Decal blisters on plastic tanks

[Smyway]

Can you believe it's December already? (!!!!)

Need to troll the experience of the forumites.....

I put some sizable effort into improving the look of my 5.3 gal Acerbis tank....
Had feared all along the textured surface of the polyethylene was going to present me with a 'sticking' issue. Turns out, that has not been a problem.
Knew the polymer is very slightly permeable to solvents, and gave the risk of blistering all of 2 minutes thought... then quickly moved on.

I applied my decals in early Nov and very pleased with the result. Looked fantastic for all of 3 weeks... and then Thursday morning, I find this:

Easily flattened again if you lift one edge and re-apply.... but heavily blistered by the next morning and again today. Repeating the re-application each time and somehow expecting a different outcome has confirmed the futility and madness.
As the vinyl is peeled back I can actually smell the gasoline at the tank surface. This is happening overnight! Crazy!

Gave it some thought... and the only thing that had changed from the previous 3 weeks was the weather.
Then it dawned on me! We had been experiencing cold, clear, high pressure cells until the recent weather came through with the warmer, low pressure weather over the past 3 days.
I opened the gas cap and the tank barfed out a large gas volume with an audible 'thunk'. The lousy Acerbis locking cap is exactly that: Lousy. Stupid thing does not vent properly and I'd effectively trapped high pressure inside the tank, making for an excellent osmotic potential across the tank wall.

Scratching my head now. Spent the afternoon with Google and friends to see if there is anything out there that might work as a sealant barrier AND actually bond to the plastic.
The old stuff like Red Kote and others are all designed for metal tanks. Found some frighteningly expensive ($140/quart) polyamide coating by DOW, but it's primary solvent is ethanol! Yip. Pretty much makes that stuff useless right out the can. For the same reason, my best idea of a shellac undercoat is probably also dead in the water.

Anyone out there discovered a successful workaround for this problem?
Would love to know what folk have tried. What worked, for sure - but what did not work is just as educational.
Appreciated.

 

[Rydah]

Plastic tanks "breath" over time; that's one of the reasons they darken as they do. You can (or used to anyway) purchase perforated decals, but the home remedy I've used is to get a "serrated edge tracing wheel" and go over your decals before applying. It gives the trapped gas a way to escape, and not bubble. Something like this:

Robot or human?

You could probably still do it even on a decal that's already been applied, or if you're really bored, get a pin and start "puncturing" each bubble.

 

[Smyway]

Mmmm... Could give it a go. Yanked it off enough times in the past few days, so nothing to lose.
I wonder what sort of pinhole density I'd need on such a large decal. Any thoughts?
Images of a paper doily!

BTW: Cannot say there is no-action this morning, but you have to look hard to see the blisters. Replaced the gas-cap with the original yesterday. So if this is going to be a permanent issue from here, I've at least found a knob with which to dial it down.

 

[Irishcoffee]

I use a sewing needle from my wife's kit. But in the long run with the gases coming thru the plastic it is a losing battle. Like trying to prevent baldness without implants. FAIL!

 

[sandman]

Like others have said use a large needle and work the air out.

 

[Thrasherg]

As stated, plastic gas tanks are porous, you have to provide some means for the gas to escape through the sticker, perforated stickers are the best solution at this time..

 

[JackSubrosa]

Can you believe it's December already? (!!!!)

Need to troll the experience of the forumites.....

I put some sizable effort into improving the look of my 5.3 gal Acerbis tank....
Had feared all along the textured surface of the polyethylene was going to present me with a 'sticking' issue. Turns out, that has not been a problem.
Knew the polymer is very slightly permeable to solvents, and gave the risk of blistering all of 2 minutes thought... then quickly moved on.

I applied my decals in early Nov and very pleased with the result. Looked fantastic for all of 3 weeks... and then Thursday morning, I find this:

View attachment 369917

Easily flattened again if you lift one edge and re-apply.... but heavily blistered by the next morning and again today. Repeating the re-application each time and somehow expecting a different outcome has confirmed the futility and madness.
As the vinyl is peeled back I can actually smell the gasoline at the tank surface. This is happening overnight! Crazy!

Gave it some thought... and the only thing that had changed from the previous 3 weeks was the weather.
Then it dawned on me! We had been experiencing cold, clear, high pressure cells until the recent weather came through with the warmer, low pressure weather over the past 3 days.
I opened the gas cap and the tank barfed out a large gas volume with an audible 'thunk'. The lousy Acerbis locking cap is exactly that: Lousy. Stupid thing does not vent properly and I'd effectively trapped high pressure inside the tank, making for an excellent osmotic potential across the tank wall.

Scratching my head now. Spent the afternoon with Google and friends to see if there is anything out there that might work as a sealant barrier AND actually bond to the plastic.
The old stuff like Red Kote and others are all designed for metal tanks. Found some frighteningly expensive ($140/quart) polyamide coating by DOW, but it's primary solvent is ethanol! Yip. Pretty much makes that stuff useless right out the can. For the same reason, my best idea of a shellac undercoat is probably also dead in the water.

Anyone out there discovered a successful workaround for this problem?
Would love to know what folk have tried. What worked, for sure - but what did not work is just as educational.
Appreciated.

 

[JackSubrosa]

https://www.twtex.com/forums/attachments/img_8889-jpeg.370042/

That’s a link to my ad currently on TWTs for my Moto Guzzi Griso. The bike is pristine except for the small bubbles under the graphics on the tank. The tanks on Grisos are all Acerbis. And if one allows gas with ethanol into their tank, it’ll for certain off gas and make bubbles. The guy from whom I bought had no access to ethanol free premium. I do and it hasn’t had a drop of ethanol in it since I got the bike, and therefore no more bubbles. The solution is tank removal, allowing it to dry for days in a warm/hot place like your attic, then repaint or re-apply the stick-on graphics. And if you just can’t avoid ethanol gas, then it’d be best to coat/line the inside of your tank. My graphics are clear-coated over from the factory, so if I were to pull them all off, it’d need to be repainted. I simply popped the bubbles, then trimmed the edges, then covered with an 4” long adhesive oval of foam rubber. And it looks good, and intentional. Gas w/o ethanol will off-gas if tank venting is poor, but very little. Likely not enough to cause any bubbles or discoloration as long as the tank is regularly opened. But gas w/ethanol will heavily off-gas constantly the H2O in the ethanol whether well vented or not. And by drying the tank, that’s what you’re actually drying from the tank walls - the water which is causing your bubbling.

 

[JackSubrosa]

The water vapor I mean

 

[Smyway]

Huh! Thanks for that. Yes, do need to make a bigger effort to seek out ethanol-free gas.
Tank looks pristine, as you say. What was the purpose of the 4" foam rubber oval?

 

[JackSubrosa]

The stripes/graphics are actually foil. Black on the up/visible side and silver on the down side. At the place where I placed the ovals (there’s one on each side) are contours or ridges. The bubbles occurred on each side at the ridges near the edges of the foil. Dirt was collecting and it had begun to split. So I cut it perpendicular in hopes that I could get it to re-adhere. It didn’t. So, being a perfectionist, I had to cover it so I didn’t see it. I cut two ovals out of 3M ‘wrap’ and applied. It matched well and looked as if they were supposed to be there, except that you could see the impression of the cut foil through the wrap. So I stepped it up and used 1/4” foam rubber to do the same thing. It turned out good. So good that despite my OCD self, I decided not to pull the tank and have it repainted. I can always do that when and if the rubber foam ovals fail. But I only ride it a short distance every couple of weeks, and never in the rain, and she sleeps in the garage, so the rubber foam will likely last a good while.