Fuel Tank cleaning ~ Dusty rust.

[Garn 1]

Well I looked in the fuel tank of my Z900-A4 and it is full of dusty rust as opposed to scaly rust.
I seem to recall some great methods of cleaning them up from older forums.
I intend to seal it at a later date.
I don't think it's rusted thru anywhere.

I think the method I used previously consisted of the use of two different acids and flushing in between, over a period of a couple of days.
I am not worried about external finish at this stage.
Any help appreciated.

RegardZ.

[chrisu]

the patented harpic/coke method should sort this out.......

[Garn 1]

Thanks ChrisU, I thought I would check out the archives of a USA forum... KZrider.com.
They certainly had a wealth of info. I avoided their industrial products , also POR and Cream. Here are some of their answers for other interested members.

1.
Well this is a popular thread....have heard a 100 cures for the rust in tanks....I havent had to deal with it myself....yet! I think the Kero seems to work best from what I have seen....heard. Dont know what mixing with gas does??? to carbs....that would be my only question. When done....couldnt you stick some wd-40 sprayed wrags inside the tank and seal it up....when you want to use pull the wrags out????

2.
The paint Company were saying to use muriatic acid with a chain and shake the crap out of it, and then use diluted phosphoric acid to neutralize it and it shouldnt get flash rust. doesnt that sound like it should work? the flash rust is what im worried about once it’s done.

3
To do the job you first have to decide if the tank has scaly rust or just surface rust. If the rust hasn't gotten to the point where it's scaly you can skip the 1/4" nuts, referred to later.

First, flush out any oily varnish that may be coating the lower regions of the tank with acetone or any of those engine degreasers. If you choose the engine degreaser flush the tank with water.

Remove the fuel level sensor. Seal it's opening with GOOD duct tape.
Remove the petcock and seal it up with an appropriate plug or capped section of hose. Dump 30 or so 1/4" nuts into the tank.
Pour in a pint or so of muriatic acid. Seal up the fill spout with GOOD duct tape.
While wearing gloves, old clothes and safety goggles. Agitate the tank for 10 to fifteen minutes. During this time you can monitor the pressure in the tank by watching the duct tape bulging at the fill hole. If too much pressure develops, carefully vent it by peeling the tape back than reseal and keep shaking.

Next pick a piece of concrete that you don't particularly care about. Remove the tape from the sender opening and fill hole and flush the tank with cold water. The acid that has not already been consumed will neutralize itself on the concrete. You're still wearing goggles and gloves right?

Now dry off the openings and reseal them with GOOD duct tape. This time pour in a pint of naval jelly, or milk stone remover or tile haze remover. These are all phosphoric acid formulations. Phosphoric acid is not as aggressive as muriatic acid and therefore is mostly a waste of time if you're trying to really remove rust. What phosphoric acid will really do well is leave the inside of the tank coated with iron phosphate, which is somewhat rust resistant. For this step you do not need much agitation. Just tumble the tank over several times and let it set for a half hour or so and then tumble it again. After about two hours of this and go back to the concrete slab, open the tank, drain it and immediately spray WD 40 into the openings trying to coat as much of the metal as you can. Now flush it out thoroughly with clean water. One more application of WD40 and you're ready to force dry the tank.

Back in the shop, prop a blowdryer so that it forces warm air into the tank and let it blow for an hour or more. Position the tank in different orientations during this process to make sure that no seam holds water. Once it's really dry you're done.

I used to say that the phosphoric acid step was critical to avoid flash rusting. Now, I still think it's a good idea for future rust resistance but since I started spraying WD40 into the still wet tanks, flash rust's no longer a concern.

I've probably cleaned twenty tanks with some variation of this method I've described here and never damaged the exterior paint or eaten through the steel.

RegardZ