[Sam Simons]

This is directed more towards either the ATV/ dirt bikers,or professional painters (should there be any in the group).
Painting polystyrene pieces is sometimes difficult,particularly poly gas tanks.
I'm restoring an old d/bike that will require respraying all of the plastic. One
reportedly successful procedure involves sanding the surfaces,applying
a adhesion enhancer,followed by a flexible primer and then spraying the color
of choice. This is what I will do,unless,someone has found another method that was successful(i.e., the paint stayed on,didn't bubble,etc., after being put into use)  .


Sam

[Ice]

Sam is the tank polystyrene or polyethylene ?

[r80rt]

Krylon makes a spray paint specifically for user on plastic, Never used it so I can't say if it works or not.

[single]

Painting flexible plastic is now a science,process is well known at all real automotive paint supply stores.Just tell them whatcha gonna do and they will supply the needed materials and advice.The Krylon stuff seems to work good but time will tell.I personally have good luck with the adhesion promoters,flexible primer and acrylic enamel,but have only done a couple of bumpers.One was still lookin' good 2 years out,tho.

[Sam Simons]

My error,ICE,the material is polyethylene......BIG diff !
 I've acquired "Bulldog" brand adhesion promoter,to be used along with SEM brand flexible primer and Krylon FUSION color coat.
  In reading the many experiences on the 'Net,there's the opinion that the gasoline
permeates the wall of the tank and causes loss of adhesion.... I don't think that's
the case. Technically,on a very microscopic scale, that would be leaking. And,
neither do any of the paint coatings professionals believe that the presence of
gasoline is the culprit. Their common explanation is simply the 'oily' nature of
polyethylene and the difficulty in purging the material for painting(as one
rep told me,"that's why the color is in the material....").
  There are accounts of successful tank paint jobs....unfortunately,these
experiences range from-"'just sand it and shoot it with FUSION.." to the
involved process I'm planning to do.
In summary,it appears that successfully painting a  gas tank is no more dicy
than painting any other plastic component (on the same bike);gasoline isn't
the  show stopper,simply the plastic itself......which  will vary from brand to brand.
 I'm fixin' ta find out here reel soon......after MidOhio.

[Ice]

 Could post about the process along the way ?

[Sam Simons]

Certainly,ICE,with pics of the process and product details.
I've already wet sanded the entire tank with 320 grit paper,which dramatically reduced that slippery surface feel-not only because the surface is obviously rougher,but also because the surface  now has had the dead,hardened layer removed.

I'm convinced it can be(successfully) done,because  I've seen quite a few
such paint jobs,that,despite being poorly done or badly worn,were still
adhering very well to the plastic surface..........

My guess is that painting a 'mature' surface(this tank is 24 years old) is also
an advantage,versus a newer unit,which would have a higher content of
the chemicals present.....

[Sam Simons]

 So far,so good...All parts were:

 Initially decreased using lacquer thinner.

 Wetsanded with 320 paper

 Sprayed two light coats of Bulldog brand adhesive promoter

The sprayed two light coats of  Fusion color

Then lightly wet sanded using a 3M Scotchbrite (fine) pad

Adhesion test-with fingernail-no problems.


One more final Scotchbrite sand and then a 'wet' final coat of Fusion to finish.

[Ice]

Thanks for the update.

Q; Is it advisable to let the various coats dry completely or are the follow on coats applied when the previous one is still tacky ?

[Sam Simons]

The "Bulldog" adhesion promoter dries very quickly-15 mins. The coats of Bulldog were dry,but,did have a very minor tacky feel....
 I began spraying the Fusion
in very light ,'dry' coats shortly there afterward. Fusion says to recoat within 24 hours ,OR, 7 days later,so,I resprayed the following coats of Fusion approximately 12 hours
later.
 I decided to omit using the flexible primer,because I felt the addition of yet another layer
was an invitation for problems......

[Sam Simons]

Pic of the  products used and items painted...

[Ice]

 Looks good  . How long did it take to fully cure ?

[Sam Simons]

The Fusion product suggests a recoat (if desired) within 24 hours for the previous coating.....with full cure in 7 days. The adhesion promoter should be coated over
within an hour,IMO, while it still has a bit of a tacky feel to it.I used two different methods of abrasion on the plastic pieces - 3M Skotchbrite pads and  #80 grit aluminum oxide media.

[Ice]

Thanks Sam !

[Sam Simons]

Painted parts after reassembly.....I've got two more BW80's to do,and  will use Rustoleum  paint (with the same prep) on the next one.....

[Sam Simons]

Update: PROBLEMS.....

 In case someone is about to paint a plastic gas tank-hold on! One of my repainted
tanks(using the Fusion & adhesion promoter) has began to bubble,but only the
area of the tank covered by my graphics......
All other areas are fine,which is a bit puzzling. Apparently,the paint is able to
allow the fumes/gasses to continue on passing thru to atmosphere,thereby preserving
the bond. That's acceptable for a solid color respray,with the option to utilize a second
coat of another color for contrast.
I,however,want to add graphics,so I'm going to strip the tank externally,apply a
interior coating from Caswell Plating for plastic gas tanks and respray again.....
We will see.....

[zentrax]

stickers will not let fumes from fuel pass through, which is why it bubbles. does this on all plastic tanks. i dont know how durable the painted plastic in general will be, thought it might crack with any flex. most people i know who want to refresh plastic on their dirtbike without buying new is to use a product called plastic renew. you rub the plastic back with this stuff and its spose to bring it to a like new lustre. i've never used it myself, i just buy new plastic

[Sam Simons]

"....which is why it bubbles. does this on all plastic tanks..."
No,not in all situations.Plastic gas tanks have been on off road bikes since the
early 1980's,and only after many years of use and gasoline do some of them
begin to resist paint and/or graphics.The majority of the vintage bikes that I've restored were wearing their oem graphics,worn,but still tight on the tanks,when they arrived.
"buying new plastic" is a possibility,IF there a source for it,and IF the desired color is available....
The situation is one of having to insulate the gasoline from the exterior surface if the tank is resisting paint or graphics adhesion.
New plastic tanks resist paint adhesion because of the oils/esters present from their recent manufacture,and that is why the manufacturer (and owner) plaster all of those
garish graphics on them-which don't bubble either.
It's a matter of age and porosity-if the porosity can be checked,the surface purged,the coating will stay on.

[zentrax]

I can tell you every dirtbike i have owned has had the stickers bubble. Have had too many dirtbikes  to mention over the last 20yrs, many from new, and the stickers bubble within first few months. You are right though that there are exeptions, I had one that didnt bubble. It was a yamaha IT400 tank, bout 1976 model i think. The stickers seemed extremely thin and were incredibly difficult to get off. That tank cracked and i got one off a slightly newer model to replace it.......and the stickers bubbled. A lot of the dirt bikes I've had could be fitted with generic plastic if needed. I see from your pics you've got a mini, often they fit unique moulded stuff you cant fit anything else too. Makes you wish they kept to some sort of standard when it comes to these sort of things hey. Less of a headache when you restore in the future. Good luck with that plastic

[Cabo Cruz]

Very, very cool, Br. Sam!