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Mon Sep 02, 2013 10:12 am

ivwshane wrote: I just used evaporust on my ghia's gas tank, I rotated it every few hours. I then washed it out and dried it with compressed air, I then coated it with master coat. I let it sit for three days. We shall see how it goes but if it starts peeling I'll be buying a new one:(

I was told if you get all the debris out and use evaporust there shouldn't be a need for a sealer. Guess it all depends on the condition of your tank.

I have a 71 tank and plan to just use evaporust and a chain to clean then its a good flush and fill with fuel.

Mon Sep 02, 2013 10:51 am

That's right, unfortunately I decided to seal it and it was a mistake. I used muratic acid to clean it. 1 gallon of acid, fill the rest of the way with water and let it soak overnight. Shaking/moving it around to get all surfaces. Dumped it out and the tank was spotless. Wish I had stopped there!

Mon Sep 02, 2013 12:56 pm

guitarman63mm wrote: busdaddy wrote: guitarman63mm wrote: I will never understand why people use muriatic acid. Hydrogen chloride gas is one of the most corrosive gases in existence - the moment you remove rust in one spot, you're creating it in another.

Because it gets the rust out in a hurry and it's cheap and easy to use, TSP is a strong base and neutralizes it if you are lazy on the rinsing but I like the phosphate treatment right after myself followed by a drying and oiling.

Any better options you can suggest for home use?

I use electrolysis to remove the rust and paint on all my parts, followed by an acid etch for 20 minutes or so with ospho to remove loose iron and any residual rust. Then I wire brush and rinse it off, hand dry with a towel, and toss it in the oven at 175 or hit it with a heat gun for a few moments. This is time-consuming, but I hate rust.

Knowledgeable motorcyclists use electrolysis to clean their tanks. It's easier on that because you can just stick a piece of rebar with some pipe foam around it right into the tank, where as we have awkward curves and a much larger volume, but when I get around to doing my tanks, I'm doing the electrolysis + phosphoric acid treatment.

You don’t understand why people use Muriatic/Hydrochloric acid…because you don’t understand the chemistry involved here.

Hydrogen chloride gas….so what? Corrosive is whats required here. Virtually every automotive machine shop that works cast iron heads and blocks uses a barrel of Muriatic acid to derust heads. It works perfectly.

Let me list the chemistry here: The original question about a gas tank sealing job going bad…..and the subsequent and probably correct answer that the metal was too clean:

1.The primary ingredient in both primer and sealant for POR-15 (and most similar sealer systems)…..is phosphoric acid. Read the MSDS sheets.

Why Phosphoric acid? Because it converts rust….to iron phosphate on ferrous metals.

Why iron Phosphate? Because hands down it is THE very best primer for epoxy and many other finishes….far better than Zinc dichromate.

2.What is required to produce iron phosphate using Phosphoric acid?……

RUST

Preferably thin rust under .001” thick. The Phosphoric acid must have some rust to convert to be able to leave a nice primer coat of iron phosphate.

Back to the hydrochloric acid:…..hydrochloric/Muriatic acid dissolves rust like butter…right down to bare metal.

BUT…and here is where the REAL chemistry comes in….yeah…it creates minor hydrogen embrittlment of the surface….yeah…so what….its REQUIRED.

Why is this required? Because it allows FLASH RUSTING….in minutes. This flash rust will be less than .001” thick (typically about 5-7 microns thick)

Why is this flash rust needed? ……So the phosphoric acid in POR-15 primer and sealant coat can convert it to iron phosphate …..so the sealant (usually an epoxy base)….to have something to stick to.

So…back to YOUR original question….why use Muriatic acid?….because Phosphoric acid does not have the solution strength to eat through crusty rust more than about .003”-.005” thick. Muriatic acid DOES have the solution strength and its cheap.
Rust neutralizes any acid as the acid oxidizes it. Crusty rust will requires large quantities of phosphoric acid.

And no….the Muriatic acid does not leave an residue. It is no more or less an acid than Phosphoric acid. It just has a higher solution strength.

You can do this same type of treatment any items such as heat exchangers by using Muriatic acid…then allowing flash rusting…..then treat with a phosphoric acid product like Ospho.

Your exchangers will last for ages. Once the surface of virtually any ferrous metal is treated in this manner and then sealed with paint….it will not rust for ages.

Things you want to be careful with using Muriatic acid are brake parts and anything with a plated surface.

For instance….on old Teves calipers….the acid will remove the cad plating…which is actually under the gray factory paint. No big deal if you plan to repaint them with VHT paint or similar. The pistons have a very thin chrome plating.

It will remove that….which is also no big deal. Its about 5 microns or less. Just polish them starting with 2000 grit and end with 3000 grit. They will work awesome.
Ray

Mon Sep 02, 2013 1:24 pm

That's a great post, I have heard foks complain about por 15 before and in most cases it was because they didn't prep the item correctly. There are folks that sand and remove all the rust before slapping the top coat on and they wonder why it doesn't adhere well, it needs the rust people!

Mon Sep 02, 2013 2:17 pm

Yeah I had a nice layer of flash rust and I think a weeks prep time should have been enough but thanks anyway Red Fau Veh!

Mon Sep 02, 2013 3:30 pm

I didn't say it was your fault that the tank wasn't preped perfectly, it is a tough job to get right. I have had the same thing happen before to me with a product called Kreem tank liner. If the tank looked clean and useful after you cleaned it, most folks here would have told you not to line it. That is what they told me when I first came here and cleaned my tank.

Mon Sep 02, 2013 4:18 pm

Didn't say you did, just stating the facts anyway, lesson to everyone else out there. If your tank isn't like a piece of Swiss cheese, don't seal it just get it to clean bare metal and run it.

Mon Sep 02, 2013 5:48 pm

Been looking forever for this picture --- this is what was going through my 40 micron filter after I coated my tank --- OH, and this chit doesn't like injectors either

Mon Sep 02, 2013 6:33 pm

Aye, that's no good!! That makes me feel even better about getting another tank that's bare metal. Yuck, don't want any crap like that getting to my new 40 IDFs!!💩

Tue Sep 03, 2013 5:00 am

Working with inks and coatings for a living...I can tell you that this whole process is over-simplified. Going of memory here....but I "think" POR-15 is either an epoxy based or possibly polyester based.

Things these products are snsitive to:
Humidity
Temperature
Textur of surface to be coated
Oils
Fairly exact mixing
Time factor during application
Contamination by residual minerals left by water, specifically minerals that can change PH (sodium, calcium etc.)
Age of the products...ie: has it been sitting on a dealers shelf for months...and then on your shelf for months
Having ever been frozen or overheated while sitting on the shelf.

With all of the items these types1 of adhesive and sealants can be sensitive to...its amazing they sometimes work ata all.
Ray

Tue Sep 03, 2013 5:31 am

I decided to follow Ratwell's POR-15 step by step, and I did two tanks. That was a few weeks ago, and neither has been installed yet. I only have seen one issue thus far; the 1968 has a glob which looks bubbled, cheifly due to the fact I got busy doing several things and forgot about the tank draining out, and left it in a position to where it allowed about a large tablespoon of the sealer to coagulate near the filling neck. I tried to chip it out, but it was pretty solid. Hopefully, it won't decompose and foul the suction screen. :roll:

I was able to clean out both tanks very well, down to bare metal using muratic acid and water. I decided after rinsing out the acid wash to follow up with a baking soda and water solution to neutralize any acid activity, then did the phosphoric treatment 'Metal Ready'.

My reason for coating a clean tank? Eliminate rust from condensate formed with ethanol blends and normal condensation. Although I consider myself a 'Stock Nazi', I wouldn't mind a bit changing out metal fuel tanks with modern composite materials. :idea:

Tue Sep 03, 2013 6:39 am

That would be nice if you could get a poly tank that was the right size and accepted the right sender.

Tue Sep 03, 2013 12:27 pm

obx71super wrote: That would be nice if you could get a poly tank that was the right size and accepted the right sender.

Yes, that's me. Dreamer... :roll: Maybe one day...

Tue Sep 03, 2013 12:48 pm

Tue Sep 03, 2013 1:21 pm

I will send you a 72 or a 76 tank if it will help, not sure what years would work.

Tue Sep 03, 2013 6:27 pm

I appreciate it but I e got one on the way already

Sun Feb 02, 2014 6:20 am

Resurrecting this thread...

Could a tank be either copper or nickel plated as an alternative to chemical coatings? Expensive, perhaps...

Also, discounting liability concerns for the present, what might folks be willing to pay for a stainless steel box that just might happen to be the same shape and size of a late bay fuel tank, and just happen to have all the holes and tubes in all the right places?

I wouldn't be willing to risk the liability exposure fabricating fuel tanks for ANYTHING, but I can certainly fabricate boxes that an owner could (against my advisement) use for a fuel tank...

Ideas.

Sun Feb 02, 2014 6:50 am

They aren't cheap but bus depot has brand new tanks for sale now. Wish they would have had them 8 months ago cause I would have bought one!

Sun Feb 02, 2014 11:01 am

I had no problems with my POR15 tank reseal.

If you need a new tank, here is the Bus Depot link:

http://www.busdepot.com/211201075l

Sun Feb 02, 2014 11:53 am

new tanks are now available thru BusDepot in the USA and Just Kampers and VW Heritage in the UK. Just clean yours and deal with the rust with phosphoric acid. Forget the resealing. There is also a new product from Stabil that stops rust from ethanol.