Ethanol and Tern Finish inside Gas Tank

[Greg Jones]

Recently there was a post involving ethanol and its affects on Model A gas systems, and one expert stated that ethanol would indeed attack a tern finish. Now if I remember correctly the Model A gas tank was tern finished internally. So if I had, say, a NOS gas tank I could deduce that I should coat it internally before using it, to protect the finish. Is that correct?

[MikeK]

No.

[Drive Shaft Dave]

Coating a gas tank will bring you more problem's than you would believe.

[mass A man]

I inspected my tank just a minute ago, after wrestling the spark arrester out of the way, and I have to say, I don't see ANY deterioration to the lining of my fuel tank since I pulled the old truck out of a warehouse 6 years ago, as it had a drained dry, closed up tank for 47 years. I've since been running regular, ethanol laced gas but add a shot of MMO to each fill-up religiously. I don't know if that is really helping but that's what's happening.

[mass A man]

I want to add, tank coatings are a Godsend to some of us, albeit sometimes a temporary cure, as I picked up a '25 Dodge Brothers car that someone sloshed the tank years ago with some sort of sealer. It had gas left in it for years and the sealer turned to thick black goo mixed with rust. Took me all Summer to clean out the whole fuel system and rebuild it. It has the original "Stewart" Vacuum tank supply system which was all gummed up too. As most of us know, the older sealers weren't compatible with today's gas. I worry about the sealer today too, as we don't really know what the fuels will be like down the road. I vote no sealer if you can do it.

[Greg Jones]

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I guess I wasn't clear-I agree that tank sealer is not a good idea and have no plans to use it. (I did years ago in my Model T and regretted it) I was just musing about the report that was posted here a week or two ago discussing how ethanol would attack the tern and bare steel. I guess the thing to do is not worry about it and keep fresh gas in your tank. Or keep it empty.

[mass A man]

Sorry about that Greg, I stand as "no apparent change" in my tank lining using ethanol gas.

[pat in Santa Cruz]

theres an interesting article covering the ethanol/terne subject in this months "Model A News"

[MikeK]

OK, let's look at the alleged "attack".

E10 may exist in any condition from fully anhydrous to about 0.5% water, at which point phase separation occurs and ruins the fuel. The ethanol within has near zero reactivity with lead and tin (terne = 8-20% tin, remainder lead) unless the fuel contains some water, which it always does. For any type of reaction or chelation of the metal to occur, the water must be present along with some other molecular specie to initiate the reaction.

The maximum corrosive effect of E10 occurs just prior to reaching the phase separation water level AND with a significant presence of ionic contaminants within that water. At that point it is 400% as reactive as in the near-anhydrous condition that exists when it is blended.

From fuel corrosion tests done on coated steel plates by Oak Ridge National Laboratory, the average corrosive effect on terne coat with fuel containing some dirty water (rain, etc.) but not enough to trigger phase separation shows the surface loss of the terne to be about 0.9 to 1.0 millionths of a meter per year (um/y). Just for the record, the surface loss effect of E10 on brass is six times higher, so maybe everyone should get rid of all the brass fittings, too?

Using that data, in a real world, ten years exposure of the terne to E10 will remove less than 0.0004" (four ten-thousandths of an inch). I guess some alarmists call that an "attack", but I see it as an extremely mild reaction. Yes, if you had a polished terne surface, it would eventually appear somewhat frosted, but you are not going to lose chunks and flakes, like a rusting tank or failing sealer. FWIW, about the very tiny amount of lead compounds that do go through the fuel system of a carbureted car, there are no abrasive or sticky, clingy qualities to any lead compounds that would cause problems. Maybe if you had port injectors the needles could eventually coat with slight deposits. To preclude that possibility, steel fuel tanks are now often coated with a tin-zinc layer.

[Pinstripe]

Thank you Mike K. Interesting data

[spdway1]

Holy Cow Mr Wizard!
Good information Mike K.

[Greg Jones]

Yes, thanks for the factual information and it was the article in the MA Times that I was referring too. I am grateful that you quantified the "attack." This matter can now be filed under the "least of my worries" folder.

[john in illinois]

Here is a guy that ran his model T for one year on E 85. Did not bother gas tank coating.


http://www.mtfca.com/discus/messages...tml?1341064408

John

[Bob S]

My limited experience with tank coating has been negative like most posted here, but I recently helped a friend do a tank with the POR tank sealer kit (cleaner, prep, and sealer), and my initial reaction was positive. Unlike others that I've used that left a thick rubbery coating, this left a thin, very hard coating. After dumping in a quart and sloshing it around to get everything thoroughly coated, the instructions have you allow the excess (much more than half) to drain out. Thus the thin coating. Residual sealer left on the sides of the drain can dried to a very hard coating that was hard to scratch and pretty much refused to be pealed of chipped from the can. And the can hadn't even been properly prepped. I'm curious if anyone has any longer term experience with that product.

Bob

[pat in Santa Cruz]

its been in one of my cars for 5 years now, ethanol and all. Its still hard as a rock. We'll see what 15% ethanol does some day I imagine, but for now it seems to resist 10% quite well.

[Mikeinnj]

I have had the same sealer in my tank for the last 18 years and always run ethanol 10% with never a problem. It is all in the preparation. Clean, etch, and seal allowing the sealer to dry for at least a few weeks before filling up. You cannot rush this process.

[Old182]

Great response, MikeK!

While not a "front burner" concern, there are a few issues that deserve some consideration. The take away from the article in the Model A News should be: 1. If phase separation occurs, then the concentration of ethanol/water (possibly contaminated water) would be increased at the bottom of the fuel tank and the possibility of corrosion (attack?) of the terne plate would be increased, as would corrosion of any bare steel. It would no longer be E10, but some higher concentration of ethanol mixed with water, perhaps from acid rain. 2. While E10 has been around for decades with very few tank problems, the chemistry is there for problems to occur under certain conditions, notably those mentioned above. It's not an "alarming" situation by any means, but shouldn't be ignored either.

According to the SAE Automotive Fuels Handbook, Chapter 11, Section 11.5.3: "Such materials as terne plate (lead/tin-coated steel used in fuel tank construction), zinc die castings, and aluminum fuel system components are all attacked by alcohols..." (their words, not mine). I don't wish to dispute what you wrote, but question whether Oakridge tested with ethanol (you mention they used rain water) and at what concentration. As we've all seen, there are a lot of rusted Model A tanks that, somehow, over the years have lost their terne plate. Even using a deterioration rate of 0.0004"/10 years, a tank subject to E10 for 30 years (like mine) will have lost over 0.001" of terne plate by now just from the ethanol (not counting the previous deterioration), and E15 will only exacerbate the deterioration. The question should be how much terne did I start out with and how much do I have left?

Please don't misunderstand: this does not keep me up at night and I am not an alarmist; at no time during the 54 years that I've owned my coupe have I added anything to the gas tank (except Bill Hirsch yellow sealer when I rebuilt the car in 1988) and no problems so far. I believe, as you and others do, that there is no cause for alarm because of E10, but I also believe that if a tank is subject to long periods of non-use in a humid area where the fuel is E10, then it's a wise idea to run the car and replenish the fuel often to preclude rust and the further deterioration of the terne.

[SkipShift]

Thanks for explaining terne finish. I didn't know what it was.

[Lowell Fast]

Has anyone ever heard of plating the inside of a tank? If you can derust by electolysis, why not reverse and plate inside surface with a metallic coating that would resist rusting and allow you to protect the inside top of the tank and the hard to reach baffles? It could be done ON the car.
How much trouble is it to remove one of these tanks anyway ? It looks theatening.

[caboose]

I have been cleaning my ’29 Phaeton’s gas tank for quite some time—using solvents and marine clean.A friend who worked for the Ford for many years has just about convinced me not to coat the inside of the tank.(Same concerns expressed by others in this forum; what evil will lurk in the gas pumps of tomorrow.)However, the POR 15 metal prep states that:It also provides long-term corrosion protection.

The tank seems to be very solid, and hopefully as clean as I can get it in one lifetime.

So, would it make sense to use the metal prep as directed, even if I skip the coating?