you want to do submarine in a tank with rust, mount a solenoid on the tank bottom and drive it thru a diode to give you 3600 pulses a minute. There is no need to go to UT frequency and it's cheaper.

                      It's a black art gents, based on crude science. Rust will always win, but it can be slowed.

                      Don't buy cap in rattle cans, especially don't buy Fluid Film. The formula was changed in 2015 to fire sheep from the company, but nobody mentioned the sheep going out to pasture because over 50 years of advertising and government contracts depend on them fuzzy girls.


                      Comment


                      • #12
                        Franz, you obviously have good hands-on expertise and valuable real world experience, but your grasp of the chemistry is sometimes off. For example, chelates dont "rob the oxygen" and leave the iron. They actually grab the metal ion (e.g. iron) from the rust and sequester it.
                        For just a little more, you can do it yourself!

                        Comment


                        • #13
                          Originally posted by Franz© View Post
                          .......

                          I'll also stick with Phosphoric doesn't attack good iron and steel.
                          ........
                          As to phosphoric or any process eating springs and causing cracking, did you inspect the steel with a microscope prior to removing the rust? The cracks were there, and the rust was both expanding them and filling them. If you scrape the rust layer off and do Magneflux you'll see the cracks. I know it's easier to blame the rust removal process. ..........
                          That is a fair statement.

                          The issue is that there NEVER IS any "good" steel underneath. There is just steel with less rust and fewer cracks or pores. All steel is defective, but better steel has defects that are not a big deal for most purposes.

                          And nobody is "blaming" the phosphoric, it is just the acid that happens to be there. Phosphoric does two things if left on too long.....

                          1) It will put on a heavy coating of iron phosphate, and keep doing that until the coating impedes the reaction. The coating is grayish black, and may not be what you want on the iron.

                          2) As with any material that is the slightest bit corrosive (and some that are not), it will exploit the cracks and defects that are in the steel, but it does so much MORE if there is STRESS.

                          Normally it would convert the surface of the crack and stop. But if there is significant stress, the concentration of stress at the tip of the crack permits attack where normally there would be minimal or no attack. The crack gets extended, and, in a spring, the stress concentration gets worse, so attack increases. Each bit the crack extends adds new fresh surface, and concentratrs a bit more stress. Phosphoric coats that surface, other acids might attack it, but the stress allows the phosphoric (or other material) to continue attacking the end of the crack.

                          The stress in the spring or due to the hardening process is the real culprit, it allows normally not-very-damaging materials to attack and corrode the steel. That's "stress corrosion". The phosphate coating does not stop it, because there is new surface continually being exposed.

                          Water would do the same thing, given time, but the phosphoric is more active, so if it is present, the process goes faster. I understand that "Evapo-Rust" will also do the same thing, and it is supposed to be much more benign than phosphoric.
                          1601

                          Keep eye on ball.
                          Hashim Khan

                          Comment


                          • #14
                            Speaking of phosphoric derusting, I just pulled this out of the tank this morning. My 5-gallon bucket isn't big enough to do it all in one go. It had the black smut, but it brushed off pretty easily. The other half is back in the tank now.

                            Ed

                            Click image for larger version  Name:	DSC08231.JPG Views:	36 Size:	484.3 KB ID:	1850109
                            Last edited by ed_h; 01-20-2020, 09:17 PM.
                            For just a little more, you can do it yourself!

                            Comment


                            • #15
                              Ed I never claimed to be a chemist, but you'd be surprised what I can do with peanut butter demonstrating Munro effect on a good day. I normally phoned in Chemistry questions to Kodak where they hired PHD Chemists when there was a Kodak. Generally they told me I couldn't possibly do what I just did and called to ask what happened.

                              JT, you're over thinking the rust in a crack situation, which ain't a whole lot different from rusting Re-bar spalling concrete off a deck. Most cracks are far longer than they appear to the Mark 1 eyeball, which is why we drill holes in what we hope is the end of the crack before trying to weld it.

                              You're also misunderstanding the phosphating thing a wee bit. Phosphating occurs real well with acid at from 5 to 10% concentration. Higher acid concentrations don't phosphate for Diddle Q Squatt but they do walk rust off. In the big picture Iron Phosphate is one of the good guys. Coatings such as enamel DON'T adhese to steel, which is why primer goes between steel and enamel. Both adhese to the primer on their respective side of the layer. Iron Phosphate goes beyond adhesing and chemically bonds to steel as well as killing rust in porosity and getting toenails into the steel. Enamels stick to Iron Phosphate usually better than they adhese to primers. End result, is a superior & longer uselife to the coating, including greater resistance to spalling from impact. I have 40+ year old paint jobs in the yard with Cat enamel still clinging to Iron Phosphate with no primer layer.
                              I don't think wet Iron Phosphate exerts pressure anything near sufficient to expand a crack, it might, but I don't have the instrumentation to prove or disprove. Bottom line, the object was rusty to begin with, and more probably defective under the rust. I've only been on 1 job where the customer had the $$$ to Xray the object prior to derusting in over 50 years. They also had a squadron of people in white lab coats who assured me they knew more than I did, and my idea was insane. I left, they did what they wished, and the object became a pile of something in the bottom of the tank.

                              I can assure you adding DC electrons to a Phosphoric tank will deliver spectacular erosion to the object being derusted, looks similar to a wet cylinder liner in a Diesel that has eroded thru from the liquid side. You play with rust long enough you see some strange results nobody I've met can explain. Also electric don't help in a Molasses tank, do't even cut the stink or keep the visiting flys away.

                              Accept rust removal as a Black Art and get the job done. Over time 2 things happen, you develope a good process and you run out of rusty objects to play with. Shoot, I spent 2 years developing graphite electrodes and 8 more finding the right filter media to get my tank running clear without the slop on top. Then I spent a few more mad I hadn't remembered what media did what I wanted because I knew that years before. Sure talked to a lot of white coats in that time who assured me filtration couldn't accomplish what I got it to do. You just gotta think beyond the white lines at the edge of the road.

                              Comment

                              Working...
                              X