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Plastic identification? Help?

Wondering what type of plastic a dirt bike gas tank is?. About the trick with some acetone to check if it's ABS or otherwise but not sure if that applies here. I know plastic gas tanks in general are tricky, not even sure they can be done. I've tried in the past but with the sweat the tank produces it just bubbled the paint. Am I missing something when it comes to these types of Tanks?


  • PagesHydroDippingPagesHydroDipping Posts: 222Member ✭✭✭
    When you rub the acetone on there if it get tacky your good to go. If it doesn't do anything then you need to flame treat. As far as the had tank sweating and bubbling the paint im not sure about. That shouldn't effect it in my opinion. It doesn't effect the paint on any other gas tank, but you might wanna let some of the big dogs on here chime in. Sounds more like an adhesion problem to me.
  • DeviousDipsDeviousDips Posts: 1,235Member ✭✭✭✭
    edited January 26
    The tank I did on a KTM had the mark on the tank and the seat part. They were LDPE. I doubt any atv or dirt bike is abs. I would flame treat it
  • WileECoyoteWileECoyote Posts: 5,750Member, Moderator, Business Ninja El Moderator
    If it was ABS the gas would eventually eat through it. Typically it is PE (LDPE more than likely) you need to practice your flame treat technique. Only one way to do it, and it has to be flamed.
  • winterwinter Posts: 18Member
    Thought I read or heard that if using OHW paint, the ONLY plastic that had to be flamed treated was HDPE, regardless of whether acetone made any other plastic types gummy or not. Think there are a few plastics that rubbing with acetone has no effect on.

    Regarding OHW paint, is this right or not?


  • smedlinsmedlin Posts: 1,240Member, Business Ninja ✭✭✭✭
    @winter , don't believe all the stuff you read on face book....

  • DeviousDipsDeviousDips Posts: 1,235Member ✭✭✭✭
    Ohw is great paint but on Hdpe and LDPE you are gonna have to flame regardless of the paint. 
  • winterwinter Posts: 18Member
    edited January 28
    Sorry @smedlin but nope, couldn't been FB. Rather go to the dentist! Ain't FB only for soccer moms or drama queens in between morning joe breaks? )

    Hmm, this is off ohw website and HDPE only plastic mentioned, so just not wanting to take a chance flame treating unless really necessary.

    "just degrease, scuff, and tack cloth. HDPE plastics require flame treatment before degrease and scuff."
    Post edited by winter on
  • NotSoFastNotSoFast Posts: 3,147Member, Moderator El Moderator
    I know that with decals, they bubble up over time from the gas fumes slowly leaching out. Is this a problem with painting them? Most aftermarket decal kits that go on the gas tank itself are perforated to allow the fumes to escape.
  • MidOhioHydrographicsMidOhioHydrographics Posts: 8,817Member, Moderator, Business Ninja El Moderator
    HDPE (high density polyethylene)
    LDPE (low density polyethylene)

    Both are polyethylene and both should be flame treated.
  • winterwinter Posts: 18Member
    OK and thanks for your replies!

    Even though I've painted a few gas tanks in my earlier days, I've never experienced the bubbling mentioned, so can't comment on that.

    Understood regarding HDPE and LDPE, but should the acetone test mentioned earlier affect either once flame treatment is done?

    Thanks again.
  • MidOhioHydrographicsMidOhioHydrographics Posts: 8,817Member, Moderator, Business Ninja El Moderator
    edited January 29
    Nope. Acetone will never affect polyethylene... or polypropylene for that matter, or nylon.... But you can get away with not flaming PP and nylon. If you’re unsure if it’s PP or PE or something else that doesn’t gum up? Just flame to be safe. It’s just a safety net to flame if it doesn’t gum up with the acetone test. Spend a few minutes now to sleep better knowing it won’t come back in a few months.
  • WileECoyoteWileECoyote Posts: 5,750Member, Moderator, Business Ninja El Moderator
    edited January 29
    The acetone test is exclusively to determine if a plastic is ABS or not. Nothing else. If it doesn't gum up with acetone, all you have determined is that it is some other plastic. 

    OHW version 2 will go directly to all other plastics without flame treatment EXCEPT polyethylene (this is according to @onehitwonder himself) without an adhesion promoter, or the NEED to flame treat... But flame treating ALWAYS helps. Your results may vary depending on your process, but that is the way it is designed.

    HDPE, LDPE, PE, and UHMWPE are all polyethylene so keep that in mind, and yeah... They don't paint gas tanks exactly for the bubbling reason... So just keep that in mind when you discuss with the customer.
  • onehitwonderonehitwonder Posts: 2,635Member, Business Ninja ✭✭✭✭✭
    Yessir, these guys are right. OHW will go directly to EVERY material, not just plastic, except anything ending in PE. The release agents continue to sweat from inside PE, and will eventually pop ANY paint off. Sweat the chemicals out first with flame - and this may take more than 5 treatments!
  • winterwinter Posts: 18Member
    Appreciate all but gotta ask ... how do you know when you've reached the necessary number of treatments? Sorry if this was discussed before, but can't seem to find it.

    Based on what I've seen in Jim's video, it seems that once you can spray water on the plastic and it sheets, you're ready to paint (using OHW). (adhesion promoter before paint otherwise) This seems like it can work on some items in just 1 treatment or "may take more than 5 treatments". Is it just whenever the water sheets?
  • TroubleTrouble Posts: 265Member ✭✭✭
    I flame until it no longer sweats there is no set number passes (treatments) they will vary some will take 2-3 passes and I did a cooler that took over 6.There is no set number of passes every part will be different. I keep doing it until it no longer sweats then make 1 additional pass then test with water. If water beads anywhere on your part repeat process.
  • WileECoyoteWileECoyote Posts: 5,750Member, Moderator, Business Ninja El Moderator
    Ok, guys, I was going to try to figure out what the numbers were that we needed to give you guys a shortcut, but I am not involved in the process enough anymore to get the testing I need. I talked to Jim about this a while ago and he nearly wet himself with anticipation. The problem you guys are running into is the surface energy, this is an issue with all sorts of plastic manufacturing processes. The way they test this a little more scientifically than spraying water is called a dyne pen.

    McMaster-Carr sells them, as well as many others
    Surface Energy Testers

    Test the surface energy (dyne level) of film and other nonabsorbent surfaces before printing, coating, or laminating. Also known as dyne pens, these work like a felt-tip marker. A continuous line will appear if the material meets the tester's surface energy level, while insufficiently treated material results in air bubbles and a disappearing mark.
    Surface Energy For
    Use On Lg. Each
    30 dynes/cm Plastic 5" 5590K26 $25.84
    32 dynes/cm Plastic 5" 5590K11 25.84
    34 dynes/cm Plastic 5" 5590K12 25.84
    36 dynes/cm Plastic 5" 5590K13 25.84
    38 dynes/cm Plastic 5" 5590K14 25.84
    40 dynes/cm Plastic 5" 5590K15 25.84
    42 dynes/cm Plastic 5" 5590K16 25.84
    44 dynes/cm Plastic 5" 5590K17 25.84
    46 dynes/cm Plastic 5" 5590K18 25.84
    48 dynes/cm Plastic 5" 5590K19 25.84
    50 dynes/cm Plastic 5" 5590K21 25.84
    52 dynes/cm Plastic 5" 5590K22 25.84
    54 dynes/cm Plastic 5" 5590K23 25.84
    56 dynes/cm Plastic 5" 5590K24 25.84
    58 dynes/cm Plastic 5" 5590K25 25.84
    60 dynes/cm Plastic 5" 5590K27 25.84

    As you can see, there are a number of levels, and these aren't cheap... but they WORK. If the line you draw an the part stays solid, its good, if it breaks up, keep treating. The problem is, that I don't have any data to help you get started, as in

    Polyethylene needs to be treated to a level of 40 Dynes to be coated. Or, OHW needs treatment to 40 Dynes, but Water based paint needs to be treated to 50. So I am going to Leave it up to you guys how we progress with this. I can just leave this information here, and it will eventually get buried, or I can start a new thread, where some guys can order one or two of these and do some real world testing and post results for everyone.

    Honestly, I don't think that it will be all that hard, I think ANY surface treatment is enough to get it to stick, so I am thinking we are talking the 30-34 Dyne range. Keep in mind, this is really for ANY plastic, and it is a 99% positive way (after we determine what the right numbers are) to know that you have prepped your plastic correctly, or if you are overworking the process and could dial it back a few passes.

    I will leave this here for all, and you guys tell me what you want to do. I will process the info and present it, but I need help on the testing (plastic samples, different paints, and adhesion testing) Any of you that haven't been to a remote training will know I LOVE testing, so there are gonna be some rules to follow...
  • K2ConceptsK2Concepts Posts: 12,571Administrator El Jefe
  • WileECoyoteWileECoyote Posts: 5,750Member, Moderator, Business Ninja El Moderator
  • LibertymanLibertyman Posts: 744Member ✭✭✭
    @WileECoyote , Trevor, I think your a rocket scientist in disquise. Simply amazing the things that come out of the brain of yours :o :o
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