TheSamba.com :: View topic - Fuel tank replacement question and Por-15 experience (photos

Wed Oct 23, 2013 12:01 pm

My late 73 Westy is scheduled to have a fuel tank installed tomorrow and I have two tanks that I am having trouble deciding between. The first is a used tank from a 74 bus that I bought here that is in great shape with a very small amount of rust and the second is the original tank that has been treated with a Por-15 tank sealing kit. Sealing the tank didn't go as I expected (full story below) so now I am having trouble deciding which one to put in.

Untreated 1974 tank:

Por-15 sealed original 1973 tank:

I'm leaning toward using the Por-15 coated tank, but I can't decide. Help.

Wed Oct 23, 2013 12:02 pm

Full Story

I've had problems with rust in my tank for over a year and putting an in-line filter between the tank and pump didn't help. It is time to have the tank replaced and I am having a garage do it for me. I understood they didn't want to have my bus apart in their shop while I repaired the tank so I bought a used 1974 tank and a Por-15 tank sealer kit (after reading Richard Atwell's tutorial and several reviews on line).

The guys at the garage questioned the Por-15 sealer so I did some more research on here and found very mixed reviews of the product. Since the used tank I got was in such good shape I decided to use it without sealing it.

Then the garage removed the original tank from my bus and pushed it out into their yard. Now I had a rusty tank I could try the Por-15 tank sealer kit on without risk since I could always fall back on the used 1974 tank.

I assumed most of the failures of the Por-15 sealer were either due to people not following the directions or possibly that their tanks were not rusty enough and had some kind of original factory coating that caused adhesion problems. So, in addition to following the kit directions as closely as possible, I added an additional step of tumbling it many times with a bucket of ~3/4" pebbles and either dish soap or TSP in it. I have read of other people using chain or nuts and bolts, but I didn't have enough of that sort of thing and thought rocks were fairly inert and would act like coarse sandpaper and knock off all the loose rust and scratch up any pristine surfaces for better adhesion. I actually rigged up a way to strap the tank to a cement mixer and let it tumble with the pebbles and soap for hours. When I was done I rinsed it out many times, both with a hose and with hot water and it was very clean wen I was done. If you have read Richard Atwell's tank restoration tutorial (http://www.ratwell.com/technical/FuelTankRestoration.html), my tank was way cleaner to start with, basically only having rust and none of the sludge and goo. Here is a before photo:

Preparing the tank for sealing was a 3-4 day process for me because I wanted it done as well as possible. When I was ready to use the sealer the tank looked like this:

Everything seemed to be going well until late Friday night when I opened the can. The instructions said to stir it until it was a consistent color and I remember from Richard Atwell's tutorial that you aren't supposed to stir it very much. I was surprised to find that about a quarter of the can was semi-solid sludge and that no amount of stirring would make it a consistent color.

With the 4 day drying time, waiting to contact tech support on Monday would mean it would be at least another week until the tank would be ready so I decided to stir until the lumps were dissolved and proceed.

After pouring the sealer into the tank I found that there were still some small lumps remaining in the bottom of the can. It was too late to turn back at this point so I finished sealing the tank and left it to drain.

When I was done there were a couple of things that bothered me.
1. There were lumps, streaks, and even a few small bubbles around the tank outlet.
2. 80-90% of the sealer drained out of the tank, which must leave a very thin coating.

So now I wonder if something went wrong or if I had a bad batch of sealer. I have a huge amount of time and money invested in this tank now, but having a garage remove and install the tank is an expensive job.

If sealing the tank went well it would be the obvious choice, but if it fails like I have read some do, with sheets of sealer coming off and blocking the tank outlet, then I am looking at a costly or time consuming tank replacement.

If I use the slightly rusty tank and am careful to keep it full and use fuel conditioner I may never have trouble with it, but then again I could forget a few times and run into this problem again in a few years.

Wed Oct 23, 2013 12:25 pm

Your POR15 experience and mine are almost identical. I was surprised to pour a quart of POR15 into the tank and drained over a pint back out again. I have the same streaks and thick spots too. For fun I poured some of the POR15 into the bottom of a 5 gallon plastic paint bucket (which was not cleaned prior) and let it dry. I've hit the dried POR15 with a hammer and can't make dent. This bucket will never leak. Have not yet installed the tank but feel good about things. I realized that the inside of the tank does not need to be pretty it just has to be sealed...also out of sight out of mind.

Wed Oct 23, 2013 9:52 pm

Your POR15 application looks fine. Roll with that!

Wed Oct 23, 2013 10:41 pm

If you used all the marine clean then the metal prep in the amounts in the instructions and it was pouring out clean you were good there. you are only putting on a coat of paint inside so most does pour out again. A lot of guys have another project sitting there that they can brush it onto and not waste it.

Thu Oct 24, 2013 10:26 am

Yes, I actually pre-cleaned it so the Por-15 cleaner came out clean the first time, but I did it twice and kept it in there for almost 24 hours anyway. I'm pretty sure I did all the prep work correctly. I'm just worried I got a bad batch of the tank sealer.

I just dropped both tanks off at the garage that is doing the work for me and let them decide which one to use. I assume they will also decide on the Por-15 coated one, but it will be interesting to see which one they pick.

Thu Oct 24, 2013 10:39 am

I also sent an e-mail describing my experience and with photos to the distributor, who forwarded it to the manufacturer.

I just got a reply saying it would be fine and the streaks and lumps would not be an issue. I phoned the garage and they will be putting the coated tank in this morning. I will try to remember to update this thread in the future if I have any issues with it.

Thu Oct 24, 2013 11:07 am

I followed the POR-15 directions to the T and I have had zero trouble with my coated tank for 12+ years now, so I wouldn't worry about it.

Thu Oct 24, 2013 2:54 pm

I spent a total of a week prepping and sealing my tank and it failed miserably!! Wish I had just acid washed it and left it alone. That's what I did with the used tank I bought after the sealer didn't work. Not a speck of anything in my fuel filter and my "sealed" tank is still out in the yard rusting, but all that damn sealer still hasn't come out.

Thu Oct 24, 2013 3:02 pm

obx71super wrote: I spent a total of a week prepping and sealing my tank and it failed miserably!! Wish I had just acid washed it and left it alone. That's what I did with the used tank I bought after the sealer didn't work. Not a speck of anything in my fuel filter and my "sealed" tank is still out in the yard rusting, but all that damn sealer still hasn't come out.

In what way did it fail miserably?
Ray

Fri Oct 25, 2013 10:18 am

I almost don't want to know, but how did you prep the tank, what sealer did you use and how did it fail? (My sealed tank is now in the bus, but it is still in the shop waiting for other parts).

Fri Oct 25, 2013 6:46 pm

raygreenwood wrote: obx71super wrote: I spent a total of a week prepping and sealing my tank and it failed miserably!! Wish I had just acid washed it and left it alone. That's what I did with the used tank I bought after the sealer didn't work. Not a speck of anything in my fuel filter and my "sealed" tank is still out in the yard rusting, but all that damn sealer still hasn't come out.

In what way did it fail miserably?
Ray

Here is a detailed explanation of obx71super's experience with POR-15. http://www.thesamba.com/vw/forum/viewtopic.php?t=566950&highlight=

Pearl's experience with resealing looks just like mine and I have had no issues at all.

Fri Oct 25, 2013 7:46 pm

I have used with good success the Ospho process suggested by Ray on Shoptalkforums years ago. Ospho is just a phosphoric acid based primer similar to Metal Ready. If exposed to sunshine it would need to be painted over like Metal Ready is by POR 15. But since there is no sun shining inside your fuel tank the paint isn't needed.

No paint, not adhesion problems and no paint flakes that can clog filters and such.

I assume that Ray will respond to this point and give more info on tank sealing than I could if I live to be 100. :wink:

Sat Oct 26, 2013 10:08 am

Thank you for the compliment....I think... :lol:

The problem is (most likely) with obx71super's tank...is that it was gotten "too clean".

A few items that everyone really needs to think about with sealers in general...is what they are made out of. Typically there are only two main types. Epoxy based and polyester based.
Among these two types there can be a zillion varied chemical formulations and no two will wwork exactly alike....and some that are chemically almost identical may work differently in a worlds apart fashion beacvuse of what the slight chemical variation makes it sensitive to.

whether POR isnt as good as it used to be or not may or may not be true. It is true that epoxy manufacture has to be very tightly controlled or ther WILL be large variations.

Let me explain two things without getting too long winded here.

1, Epoxies are sensitive to:

a. Moisture:

If the tank or the area you are working in has excessive moisture…meaning you washed it, dried it and did not let it dry for a while….that moisture can be absorbed by the epoxy. That moisture will insert itself into the chemical chains interfere with the cross linking between the catalyzed molecules.

I use….especially after using Ospho (phosphoric acid)…either Berrymans B-12 chemtool, acetone (works but not the best). Do not use 99% Isopropyl alcohol or denatured alcohol (methanol) to rinse the tank. Both acetone and most alcohols entrain moisture and will leave a layer of it at the microscopic level in rough metal. The idea is to remove the residue that can come from phosphoric acid in non-rusty areas. It actually in the directions. A very fast evaporating non-oily solvent is best.

If its humid where you are working…ie. Over about 45-55%…excessive mixing will pump moisture into the epoxy and can cause problems

b. Temperature

Too cold….and the mixture is too stiff. Not enough mixing. Too cold and humid…and moisture can condense into the mix. Too hot and the cross linking can accelerate….weak adhesion and poor film cohesion.

Same goes for application. Epoxy warms when its curing. Even adding a slight amount of heat helps. Just make sure the tank or metal surface is not too hot or cold.
Again…cool metal and humid area means condensation even if you cannot see “beads” of it.
c. Proper mixing:

Mix it well….but do not whip it into an ultra smooth batter. It puts too much oxygen and moisture into the mix. This varies with the epoxy. Make sure your ratios are spot on. If you over catalyze…it will be brittle and prone to shrinking. As it shrinks…it will crack or get fissures…then peel off.
Do not use old product. The base can tend to polymerize with age and the activator gets week. Do not buy it on sale and save it for 6 months. Buy these products shortly before you use them.
Most epoxies will heat cure to a certain extent…even without activator. It may not turn solid…but will have clumps of solids dispersed through it…and will not work well.

If the epoxy or sealer “kit” you bought has ever been in th 140-150* F range in its life for any period of time….it will most probably fail due to this problem.

d. Contamination

As noted…moisture will be the biggest contaminant. But…solvent fumes that mix into the epoxy while applying it to the tank…are SOLVENT that is evaporating. These will condense in the material and can make the epoxy utterly fail. These sealers….are not to be confused with epoxy putties which can work in wet fuel. Most liquid epoxies ….until cured …will fail in the presence of many hydrocarbons.

Bluntly put…if your fuel tank smells heavily of any solvent including gasoline….it is not clean enough to put a sealer in without some risk.

Any of these items can degrade adhesion (meaning it doesn’t stick) or film strength/cohesion (meaning it flakes apart or becomes porous)

2. Being “too clean”.

The problem here is that spotless metal has no tooth. Nothing to grip to. In short…not enough surface area. The idea of rolling chains and sand around is commendable…and if done diligently…can actually work well. But its also hit and miss because even though you scratch up the surface…the metal itself inside of the scratches may actually be smooth. DO NOT confuse texture with surface roughness. They are on a different scale.

This is getting a little scientific…but I deal with high tech coatings EVERY DAY…and as simple as you would like to make it…its actually chemically and physically complex.

Sealers and epoxies NOT wall paper paste. They don’t require texture on a level that large…that can be seen. They require large amounts of surface area on a micro scale.

Most wont care about these comments….so you are welcome to get a beer….but for instance…bare mild steel like a gas tank when new has a surface texture of about 8-12 microns or less (depending upon whether you are measuring Ra, Rz, Rp, Rt yada yada yada).
We are simply talking the peaks and valleys of the roughness measured in microns (a micron is roughly 1/25,000th of an inch)

Scratch that metal up…say like with cross hatching like in a cylinder or with the chains and sand method…and you make big valleys …but the metal between scratches is still about 8-12 microns. The scratches make great texture…but for something like epoxy….they are actually not that much surface area compared to….etching the entire surface with muratic acid or phosphoric acid……and multiplying the peaks and valleys to 12-18 microns. These peaks and valleys may only be 5-10 microns apart…so they are very “toothy” and have loads or surface area…like a sponge.

A very important part of products like POR-15 is that they use phosphoric acid in the primer and sometimes in the epoxy as well.

What does this do? Phosphoric acid turns rust…as long as it is only a few thousandths of an inch thick so it can penetrate….into IRON PHOSPHATE. Iron phosphate as HUGE surface area. Once of THE BEST primers in the world.

But it does nothing to clean smooth metal.

This …is what the epoxies want to stick to. So…if the tank is 100% rust free….the phosphoric acid in the POR-15 primer has nothing to convert to iron phosphate. This means that its ability to be an effective primer is low. Even perfect epoxy may peel off.

As Wildthings mentioned…if you have a tank with no holes and no real rough spots but basic light, thin rust…..and you are diligent to keep your tank full and as moisture free as you can….you can simply treat it with Ospho (commercially available phosphoric acid)…this will leave a bluish black coating anywhere there was rust….and as long as the oxygen content is very low (keep fuel in the tank and do not let it sit around over winters without fuel treatment)….it will never rust again.

The best I have found to do for a rusty tank with no holes but heavy crusty rust….is to acid wash the tank…which will dissolve 100% of all rust to bare metal…and lightly etch the surface. Then wash, rinse, wash, rinse, neutralize with baking soda and water….rinse, rinse, rinse, rinse.
Then….just let it dry……and it will flash rust…all over the inside. Great! This is what the ospho…and the phosphoric acid in POR-15 primer….IS HUNGRY FOR!

Then treat it with ospho or POR-15 primer….let it dry 24 hours…no kidding! Then wash it with fast evaporating solvent. Let it dry…treat it again with Opsho or POR-15 primer. Let it dry 24 hours. Then rinse with solvent.

At this point if it was flash rusted you should observe a uniform blackish blue powdery finish.
Make sure that the surrounding temp and humidity is optimum…then use your POR-15. If the product is good…..it should work well. Ray

Sat Oct 26, 2013 10:16 am

That, Sir, was brain candy. Thank You.

Sat Oct 26, 2013 10:27 am

I'm curious why you just can't use an etching primer and paint, epoxy or urethane. Por15 seems to be too problem prone. Great for battery tray, but fuel immersion with the possibility of water?

Sat Oct 26, 2013 10:56 am

I agree with Ray that there are too many variables to simply blame the POR15.

IMHO, obx's tank looked way too clean for a POR15 application. If mine looked like that after cleaning, I would not have put anything in there except for a full tank of gas.

Sat Oct 26, 2013 11:19 am

1967250s wrote: I'm curious why you just can't use an etching primer and paint, epoxy or urethane. Por15 seems to be too problem prone. Great for battery tray, but fuel immersion with the possibility of water?

A primer...even a self etching primer....is porous by nature. High surface area. Thats how it works.
Unfortunately....self etching primer would eventually be dissolved by fuel.
the problem with any coating is that you could NEVER be sure that there are no small pinholes. Especially inside of a gas tank you have no way of making sure your coating is perfect.
In fact...it will likely never be perfect. Fuel would exploit any pinhole or pore...and start disolving your primer. In that condition...the coating is only stuck to the primer. You could surmise the evntual end. itwill keep eating and start coming off in sheets.

The things about phosphoric acid primer is that its not a coating. Its a surface reduction process that creates an oxide that is bonded at an ionic level. Apinhole in the epoxy coating....will simply come up against a primer that in itself is rust preventive as long as its kept out of oxygen. keep it under fuel and it will not rust.
Ray

Sat Oct 26, 2013 11:20 am

BUSBOSS wrote: I agree with Ray that there are too many variables to simply blame the POR15.

IMHO, obx's tank looked way too clean for a POR15 application. If mine looked like that after cleaning, I would not have put anything in there except for a full tank of gas.

I agree with that. In fact...Im debating on whether to coat my current tank at all.
Ray

Mon Oct 28, 2013 8:01 am

Thanks Ray. Your information backs up my choice not to coat the first tank. I thought it wasn't rusty enough for the Por-15 sealer, which I understood bonds better to rust.

I wish I had read about treating with phosphoric acid multiple times to convert the flash rust from the previous treatment. That makes a lot of sense. Looking at the photo of my tank after phosphoric acid treatment, I am a little concerned that I don't see much flash rust and no black/blueish converted rust.

The coated tank is back in the bus now so time will tell if it worked or not. I will try to remember to update this post if it fails. I will also keep the second tank around for a year or two until I am sure it worked.