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Gas Tank Rust Repair and Restoration

Do you have a rusty tank ? Perhaps a hole or two ?

I have a couple of old bikes in need of restoration. I spent a lot of time searching the web for a way to completely remove the rust from the inside of the tank. Then, I needed to seal the metal afterwards. I had a Kreem kit but there were too many horror stories; probably from incorrect application, but I didn't want to take any chances. I bought a 1 litre ( 500ml part A + 500ml part B) pack of "S1" from Industrial Formulators for $29 Canadian.  The epoxy is clear but they also make a product called Titanium Surface Finish which has a white finish and is also tintable. The retailer I bought from didn't have any so I'll try the clear which is not tintable. The epoxy is clear as water so I may give it another treatment with the Titanium.

This is the tank from my 1972 Yamaha XS 650. I needed something to clean the rust out of the inside without destroying the exterior paint. The paint isn't great but I wanted to preserve it until I was ready for a repaint.

In order to clean the tank, I first sealed off the petcock holes. I didn't need or want the petcocks on while I had harsh chemicals inside the tank to clean. I used the same cleaner on the petcocks but I didn't want the rust from the tank filling them up.

First, I ran a bead of RTV silicon around the opening.

Next, I took some scrap aluminum strips and drilled a couple of holes in each one to fit the petcock screws. I found that when I tested the tank with water to see if the RTV would hold, the tank leaked around the screws. I unscrewed them half way, ran a quick bead of RTV around the holes, and tightened them down again; no more leaks.

The next step was to fill the tank with something to get rid of the rust. I had really good luck with a product called Zep that I bought at Home Depot (in the cleaning supplies department) for about $10 Cdn.

Do this outside or you'll stink up the house. Wear rubber gloves and good eye protection. The label says it makes up to 5 gallons but I normally use it full strength. Zep cleans away rust in minutes without scrubbing. It'll do the same for aluminum and didn't harm my paint. Most other rust removal solutions seem to involve acid which can destroy your paint although I've been told that Zep is basically phosphoric acid..

For the first attempt on this tank, I used what I had left - about 3/4 of a gallon and then topped it off with water. This is what it looked like after soaking for about an hour.

After the Zep treatment, I rinsed the tank thoroughly with water and then used a blow dryer to quickly dry it. The blow dryer fit the hole perfectly. And the brand name of the dryer.... a "Conair"... no kidding

For my purposes, this is clean enough since I'm going to line it with 2 part epoxy. All of the heavy scale is gone. From what I've read, it's only necessary to remove the heavy loose scale and that a slightly rough surface is necessary for the epoxy to adhere to. I'm sure that using Zep full strength would have removed all of the rust.

The next step after lining will be to soak the outside of the tank and repair the underside paint. Eventually, I'll strip and repaint the entire tank.

After the first 3 coats this is what I learned and will do on the next tank:

Remove the aluminum strips that you covered the petcock holes with; I let the excess drain out here. I did however leave the screws in place, screwed in only 1/2 way. They continued to turn freely throughout the process but I'd keep checking them after each coating anyway and then for a couple days after the last one.

The first treatment of the epoxy should total 100ml or about 4 ounces. Since the epoxy is clear, I would suggest tinting it. I bought a tube of tint for under $4 Cdn. Mix the two parts and let sit in an air tight container (I just used Saran Wrap) for at least one hour. Pour the epoxy in the tank and roll  around for 10 minutes or so trying to cover ever square inch. Check the insides where possible with a flashlight to make sure everything is covered. I  found that it's easy to miss spots. It takes very little epoxy to actually cover the tank but you need a fair bit rolling around  inside to ensure you do. When you think you've covered everything, pour the excess out and dump in the garbage since it may have picked up some loose crud previously missed.

Wait at least 12 hours between coatings but not more than 24 hours.

For the second and subsequent coatings, repeat the procedures for the first coast but pour the excess out into a clean container. (The epoxy has a pot life of 48 hours.) Seal with an airtight lid. If it's clean, reuse the epoxy for the remaining coatings. It won't harden and stays completely liquid long enough to complete 4 coatings at 12 - 14 hour intervals.

I opened the basement door and turned on the fan since the fumes, while not overpowering, don't feel very healthy.

If you must work outside, try a Cold Cure Epoxy. The literature says it's moisture tolerant, has excellent resistance to common chemicals, use as a corrosion resistant coating for steel, and can be applied at temperatures down to 2 degrees C. / 35 F.

Some application details from the can:

  • Mix 1:1 and allow mixed material to stand in an air tight container for at least one hour before applying
  • Pot life and working time - 48 hours
  • Cure time (80-90%) - 24 hours
  • 3 coats recommended
  • Minimum time to recoat-12 hours (after 24 hours, sand surface)

Technical notes from the epoxy manufacturer:

  • Mix ratio - 1:1
  • Total solids - 50%
  • Viscosity - extremely thin
  • Color - clear
  • Application temperature range - 15 to 40 degrees C. / 59 to 104 degrees F.
  • Coverage - 75 to 100 Sq. Ft. per liter (about 1 U.S. quart)
  • Service temperature range -  -20 to +72 degrees C / -4 to +162 degrees F.


This is what it looks like after the second coat of epoxy. The only difference that you can really notice is a bit of a shine to the insides. It's perfectly clear which is why you still see a little rust. If you're a purist, you should have used full strength Zep and left it until the rust was all gone. Then, you would use a tinted epoxy, or at least I would have. I found that the epoxy I used could be tinted; I added tint to the fourth and fifth coats. Otherwise, I probably would have stopped at 3 coats. And I only used half of the epoxy that I bought.

Here's a couple more solutions

Rust is easily removed with Oxalic acid. It can be found in your local hardware store, labeled as wood bleach. It comes in a plastic tub. You mix the granules with hot water and simply soak the rusted item's in it. I have used it in a fuel tank to remove even thick scaly rust. It seems to only have a harsh reaction with the rust itself. If left on a painted surface it can discolor it. Clean metal seems to be unharmed by the solution. After a couple hours of soaking, I neutralized the surface with a baking soda solution and rinsed with plain water. Remember it is acid, so read the warning label.

 Fred Harmon <,
COG digest 2167, October 28, 2000
Subject: Gas Tank Preventative Maintenance
I bought a rust dissolver called Oxi-Solve from J.C. Whitney a couple years ago for $5.  I emptied and dried my tank and sloshed the stuff around in my then 6 month old tank. I let it sit in the corners of the tank overnight.  The acid in it dissolved the rust and it left a zinc phosphate coating in it's place. I then vacuumed it out (with a Mity Vac).  I got a lot of dissolved "orange goo" globs out of the tank.  I was surprised how much rust came out of my brand new tank.  Especially since I cover the filler with saran warp when I wash the bike and I rode every day and had also ran alcohol through the tank once every couple of months.  I had to flush out the remaining Oxi-Solve with two or three hot soapy water rinses.  I then re-dried the tank and flushed it with two bottles of dry gas to remove any remaining water from the rinses. Yes it took some time but it removed all the existing rust and it thoroughly coated the inside of my tank with a rust preventative coating (zinc phosphate). The Oxi-Solve seemed to do a real good job on getting the rust out, but I had to be real careful not to get any on the paint, as it is an acid. I also would recommend that everyone who own a Concours should buy and install an in-line gas filter.

June 8, 2000 Curt Hollis.
I have used the Kreem kits in the past and you do have to be very careful during the process of you will ruin the paint on the tank. However, being very careful you can successfully coat the tank with the Kreem kit. There is also another coating system gaining popularity out there, it is the POR-15 system, some people say this is better than the Kreem kit stuff. I have not used it so I really do not know.

I stopped using the Kreem kit a few years back. I now use a fiberglass resin to coat the tank. You still need to be careful getting the rust out. I put sand blast sand in the tank and shake it around for awhile. This works pretty good. I then wash the tank very well with water and then clean the water out with an alcohol wash. Then I apply the fiberglass resin by rolling it around the tank until it starts to gel. Then I pour the remaining resin out. I did this with a Z-1 900 tank that had a rust hole in the bottom of the tank, the tank had an excellent paint job on it and I didn't want to lose the tank. After I poured the resin out I set the tank down were the left over resin would pool over the rusted area. The tank has worked great ever since.

From Caswell internet site
Using the very latest in 2 part Epoxy Resin technology, we have developed a simple yet very durable lining for all type of fuel tanks. This Epoxy has much better bond strength than single component products, with strengths of up to 3000 PSI, and this higher strength reduces the need for a clinically clean surface, as the epoxy actually prefers to bond to a rough rusty surface.

To prepare the tank, simply place several nuts & bolts inside and about a pint of lacquer thinner, MEK or toluene. Shake the tank around to dislodge any loose particles, then drain off the liquid and allow to dry. This procedure removes any oils left over from the fuel.

Block off any weeping seams or holes by placing duct tape over them, and fill any ports with putty, then mix up the Epoxy Gas Tank Sealer and pour into the tank. Slowly rotate the tank in every direction for several minutes, then pour out any excess resin. Allow to harden overnight before putting into use.

Epoxy Gas Tank Sealer coats up to 2 x 5 gal tanks PROD GTS1750 Epoxy Gas Tank Sealer $19.50

August 28, 2000 Andy Donohue, COG # 2545
Here's how I did my tank last winter. So far so good.

I posted last week soliciting help for rust in my gas tank and carbs. Going on advice from this list [COG listserv] and searching the web I decided on a 2 part epoxy product from Caswell Plating to line my gas tank. The kit cost about $25 including shipping and consisted of a can of Part A and a can of Part B and some meager instructions.

I went to Home Depot and purchased a quart of acetone, a rubber plumbing coupler and a cheap disposable paint bucket. I drained the tank as much as possible with the petcock on prime and removed the tank from the bike. I then siphoned the rest of the gas with one of those cheap siphons with a squeeze bulb. I removed the gas cap, petcock and fuel level sensor. I fabricated plugs for the holes left by the petcock and fuel level sensor out of some scrap aluminum, using pieces cut from the rubber plumbing coupler as gasket material (an old inner tube would probably also work). I then put the tank inside a heavy duty plastic bag and used duct tape to tape the bag around the filler opening. This was to protect the paint from the acetone rinse. The directions said to rinse the tank with a pint of acetone then drain. Then shake a handful of bolts around in there, then rinse with another pint of acetone. I threaded the nuts on a string (natural fiber as the acetone will eat plastic) so I could get them out easily. After the final rinse with acetone you have to drain the tank and let it dry thoroughly. It is almost impossible to drain the Connie tank completely so I tried to siphon the acetone. It quickly dissolved the rubber bulb on my siphon so I had to wait for the acetone to evaporate, leaving behind a small pile of rust. I removed the rust with some duct tape on a coat hanger.

I was now (finally) ready to coat the tank. I mixed all of the part A with all of the part B because the instructions didn't mention a ratio. The instructions say that the kit will coat two, 5 gallon tanks, so I poured the majority of the epoxy in the tank and covered the filler hole with saran wrap. I then slowly rotated the tank hopefully covering every inside surface. After I was reasonably certain that I had coated the whole tank, I set it aside to dry for about an hour. I then removed the plugs from the petcock and fuel sensor holes. They came right off and the epoxy had coated them evenly and was dry to the touch. The next step is to let the epoxy cure over night and that is where I am now. I can say that this was fairly easy although time consuming. It would be much easier if the Concours tank drained completely through the petcock. I did get a little acetone on the paint, but wiped it up quickly and it doesn't seem to have done any damage. I have never used Kreem, but have heard horror stories of trashed paint jobs, from the acid etching and the sealer itself. This method seems to be less hazardous to your paint job. Heeding warnings on the acetone can, I did that part of the process outside (in 15F weather), but I did the epoxy part in the house and there was really no odor. The cat didn't even seem to notice. I hope this rambling post is understandable and helps someone else planning to do this. Email me if you have any other questions.

Article By: David J. Morrow

August 2005

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