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Effect of purple cleaner on aluminum parts... tested

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  • Effect of purple cleaner on aluminum parts... tested

    There was a discussion of the proper way to clean an old machine on one of the email groups recently. During that discussion, it was repeatedly stated that Zep Industrial Purple Cleaner, a lye-based cleaning solution available in the US, and other similar cleaners will destroy aluminum parts, and aluminum alloy parts. Bead blasting (is that not destructive?) was suggested as a non-destructive alternative.

    Now, I am familiar with the fact that there is a reaction between lye and aluminum. No question there. But I have found it isn't instant death to parts.... in fact in cases where I wanted some smoothing and rounding of parts , I found I ended up tumbling them with abrasive because the chemical reaction was not effective.

    The folks were not having any of that, insisting it would "eat aluminum right up", complete with lurid stories of "som guy" who had the aluminum head of an engine disappear, leaving only the valve seats, etc, etc. If they would ever use it for cleaning aluminum, it would be a panicked fast dip and rinse...

    So I decided it was time for some data, and I produce it here.

    I filled a small yogurt cup about half full of undiluted purple cleaner (Zep Industrial Purple Cleaner from Home Depot). A square of foil (2.25" x 2.35") was immersed approximately halfway in the purple cleaner.

    After 20 seconds or so, it began to foam up, and looked like this


    I waited 10 minutes, until the reaction seemed to slow down, and removed the aluminum foil.

    The remaining cleaner in the cup had foamed up and held a "head" on it for some time.


    The aluminum foil was not visibly affected by the test.


    The immersed portion measured at approximately 1.2 thousandths of an inch thick at the thinnest part, and the non-immersed part at 1.8 thou. The difference was therefore 6 ten-thousandths of an inch.

    Another piece of foil was immersed in the remaining purple cleaner, and did show some bubbling, but nothing like the original hick "head" was present after several minutes. After an hour of immersion, the second piece of foil did have portions removed. Apparently while the reaction was not "showy", there was still enough reactive material in the solution to do that. Of course the mass ratio of solution to metal was quite large, and it is no surprise there was lye" left in the cleaner.

    So, by test, aluminum is "eaten" only in the most minimal amount, about 3 tenths off a surface (6 tenths total off two surfaces) in 10 minutes of submersion in purple cleaner. It sure looks to me as if you are perfectly safe scrubbing virtually any aluminum parts in purple cleaner. You won't have them in solution for very long doing that, and have no need to work in a panicky rush, either.

    Just do not soak them for an extended time.
    1601

    Keep eye on ball.
    Hashim Khan

  • #2
    Good to know, Thanks!
    "Let me recommend the best medicine in the
    world: a long journey, at a mild season, through a pleasant
    country, in easy stages."
    ~ James Madison

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    • #3
      I use lye dissolved in water to clean aluminum prior to anodizing - just a quick dip, 10 seconds or so, mostly to remove any skin oils from handling. Too long and it imparts a matte finish to the object. The solution is also useful to remove the anodized layer on a botched job, but does begin to change the dimensions.
      Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
      ~Practitioner of the Electromechanical Arts~

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      • #4
        It's not instant, it's all about rate of reaction, depends on temperature, concentration and surface area, small coal burns faster than big coal as my chemistry lecturer used to say, there is a danger of rounding off corners on precision parts though.
        I use caustic soda as an etch for Ali, never had a problem with disappearing things!, watch that stuff when mixing, cold water and metal bucket!, it's exothermic and will boil the water sharpish!
        When I started work eons ago it was at an aluminium works, extruding and rolling, the extrusion dies got cleaned in boiling caustic, as conc as it could be, still took 8 hours to clean a dies cavity out.
        I had heared that electro cleaning by adding some amps to the part was quick but have never given it a go
        Mark

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        • #5
          I've been using it (usually "Castrol "super Clean") on chainsaws (some mag alloy, most aluminum) and for cleaning Al for years. It dulls the paint more than it materially corrodes the aluminum. Yes, you don't leave it in longer then required. I dilute mine 2:1 (one gallon of PC make 3 gallons of solution) for most heavy degreasing and cleaning. I rarely use my brand of PC undiluted - it is pretty rough on paint / powder coat like that and offers little advantage.

          To "dissolve a head and leave the valves", you'd need a lot of sodium hydroxide. Some chemist can calculate the amount required per lb of Al. On the other hand, a concentrated solution of lye (way more than Purple Cleaner concentrations) is very good at removing Al bound to an end mill - I leave it in overnight and it's clean in the morning.
          Last edited by lakeside53; 10-21-2014, 12:43 PM.

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          • #6
            It's this damned stoichiometric thingy, 2Al+2NaOH+H2O, little arrow to right!2NaAlO2+3H2
            Means 1Kg of Al takes 1.5kg of caustic, makes .15 Kg of hydrogen and makes a nasty scum of NaAlO2 of around 3.25 Kg, according to and old notebook of mine, we were dumping sacks of caustic into the baths, and shovelling the crap from the dead baths
            The hydrogen can go bang, or squeak as it were!
            Mark

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            • #7
              Regarding
              • Zep Industrial Purple Cleaner and Degreaser
              • Castrol Super Clean
              • Simple Green

              and other products that clean 'miraculously' better than
              the traditional solvents used by our forefathers.

              Invariably, after water, the second principle ingredient
              is 2-Butoxyethanol. It will be present in concentrations
              of 1-10%, 10-25% and even up to 40%.

              Despite marketing claims that these products are
              environmentally friendly, use them with care.

              DO NOT spray these cleaners from atomizer bottles, apply
              with a brush or by dip/immersion. Work area should be
              WELL ventilated. Wear gloves, an appropriate respirator,
              face shield and cover all skin. Shower and change clothes
              afterward.

              Minimize or avoid application to rubber-based objects.

              .

              Comment


              • #8
                Don't recall the thread mentioned. I do recall the process of soaking new aluminum electronic chassis in a lye solution to impart the fresh aluminum with a nice uniform finish. Don't recall ever hearing any caution about watching over the bath or you will ruin the chassis.

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                • #9
                  I have used Zep purple to dissolve the aluminum out of plugged up end mills. Leave it overnight and it is mostly gone.

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                  • #10
                    DO NOT spray these cleaners from atomizer bottles, apply
                    with a brush or by dip/immersion. Work area should be
                    WELL ventilated. Wear gloves, an appropriate respirator,
                    face shield and cover all skin. Shower and change clothes
                    afterward.
                    so its a little late for me?

                    Have been using Simple Green since it has been on the market (was delivery driving for an industrial supply place at the time, we only got it in drums at first so did not use it a lot then, 20 years ago), almost always from atomizer bottles (aside from full strength gallons and larger that is how it comes on the shelf)...have never gone out of my way to wear gloves, never a respirator or face shield and definitely have not covered all skin.

                    We talking the same Simple Green?

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                    • #11
                      I had a funny accident with a really nice Chris King headset (bearing which allows the fork to rotate) and Purple Cleaner. I need to clean the old dirty grease out of the bearings and my usual technique was to take off one bearing shield and throw the lot into PC overnight, then rinse out, air dry and repack with fresh grease. Well, came back the next morning and my lovely black headset was now mottled silver! Spent some time with fine sandpaper and polish, now it's a somewhat polished silver.

                      Once I get my anodising set up running, I'll also be using a short 10% NaOH dip after cleaning, followed by desmut before anodising. If you want to avoid the slightly matt finish you can skip the NaOH step or use a stronger desmut (crazy % nitric acid I think) to get it nice'n'shiny.

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                      • #12
                        Originally posted by RussZHC View Post
                        so its a little late for me?

                        Have been using Simple Green since it has been on the market (was delivery driving for an industrial supply place at the time, we only got it in drums at first so did not use it a lot then, 20 years ago), almost always from atomizer bottles (aside from full strength gallons and larger that is how it comes on the shelf)...have never gone out of my way to wear gloves, never a respirator or face shield and definitely have not covered all skin.

                        We talking the same Simple Green?
                        Alkaline things generally turn your fats into soap. So yes you likely have minor damage to everything its touched. Doubt its going to cause you cancer or anything but could cause long term lung/eye damage as those don't self repair too well. I suspect its more about large or often repeated doses that are worse. Also droplets getting and drying on things that react with them (aluminum) would leave ugly marks.

                        That soapy feeling you get from lye cleaners is the fats in your skin turning into soap.
                        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

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                        • #13
                          You definitely don't want to use that stuff on polished aluminum. (unless you want to re-polish it)

                          John

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                          • #14
                            Don't mean to harp on this but the MSDS is very different in terms of eye contact, skin contact, inhalation and ingestion when comparing Simple Green to Zep Purple (as example)

                            Simple Green

                            Skin Contact: No adverse effects expected under typical use conditions. Prolonged exposure may cause dryness. Chemically sensitive individuals may experience mild irritation.

                            Inhalation: No adverse effects expected under typical use conditions. Adequate ventilation should be present for prolonged usage in small enclosed areas.
                            but it certainly has me wondering since as Eddy stated, the second ingredient is indeed 2-Butoxyethanol within the range of concentration he gave/listed. But to mistrust a MSDS document though certainly nothing is infallible.
                            Personally I have never felt the same "soapy" feeling using Simple Green but certainly did during a mistaken but brief exposure to hands using the Castrol product.
                            Last edited by RussZHC; 10-21-2014, 10:48 PM.

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                            • #15
                              About 25 years ago I was working in a furniture factory grinding knives and responsible for all of the cutting tools. The lady who did the saw sharpening had a vat of caustic cleaner that makes the retail varieties look downright wimpy. One day about quittin' time the guy who ran the tenon machine gave me a pair of cutterheads to sharpen. These had HSS knives in aluminum bodies, and I didn't give it a thought, I just dropped them into the saw cleaner vat and headed out the door to go home.

                              Before I got out the door my boss cornered me and wanted to know about whether something or other was ready. I didn't know so we went back into the grinding room and as I passed the vat of saw cleaner it looked like someone had dropped a ten pound Alka Seltzer in. I grabbed the gloves and reached in and removed the cutterheads and rinsed them off. Fortunately they were only discolored a bit and not damaged.

                              I experimented a bit with pieces of aluminum and found that they would only be damaged only to a limited degree, then were protected by a sort of crust that formed on all the exposed surfaces.

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