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coating over cast aluminuim

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  • coating over cast aluminuim

    Do you think it would be better to polish out the part or to just smooth out the casting marks so you cant see the cast marks and minimize gasout?

    Thanks Mike

  • #2
    I would just smooth it out and not polish it. Either way, it will not prevent out-gassing. To help prevent bubbles (out-gassing) on aluminum parts you will need to heat the part (no powder) to 400* to 425* for 15 to 20 minutes. Allow to cool completely, then sand blast and powder coat like normal. Any oils or trapped gasses should be "baked out" that way. It's especially a good idea to do this on automotive parts because they have almost certainly been in contact with oil, even if new (casting sand). Hope this helps.



    • #3
      I coated a set of front calipers for my Honda VFR and I got a fear bit
      of bubbling. I thought it was because I didn't have them clean enough
      even though I cleaned them with varsol then sand blasted and clean
      them with alcohol before I coated them. I did preheat them before I
      coated them but maybe not long enough. Now I think it was a gassing out
      problem. What do you guy's think?
      Art in Peterborough


      • #4
        I'm wondering if using a zinc-rich primer in some cases would help. I would think that if you slow bake the primer it would complete the out-gassing and flow into the open spots giving you a nice barrier and also filling in some of the rough spots giving you a smoother surface.


        • #5
          look into the Tips and Tricks thread for outgassing techniques. Amazingly enough, the information there is what you would pay for in most "how to" powder coating books found on the internet today.

          The zinc primer once applied will not flow like you probably would like it to. Just follow the method of success that others have in outgassing and all should be fine. Patience is key. You only get one chance to do the job correctly. Otherwise..... I'm sure somebody here can tell you firsthand how stripping powdercoating is not a fun way to spend an afternoon,lol. Good luck with it.


          • #6
            This will be the third time i will be coating it. So no one has to tell me hard stripping powdercoat is. The first time i coated it it gased out pretty bad. The second time was just bad in one spot but that was the most visible spot on the part that your going to see. Now i got some Metal-2-Metal and i am going to try applying it to the few spots that were out gassing if that don't work then that will be the best i can do. I have preheated the part both times. I think the Metal-2-Metal will be my ticket to success. I tested the Metal-2-Metal on a scrap piece to see how it will work with the powder and curing process and it seems to do excellent. It didn't cause any out gassing its self. I have read every post on this board that has to do with powder coating


            • #7
              The easiest way that I have found to strip powder coating on small parts is to buy a gallon or two of aircraft remover and just let the part set in it for about 15-30 minutes. After that you can just about remove all the coating with a paint brush.

              I just did a set of calibers not to long ago that did the same thing that you are describing. Instead of stripping the caliber down, I just ruffed it up with some 400 grit, cleaned with alcohol and recoated. No problems what so ever with the second coating. and a lot easier than stripping them down.


              • #8
                I finally got around to getting my part done. First i used a stripper to strip the coating off. Then i rinsed with water and then washed with car soap. I then went over all the spots that i could remember where it outgassed bad at with Metal-2-Metal. After sanding all the high spots off i washed the part back off the soapy water. I air dried and cleaned with acetone. 4th i preheated the part to 425 for 20mins. Pulled it out the oven and coated it with the Chrome. Cured it at 350 for 25min and then applied the clear and cured it at 350 for 25min. There was just 2 little specks where it tried to out gas. The reason for me to worry about this piece is because i am trying to sell it. Just in case some one here is die hard ford this is a Pro Mustang EFI Spyder intake. Just for some one that doesn't know what that is, it is a Victor Jr intake that is converted to Fuel Injection. It has an Elbow that sits on top, where a carb usually sits. I'll get some pics and post them. Hope this helps some one here.


                • #9
                  Spyder intake eh? My brothers and I were just talking about that the other day. My little brother, 18 years old, just bought a bunch of parts for his 89 stang and a 306 DSS motor. He wants to beat me in my stang, not gonna! lol My other brother does Superchip tuning, he has the wide band O2 sensor, laptop and software and chip burning hardware, pretty amazing what can be done with that thing. Can't wait to try it on my car. Ever heard of the Parker Funnelweb A guy I work with has one on his 347, he ran it last week in a 66 stang, went 10.60 on motor, but it was a wild ride, stock suspension up front and back. Those 65 and 66 stangs don;t like to go straight......quickly! lol