Fuel Drum Clunk Corrosion

[Curare]

Hey guys, just wondering if you might be able to shed some light on my recent find. I recently noticed that my fuel had changed colour from pink to grey, and upon closer inspection, I'd noticed that my clunk (sintered brass) had completely corroded down to a nub! the whole bottom of the fuel drum was covered in black brass particles.

I've never seen anything like this, and needless to say I threw the fuel out and fitted a plastic clunk, but this does make me concerned for what it's doing to my tanks and engines.

Could it be water in the fuel or degrading nitro turning to nitric acid?

[Brett Buck]

Hey guys, just wondering if you might be able to shed some light on my recent find. I recently noticed that my fuel had changed colour from pink to grey, and upon closer inspection, I'd noticed that my clunk (sintered brass) had completely corroded down to a nub! the whole bottom of the fuel drum was covered in black brass particles.

I've never seen anything like this, and needless to say I threw the fuel out and fitted a plastic clunk, but this does make me concerned for what it's doing to my tanks and engines.

Could it be water in the fuel or degrading nitro turning to nitric acid?

    I am not sure, I though it was the zinc being leached out of the brass. But yes, I have seen that many times in similar situations. Brass will not last in contact with fuel for more than a year or so. That's why you make your fuel tank with copper, and not brass, fuel lines.

     Brett

[Dan McEntee]

    It's the nitro I think in today's fuel that comes from "you know where". Years ago at the hobby shop I worked at, we carried K&B and Fox fuel. I'm not sure of what year, but another company hit the market with fuel about a buck cheaper per gallon. It was reputed to be cheaper because they got their nitro over seas. R/C guys started top have issues with anything brass, and bearings in engines rusting when idle too long. We were advised by K&B to put up a display with a baby food jar with their fuel in it, and to put a length of brass tubing in it. Next to it, another baby food jar with "Brand X" fuel in it and a length of brass tube. After a few days, the tubing would start to turn black and decay in the "Brand X" fuel, but not in the K&B fuel. We used to have to put new tubing in "Brand X" weekly.
    I have recently noticed on older tank that I have with copper tubing that even those have been changing color, but not at the rate it does with brass, and have not had any split. Brass will get brittle and split over time also. Wish we could get the good stuff again!
     Type at you later,
      Dan McEntee

[Brett Buck]

    It's the nitro I think in today's fuel that comes from "you know where". Years ago at the hobby shop I worked at, we carried K&B and Fox fuel. I'm not sure of what year, but another company hit the market with fuel about a buck cheaper per gallon. It was reputed to be cheaper because they got their nitro over seas.

  I don't think this is new or related to Chinese nitro, my father said they found the same thing in the early 50s.

    Brett

[John Park]

I found the same thing as soon as I got my first glowplug engines back in the '60s.  The tanks we bought or made for our diesels all had brass tubing, and as soon as we began using the same tanks with glow fuel, we saw discolouration, green or black, on the brass.  Finding that this didn't happen with copper tubing, we adopted the rule: copper for glow, brass (or copper) for diesel.

[CircuitFlyer]

From the Angus technical datasheet:

Aluminum or stainless steel construction is recommended for
handling wet nitromethane. In the presence of 0.2 percent by
weight water or more, nitromethane is slightly corrosive to steel.
Contact with moisture can be minimized by storing/handling
nitromethane under a dry inert gas such as nitrogen.

Solutions containing nitromethane should not be exposed to
copper, brass, or bronze without thorough pre-testing. The presence
of acidic materials may cause nitromethane to become highly
corrosive to copper and its alloys after several weeks of contact.
Lead and its alloys should never be used with nitromethane.

A number of synthetic polymeric materials can be used with
nitromethane. The actual choice depends upon the degree of
exposure, the presence of fillers or plasticizers and the importance
of color. Materials that are generally satisfactory include Teflon,
polyethylene, polypropylene, polyester fiberglass, vinylidene
chloride copolymers and nitrile rubber. Nevertheless, pre-testing
of all materials is advised. Natural rubber, synthetic rubber, Viton,
Hypalon, Nordel and silicon rubber are not suitable for use with
nitromethane.

[frank mccune]

     I have noticed for years that the brass lines in metal fuel tanks would corrode very badly on the insides.  This took the form of a black deposit that would block the fuel and airflow.  I used a piece of music wire to “clean out” the inside of the tubes.  Needless to say, I replaced these lines with copper.  Did I make a wise choice, only time will tell.


     Be well,

     Frank McCune

[GERALD WIMMER]

Hello
I have made up my own fuel for the last 33 years and found I have to regularly change out metal containers due to corrosion , not just glow fuel or methanol containers but also my diesel fuel containers. I presume it is the cetane improvers in the diesel that start the acid/rust reaction. After a few use cycles my metal diesel fuel containers have brown rusty fuel at the end of the can with a fine rusty sediment. All I can say is check each time you make up new fuel with a flashlight the interior condition of your containers .
On another corrosion issue the worst fuel tank I have ever uncounted was made of galvanized iron (came in a model I brought) , on adding glow fuel out came a white zinc slurry that could not be flushed out and I had to rebuild the nose of the plane to replace that very heavy small tank .

Regards Gerald

[Curare]

Gerald, funny you should mention diesel as well, in my recent house move I went to go pick up my diesel can to find the bottom had rusted through and there was a brown sludge everywhere. Thankfully I store most liquids in plastic containers to stop things getting out of hand, but everything in that particular container is covered in brown goo now.

I have to point out that this was the first time in as long as I can remember that this was not fuel mixed myself. I suspect that perhaps my LHS may have water in their methanol, or a substandard brand of nitro?

If the general concensus is that brass is not an ideal material to use for glow fuel, why then do we have brass NVA's brass liners, brass tubing, and sintered brass clunks? This seems very odd to me.

[Lauri Malila]

Because brass is cheap and easy to machine. But in engine parts you don't see that much corrosion because the fuel remains usually evaporate due to heat before they do much harm.
The only bras part where I've seen corrosion in my engine is the fuel spigot in venturi, so now I make them in titanium.
What materials could be used instead? German silver, mild steel, stainless steel, titanium. I could make an one-off valve in Ti, but it can be a bit nasty in mass production.
Plating the brass would help a little too. L

[Curare]

Thats a good enough answer for me!