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  • Anodizing and Ventilation

    Quite a few years ago I purchased an anodizing system (and I still have it). I received it in the dead of winter (it was 30F below zero) so I acted STUPID and decided to anodize some parts in my kitchen. This was NOT a bright thing to do. Although the process only produces hydrogen gas, H2SO4 is picked up with effervescence and H2SO4 fumes quickly filled the house. We had to open every door and window to vent our home. It must have been bad because I am still cleaning feces out of my underwear.

    All being said, I was considering the fabrication of an enclosed hood, 3X4X2 feet, (like the ones used in chemistry labs) with exhaust fan. I would like to keep it simple. Anodizing will not be a frequent event therefore I don’t want to spend a lot of money on a “protected” exhaust fan. My concern is, H2SO4 will attack the fan’s metal components cutting its life expectancy short. I considered cutting a hole in the top of the hood and using a Wet-Dry vac as the ventilating source. The exhaust hose would be vented to the outside.

    For those having some experience with anodizing, what are your thoughts on using the Wet-Dry vac to vent gases to the outside?

    Harold
    For those having fought for it, Freedom has a flavor the protected will never know.
    Freedom is only one generation away from extinction.

  • #2
    Can you spell suicide..... H2 is extremely flamable. You need an expolsion proof fan for that application.

    Comment


    • #3
      I dont know if I would trust a shop vac to do the job. Not to say that it couldn't but I would have to think more about it. The bigger issue is the air that is replacing the exhausted air. If you remove air from a room, where does the air that replaces it come from? Generally, it is from the leaks and cracks in the house letting outside air in. Why not force outside air into the area where the work is being done and then out an exhaust? That being said...

      A similar subject was kicked around here before concerning paint booths. You might want to take a look at small portable paint booths that use positive ventilation to force the air in the area out. This method keeps fresh clean air moving past the fan and there is little chance of the fan being an ignition source or becoming corroded from the fumes.

      Search the past threads around here and see what comes up for paint booths.
      Rock~
      Civil engineers build targets, Mechanical engineers build weapons.

      Comment


      • #4
        How about venturi action?

        Shopvac 2" *exhaust* hose run into the center of a 6" exhaust pipe near the exit. Result is high speed air picks up air from around the 2" exhaust point and takes it along for the ride out the 6" exhaust pipe.
        (Alternatively, compressor can be used, But could be more of a waste of energy.. Not sure)

        Id also consider doing it outside... Iv heard vaporised acids love to attack (rust) everything metal in the room.
        Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

        Comment


        • #5
          You might create a venturi in the ductwork and use your shop vac as a blower to exhaust the gases. There would then be no fan in the ductwork, thus no explosion issues. You would probably need to fool with dimensions and flow rates a little.

          Just a thought.

          Mark

          On edit, Black Moons beat me to it.... So it must work if we both think so.

          Comment


          • #6
            Running for an continuous hour or so is hard work for most consumer-duty shop vacs.

            Black Moon's suggestion for a venturi-type system, but driven by a continuously-duty blower makes sense.

            Why not just do your work outdoors? Well, not at 30 below, but cold is better when anodizing, as deeper penetration is possible and cooling the bath is easier. You don't need to hover over the pot during the whole process.

            I did some indoor anodizing once, but later found some badly rusted tools in the vicinity of where I did the dirty deed.
            Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
            ~Practitioner of the Electromechanical Arts~

            Comment


            • #7
              Anodizing Safety

              You might be well advised to cobble together a proper chemical lab style fume hood. A four foot wide hood, with the front sash open 12 inches, needs enough air through it to give an average face velocity of 100-125 ft/min. This translates into about 500 cfm. Not a lot, any small furnace circulating fan will easily give that output.
              DO NOT believe that more is better in this application. Any less can cause problems and much more will only cause more problems. This air flow will, by the way, create a safe working environment for virtually ANY gas or fume. There are exceptions, but you wont run into them.
              How do I know this? This is what did for a living for about 20 years. I worked mostly in research labs, but the principles are a constant.
              Duffy, Gatineau, Quebec

              Comment


              • #8
                Here is one option for a fan. There are others and the little computer fans are all plastic and cheap enough to pitch if they die.
                http://www.surpluscenter.com/item.as...958-A&catname=

                Comment


                • #9
                  Fan problems

                  Because of the entrained sulfuric acid, the exhaust will play hell with any ordinary blower or fan. Ideally, you want a belt driven all-plastic utility set or a vane axial unit. THAT is unlikely to happen. The one listed in the Surplus Center MAY work. The only problem that I forsee is with the motor being in the air stream.
                  Do not forget, this will not be a full-time operation, so maybe a fan that dies an early death is alright for the purpose.
                  A decent double-spool range hood fan would work and they turn up in the garbage or garage sales or at Habitat.
                  Duffy, Gatineau, Quebec

                  Comment


                  • #10
                    Iv run a few shop vacs for over 24 hours... And indeed it is hard on them.. they only lasted about 15 days on average. Thankfuly that was only 3 days outta every year they had to be used in my case. (Basement floods that occured about once a year)
                    Play Brutal Nature, Black Moons free to play highly realistic voxel sandbox game.

                    Comment


                    • #11
                      Originally posted by Black_Moons
                      Iv run a few shop vacs for over 24 hours... And indeed it is hard on them.. they only lasted about 15 days on average. Thankfuly that was only 3 days outta every year they had to be used in my case. (Basement floods that occured about once a year)
                      Those must have been the older good ones, the el cheapo's get very hot after a few minutes.

                      Comment


                      • #12
                        Originally posted by Duffy
                        You might be well advised to cobble together a proper chemical lab style fume hood. A four foot wide hood, with the front sash open 12 inches, needs enough air through it to give an average face velocity of 100-125 ft/min. This translates into about 500 cfm. Not a lot, any small furnace circulating fan will easily give that output.
                        DO NOT believe that more is better in this application. Any less can cause problems and much more will only cause more problems. This air flow will, by the way, create a safe working environment for virtually ANY gas or fume. There are exceptions, but you wont run into them.
                        How do I know this? This is what did for a living for about 20 years. I worked mostly in research labs, but the principles are a constant.

                        Originally posted by hwingo
                        All being said, I was considering the fabrication of an enclosed hood, 3X4X2 feet, (like the ones used in chemistry labs) with exhaust fan. I would like to keep it simple. Anodizing will not be a frequent event therefore I don’t want to spend a lot of money on a “protected” exhaust fan. My concern is, H2SO4 will attack the fan’s metal components cutting its life expectancy short. I considered cutting a hole in the top of the hood and using a Wet-Dry vac as the ventilating source. The exhaust hose would be vented to the outside.
                        I think Duffy's comments and reasoning are more in order with my thinking. That's why, in my initial statement, I talked about an *enclosed* hood being 3 feet tall, 4 feet wide, and 2 feet deep.

                        Yes, I can spell H2 (hydrogen gas). I can also spell Hindenburg and I am aware that hydrogen gas can be explosive if the percentage of hydrogen gas increases to as little as ~18% in air. I do believe that the *percentage* of the mix is what is important rather than the *presence* of H2. I have never done a quantitative analysis to determine just how much H2 is generated when anodizing small parts but I suspect it is small. I also suspect, though I admit it's a leap of faith, that having an adequate "draw" of room air into the hood (and out the other end to the outside) will quickly mix generated H2 and "dilute" the small amount of H2 generated significantly decreasing the percentage of H2 in the mix and lower the risk of explosion. We generated some ugly gases in college and to the best of my knowledge, there were no remarkable events when using the hood.

                        I like the venturi idea. I also like the explosion proof motor idea but those things are expensive. Still, with all being said, H2SO4 (in vapor form) is still my greatest concern. One has suggested doing this out side and that is a reasonable suggestion ...... except Alaska winters get quite cold. This would limit latitude and I desire unfettered time if needing to anodize a part.

                        I appreciate all suggestion and thoughts on this matter and I thank you for making the effort to consider my dilemma.

                        Harold
                        For those having fought for it, Freedom has a flavor the protected will never know.
                        Freedom is only one generation away from extinction.

                        Comment


                        • #13
                          Harold, venturis sure do work, but they have a very high operating cost. For a 4 to 5 foot wide perchloric acid fume hood, figure a 2 hp induction fan. These used to be plumbed up with type 316 SS all-welded duct work, washdown rings every eight vertical feet and all assembly using 316 SS bolts, nuts and washers. I was paid A LOT of money to prepare the protocols and supervise the dismantling of many systems that had a few "substitutions" in the assembly.
                          I have just been working on a newer unit,all SS but with a plastic vane-axial fan, ($10,000.00 for the fan, by the way,) and an all plastic fume hood with an integral scrubber system.
                          Incidentally, Gatineau/ Ottawa weather takes no backseat to yours!
                          For your purposes, and to leave you some funds to build guns, I would suggest the following: Build your enclosure, with a sloping top to the exhaust stack, from melamine board, with carefully caulked along the seams. hinge a piece of polycarbonate, (1/8") across the front, with a 6 to 12 " gap at the bottom. Scrounge up some 6" plastic sewer pipe off-cuts to use for exhaut duct and mount whatever fan you can find on the terminal end. Accept the fact that its life WILL be short.
                          You dont have to worry about a rear-mounted exhaust plenum with upper and lower pickups; your only problem will be damp, acidic, warm air with a bit of hydrogen in itand it will rise by itself.
                          Duffy, Gatineau, Quebec

                          Comment


                          • #14
                            Originally posted by Duffy
                            Harold, venturis sure do work, but they have a very high operating cost. For a 4 to 5 foot wide perchloric acid fume hood, figure a 2 hp induction fan. These used to be plumbed up with type 316 SS all-welded duct work, washdown rings every eight vertical feet and all assembly using 316 SS bolts, nuts and washers. I was paid A LOT of money to prepare the protocols and supervise the dismantling of many systems that had a few "substitutions" in the assembly.
                            I have just been working on a newer unit,all SS but with a plastic vane-axial fan, ($10,000.00 for the fan, by the way,) and an all plastic fume hood with an integral scrubber system.
                            Incidentally, Gatineau/ Ottawa weather takes no backseat to yours!
                            For your purposes, and to leave you some funds to build guns, I would suggest the following: Build your enclosure, with a sloping top to the exhaust stack, from melamine board, with carefully caulked along the seams. hinge a piece of polycarbonate, (1/8") across the front, with a 6 to 12 " gap at the bottom. Scrounge up some 6" plastic sewer pipe off-cuts to use for exhaut duct and mount whatever fan you can find on the terminal end. Accept the fact that its life WILL be short.
                            You dont have to worry about a rear-mounted exhaust plenum with upper and lower pickups; your only problem will be damp, acidic, warm air with a bit of hydrogen in itand it will rise by itself.
                            Hi Duffy,

                            I just got home from work and just read you last comment. Like I stated previously, I’m not too terribly concerned with H2. As a side note, minus a barrel (which will not be parkerized) I parkerized the remainder of a rifle last night. This was done on my gas kitchen range under a conventional stove top hood. The parts “fizzed” H2 angrily for nearly 12 minutes at 185F. Either I was fortunate or there was insufficient H2 generated to create an explosion. Another way of approaching this is, there was ample surrounding air that mixed with hydrogen gas to sufficiently lower gas percentage below the percentage necessary to have an explosion. I can never recall that much activity when anodizing.

                            As I drove home, I had visions of my future vent pipe becoming a “cooling tower” during the anodizing process. I imagined the fan drawing H2SO4 fumes from the hood and pushing it along the vent pipe, all the while condensing and collecting on the inside walls of the pipe. When sufficient amounts had collected, I envisioned small streams of acid running back from whence it came forming an ever growing pool of concentrated H2SO4. Without cleaning out the exhaust pipe after every session, such is more than plausible.

                            Although it would be a pain in the rump, I can see no way of escaping the need to disassemble the vent pipe and wash the inside with NaHCO3 after every session. In the summer or even in less extreme winter conditions, an alternate site could be used out-of-doors. As one contributor pointed out, “cooler temperatures are the anodizer’s friend”. Still, it would really be nice to have everything indoors and not have to worry about local moose, wandering brown bear, and the dreaded summer black flies and mosquitoes disrupting me or works in-process.

                            Harold
                            For those having fought for it, Freedom has a flavor the protected will never know.
                            Freedom is only one generation away from extinction.

                            Comment


                            • #15
                              How big is this setup?

                              Used to do sulphuric anodising in an enclosed environment 19% mix but more worried about the fumes from hydrochloric acid.

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