Topic: Prep & Etch for Rust Removal

[AintNoEasyWay]

Hi guys, I've been searching through old threads on rust removal in gas tanks.

I tried the simple vinegar process. 5 gallons of vinegar in my 1977 cb750 5 gallon tank. Then drain & fill with water/1 cup of baking soda to neutralize. I drained that solution out, & still had some rust in the tank. I quickly filled to top with gas & some Seafoam, but have decided to look for another process to de-rust.

I've had Klean-strip Prep & Etch recommended to me, but not sure of what else should be done besides sloshing it around in the tank for about 30 minutes. Some threads seem to say you can just fill immediately with gas & be ok. Is this true or do I need to rinse with water/baking soda or do anything else?

[flybox1]

I've had Klean-strip Prep & Etch recommended to me, but not sure of what else should be done besides sloshing it around in the tank for about 30 minutes. Some threads seem to say you can just fill immediately with gas & be ok. Is this true or do I need to rinse with water/baking soda or do anything else?

Prep-n-etch works well
fill your tank with old golf balls, or something of the like, first, to take up the volume.
pour in and leave it for an hour or a day, rotating it so it gets all parts of your tank.
rinse with water, and then rinse the water out with acetone. no flash rust.
fill with gas
done.

[Mo]

Well, it's an acid. Best to neutralize it. Actually this is basically a requirement. Why risk your carbs/engine with gas/acid mix? Acid + Alcohol will react and one of the by products is generally water. Water in an engine is bad.

Thus Prep n Etch, followed by baking soda and water mix solution. Prep N Etch also leaves behind a surface that won't flash rust, so after the baking soda and water, dry with some sort of heat (hair dryer) and then fill with gas and enjoy.

[Mo]

I've had Klean-strip Prep & Etch recommended to me, but not sure of what else should be done besides sloshing it around in the tank for about 30 minutes. Some threads seem to say you can just fill immediately with gas & be ok. Is this true or do I need to rinse with water/baking soda or do anything else?

Prep-n-etch works well
fill your tank with old golf balls, or something of the like, first, to take up the volume.
pour in and leave it for an hour or a day, rotating it so it gets all parts of your tank.
rinse with water, and then rinse the water out with acetone. no flash rust.
fill with gas
done.

Never even thought of the volume trick. That's pretty solid, and certainly relieves a lot of shaking around!

[AintNoEasyWay]

I've had Klean-strip Prep & Etch recommended to me, but not sure of what else should be done besides sloshing it around in the tank for about 30 minutes. Some threads seem to say you can just fill immediately with gas & be ok. Is this true or do I need to rinse with water/baking soda or do anything else?

Prep-n-etch works well
fill your tank with old golf balls, or something of the like, first, to take up the volume.
pour in and leave it for an hour or a day, rotating it so it gets all parts of your tank.
rinse with water, and then rinse the water out with acetone. no flash rust.
fill with gas
done.

Never even thought of the volume trick. That's pretty solid, and certainly relieves a lot of shaking around!

Yea, what a great idea.

I had planned on using acetone this time if I needed to use water at any point. I wasn't aware of that trick before, & had trouble getting some of the water/baking soda out when blowing with compressed air.

[flybox1]

after the prep-n-etch, rinse your tank several, 3 or more, times with water.  then the acetone rinse.
i used a whole can of acetone, shook it around, and drained it all right back into the can.
My tank came out with a nice grey coating and no rust.

[Lazerviking]

I've seen a post about someone putting a bunch of Sheetrock screws in his tank and then putting it in the dryer with a bunch of pillows and letting it run for a few hours. Is this done in order to move that or the old liner?

[Mo]

I cant imagine putting the tank in the dryer is a good idea.

[vames]

Try phosphoric acid instead of toilet cleaner (usually hydrochloric acid).

The phosphoric acid converts any remaining rust (iron oxide) and the outer-most layer of metal into iron phosphate, which is very stable and actually acts as a coating that prevents flash-rust from happening when you're drying it. .

[750K]

^^^Prep & etch is phosphoric acid from what I gather.

[AintNoEasyWay]

I've seen a post about someone putting a bunch of Sheetrock screws in his tank and then putting it in the dryer with a bunch of pillows and letting it run for a few hours. Is this done in order to move that or the old liner?

It's done to remove rust. I've seen Youtube videos of it. You wrap the tank up firmly with tons of blankets, throw a lot more blankets in the dryer, then put in the dryer for some period of time. I've also seen videos of guys tying it onto back wheels of 4-wheelers. It's all a little crazy, but apparently works. Definitely wouldn't be my first course of action. Or second... or third...

after the prep-n-etch, rinse your tank several, 3 or more, times with water.  then the acetone rinse.
i used a whole can of acetone, shook it around, and drained it all right back into the can.
My tank came out with a nice grey coating and no rust.

This sounds good. I don't want to use baking soda, just water, right?

[flybox1]

just water.  partly fill, shake, drain, repeat.
have a buddy hold the tank upside down while you full power spray inside with a hose.
be SURE all of the prep n etch is rinsed out. 
get as much water out as you can, then the acetone to dry it out.
fill with gas.
10 min, tops.

[AintNoEasyWay]

just water.  partly fill, shake, drain, repeat.
have a buddy hold the tank upside down while you full power spray inside with a hose.
be SURE all of the prep n etch is rinsed out. 
get as much water out as you can, then the acetone to dry it out.
fill with gas.
10 min, tops.

Straight forward. Exactly what I was looking for. Thanks, Flybox. Will give it a shot tonight after work.

[flybox1]

Cool.  have a bucket you can drain the solution into.  that way you can check to see how its doing, based on your 'soak time'.... so you can add it back if it needs more.   i let my tank sit for an hour.

[Duanob]

"Prep N Etch also leaves behind a surface that won't flash rust," The problem is you need to neutralize the acid and water works well but it will flash rust. The acetone or paint thinner will help but you shouldn't let it sit to dry, it will flash rust. try using a hair dryer in the fill neck. Or filling it with gas ASAP.

I usually buy 2 containers of Prep-n-etch and top off with water. I just found out the last time that it doesn't come in a gallon container it comes in a 3 QT! Another marketing rip off. But Fly's idea to take up volume is a good one.

The dryer trick  did you get that off the internet? It must be true! 

[Lazerviking]

The dryer trick  did you get that off the internet? It must be true! 
[/quote]


Ha, I saw it on these forums somewhere. Seems like an intense way to go but whatever works... or something.

[KayOne]

Another method is to acid wash several times, rinse with 50/50 methanol/water several times, final rinse with 100% methanol, hair dryer and tank sealer in immediately. Methanol (methyl hydrate or gas line antifreeze) is hydrophilic and will remove any water left over from the acid and methanol/water rinses. Just did my K1 tank yesterday. This method insures you have little to no flash rust.

I prepare all the acid , meth/water and pure methanol rinses before hand so rust has no time to form. This is the third tank I have done and it works like a charm. I use POR15 with good results...make sure you have LOTS of cure time with the POR, I'm talking weeks. I know there are other products that also work well.

If you have heavy rust don't scrimp on the HCL (Muriatic acid) I mix 1 part acid to three parts water and it just blows the rust away! Make sure you do this outdoors and wear a good mask, eye protection and heavy clothing, rubber gloves etc..

[greenjeans]

I've actually done the dryer trick.   It was mainly to get rid of the scaley loose rust - and it definitely did.

the tank had been rinsed of gas and had been sitting well over a year before I tried it.   No heat.   Stuffed it in a sleeping bag and then jammed a

big quilt in there as well.    I'm a fan of electrolysis and the prep & etch.

[Irukandji]

any problem with the golf balls outer coat disolving, or the petcock screen being damaged ??

[AintNoEasyWay]

One issue I had during the vinegar process that I forgot to ask about:

The tank drained very slowly when removing the vinegar & then again after with the baking soda/water mix.

Does anyone have any idea why this might be? I removed the petcock & used rubber tubing with clamps in order to seal everything off.

I feel like an idiot, but I realize now that I didn't remove the petcock filter screen from the tank. I didn't even know there was anything else to remove besides the petcock  . Anyway, is the possibly the thing causing the draining trouble? If so, I'll have to start looking for a place to find one for my 1977 cb750 tank.

[MoMo]

On the prep and etch,   be very carefull how long you leave the solution in as it does etch the metal. So if the metal is thin in an area the solution will continue to etch(eat) the metal and eventually erode and cause pinholes in the tank.  Know this from first hand experience ...Larry

[flybox1]

One issue I had during the vinegar process that I forgot to ask about:

The tank drained very slowly when removing the vinegar & then again after with the baking soda/water mix.

Does anyone have any idea why this might be? I removed the petcock & used rubber tubing with clamps in order to seal everything off.

I feel like an idiot, but I realize now that I didn't remove the petcock filter screen from the tank. I didn't even know there was anything else to remove besides the petcock  . Anyway, is the possibly the thing causing the draining trouble? If so, I'll have to start looking for a place to find one for my 1977 cb750 tank.

why not drain it out the filler hole? 

[AintNoEasyWay]

One issue I had during the vinegar process that I forgot to ask about:

The tank drained very slowly when removing the vinegar & then again after with the baking soda/water mix.

Does anyone have any idea why this might be? I removed the petcock & used rubber tubing with clamps in order to seal everything off.

I feel like an idiot, but I realize now that I didn't remove the petcock filter screen from the tank. I didn't even know there was anything else to remove besides the petcock  . Anyway, is the possibly the thing causing the draining trouble? If so, I'll have to start looking for a place to find one for my 1977 cb750 tank.

why not drain it out the filler hole? 

I can do that... I'm just wondering if gas will have trouble getting to the carbs once I put the tank back on the bike. I realize now that the screen didn't come out of the tank when I removed the valve, it looks like this but without the screen pictured on the left (actual part # for screen set is 16952-388-015):

http://www.ebay.com.au/itm/Honda-NOS-CB750-Fuel-Petcock-Valve-CB-750-CB750A-78-16950-393-015-/321217434002

When I removed the valve, the screen must have stayed in the tank. Will have to see if I can remove it this evening. Hopefully is just has a lot of rust & debris in it, & doesn't need to be replaced.

[750K]

The plastic screen comes out, you need to get a big tap or bolt that will thread into the opening and snug up. Then just pull down, it should pop out as its just pressed in there. I've removed 3 like this with no issues, a tap works well as they are tapered at the top.

[flybox1]

replace it if you can, or go without and run an inline filter.
you will need one or the other.