# metal gas tank with corrosion



## nbpt100 (Jun 1, 2015)

Any practical ideas to clean up the inside of a metal gas tank on a Briggs 3.5 hp mower.

The inside is corroded from leaving untreated fuel in it for extended times.

I know it will continue to rust over time and likely clog the screen on the carb.

The owner does not not want to spring for a new tank as it is not an expensive mower.

Is there something I can use to clean it out somewhat and help him get another year out of it. I think it is an aluminum tank. This is the type where the carb sits on top and the bowl is machined into the tank.

Thanks!


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## geogrubb (Jul 28, 2006)

nbpt100 said:


> Any practical ideas to clean up the inside of a metal gas tank on a Briggs 3.5 hp mower.
> 
> The inside is corroded from leaving untreated fuel in it for extended times.
> 
> ...


I use a hand full of small gravel and shake it then rinse it out with water and let it air dry. Have a good one. Geo


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## nbpt100 (Jun 1, 2015)

Thanks Geogrubb,

I did some more poking around the web and some have suggested muriatic acid which is used in swimming pools and in masonry. Many people did talk about putting small gravel, nuts and bolts or a small chain to agitate loose any adhered crap on the inside. Kinda like a tumbler concept.

Others have used white or apple cider Vinegar. It is the acetic acid in the vinegar that does the work. Although most, if not all of these people were working on steel so I am not 100% sure how well it will work with Aluminum. It sure looks great on Steel.

Others have used products that are sold specifically to clean aluminum. I don't want to etch it or cause more trouble than it may be worth. In general it looks like acids will clean oils and minerals away while caustics (alkaline) will etch the aluminum. 
This is just stuff I got from reading other boards and watching You Tube videos. If there are any experts reading this feel free to chime in and correct me if any of this is not quite accurate.

Thanks!


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## 30yearTech (Sep 14, 2006)

I have used muriatic acid to clean aluminum transfer off of crankshafts. I don't think it would be a good choice for an aluminum fuel tank. Will likely clean it until there is nothing left of the tank.


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## mikel m14 (Jul 27, 2009)

I do it like Geo, I use smooth rocks and marbles with water. Get it as clean as I can then air dry. I like to use compressed air after air dried to remove dry rust dust. Might need some cotton in your ears from all the clanging in the metal tank.lol


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## nbpt100 (Jun 1, 2015)

Thanks for all of your replies!

Since it is aluminum it is not the type of red or black rust you typically see on steel.

Aluminum corrosion tends to be white. It is appearing to be a combination of that and just gunk from stale untreated gas. Which the latter is by far the biggest issue. Kinda like a yellowish redish film.

Carb and break cleaner seemed to have a very limited effect.

I decided to experiment with some apple cider vinegar. I only poured in little to cover the entire bottom and play it safe. I monitored it closely and noticed more gunk was floating around. I decided to leave it in over night. The next day I was able to easily scrap away the film with a screwdriver. The exposed aluminum was more shinny as the vinegar was working on the entire surface. I am not sure it it technically etching or not. I read that it does and it doesn't on aluminium. Two semesters of Chemistry was enough for me.
The only problem is that I can only reach a small percent of the total tank with a screw driver or similar. I decided to leave it in another day. I added more to contact the side walls. I am hoping to be able to remove all of the film and flush it out with water and compressed air. So far I think it will work as I see more gunk floating around. The tank has very good wall thickness so eating though is not a concern.

I will let you know the end result. Thanks.


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## geogrubb (Jul 28, 2006)

nbpt100 said:


> Thanks for all of your replies!
> 
> Since it is aluminum it is not the type of red or black rust you typically see on steel.
> 
> ...


Sounds like a good time to put some gravel in it. Have a good one. Geo


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## nbpt100 (Jun 1, 2015)

I think the process worked well to clean up the tank. I used the apple cider vinegar over 2 days and on the 3rd day I switched to white vinegar (5% acidity) as it was much cheaper. I read higher acidity levels are available and they may have been a better choice but the store did not carry it. Each day I would dump out the vinegar, rinse it out with high pressure water then use compressed air to remove any remaining debris and water as best I could. I would refill it with fresh vinegar and let it sit. I did put it in the sun thinking warmer vinegar would speed up the chemical reaction. Each day less debris and crud was found in the vinegar when I dumped it out and the inside walls looked cleaner. As suggested, I did try using some steel nuts and bolts inside the tank and shake them up. I chose these instead of rocks because I could use a magnetic pick up tool to remove everything and I don't have to worry about creating more debris should the rocks make dust. (if dong this hearing protection is advised). While using the magnetic tool I found out the bottom and sides of the tank are steel. The top is aluminum so it must be brazed together. I assume it was all one material. My mistake. So it is a composite of aluminum and steel. Interesting!

The process worked pretty good. The inside of the tank is not perfectly clean but it did a reasonably good job.
If you can take a few days this is a decent alternative to a new tank. If your customer needs it back fast then sell them a new tank.
Thanks to everyone who provided some input!


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## PhillT (Sep 16, 2015)

I have used a length of suitable sized chain in the tank,...give it a good shake around for a few minutes, the drag it out.
Phosphoric acid seems to be a good cleaner, and does no damage if not left in there.


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## paulr44 (Oct 14, 2008)

As you probably learned years ago, naval jelly works wonders on ferrous metal oxidation, AKA rust. Aluminum oxidation requires a different approach.


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## PhillT (Sep 16, 2015)

paulr44 said:


> As you probably learned years ago, naval jelly works wonders on ferrous metal oxidation, AKA rust. Aluminum oxidation requires a different approach.


Never seen Naval Jelly here (Downunder) but I see it has Phosphoric acid as a main active ingredient, so it should be good stuff.


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