'83 KZ550 - Surface Rust inside Gas Tank

Rebuilding my 1983 KZ550 Spectre after several years of inactive service. Used Evaporust in gas tank ~5 years ago that removed some surface rust. Left tank full of gas with fuel stabilizer in it for ~3 years. Dumped out all fuel and have refilled with new fuel, but still have minor surface rust in ~50% of inside of tank - no rust that is even close to compromising the tank. Installed new petcock. I have read elsewhere about putting some large bolts/nuts in the tank with fuel and sloshing it around to knock off surface rust. Any DYI rust removal anyone can recommend? Thx.

Evaporust works well to clean the tank. You must first remove the petcock, fuel sending unit, gas cap, etc, and fashion some fluid tight plugs, then dump in a gallon or two of the sauce. Shake the tank and rotate it through all angles, allowing the fluid to cover all areas of the tank for several hours each. It will take a day or two to get all areas. After you are done you can recycle the Evaporust and save it for it's next use, and rinse the tank with water. Once you are finished rinsing quickly dump in a couple quarts of rubbing alcohol and swish it around then dump, followed quickly by half a can of WD-40. Be sure to swish the WD-40 around really well and then dump that out too.

As an alternative to Evaporust you can use phosphoric acid in the form of Kleenstrip Etch and Prep as sold by Home depot. That stuff works awesome, it's just not as friendly to your paint as the Evaporust in case of spillage. If you use that stuff you can dump in a gallon and then top up the tank with water to dilute, and then just leave the tank sit. After the rust is gone dump it out and do the rinse and alcohol/WD-40 business same as described earlier. The last part is critical or flash rust will form.

Good luck

Before you go with rust remover you have to degrease your tank with POR15 Marine-Clean.
This sort of grease protect the rust under the thin grease surface in the tank and disabled a 100% rust remove by phosphoric acid.

Thx or the advice so far. Here is a picture showing some of the tank inside.

Its time to do a rust removal before you get pin holes by the rust.
Get a POR15 gas tank sealer Kit for motorcycles

www.por15.com/POR-15-Motorcycle-Fuel-Tan...pair-Kit-_p_106.html

I used the same kit over 10 years ago on my project bike,

That tank looks to have a combination of gasoline varnish and rust in it.

1st step is to remove the varnish. That Degreaser Cleaner stuff Scorocco linked works well. Carb dip works well too as would that Yamaha carb dip stuff.

2nd step is to derust. You can't do this properly until step 1 is complete.

Perhaps you should read this:
www.kzrider.com/articles/technical-tips/22-rusty-tanks
Also those epoxy coatings are really unnecessary unless you already have pinholes in the tank.
IMHO
Bill

KZQ wrote: Perhaps you should read this:
www.kzrider.com/articles/technical-tips/22-rusty-tanks
Also those epoxy coatings are really unnecessary unless you already have pinholes in the tank.
IMHO
Bill

Bill,

Sorry to go against you here but I do not like the idea of using muratic acid to clean rust. It's super harsh and dangerous. Phosphoric acid is the proper material to derust steel. It's far safer and doesn't need to be neutralized after use. If you purchase a gas tank liner kit such as the one from Por-15 or Kreem they include a bottle of phosphoric acid to derust the tank. Further, if you get some parts professionally powder coated they will have a phosphate tank to clean the parts as part of the prep process. PPG and Dupont paint also sell phosphoric acid solution as part of the metal prep process prior to painting.

Kleenstrip Etch and Prep is sold by Home Depot for something like $17/gallon, and that stuff will eat off nasty tank rust in just an hour or so of soaking. It leaves behind a phosphate coating on the metal which helps protect it against flash rust too. The concentration level is such that you can cut it will water several times and it will still be effective, just slower. I prefer to use it full strength though and recycle it for reuse. I've got a gallon that has done countless parts.

Phosphoric acid is not overly harsh but you don't want to leave it dwell on a nice painted surface. Rinse off and dry quickly if you spill on good paint. Evaporust on the other hand won't hurt paint, thus that's my recommendation if anyone has a pristine paint job they don't want to put at risk. It works well, just a little slow. It's not cheap though and after usage it's effectiveness will diminish.

After reading all the replies to date, and thank you all, I have decided to do the following this weekend:
1. Use cleaner/degreaser (do I have to remove the petcock and fuel sensor before doing this or should I leave them in from this step?)
2. Remove sensor and petcock and seal all openings with good duct tape (any other suggestions?)
3. Fill tank with KleanStrip - Prep & Etch (phosphoric acid) - 1 gallon and then fill rest of tank with water (how long should I leave in tank?)
4. Dump KleanStrip, rinse with water, and then fill with 1 quart rubbing alcohol - then dump
5. Immediately spray 1/2 can WD-40 on all surfaces and rotate tank
6. Rinse with water - then another 1/2 can WD-40
7. Use blowdryer to dry tank for ~1hour

NDSpectre wrote: After reading all the replies to date, and thank you all, I have decided to do the following this weekend:
1. Use cleaner/degreaser (do I have to remove the petcock and fuel sensor before doing this or should I leave them in from this step?)
2. Remove sensor and petcock and seal all openings with good duct tape (any other suggestions?)
3. Fill tank with KleanStrip - Prep & Etch (phosphoric acid) - 1 gallon and then fill rest of tank with water (how long should I leave in tank?)
4. Dump KleanStrip, rinse with water, and then fill with 1 quart rubbing alcohol - then dump
5. Immediately spray 1/2 can WD-40 on all surfaces and rotate tank
6. Rinse with water - then another 1/2 can WD-40
7. Use blowdryer to dry tank for ~1hour

Skip step 6. You do not want more water on top of the WD-40 you added.

I've tried duct tape to seal tank openings before but they always sprung a leak. I prefer mechanical plugs w/rubber like shown below.

The last photo shows some white scale on the tank surface which is a build up of the phosphate coating. I left this tank too long with the sauce inside (more than a week). It was my first attempt with the stuff. That particular tank had some seriously deep rust though.

Nessism wrote:

KZQ wrote: Perhaps you should read this:
www.kzrider.com/articles/technical-tips/22-rusty-tanks
Also those epoxy coatings are really unnecessary unless you already have pinholes in the tank.
IMHO
Bill

Bill,

Sorry to go against you here but I do not like the idea of using muratic acid to clean rust. It's super harsh and dangerous. Phosphoric acid is the proper material to derust steel. It's far safer and doesn't need to be neutralized after use. If you purchase a gas tank liner kit such as the one from Por-15 or Kreem they include a bottle of phosphoric acid to derust the tank. Further, if you get some parts professionally powder coated they will have a phosphate tank to clean the parts as part of the prep process. PPG and Dupont paint also sell phosphoric acid solution as part of the metal prep process prior to painting.

Kleenstrip Etch and Prep is sold by Home Depot for something like $17/gallon, and that stuff will eat off nasty tank rust in just an hour or so of soaking. It leaves behind a phosphate coating on the metal which helps protect it against flash rust too. The concentration level is such that you can cut it will water several times and it will still be effective, just slower. I prefer to use it full strength though and recycle it for reuse. I've got a gallon that has done countless parts.

Phosphoric acid is not overly harsh but you don't want to leave it dwell on a nice painted surface. Rinse off and dry quickly if you spill on good paint. Evaporust on the other hand won't hurt paint, thus that's my recommendation if anyone has a pristine paint job they don't want to put at risk. It works well, just a little slow. It's not cheap though and after usage it's effectiveness will diminish.

No Problem Nessism,
Muratic acid is more aggressive, it also does a better job. I've previously tried Phosphoric acid alone and been frustrated when it doesn't get the tank clean. By that I mean it has, for me, left scaly rust behind. One of my favorite reasons for choosing muratic acid is that there is no need for rocks, screws or any other sort of abrasive material needed to loosen the tough scaly rust. Additionally, I've cleaned many tanks using muratic acid and never damaged any paint.
Still, if phosphoric acid works for you go for it.
Regards
Bill

Nessism - how long do you recommend leaving the acid/water combination in the tank for surface rust? Thanks for the pics on the sealing technique.