Gas tank exterior coating

[Bob McCoy]

What is the exterior coating for a 1956 190 gas tank ,California delivered car? Mine has a mixture of bare metal and some kind of undercoating. Also takes forever to fill the tank at gas station.
Thanks in advance, Bob

[Jim Rombough]

Bob ,you can`t go wrong painting it with por 15 it likes bare metal or you can paint over rust .I would take the under coating off .furniture stripper works pretty good .
Check out previous threads on vented gas tanks . I believe earlier models are non vented .But is critical to know so you have the correct gas cap on .or you can get a collapsed gas tank .The later models are normally vented with the line coming up in the trunk then turns & goes back out under car , behind passenger side spare tire .
I find if you just stick the gas nossel part way into filler pipe it fills much quicker .
Hope this helps !

[Henry Magno]

When POR-15 came out years ago, the makers specifically advised against using it on bare metal. I believe even now they recommend that bare metal be well scuffed (as it should be anyway) before using it. What happened since those early days of the product? Personally, my impression of this product given my limited use of it and what they say about it, is that its adhesion depends on its mechanical bonding with the rust structure coupled with its moisture curing ability to absorb remaining moisture from the surface, thereby reducing the possibility of future rusting. My deduction from this and what I have observed is that its bare metal adhesion was hardly optimal. Perhaps the product has been improved since then.

While it's a useful product for treating rusty surfaces, I don't think the original intent was as a bare metal primer. As far as I know, the best metal finishing method for both adhesion and protection is clean sandblasted or sanded bare metal then coated with catalyzed epoxy primer then preferably a catalyzed top coat. These materials do present a safety issue when spraying. At least a vapor respirator should always be used. If spraying isn't an option and brush painting is the method of choice, there is still no reason why a good automotive epoxy primer can't be used. Another preparation which has some merit for painting over somewhat rusty surfaces, is the use of a rust conversion coating, then followed by epoxy primer.

Many years ago, Skinned Knuckles magazine tested a number of rust treatment products and did a year long test of leaving the samples out to the weather. If I'm remembering correctly, they used all the products over both rusty and bare samples. As sort of a control, they had a sample of clean metal painted with epoxy primer alone with no topcoat. After a year, this sample had no rust and was better than any of the other products. The test included both rust conversion products and moisture cured urethanes, including POR-15.

[Bob McCoy]

Thanks for the information, my tank has no rust at all, thanks to California. My problem is one half has some kind of spotty undercoating and one half has bare shiny metal. Was undercoating standard from the factory?

[drjake]

Rubberized or tar undercoating was not standard from the factory.

[Jim Rombough]

Henry
I don`t mean to be rude but before you contradict another members post .I suggest you get your facts straight & not refer to many years ago .
I and a lot of other members have been using Por 15 with great success Directions state recommended for bare metal & is sold with a metal wash & a etching solution to be hosed off & dried well before applying the paint .

[Henry Magno]

Bob asked what the original coating on the tank was. You gave a suggestion on refinishing it. I offered some opinions I have on the subject, and I did not suggest what Bob should do in his situation, because every owner has a different need or goal in mind. POR-15 may be a solution that works for him.

As for POR-15, I have read their current product information within the last few months. What are the facts that I need to get straight? I know that they offer metal etch and instructions on its use over bare metal. What is not a fact is whether this is the best method to coat bare metal. I asked the question whether anyone has specific information whether the product has been changed over the years, because obviously their promotional material has changed. The mere stating that their product is good for a certain type of application does not mean it is best for that. As for the past, sometimes it's useful to know what happened in the past. When this product first was marketed as "paint over rust" that's what they said it was for.